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  • 1.
    Amanda, Holmkvist
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad mekanik, Byggteknik.
    Inverkan av torktemperatur vid vattenmättning av bruk och betong: Bestämmning av vattenmättnadsgrad och hydraulisk konduktivitet2016Självständigt arbete på grundnivå (yrkesexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Today, there is uncertainty about how much the results differ when drying concrete

    at 20, 50 and 105 °C prior to saturation of concrete in order to determine the

    degree of saturation and hydraulic conductivity. Micro-cracks occur when concrete is

    dried at higher temperatures and causes increased hydraulic conductivity. Further, the

    concrete is believed not to be completely saturated if not all the physically bound

    water, so called free water, has been dried out prior to saturation.

    This thesis compares the effect of three different drying temperatures on the

    possibility to saturate concrete with water. The work was conducted at Vattenfall’s

    concrete laboratory in Älvkarleby. The three drying temperatures were +20 °C

    (room temperature), 50 °C and +105 °C. The objective was to determine if

    differences on the degree of saturation and hydraulic conductivity were non-existent

    or negligible. Vacuum saturation after drying at 105 °C is considered to be complete.

    The results after drying at 20 °C and 50 °C were compared to those after drying at

    105 °C. The results of the tests indicate that the concrete should be dried at +105°C

    prior to saturation with water. Then the risk of frost damage to concrete in hydro

    power structures can be assessed.

    How determination of the hydraulic conductivity is affected by the drying

    temperature gave more vague and dubious results. All specimens showed a maximum

    hydraulic conductivity after drying at 50 °C, not after 105 °C as expected. It was

    believed that the hydraulic conductivity theoretically would increase because of

    (more) micro-cracks when being dried at 105 °C. Results from the concrete with vct

    1.0 gave results that indicated that the specimens had been damaged by method 1. To

    sum up, the results of the tests indicate that further studies on the effects of drying

    temperatures should be made.

    Ladda ner fulltext (pdf)
    Inverkan av torktemperatur vid vattenmättning av bruk och betong
  • 2.
    Ayotte, John
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik.
    Dynamic positioning of a semi-submersible, multi-turbine wind power platform2015Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    As a growing market for offshore wind power has created a niche for deep-water installations, offshore floating wind solutions have become more and more viable as a renewable energy source. This technology is currently in development and as with many new technologies, many traditional design methods are found lacking. In the multi-turbine platform design investigated, turbine units are placed closely together to conserve material use and reduce cost, however with such tightly spaced turbines; wake interaction poses a threat to the productivity and the lifespan of the installation. In order to fully capitalize on the substantial increase in available wind energy far at sea, it is important that these floating parks operate in an optimal way. The platform investigated in this report sports 3, 6MW turbines which must be positioned such that wake interference is minimized; the platform must always bear a windward heading. 

    Maneuvering ocean going vessels has been practiced using automated dynamic positioning systems in the gas and oil industry for over 50 years, often employing submerged thrusters as a source of propulsion. These systems are mostly diesel powered and require extra operational maintenance, which would otherwise increase the cost and complexity of a floating wind farm. In this paper, it is suggested that the wind turbines themselves may be used to provide the thrust needed to correct the platform heading, thus eliminating the practical need for submerged thrusters. By controlling the blade pitch of the wind turbines, a turning moment (torque) can be exerted on the platform to correct heading (yaw) relative wind direction. Using the Hexicon H3-18MW platform as a starting point; hydrodynamic, aerodynamic and electromechanical properties of the system are explored, modeled and attempts at model predictive control are made. Preliminary results show that it is possible to control the H3’s position (in yaw) relative the wind using this novel method.

    Ladda ner fulltext (pdf)
    Dynamic positioning of a semi-submersible, multi-turbine wind power platform
  • 3.
    Bender, Anke
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Francisco, Francisco G. A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Sundberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    A Review of Methods and Models for Environmental Monitoring of Marine Renewable Energy2017Ingår i: Proceedings of the 12th European Wave and Tidal Energy Conference, EWTEC , 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    A continued expansion of the marine renewable energy sector will result in an increased demand in monitoring the natural marine environment. This may be due to a basic scientific interest but is foremost linked to the requirement of pre- and post-construction studies in relation to environmental impact assessments and consenting processes for marine renewable energy projects. With focus on wave and tidal power, but without attempting to provide a comprehensive list, we review methods, technologies and other scientific tools used for monitoring and predicting possible impacts from marine energy installations, on both population and behavioural levels. This includes traditional methods such as fishing gear, like nets and cages, modern technologies such as platforms with multi parameter equipment and the use of deterministic models. This paper is intended to serve as an overview for technology developers as well as authorities, regulators and decision makers with interests in general techniques, and naturally for scientists and consultants commonly being executors of studies and monitoring programs. By giving relevant and up to date references this paper may also be useful for finding more detailed information on study methods and variants. Finally, we give recommendations on where development of technologies is needed in order to face future requirements.

    Ladda ner fulltext (pdf)
    fulltext
  • 4.
    Braune, Yann
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för samhällsbyggnad och industriell teknik, Industriell teknik.
    Investments in Academic Renewable Electricity Generation Technology Spin-Offs: A Qualitative Study on High Capital Limitations for Underexplored Renewable Energy Sources2020Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Due to an intensified climate change discourse, renewable energy technologies find higher attention within the energy system and increasingly compete with traditional energy conversion systems. Electricity is progressively being generated through renewable electricity generation technologies (REGT) which harness naturally existing energy fluxes (wind, tide, heat, sun) and convert it to electricity. High investments are currently being made into well-developed REGT using explored energy sources such as wind, hydro or solar. In order to increase cost- and energy efficiency of REGTs, university research projects are developing new REGTs that harvest underexplored energy sources such as the marine energy source. These capital-intensive marine energy research projects are entering the market through university spin-off firms but are often confronted with funding gaps, for the current or future operations. Capital rich investors could provide these funds but are often investing in well explored energy sources rather than into underexplored but more cost- and energy-efficient energy sources. Utilizing a qualitative, grounded theory-influenced approach and combining empirical material of semi-structured interviews, data from a participant observation of an innovation system workshop attendance and data from continuous meetings with an academic REGT spin-off from Uppsala University, this study investigates 1) the drivers and barriers within the funding ecosystem for academic REGT spin-offs in Sweden, 2) the limited access of high capital to underexplored energy sources on the specific case of the marine energy source and 3) a potential common ground for investors with high capital and academic REGT spin-offs in order to allow an accelerated diffusion of the marine energy source. The results indicate that the physical properties of the underexplored marine source should not be accounted for as driver but rather as the foundation of an academic REGT spin-off. This frame allows to bridge practitioners of both the investment field and the academic field of REGT spin-offs through the degree of utilization. An inversion of relations, where not only entrepreneurs increasingly link their field of study to economy and business, but also investors adapt cross-disciplinary knowledge towards academia and natural sciences via the degree of utilization, could be beneficial for an accelerated diffusion of academic REGTs. Bridging practitioners of both fields through the degree of utilization and other means might together with a full commercial application and proof of marine REGTs reduce the funding gap of academic spin-offs in the marine sector and allow access to investors with high capital.

    Ladda ner fulltext (pdf)
    Investments in Academic Renewable Electricity Generation Technology Spin-Offs (2020)
  • 5.
    Carpman, Nicole
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Marine Current Resource Assessment: Measurements and Characterization2015Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Det ökande intresset för att producera elektricitet från förnybara energikällor har lett till en satsning på forskning inom området marin strömkraft, främst när det gäller tidvattenströmmar och tidvattenturbiner för fritt strömmande vatten. Tidvatten har fördelen att vara förutsägbar årtionden i förväg. Dock så är tidvattenresursen periodisk och varierar lokalt vilket påverkar effektuttaget från ett kraftverk. Variationerna beror till största delen på fyra aspekter: antal hög- och lågvatten per dag, tidvattencykeln, djupförhållanden på platsen (batymetri) och vädereffekter. Varje potentiell plats är unik, vattnets hastighetsfält påverkas i hög grad av lokal batymetri och turbulens. Därför krävs noggranna undersökningar för att karakterisera resursen. Att tillhandahålla hastighetsdata av hög kvalitet från mätningar är därför av stor betydelse. I denna avhandling har mätningar av flödeshastigheter utförts på tre typer av platser.

    En plats med tidvattenströmmar, belägen i en av alla fjordar längs Norges kust, har undersökts för sin resurspotential. Mätningar har utförts för att kartlägga resursens variation i både tid och rum. Resultaten visar att strömmar i storleksordningen 2 m/s återfinns i mitten av kanalen. Dessutom uppvisar flödet liten variation från huvudriktningen för både inkommande (flod) och utgående (ebb) flöden. Platsen har således potential för energiomvandling av fritt strömmande vatten. En modell föreslås som förutsäger strömmarnas maxhastighet från information om höjdskillnaden mellan ebb och flod och vice versa. En motsvarande modell kan ställas upp och användas på andra platser med liknande förhållanden som berörs av tidvatten, dvs. fjordinlopp som förbinder havet med en fjord eller en bassäng.

    En älv fungerar som en plats för experiment för ett marint strömkraftverk som har utvecklats vid Uppsala universitet och sjösatts i Dalälven, Söderfors. Flödeshastigheten på platsen regleras uppströms av ett närliggande vattenkraftverk, vilket gör platsen bra för att utföra experiment på prestandan av den vertikalaxlade turbinen i dess naturliga miljö. Turbinen har körts i jämnt flöde och mätningar har utförts för att karaktärisera vakens utbredning.

    En plats med havsströmmar var mål för en utredning av dess potential för att ge användbar förnybar energi. En mätningskampanj genomfördes för att kartlägga flödets variation både rumsligt och tidsmässigt. Emellertid visade sig platsen inte vara lämplig för energiomvandling utifrån användning av nuvarande teknik.

    Delarbeten
    1. Measurements of tidal current velocities in the Folda fjord, Norway, with the use of a vessel mounted ADCP
    Öppna denna publikation i ny flik eller fönster >>Measurements of tidal current velocities in the Folda fjord, Norway, with the use of a vessel mounted ADCP
    2014 (Engelska)Ingår i: 33Rd International Conference On Ocean, Offshore And Arctic Engineering, 2014, Vol 8A: Ocean Engineering, 2014Konferensbidrag, Enbart muntlig presentation (Refereegranskat)
    Abstract [en]

    Measurements of tidal current water velocities is an important first step in evaluating the potential for a tidal site to be used as a renewable energy resource. For this reason, on site measurements are performed at the inlet of a fjord situated at the coast of Norway. The site has an average width of 580 m and adepth of 10-15 m which is narrow and shallow enough to give rise to water velocities that can be of use for energy conversion. With the use of an Acoustic Doppler Current Profiler (ADCP) cross-section measurements are conducted along four transects. The measurements covered flood and ebb currents around one tide and the data give a first approximation of the magnitude and distribution of the flow field. Depth averaged mean current velocities are calculated along the transects for horizontal bins with sizes in the order of 50 x 50 m. Maximum mean velocity for the flood currents were 1.31 m/s and 1.46 m/s for the ebb currents. The measurements show that even a small amount of data can give an indication of the potential and characteristics ofthe site.

    Nyckelord
    Acoustic Doppler Current Profiler (ADCP), tidal energy resource
    Nationell ämneskategori
    Marin teknik Havs- och vattendragsteknik Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-230659 (URN)000363498500053 ()978-0-7918-4550-9 (ISBN)
    Konferens
    33rd International Conference on Ocean, Offshore and Arctic Engineering (OMAE2014), San Francisco, California, USA, June 8-13, 2014
    Tillgänglig från: 2014-08-27 Skapad: 2014-08-27 Senast uppdaterad: 2017-04-04Bibliografiskt granskad
    2. Tidal resource characterization in the Folda Fjord, Norway
    Öppna denna publikation i ny flik eller fönster >>Tidal resource characterization in the Folda Fjord, Norway
    2016 (Engelska)Ingår i: International Journal of Marine Energy, ISSN 2214-1669, Vol. 13, s. 27-44Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    For tidal-stream energy industry to be fully realized, lower velocity sites and fjords should be developed. Finding new prospective sites for in-stream energy extraction from tidal currents is an area of ongoing research. In this paper, the tidal flow at a fjord inlet has been characterized using acoustic Doppler current profiler (ADCP) measurements. This work is based on two survey measurement techniques: transect measurements to map the spatial variability, and seabed measurements to map the temporal variability. The data was analyzed in terms of characterizing metrics, to ensure they are comparable with other resource assessments. Results show that currents exceed 1 m/s for 38% of the time with peak currents of 2.06 m/s at hub height (middle of the water column) and the directional asymmetry is less than 1° between ebb and flood, indicating a truly bi-directional flow. A simple prediction model is proposed which allows peak current speeds to be accurately predicted in the channel center from tidal range data using a linear relationship. The relationship is shown to be strong, with a correlation coefficient of 0.98 at hub height, and a standard variation typically less than 10 cm/s. Furthermore, it is show that a minimum of 9 days of measurements are required to set up the model, although it takes 29 days to reduce the error in peak speed to less than 1%. However, the error is expected to vary depending on where in the monthly tidal cycle the survey begins, it is thus recommended to measure around spring tide if the measurement period is short.

    Nyckelord
    Tidal resource assessment, ADCP, Characterizing metrics
    Nationell ämneskategori
    Teknik och teknologier Havs- och vattendragsteknik Oceanografi, hydrologi och vattenresurser
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-266674 (URN)10.1016/j.ijome.2016.01.001 (DOI)000381687600003 ()
    Forskningsfinansiär
    StandUpCarl Tryggers stiftelse för vetenskaplig forskning
    Tillgänglig från: 2015-11-10 Skapad: 2015-11-10 Senast uppdaterad: 2021-04-29Bibliografiskt granskad
    3. The Söderfors Project: Experimental Hydrokinetic Power Station Deployment and First Results
    Öppna denna publikation i ny flik eller fönster >>The Söderfors Project: Experimental Hydrokinetic Power Station Deployment and First Results
    Visa övriga...
    2013 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    The Division of Electricity at Uppsala University recently deployed an experimental hydrokinetic power station for in-stream experiments at a site in a river. This paper briefly describes the deployment process and reports some initial results from measurements made at the test site.

    Nyckelord
    Marine Current Power, Renewable energy, Söderfors, Strömkraft, Förnybar energi, Söderfors
    Nationell ämneskategori
    Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-209220 (URN)
    Konferens
    10th European Wave and Tidal Energy Conference (EWTEC), 2-5 september, 2013, Aalborg, Denmark
    Projekt
    Marine Current Power
    Forskningsfinansiär
    StandUpVetenskapsrådet, 621-2009-4946
    Tillgänglig från: 2013-10-15 Skapad: 2013-10-15 Senast uppdaterad: 2019-01-22Bibliografiskt granskad
    4. Studying the Wake of a Marine Current Turbine Using an Acoustic Doppler Current Profiler
    Öppna denna publikation i ny flik eller fönster >>Studying the Wake of a Marine Current Turbine Using an Acoustic Doppler Current Profiler
    2015 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Wake characteristics of marine current turbines are of significant importance to the development of the marine current power source. Turbine wake recovery determines spacing of turbines in arrays, and environmental impact on e.g. the seabed is heavily influenced by wake behaviour. The majority of previous studies on wakes has been performed on flow-aligned (horizontal) axis turbines and mainly carried out as scale model experiments or numerical simulations.

    This paper describes the performance of wake measurements at the Söderfors test site, where an experimental marine current power station is operated in a river. The turbine is of the cross-flow (vertical) axis type, and the measurements are performed using an Acoustic Doppler Current Profiler (ADCP) towed on the surface by a boat. Positioning data is taken from a high-accuracy Global Navigation Satellite System. The paper discusses various aspects of the methodology employed and provides examples of taken measurements.

    Nationell ämneskategori
    Energiteknik Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-265358 (URN)
    Konferens
    11th European Wave and Tidal Energy Conference, EWTEC15, 6-11 September 2015, Nantes, France
    Tillgänglig från: 2015-10-27 Skapad: 2015-10-27 Senast uppdaterad: 2021-04-29Bibliografiskt granskad
    5. Variability Assessment and Forecasting of Renewables: A Review for Solar, Wind, Wave and Tidal Resources
    Öppna denna publikation i ny flik eller fönster >>Variability Assessment and Forecasting of Renewables: A Review for Solar, Wind, Wave and Tidal Resources
    Visa övriga...
    2015 (Engelska)Ingår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 44, s. 356-375Artikel i tidskrift (Refereegranskat) Published
    Nationell ämneskategori
    Energiteknik Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära; Teknisk fysik med inriktning mot fasta tillståndets fysik
    Identifikatorer
    urn:nbn:se:uu:diva-225870 (URN)10.1016/j.rser.2014.12.019 (DOI)000351324300025 ()
    Tillgänglig från: 2014-06-09 Skapad: 2014-06-09 Senast uppdaterad: 2018-08-01
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    fulltext
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    presentationsbild
  • 6.
    Carpman, Nicole
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Measurements of tidal current velocities in the Folda fjord, Norway, with the use of a vessel mounted ADCP2014Ingår i: 33Rd International Conference On Ocean, Offshore And Arctic Engineering, 2014, Vol 8A: Ocean Engineering, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Measurements of tidal current water velocities is an important first step in evaluating the potential for a tidal site to be used as a renewable energy resource. For this reason, on site measurements are performed at the inlet of a fjord situated at the coast of Norway. The site has an average width of 580 m and adepth of 10-15 m which is narrow and shallow enough to give rise to water velocities that can be of use for energy conversion. With the use of an Acoustic Doppler Current Profiler (ADCP) cross-section measurements are conducted along four transects. The measurements covered flood and ebb currents around one tide and the data give a first approximation of the magnitude and distribution of the flow field. Depth averaged mean current velocities are calculated along the transects for horizontal bins with sizes in the order of 50 x 50 m. Maximum mean velocity for the flood currents were 1.31 m/s and 1.46 m/s for the ebb currents. The measurements show that even a small amount of data can give an indication of the potential and characteristics ofthe site.

  • 7.
    Carpman, Nicole
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thomas, Karin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Tidal current phasing along the coast of Norway2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Tidal currents provide an intermittent source of renewable energy. A high degree of intermittency is unfavorable in the existing power system. However, by aggregating tidal power from sites with variable tidal phase a more firm power outpu tmay be achieved. In this paper, the tidal current phasing between 114 potential tidal energy sites along the Norwegian coast is investigated. Time series of tidal currents are generated with a model that considers the variation in current strength due to the variability in the semi-diurnal tidal cycle (spring to neap, flood to ebb, first to second daily tide etc.). From these, available kinetic energy in the natural flow is calculated. A constant conversion rate is then applied to give the power output at each site. Three scenarios, with varying number of sites and energy extraction, are investigated. The variability in each scenario is quantified on different time scales by filtering the aggregated power and calculate standard deviation and step change. It is found that the variability can be lowered by choosing sites with an advantageous time lag and limit the power output from the most energetic sites. As expected, smoothing is most distinct on short time scales.

  • 8.
    Castellucci, Valeria
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Strömstedt, Erland
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Sea level variability in the Swedish Exclusive Economic Zone and adjacent seawaters: influence on a point absorbing wave energy converter2019Ingår i: Ocean Science, ISSN 1812-0784, E-ISSN 1812-0792, Vol. 15, s. 1517-1529Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low-frequency sea level variability can be a critical factor for several wave energy converter (WEC) systems, for instance, linear systems with a limited stroke length. Consequently, when investigating suitable areas for deployment of those WEC systems, sea level variability should be taken into account. In order to facilitate wave energy developers finding the most suitable areas for wave energy park installations, this paper describes a study that gives them additional information by exploring the annual and monthly variability of the sea level in the Baltic Sea and adjacent seawaters, with a focus on the Swedish Exclusive Economic Zone. Overall, 10 years of reanalysis data from the Copernicus project have been used to conduct this investigation. The results are presented by means of maps showing the maximum range and the standard deviation of the sea level with a horizontal spatial resolution of about 1 km. A case study illustrates how the results can be used by the WEC developers to limit the energy absorption loss of their devices due to sea level variation. Depending on the WEC technology one wants to examine, the results lead to different conclusions. For the Uppsala point absorber L12 and the sea state considered in the case study, the most suitable sites where to deploy WEC parks from a sea level variation viewpoint are found in the Gotland basins and in the Bothnian Sea, where the energy loss due to sea level variations is negligible.

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  • 9.
    Chatzigiannakou, Maria A.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Temiz, Irina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Mooring types of point absorbing wave energy converters2021Ingår i: European Wave and Tidal Energy Conference, EWTEC 2021, 2021Konferensbidrag (Refereegranskat)
  • 10.
    Chatzigiannakou, Maria Angiliki
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dolguntseva, Irina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Offshore Deployments of Wave Energy Converters by Seabased Industry AB2017Ingår i: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 5, nr 2, artikel-id 15Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Since 2008, Seabased Industry AB (SIAB) has manufactured and deployed several units of wave energy converters (WECs) of different design. The WECs are linear generators with point absorber buoy systems that are placed on the seabed, mounted on a gravitation concrete foundation. These deployments have taken place in different areas, using different deployment vessels. Offshore deployments of WECs and underwater substations have so far been complicated procedures, that were both expensive and time-consuming. The focus of this paper is to discuss these deployments in terms of economy and time efficiency, as well as safety. Because seven vessels have been used to facilitate the deployments, an evaluation on the above basis is carried out for them. The main conclusions and certain solutions are presented for the various problems encountered during these deployments and the vessel choice is discussed. It is found that the offshore deployment process can be optimized in terms of cost, time efficiency and safety with a careful vessel choice, use of the latest available technologies and detailed planning and organizing.

    Ladda ner fulltext (pdf)
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  • 11.
    Chen, WenChuang
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Tsinghua Univ, State Key Lab Hydrosci & Engn, Beijing 100084, Peoples R China..
    Dolguntseva, Irina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Savin, Andrej
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Zhang, YongLiang
    Tsinghua Univ, State Key Lab Hydrosci & Engn, Beijing 100084, Peoples R China..
    Li, Wei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Svensson, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Numerical modelling of a point-absorbing wave energy converter in irregular and extreme waves2017Ingår i: Applied Ocean Research, ISSN 0141-1187, E-ISSN 1879-1549, Vol. 63, s. 90-105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Based on the Navier-Stokes (RANS) equations, a three-dimensional (3-D) mathematical model for the hydrodynamics and structural dynamics of a floating point-absorbing wave energy converter (WEC) with a stroke control system in irregular and extreme waves is presented. The model is validated by a comparison of the numerical results with the wave tank experiment results of other researchers. The validated model is then utilized to examine the effect of wave height on structure displacements and connection rope tension. In the examined cases, the differences in WEC’s performance exhibited by an inviscid fluid and a viscous fluid can be neglected. Our results also reveal that the differences in behavior predicted by boundary element method (BEM) and the RANS-based method can be significant and vary considerably, depending on wave height.

  • 12.
    Crespo, Alejandro J.
    et al.
    Universidade de Vigo, Spain.
    Tagliafierro, Bonaventura
    Universidade de Vigo & UPC, Spain.
    Martınez-Estevez, Ivan
    Universidade de Vigo, Spain.
    Domınguez, Jose M.
    Universidade de Vigo, Spain.
    deCastro, Maite
    Universidade de Vigo, Spain.
    Gómez-Gesteira, Moncho
    Altomare, Corrado
    Brito, Moises
    Bernardo, Francisco
    Ferreira, Rui M.
    Capasso, Salvatore
    Viccione, Giacomo
    Quartier, Nicolas
    Stratigaki, Vasiliki
    Troch, Peter
    Simonetti, Irene
    Cappietti, Lorenzo
    Göteman, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Clemente, Daniel
    Rosa-Santos, Paulo
    Taveira-Pinto, Francisco
    Bacelli, Giorgio
    Coe, Ryan
    Fourtakas, Georgios
    Rogers, Benedict
    The University of Manchester, UK.
    Stansby, Peter
    The University of Manchester, UK.
    On the state-of-the-art of CFD simulations for wave energy converters within the open-source numerical framework of DualSPHysics2023Ingår i: Proceedings of the 15th European Wave and Tidal Energy Conference, Bilbao, 3-7 September 2023, European Wave and Tidal Energy Conference , 2023Konferensbidrag (Refereegranskat)
    Abstract [en]

    There are currently several types of devices capable of harnessing wave energy, exploiting a broad variety of physical transformation processes. These devices – known as Wave Energy Converters (WECs) – are developed to maximize their power output. However, there are still uncertainties about their response and survivability to loads induced by adverse environmental conditions, with a consequent increase of the Levelized Cost of Energy (LCOE), which prevents in fact their commercial diffusion. As evidenced by a large body of research, marine renewable energy devices need to have more robust design practices. To address this issue, we propose the CFD-based DualSPHysics toolbox as a support in the design stages. DualSPHysics is high-fidelity software inherently suited to numerically address most challenges posed by multiphysics simulations, which are required to reliably predict WEC response in situations well beyond operational conditions. It should be noted that WECs, generally, may be connected to the seabed and comprise mechanical systems named Power Take-Offs (PTO) used to convert the energy from waves into electricity or other usable energies. To reproduce these features, DualSPHysics benefits from coupling with the multiphysics library Project Chrono and the dynamic mooring model Moordyn+. In this work, the augmented DualSPHysics framework is utilised to simulate a range of very different types of WECs with a variety of elements, such as catenary connections, taut mooring lines, or linear and nonlinear PTO actuators. Version 5.2 of the open-source licensed code was recently released, making the numerical framework publicly available as one unit. This work aims to provide a numerical review of past applications, and to demonstrate how the same open-source code is able to simulate very different technologies.

    Specifically, this paper proposes routine modeling and validation procedures using the SPH-based solver DualSPHysics applied to five different WEC types: i) a moored point absorber (PA); ii) an oscillating wave surge converter (OWSC); iii) a floating OWSC (so called FOSWEC); iv) a wave energy hyperbaric converter (WEHC); and v) a multi-body attenuator (so called Multi-float M4). For each device listed above, we provide validation proof against physical model data for various components of the floater(s) and PTO related quantities, performed under specific sea conditions that aim to challenge their survivability. Within the scope of this research, we present the WEC response with respect to the degrees of freedom that really matter for each of the floatings due to hydrodynamic interactions (i.e., heave, surge, and pitch), along with quantities more intimately connected to the anchoring systems (e.g., line tension) or the mechanical apparatus (e.g., end-stopper force). The quality of the results, the discussion built upon them and the demonstrated solver exploitability to a wide range of WECs show that one software model can run all cases using the exact same methodology, which is of great value for the marine energy R&D community. Finally, we discuss future research objectives, which include the implementation of automation to apply open control systems and possible applications to subsets of WEC farm arrays and other floating energy harnessing devices.

  • 13.
    Dolguntseva, Irina
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Sandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Electrical Approach to Output Power Optimization for a Point Absorbing Wave Energy Converter with a Direct Drive Linear Generator Power Take Off2017Konferensbidrag (Refereegranskat)
  • 14.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hydrodynamic Modelling for a Point Absorbing Wave Energy Converter2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Surface gravity waves in the world’s oceans contain a renewable source of free power on the order of terawatts that has to this date not been commercially utilized. The division of Electricity at Uppsala University is developing a technology to harvest this energy. The technology is a point absorber type wave energy converter based on a direct-driven linear generator placed on the sea bed connected via a line to a buoy on the surface.

    The work in this thesis is focused mainly on the energy transport of ocean waves and on increasing the transfer of energy from the waves to the generator and load. Potential linear wave theory is used to describe the ocean waves and to derive the hydrodynamic forces that are exerted on the buoy. Expressions for the energy transport in polychromatic waves travelling over waters of finite depth are derived and extracted from measured time series of wave elevation collected at the Lysekil test site. The results are compared to existing solutions that uses the simpler deep water approximation. A Two-Body system wave energy converter model tuned to resonance in Swedish west coast sea states is developed based on the Lysekil project concept. The first indicative results are derived by using a linear resistive load. The concept is further extended by a coupled hydrodynamic and electromagnetic model with two more realistic non-linear load conditions.

    Results show that the use of the deep water approximation gives a too low energy transport in the time averaged as well as in the total instantaneous energy transport. Around the resonance frequency, a Two-Body System gives a power capture ratio of up to 80 percent. For more energetic sea states the power capture ratio decreases rapidly, indicating a smoother power output. The currents in the generator when using the Two-Body system is shown to be more evenly distributed compared to the conventional system, indicating a better utilization of the electrical equipment. Although the resonant nature of the system makes it sensitive to the shape of the wave spectrum, results indicate a threefold increase in annual power production compared to the conventional system.

    Delarbeten
    1. Offshore experiments on a direct-driven Wave Energy Converter
    Öppna denna publikation i ny flik eller fönster >>Offshore experiments on a direct-driven Wave Energy Converter
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    2007 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Nationell ämneskategori
    Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-14172 (URN)
    Konferens
    Proceedings of the 7th European Wave and Tidal Energy Conference, 11-13 September 2007, Porto, Portugal.
    Tillgänglig från: 2008-04-25 Skapad: 2008-04-25 Senast uppdaterad: 2022-01-28
    2. Wave Climate off the Swedish West Coast
    Öppna denna publikation i ny flik eller fönster >>Wave Climate off the Swedish West Coast
    2009 (Engelska)Ingår i: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 34, nr 6, s. 1600-1606Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper presents and discusses the wave climate off the Swedish west coast It is based on 8 years (1997-2004) of wave data from 13 sites, nearshore and offshore, in the Skagerrak and Kattegat. The data is a product of the WAM and SWAN wave models calibrated at one site by a wave measurement buoy. It is found that the average energy flux is approximately 5.2 kW/m in the offshore Skagerrak, 2.8 kW/m in the nearshore Skagerrak, and 2.4 kW/m in the Kattegat. One of the studied sites, i.e. site 9, is the location of a wave energy research site run by the Centre for Renewable Electric Energy Conversion at Uppsala University. This site has had a wave power plant installed since the spring of 2006, and another seven are planned to be installed during 2008. Wave energy as a renewable energy source was the driving interest that led to this study and the results are briefly discussed from this perspective.

    Nyckelord
    Wave climate, Wave power, Sea state, Extreme waves, Skagerrak, Kattegat
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-97856 (URN)10.1016/j.renene.2008.11.016 (DOI)000264306500024 ()
    Tillgänglig från: 2008-11-21 Skapad: 2008-11-21 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    3. The Lysekil Wave Power Project: Status Update
    Öppna denna publikation i ny flik eller fönster >>The Lysekil Wave Power Project: Status Update
    Visa övriga...
    2008 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-97846 (URN)
    Tillgänglig från: 2008-11-21 Skapad: 2008-11-21 Senast uppdaterad: 2022-01-28Bibliografiskt granskad
    4. Artificial reef effect and fouling impacts on offshore wave power foundations and buoys: a pilot study
    Öppna denna publikation i ny flik eller fönster >>Artificial reef effect and fouling impacts on offshore wave power foundations and buoys: a pilot study
    2009 (Engelska)Ingår i: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 82, nr 3, s. 426-432Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Little is known about the effects of offshore energy installations on the marine environment, and further research could assist in minimizing environmental risks as well as in enhancing potential positive effects on the marine environment. While biofouling on marine energy conversion devices on one hand has the potential to be an engineering concern, these structures can also affect biodiversity by functioning as artificial reefs. The Lysekil Project is a test park for wave power located at the Swedish west coast. Here, buoys acting as point absorbers on the surface are connected to generators anchored on concrete foundations on the seabed. In this study we investigated the colonisation of foundations by invertebrates and fish, as well as fouling assemblages on buoys. We examined the influence of surface orientation of the wave power foundations on epibenthic colonisation, and made observations of habitat use by fish and crustaceans during three years of submergence. We also examined fouling assemblages on buoys and calculated the effects of biofouling on the energy absorption of the wave power buoys. On foundations we demonstrated a succession in colonisation over time with a higher degree of coverage on vertical surfaces. Buoys were dominated by the blue mussel Mytilus edulis. Calculations indicated that biofouling have no significant effect in the energy absorption on a buoy working as a point absorber. This study is the first structured investigation on marine organisms associated with wave power devices

    Nyckelord
    biodiversity, benthos, fish, shellfish, renewable energy, wave power, Sweden
    Nationell ämneskategori
    Biologiska vetenskaper Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-107217 (URN)10.1016/j.ecss.2009.02.009 (DOI)000265573400007 ()
    Tillgänglig från: 2009-07-29 Skapad: 2009-07-29 Senast uppdaterad: 2022-01-28Bibliografiskt granskad
    5. Catch the wave to electricity: The Conversion of Wave Motions to Electricity Using a Grid-Oriented Approach
    Öppna denna publikation i ny flik eller fönster >>Catch the wave to electricity: The Conversion of Wave Motions to Electricity Using a Grid-Oriented Approach
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    2009 (Engelska)Ingår i: IEEE Power and Energy Magazine, ISSN 1540-7977, Vol. 7, nr 1, s. 50-54Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The ocean are largely an untapped source of energy. However, compared to other energies, power fluctuations for ocean waves are small over longer periods of time. This paper present a grid-oriented approach to electricity production from ocean waves, utilizing a minimal amount of mechanical components.

    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-112949 (URN)10.1109/MPE.2008.930658 (DOI)000262015100004 ()
    Tillgänglig från: 2010-01-22 Skapad: 2010-01-22 Senast uppdaterad: 2017-01-25Bibliografiskt granskad
    6. Wave energy converter with enhanced amplitude response at frequencies coinciding with Swedish west coast sea states by use of a supplementary submerged body
    Öppna denna publikation i ny flik eller fönster >>Wave energy converter with enhanced amplitude response at frequencies coinciding with Swedish west coast sea states by use of a supplementary submerged body
    2009 (Engelska)Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, nr 6, artikel-id 064512Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The full-scale direct-driven wave energy converter developed at Uppsala University has been in offshore operation at the Swedish west coast since 2006. Earlier simulations have now been validated by full-scale experiment with good agreement. Based on that, a theoretical model for a passive system having optimum amplitude response at frequencies coinciding with Swedish west coast conditions has been developed. The amplitude response is increased by adding supplementary inertia by use of the additional mass from a submerged body. A sphere with neutral buoyancy is chosen as the submerged body and modeled as being below the motion of the waves. The model is based on potential linear wave theory and the power capture ratio is studied for real ocean wave data collected at the research test site. It is found that the power capture ratio for the two body system can be increased from 30% to 60% compared to a single body system. Increased velocity in the system also decreases the value for optimal load damping from the generator, opening up the possibility to design smaller units.

    Ort, förlag, år, upplaga, sidor
    USA: American Institute of Physics, 2009
    Nyckelord
    data acquisition, ocean waves
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-113142 (URN)10.1063/1.3233656 (DOI)000270378100147 ()0021-8979 (ISBN)
    Anmärkning

    10907471 Wave Energy Converter enhanced amplitude response Swedish west coast sea states supplementary submerged body Uppsala University offshore operation passive system optimum amplitude response neutral buoyancy waves motion potential linear wave theory power capture ratio ocean wave data collection research test site Two Body System single body system

    Tillgänglig från: 2010-01-25 Skapad: 2010-01-25 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
    7. Depth variation of energy transport in fluid gravity waves
    Öppna denna publikation i ny flik eller fönster >>Depth variation of energy transport in fluid gravity waves
    2010 (Engelska)Ingår i: Journal of Renewable and Sustainable Energy, E-ISSN 1941-7012, Vol. 2, nr 2, s. 023104-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    We calculate the distribution of energy flux as a function of the distance below the surface for propagating polychromatic gravity fluid surface waves. Linear theory has been used to derive closed-form expressions for the energy flux as a function of depth. In this context we discuss the power distribution for real ocean waves measured off the west coast of Sweden and compare this to the energy flux distribution for waves with Pierson-Moskowitz and Bretschneider spectral distributions. This is done in order to get an improved understanding of how to improve the power absorption in wave energy converters, and this is also discussed in this paper.

    Nyckelord
    gravity waves, hydroelectric power, ocean waves, surface waves (fluid)
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-140346 (URN)10.1063/1.3424711 (DOI)000287922200005 ()
    Anmärkning

    11431539 energy flux distribution polychromatic gravity fluid surface waves energy transport linear theory closed-form expressions power distribution ocean waves Sweden Pierson-Moskowitz distribution Bretschneider spectral distributions power absorption wave energy converters

    Tillgänglig från: 2011-01-05 Skapad: 2011-01-05 Senast uppdaterad: 2024-01-17Bibliografiskt granskad
    8. Wave Buoy and Translator Motions - On-Site Measurements and Simulations
    Öppna denna publikation i ny flik eller fönster >>Wave Buoy and Translator Motions - On-Site Measurements and Simulations
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    2011 (Engelska)Ingår i: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691, Vol. 36, nr 3, s. 377-385Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    For a complete understanding of a wave energy conversion device, it is important to know how the proposed device moves in the water, how this motion can be measured, and to what extent the motion can be predicted or simulated. The magnitude and character of the motion has impacts on engineering issues and optimization of control parameters, as well as the theoretical understanding of the system. This paper presents real sea measurements of buoy motion and translator motion fora wave energy system using a linear generator. Buoy motion has been measured using two different systems: a land-based optical system and a buoy-based accelerometer system. The data have been compared to simulations from a Simulink model for the entire system. The two real sea measurements of buoy motion have been found to correlate well in the vertical direction, where the measured range of motion and the standard deviation of the position distributions differed with 3 and 4 cm, respectively. The difference in the horizontal direction ismore substantial. The main reason for this is that the buoy rotation about its axis of symmetry was not measured. However, used together the two systems give a good understanding of buoy motion. In a first comparison, the simulations show good agreement with the measured motion for both translator and buoy.

    Nyckelord
    Accelerometers, energy conversion, experimental results, image motion analysis, oceanic engineering, marine technology, wave power
    Nationell ämneskategori
    Energiteknik
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-160072 (URN)10.1109/JOE.2011.2136970 (DOI)
    Tillgänglig från: 2012-01-09 Skapad: 2011-10-14 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
    9. Optimization of the Dimensions of a Gravity-based Wave Energy Converter Foundation Based on Heave and Surge Forces
    Öppna denna publikation i ny flik eller fönster >>Optimization of the Dimensions of a Gravity-based Wave Energy Converter Foundation Based on Heave and Surge Forces
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    2011 (Engelska)Ingår i: 9th European Wave and Tidak Energy Conference, Southampton, UK, 2011, 2011Konferensbidrag, Publicerat paper (Refereegranskat)
    Nationell ämneskategori
    Elektroteknik och elektronik
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-160035 (URN)
    Konferens
    9th European Wave and Tidak Energy Conference, Southampton, UK, 2011
    Tillgänglig från: 2011-10-13 Skapad: 2011-10-13 Senast uppdaterad: 2017-01-25
    10. Lysekil Research Site, Sweden: A status update
    Öppna denna publikation i ny flik eller fönster >>Lysekil Research Site, Sweden: A status update
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    2011 (Engelska)Ingår i: 9th European Wave and Tidal Energy Conference, Southampton, UK, 2011, 2011Konferensbidrag, Publicerat paper (Refereegranskat)
    Nationell ämneskategori
    Elektroteknik och elektronik
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-160039 (URN)
    Konferens
    9th European Wave and Tidal Energy Conference, Southampton, UK, 5-9 September 2011
    Tillgänglig från: 2011-10-13 Skapad: 2011-10-13 Senast uppdaterad: 2017-01-25
    11. Total instantaneous energy transport in polychromatic fluid gravity waves at finite depth
    Öppna denna publikation i ny flik eller fönster >>Total instantaneous energy transport in polychromatic fluid gravity waves at finite depth
    2012 (Engelska)Ingår i: Journal of Renewable and Sustainable Energy, E-ISSN 1941-7012, Vol. 4, nr 3, s. 033108-1-033108-8Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The total instantaneous energy transport can be found for polychromatic waves when using the deep water approximation. Expanding this theory to waves in waters of finite depth, we derive an expression for the total instantaneous energy transport for polychromatic fluid gravity waves based on potential theory with linearized free surface boundary conditions. We present the results for time series of wave elevation measured at the Uppsala University wave energy research test site. We show that a significant proportion of the total instantaneous energy transport is not accounted for when using the deep water theory. This is important since many wave energy conversion devices under development will operate in waters that do not fulfil the deep water criteria.

    Nationell ämneskategori
    Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-160028 (URN)10.1063/1.4719678 (DOI)000305882200019 ()
    Tillgänglig från: 2011-10-13 Skapad: 2011-10-13 Senast uppdaterad: 2024-01-17
    12. Properties of the energy transport for plane-parallel polychromatic surface gravity waves in waters of arbitrary depth
    Öppna denna publikation i ny flik eller fönster >>Properties of the energy transport for plane-parallel polychromatic surface gravity waves in waters of arbitrary depth
    (Engelska)Ingår i: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691Artikel i tidskrift (Övrigt vetenskapligt) Submitted
    Nationell ämneskategori
    Strömningsmekanik och akustik Oceanografi, hydrologi och vattenresurser
    Identifikatorer
    urn:nbn:se:uu:diva-160026 (URN)
    Tillgänglig från: 2011-10-13 Skapad: 2011-10-13 Senast uppdaterad: 2018-01-12Bibliografiskt granskad
    13. Modelling and Simulation of Linear Wave Energy Converter
    Öppna denna publikation i ny flik eller fönster >>Modelling and Simulation of Linear Wave Energy Converter
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    (Engelska)Ingår i: IET Renewable Power GenerationArtikel i tidskrift (Övrigt vetenskapligt) Submitted
    Nationell ämneskategori
    Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:uu:diva-160304 (URN)
    Tillgänglig från: 2011-10-20 Skapad: 2011-10-20 Senast uppdaterad: 2011-11-23Bibliografiskt granskad
    14. A resonant Two Body System for a point absorbing Wave Energy Converter with direct-driven linear generator
    Öppna denna publikation i ny flik eller fönster >>A resonant Two Body System for a point absorbing Wave Energy Converter with direct-driven linear generator
    2011 (Engelska)Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, nr 12, s. 124904-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Based on an earlier conceptual model of a two body system point absorbing wave energy converter tuned to resonance in Swedish west coast sea states, an extended coupled hydrodynamic, mechanic, and electromagnetic model has been developed. The hydrodynamic characteristics of the two body system are studied in the frequency and time domain, while its response to real Swedish west coast sea states are studied in the time domain, by using a wave energy converter model with two independently moving bodies connected to a direct driven linear generator with non-linear damping. The two body system wave energy converter gives nearly 80% power capture ratio in irregular waves. The resonant behaviour is shown to be sensitive to the shape of the spectrum, and the distance between the two bodies is shown to have a large effect on the power absorption.

    Nyckelord
    direct energy conversion, linear machines, resonant power convertors, wave power generation
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-160032 (URN)10.1063/1.3664855 (DOI)000298639800142 ()
    Tillgänglig från: 2011-10-13 Skapad: 2011-10-13 Senast uppdaterad: 2017-12-08
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  • 15.
    Engström, Jens
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik.
    Shahroozi, Zahra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik.
    Katsidoniotaki, Eirini
    Eriksson, Mikael
    Johannesson, Pär
    Göteman, Malin
    Offshore measurements of hydrodynamic forces on a 1:5 scale buoyIngår i: Artikel i tidskrift (Övrigt vetenskapligt)
  • 16.
    Francisco, Francisco
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Sundberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Sonar for Environmental Monitoring: Understanding the Functionality of Active Acoustics as a Method for Monitoring Marine Renewable Energy Devices2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Active acoustics monitoring (AAM) systems can play an important role in the inspection and survey of the subsea environment around marine renewable energy devices, especially in murky and deep waters. Alternative methods comprising a multifunctional platform based on multibeam (MBS) and Dualbeam (DBS) sonar systems are being developed. The aim is to monitor the environmental impacts during installation, operation and maintenance of wave energy converters, marine current turbines, subsea substations and other offshore renewable energy technologies. At this initial phase, one of the specific objective is to understand the functionality of AAM systems. Field tests were done using the MBS and DBS systems. A platform is being tested at the Lysekil Wave Power Project test site and at the Söderfors Marine Current Project test site. Preliminary results show that the MBS produces better acoustic images when the platform is steady, and when in slow-moving waters such as in harbours and shallow rivers. At near field, the MBS is able to track targets < 20 cm such as fish swimming close to hard structures. The DBS can detect isolated targets at far field. Target dimensions estimated using the sonar match the real dimensions of the same´targets.

    Ladda ner fulltext (pdf)
    fulltext
  • 17.
    Frost, Anna E.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Uppsala University.
    Ulvgård, Liselotte
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Sjökvist, Linnea
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Sandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Experimental study of generator damping at partial stator overlap in a linear generator for wave power2017Ingår i: 12th European Wave and Tidal Energy Conference Series, Cork, Ireland, 27 August - 1 September, 2017, 2017Konferensbidrag (Refereegranskat)
  • 18.
    Frost, Anna E.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Ulvgård, Liselotte
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära. Uppsala University.
    Sjökvist, Linnea
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Sandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Partial Stator Overlap in a Linear Generator for Wave Power: An Experimental Study2017Ingår i: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 5, nr 4, artikel-id 53Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a study on how the power absorption and damping in a linear generator for wave energy conversion are affected by partial overlap between stator and translator. The theoretical study shows that the electrical power as well as the damping coefficient change quadratically with partial stator overlap, if inductance, friction and iron losses are assumed independent of partial stator overlap or can be neglected. Results from onshore experiments on a linear generator for wave energy conversion cannot reject the quadratic relationship. Measurements were done on the inductance of the linear generator and no dependence on partial stator overlap could be found. Simulations of the wave energy converter's operation in high waves show that entirely neglecting partial stator overlap will overestimate the energy yield and underestimate the peak forces in the line between the buoy and the generator. The difference between assuming a linear relationship instead of a quadratic relationship is visible but small in the energy yield in the simulation. Since the theoretical deduction suggests a quadratic relationship, this is advisable to use during modeling. However, a linear assumption could be seen as an acceptable simplification when modeling since other relationships can be computationally costly.

    Ladda ner fulltext (pdf)
    fulltext
  • 19.
    Giassi, Marianna
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Göteman, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Thomas, Simon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Isberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Multi-parameter optimization of hybrid arrays of point absorber Wave Energy Converters2017Ingår i: Proceedings of the 12th European Wave and Tidal Energy Conference, 2017Konferensbidrag (Refereegranskat)
    Ladda ner fulltext (pdf)
    12EWTECGiassi
  • 20.
    Goude, Anders
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Lundin, Staffan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Forces on a marine current turbine during runaway2017Ingår i: International Journal of Marine Energy, ISSN 2214-1669, Vol. 19, s. 345-356Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A runaway marine current turbine will typically overshoot the runaway speed significantly before it settles at that speed. Numerical simulations of an experimental turbine indicate that the peak forces experienced by the turbine during runaway are up to 2.7 times those seen during nominal operation, and 2.1 times those at asymptotic runaway speed, making peak runaway force an important consideration in turbine design. The main contribution to the force increase is found to originate from the increased rotational speed, but a significant part is also due to the temporal lag in turbine wake development. A parameter study further shows that turbines with low inertia, turbines that have low losses, and turbines designed for low tip speed ratios will experience larger increases in forces.

  • 21.
    Göteman, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Iterative multiple cluster scattering2021Konferensbidrag (Refereegranskat)
  • 22.
    Göteman, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Optimisation of wave farms2022Ingår i: Modelling and Optimization of Wave Energy Converters / [ed] Dezhi Ning & Boyin Ding, Boca Raton; Abingdon: CRS Press , 2022, s. 281-308Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Ladda ner fulltext (pdf)
    fulltext
  • 23.
    Göteman, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Wave energy parks with point-absorbers of different dimensions2017Ingår i: Journal of Fluids and Structures, ISSN 0889-9746, E-ISSN 1095-8622, Vol. 74, s. 142-157Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An analytical model for point-absorbing wave energy converters connected to floats of different geometries and topologies is presented. The floats can be truncated cylinder or cylinder with moonpool buoys and have different outer radius, inner radius, draft, mass and can be connected to linear generators of different power take-off constants. The model is implemented into a numerical code where the input is measured time-series of irregular waves. After validation against benchmark software, the model is used to study optimal configurations of wave energy arrays consisting of different wave energy devices. It is shown that the total power absorption can be improved if the wave energy array consists of devices of different dimensions, and that a higher power-to-mass ratio can be achieved.

    Ladda ner fulltext (pdf)
    fulltext
  • 24.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Hann, Martyn
    Ransley, Edward
    Greaves, Deborah
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Wave loads on a point-absorbing wave energy device in extreme waves2015Ingår i: Journal of Ocean and Wind Energy, E-ISSN 2310-3604, Vol. 2, nr 3, s. 176-181Artikel i tidskrift (Refereegranskat)
    Ladda ner fulltext (pdf)
    Paper8
  • 25.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Eriksson, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Isberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Fast modeling of large wave energy farms using interaction distance cut-off2015Ingår i: Energies, E-ISSN 1996-1073, Vol. 8, nr 12, s. 13741-13757Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In many wave energy concepts, power output in the MW range requires the simultaneous operation of many wave energy converters. In particular, this is true for small point-absorbers, where a wave energy farm may contain several hundred devices. The total performance of the farm is affected by the hydrodynamic interactions between the individual devices, and reliable tools that can model full farms are needed to study power output and find optimal design parameters. This paper presents a novel method to model the hydrodynamic interactions and power output of very large wave energy farms. The method is based on analytical multiple scattering theory and uses time series of irregular wave amplitudes to compute the instantaneous power of each device. An interaction distance cut-off is introduced to improve the computational cost with acceptable accuracy. As an application of the method, wave energy farms with over 100 devices are studied in the MW range using one month of wave data measured at an off-shore site.

    Ladda ner fulltext (pdf)
    fulltext
  • 26.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Giassi, Marianna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Isberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Advances and Challenges in Wave Energy Park Optimization: A Review2020Ingår i: Frontiers in Energy Research, E-ISSN 2296-598X, Vol. 8, artikel-id 26Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    A commercial wave energy system will typically consist of many interacting wave energy converters installed in a park. The performance of the park depends on many parameters such as array layout and number of devices, and may be evaluated based on different measures such as energy absorption, electricity quality, or cost of the produced electricity. As wave energy is currently at the stage where several large-scale installations are being planned, optimizing the park performance is an active research area, with many important contributions in the past few years. Here, this research is reviewed, with a focus on identifying the current state of the art, analyzing how realistic, reliable, and relevant the methods and the results are, and outlining directions for future research.

    Ladda ner fulltext (pdf)
    fulltext
  • 27.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Giassi, Marianna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    McNatt, Cameron
    Mocean Energy, Edinburgh, Scotland.
    Wave energy park interactions in short-crested waves2018Konferensbidrag (Refereegranskat)
    Ladda ner fulltext (pdf)
    fulltext
  • 28.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Mayon, Robert
    Liu, Yingyi
    Zheng, Siming
    Wang, Rongquan
    Fluid dynamics and wave-structure interactions2022Ingår i: Modelling and Optimization of Wave Energy Converters / [ed] Dezhi Ning & Boyin Ding, Boca Raton; Abingdon: CRS Press , 2022, s. 61-96Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Ladda ner fulltext (pdf)
    fulltext
  • 29.
    Göteman, Malin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    McNatt, Cameron
    Mocean Energy, Edinburgh EH9 3BF, Midlothian, Scotland.
    Giassi, Marianna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Isberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Arrays of Point-Absorbing Wave Energy Converters in Short-Crested Irregular Waves2018Ingår i: Energies, E-ISSN 1996-1073, Vol. 11, nr 4, artikel-id 964Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For most wave energy technology concepts, large-scale electricity production and cost-efficiency require that the devices are installed together in parks. The hydrodynamical interactions between the devices will affect the total performance of the park, and the optimization of the park layout and other park design parameters is a topic of active research. Most studies have considered wave energy parks in long-crested, unidirectional waves. However, real ocean waves can be short-crested, with waves propagating simultaneously in several directions, and some studies have indicated that the wave energy park performance might change in short-crested waves. Here, theory for short-crested waves is integrated in an analytical multiple scattering method, and used to evaluate wave energy park performance in irregular, short-crested waves with different number of wave directions and directional spreading parameters. The results show that the energy absorption is comparable to the situation in long-crested waves, but that the power fluctuations are significantly lower.

    Ladda ner fulltext (pdf)
    fulltext
  • 30.
    Kannan, Balakrishnan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik. Uppsala University.
    Design and Development of a Data Acquisition and Communication System for Point Absorber Tracking2021Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The recent trend in generating energy from the waves has led to several advancements in the methods and the various research is conducted across the world, to study the behaviour of point absorbers on the waves. The point absorbers such as wave buoys are designed to move according to the waves and the generator that is mechanically coupled with the buoys, generate electricity. But these buoys can also be used for measuring important parameters like the force acting on it due to the incident waves and their movement can be tracked to study the effects on the buoy due to the incident waves. 

    This project, as an extension of a previous work titled ‘Design and Development of a Measurement System to Track the Motion of a Point Absorber’ by Juliana Lüer, focuses on modifying and replacing the controller data acquisition and the communication system. The main aim is to increase the stability of the system and increasing the size of data storage and range of the data transmission. This is done in 3 steps that are as follows:

    - The Arduino based controller is replaced with an advanced Raspberry Pi based computer called RevPi Compact.

    - The Secure Digital (SD) card storage is replaced with a solid-state (Universal Serial Bus) USB memory stick with a large capacity.

    - The Radio Frequency (RF) based data transmission is replaced with a 4G (fourth generation) internet modem.

    The 60 W solar panels are retained from the previous project. But the Lead-Acid battery is replaced with two Lithium Polymer (Li-Po) batteries of 768 Wh capacity each. This increases the stability of the power source and enables the buoy to stay active for a longer time even when there is no useful solar irradiance for many days.

    There are two force transducers (strain gauge) to measure the line force and the angular force acting on the buoy. The Ellipse2-D Inertial Measurement Unit (IMU) from SBG systems is retained from the previous experiment. This sensor can track the Altitude and Heading Reference (AHRS) data along with the Global Positioning System (GPS) data with high levels of accuracy. 

    All the data collected are can be tracked instantaneously due to the 4G internet communication protocol and this is enabled by TelenorTM connection and HuaweiTM 4G modem. A copy of these data is also stored in a SanDisk USB memory of 500 GB capacity.

    The tests are carried out under the laboratory conditions and the outputs are as expected. The whole setup is to be installed in a metallic buoy and to be tested in the Lysekil test site in the future. 

    Ladda ner fulltext (pdf)
    fulltext
  • 31.
    Katsidoniotaki, Eirini
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Göteman, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Numerical modeling of extreme wave interaction with point-absorber using OpenFOAM2022Ingår i: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 245, artikel-id 110268Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Extreme waves are critical for the WEC's development. CFD toolboxes have been widely used in the simulation of extreme waves-structure interaction. However, the quality of the mesh is a sensitive issue; the WEC's large response can lead to mesh deformation and subsequent numerical instability. In this paper, 100-year extreme waves are chosen from the environmental contour of the Humboldt Bay site in California, and their interaction with the WEC is modeled using the open-source CFD software OpenFOAM. The overset mesh technique is an advanced method recently available in OpenFOAM, able to handle great body motions. Here, the overset method is utilized and compared with the commonly used morphing method. The two methods provide equivalent results, but the latter is prone to the mesh deformation and fails to complete the simulations. Regarding the impact of extreme waves on WECs, the results further show that the combination of wave height and steepness is critical; i.e., the 100-year wave height does not necessarily result in the maximum forces, but rather steeper sea states tend to contribute in higher wave loadings. Additionally, the WEC is studied for 40% higher generator's damping, as it is a common control strategy during the harsh environmental conditions.

    Ladda ner fulltext (pdf)
    fulltext
  • 32.
    Katsidoniotaki, Eirini
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära. Centre of Natural Hazards and Disaster Science, Villavägen 16, SE-752 36 Uppsala, Sweden.
    Nilsson, Erik O.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten- och landskapslära. Centre of Natural Hazards and Disaster Science, Villavägen 16, SE-752 36 Uppsala, Sweden.
    Rutgersson, Anna
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten- och landskapslära. Centre of Natural Hazards and Disaster Science, Villavägen 16, SE-752 36 Uppsala, Sweden.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Göteman, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära. Centre of Natural Hazards and Disaster Science, Villavägen 16, SE-752 36 Uppsala, Sweden.
    Response of Point-Absorbing Wave Energy Conversion System in 50-Years Return Period Extreme Focused Waves2021Ingår i: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 9, nr 3, artikel-id 345Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work evaluates the survivability of a point-absorbing wave energy converter at sea states along and inside the 50-year environmental contour for a selected-site in North Sea, by utilizing CFD simulations. Focused wave groups based on NewWave theory are used to model the extreme waves. The numerical breaking waves have been previously predicted by the analytical breaking criterion, showing that the latter provides an accurate estimate for the breaking state. The forces on key components of the device and the system’s dynamics are studied and compared. Slamming loads are identified in the interaction with extreme waves, particularly with breaking waves, and compared with the analytical formulas for slamming estimation as suggested by industrial standards. Considering the extreme wave characteristics, the accompanied phenomena and the resulting WEC’s response, this work contributes to the identification of the design-waves given the environmental contour of the selected site. The top-left side of the contour is identified as the more critical area as it consists of steep and high waves inducing significant nonlinear phenomena, resulting in high loads.

    Ladda ner fulltext (pdf)
    fulltext
  • 33.
    Katsidoniotaki, Eirini
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära. Centre of Natural Hazards and Disaster Science (CNDS).
    Shahroozi, Zahra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Eskilsson, Claes
    Palm, Johannes
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära.
    Göteman, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik, Elektricitetslära. Centre of Natural Hazards and Disaster Science (CNDS).
    Validation of a CFD model for wave energy system dynamics in extreme waves2023Ingår i: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 268, artikel-id 113320Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The design of wave energy converters should rely on numerical models that are able to estimate accurately the dynamics and loads in extreme wave conditions. A high-fidelity CFD model of a 1:30 scale point-absorber is developed and validated on experimental data. This work constitutes beyond the state-of-the-art validation study as the system is subjected to 50-year return period waves. Additionally, a new methodology that addresses the well-known challenge in CFD codes of mesh deformation is successfully applied and validated. The CFD model is evaluated in different conditions: wave-only, free decay, and wave–structure interaction. The results show that the extreme waves and the experimental setup of the wave energy converter are simulated within an accuracy of 2%. The developed high-fidelity model is able to capture the motion of the system and the force in the mooring line under extreme waves with satisfactory accuracy. The deviation between the numerical and corresponding experimental RAOs is lower than 7% for waves with smaller steepness. In higher waves, the deviation increases up to 10% due to the inevitable wave reflections and complex dynamics. The pitch motion presents a larger deviation, however, the pitch is of secondary importance for a point-absorber wave energy converter.

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  • 34.
    Langhamer, Olivia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    The location of offshore wave power devices structures epifaunal assemblages2016Ingår i: International Journal of Marine Energy, ISSN 2214-1669, Vol. 16, s. 174-180Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With large-scale development of offshore wave power conversion, artificial structures become more common in the open sea. To examine how wave power devices may be colonized by epifaunal organisms, 21 concrete foundations used for anchoring wave power generators were studied during two years, 2007 and 2008. The foundations were placed in two different clusters, located north and south within the Lysekil test site at the Swedish west coast. The degree to which early recruits covered the foundations and the succession of epibenthic communities were documented during two years. A succession in colonization over time was observed, with a higher degree of cover in the northern location. Furthermore, the northern location showed an increase in number of individuals, number of species and in Shannon-Wiener diversity in 2008. Dominant organisms on the foundations were the serpulid tubeworms (Pomatoceros triqueter) and barnacles (Balanus sp.). This comprehensive large-scale study about succession and colonization patterns on wave power foundations suggests that the location of wave energy devices affects colonization patterns. This gives indications on settlement patterns on already operating and planned offshore wave power parks further off the coasts.

  • 35.
    Leijon, Jennifer
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Boström, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Freshwater production from the motion of ocean waves - A review2018Ingår i: Desalination, ISSN 0011-9164, E-ISSN 1873-4464, Vol. 435, s. 161-171Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Freshwater scarcity and insufficient sanitation are global urgent problems, affecting billions of people. In this review paper, the process of desalination powered by wave power has been investigated as a potential sustainable solution to water shortage. The different desalination techniques suitable for this type of combined system, i.e. reverse osmosis, electrodialysis and mechanical vapor compression, have been outlined, as well as the different wave energy converters possible to power the desalination process, i.e. oscillating water columns, oscillating bodies (wave activated bodies) and overtopping systems. Some necessary considerations for this type of project are identified. The different wave power/desalination projects and how they have proceeded are presented. The most common design of a wave energy and desalination system includes a wave activated body to pressurize seawater; the seawater flows through a reverse osmosis membrane, resulting in freshwater. Some successful (freshwater producing) wave energy/desalination projects were identified: Delbuoy, the oscillating water column in Vizhinjam, CETO Freshwater, SAROS and Odyssee. It is concluded that wave power and desalination can be combined in a sustainable and autonomous system, generating freshwater from the ocean waves. However, questions regarding cost of produced water, variations in power production due to intermittency and environmental effects still remain.

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  • 36.
    Leijon, Jennifer
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Dolguntseva, Irina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Ekergård, Boel
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Boström, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Comparison of Damping Controls for a Wave Energy Converter with a Linear Generator Power Take-Off: a Case Study for the Lysekil and Wave Hub Test Sites2016Konferensbidrag (Refereegranskat)
  • 37.
    Lindroth [formerly Tyrberg], Simon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Buoy and Generator Interaction with Ocean Waves: Studies of a Wave Energy Conversion System2011Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    On March 13th, 2006, the Division of Electricity at Uppsala University deployed its first wave energy converter, L1, in the ocean southwest of Lysekil. L1 consisted of a buoy at the surface, connected through a line to a linear generator on the seabed. Since the deployment, continuous investigations of how L1 works in the waves have been conducted, and several additional wave energy converters have been deployed.

    This thesis is based on ten publications, which focus on different aspects of the interaction between wave, buoy, and generator. In order to evaluate different measurement systems, the motion of the buoy was measured optically and using accelerometers, and compared to measurements of the motion of the movable part of the generator - the translator. These measurements were found to correlate well. Simulations of buoy and translator motion were found to match the measured values.

    The variation of performance of L1 with changing water levels, wave heights, and spectral shapes was also investigated. Performance is here defined as the ratio of absorbed power to incoming power. It was found that the performance decreases for large wave heights. This is in accordance with the theoretical predictions, since the area for which the stator and the translator overlap decreases for large translator motions. Shifting water levels were predicted to have the same effect, but this could not be seen as clearly.

    The width of the wave energy spectrum has been proposed by some as a factor that also affects the performance of a wave energy converter, for a set wave height and period. Therefore the relation between performance and several different parameters for spectral width was investigated. It was found that some of the parameters were in fact correlated to performance, but that the correlation was not very strong.

    As a background on ocean measurements in wave energy, a thorough literature review was conducted. It turns out that the Lysekil project is one of quite few projects that have published descriptions of on-site wave energy measurements.

    Delarbeten
    1. Wave Energy from the North Sea: Experiences from the Lysekil Research Site
    Öppna denna publikation i ny flik eller fönster >>Wave Energy from the North Sea: Experiences from the Lysekil Research Site
    Visa övriga...
    2008 (Engelska)Ingår i: Surveys in geophysics, ISSN 0169-3298, E-ISSN 1573-0956, Vol. 29, nr 3, s. 221-240Artikel, forskningsöversikt (Refereegranskat) Published
    Abstract [en]

    This paper provides a status update on the development of the Swedish wave energy research area located close to Lysekil on the Swedish West coast. The Lysekil project is run by the Centre for Renewable Electric Energy Conversion at Uppsala University. The project was started in 2004 and currently has permission to run until the end of 2013. During this time period 10 grid-connected wave energy converters, 30 buoys for studies on environmental impact, and a surveillance tower for monitoring the interaction between waves and converters will be installed and studied. To date the research area holds one complete wave energy converter connected to a measuring station on shore via a sea cable, a Wave Rider™ buoy for wave measurements, 25 buoys for studies on environmental impact, and a surveillance tower. The wave energy converter is based on a linear synchronous generator which is placed on the sea bed and driven by a heaving point absorber at the ocean surface. The converter is directly driven, i.e. it has no gearbox or other mechanical or hydraulic conversion system. This results in a simple and robust mechanical system, but also in a somewhat more complicated electrical system.

    Nyckelord
    Wave power, Renewable energy, Sea trial, Linear generator, Point absorber, Environmental impact
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-107215 (URN)10.1007/s10712-008-9047-x (DOI)000260967900002 ()
    Tillgänglig från: 2009-07-29 Skapad: 2009-07-29 Senast uppdaterad: 2022-01-28Bibliografiskt granskad
    2. The Lysekil Wave Power Project: Status Update
    Öppna denna publikation i ny flik eller fönster >>The Lysekil Wave Power Project: Status Update
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    2008 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-97846 (URN)
    Tillgänglig från: 2008-11-21 Skapad: 2008-11-21 Senast uppdaterad: 2022-01-28Bibliografiskt granskad
    3. Catch the wave to electricity: The Conversion of Wave Motions to Electricity Using a Grid-Oriented Approach
    Öppna denna publikation i ny flik eller fönster >>Catch the wave to electricity: The Conversion of Wave Motions to Electricity Using a Grid-Oriented Approach
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    2009 (Engelska)Ingår i: IEEE Power and Energy Magazine, ISSN 1540-7977, Vol. 7, nr 1, s. 50-54Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The ocean are largely an untapped source of energy. However, compared to other energies, power fluctuations for ocean waves are small over longer periods of time. This paper present a grid-oriented approach to electricity production from ocean waves, utilizing a minimal amount of mechanical components.

    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-112949 (URN)10.1109/MPE.2008.930658 (DOI)000262015100004 ()
    Tillgänglig från: 2010-01-22 Skapad: 2010-01-22 Senast uppdaterad: 2017-01-25Bibliografiskt granskad
    4. Tracking a Wave Power Buoy Using a Network Camera: System Analysis and First Results
    Öppna denna publikation i ny flik eller fönster >>Tracking a Wave Power Buoy Using a Network Camera: System Analysis and First Results
    2009 (Engelska)Ingår i: Volume 4: Ocean Engineering; Ocean Renewable Energy; Ocean Space Utilization, Parts A and B, Honolulu, Hawaii, 2009, s. 799-807Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    Anobservation system has been set up on a small isleton the Swedish west coast. The purpose of the systemis to monitor the wave buoys in The Lysekil Project.The project is an attempt to harvest wave energy usinglinear generators and point absorbing buoys. The observation system isself-sufficient and uses a network camera to follow the buoymotions. The first results from the camera, which has beenoperating since July 2008, have been analyzed to examine themotion tracking capabilities of the system. The motion tracking wouldwork as a complement to the other measurements that arebeing done on the buoy. The method for extracting motiondata from the two-dimensional pictures is presented. The results aregraphs of translative buoy motion in two dimensions, and rotationalmotion about two different axes. The vertical buoy motion forthe studied sequence is in the range of ±0.5 m.

    Ort, förlag, år, upplaga, sidor
    Honolulu, Hawaii: , 2009
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-113302 (URN)10.1115/OMAE2009-79121 (DOI)
    Konferens
    ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering (OMAE2009) May 31–June 5, 2009 , Honolulu, Hawaii, USA
    Tillgänglig från: 2010-01-26 Skapad: 2010-01-26 Senast uppdaterad: 2014-04-29Bibliografiskt granskad
    5. Wave Power Absorption as a Function of Water Level and Wave Height: Theory and Experiment
    Öppna denna publikation i ny flik eller fönster >>Wave Power Absorption as a Function of Water Level and Wave Height: Theory and Experiment
    2010 (Engelska)Ingår i: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691, Vol. 35, nr 3, s. 558-564Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper investigates the sensitivity of a wave power system to variations in still water levels and significant wave heights. The system consists of a floating point absorber connected to a linear generator on the seabed. Changing still water levels are expected to affect the power absorption, since they will displace the equilibrium position for the generator translator. Similarly, changing significant wave heights will affect the rate at which the translator leaves the stator. Both these effects will in some cases result in a smaller active area of the stator. A theoretical expression to describe this effect is derived, and compared to measured experimental values for the wave energy converter at the Lysekil research site. During the time of measurements, the still water levels at the site were in the range of [-0.70 m, +0.46 m], and the significant wave heights in the range of [0 m, 2.7 m]. The experimental values exhibit characteristics similar to those of the theoretical expression, especially with changing significant wave heights.

    Nyckelord
    Energy capture, experimental results, linear generator, power absorption, wave power
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-97852 (URN)10.1109/JOE.2010.2052692 (DOI)000283226500008 ()
    Tillgänglig från: 2012-01-09 Skapad: 2008-11-21 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
    6. Experimental Results From an Offshore Wave Energy Converter
    Öppna denna publikation i ny flik eller fönster >>Experimental Results From an Offshore Wave Energy Converter
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    2010 (Engelska)Ingår i: Journal of Offshore Mechanics and Arctic Engineering-Transactions of The Asme, ISSN 0892-7219, E-ISSN 1528-896X, Vol. 132, nr 4, s. 041103-Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    An offshore wave energy converter (WEC) was successfully launched at the Swedish west coast in the middle of March 2006. The WEC is based on a permanent magnet linear generator located on the sea floor driven by a point absorber. A measuring station has been installed on a nearby island where all measurements and experiments on the WEC have been carried out. The output voltage from the generator fluctuates both in amplitude and frequency and must therefore be converted to enable grid connection. In order to study the voltage conversion, the measuring station was fitted with a six pulse diode rectifier and a capacitive filter during the autumn of 2006. The object of this paper is to present a detailed description of the Lysekil research site. Special attention will be given to the power absorption by the generator when it is connected to a nonlinear load.

    Nyckelord
    ocean wave power, linear generators, conversion systems, experimental results
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:uu:diva-133599 (URN)10.1115/1.4001443 (DOI)000283325300003 ()
    Tillgänglig från: 2010-11-15 Skapad: 2010-11-11 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
    7. Wave Buoy and Translator Motions - On-Site Measurements and Simulations
    Öppna denna publikation i ny flik eller fönster >>Wave Buoy and Translator Motions - On-Site Measurements and Simulations
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    2011 (Engelska)Ingår i: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691, Vol. 36, nr 3, s. 377-385Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    For a complete understanding of a wave energy conversion device, it is important to know how the proposed device moves in the water, how this motion can be measured, and to what extent the motion can be predicted or simulated. The magnitude and character of the motion has impacts on engineering issues and optimization of control parameters, as well as the theoretical understanding of the system. This paper presents real sea measurements of buoy motion and translator motion fora wave energy system using a linear generator. Buoy motion has been measured using two different systems: a land-based optical system and a buoy-based accelerometer system. The data have been compared to simulations from a Simulink model for the entire system. The two real sea measurements of buoy motion have been found to correlate well in the vertical direction, where the measured range of motion and the standard deviation of the position distributions differed with 3 and 4 cm, respectively. The difference in the horizontal direction ismore substantial. The main reason for this is that the buoy rotation about its axis of symmetry was not measured. However, used together the two systems give a good understanding of buoy motion. In a first comparison, the simulations show good agreement with the measured motion for both translator and buoy.

    Nyckelord
    Accelerometers, energy conversion, experimental results, image motion analysis, oceanic engineering, marine technology, wave power
    Nationell ämneskategori
    Energiteknik
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-160072 (URN)10.1109/JOE.2011.2136970 (DOI)
    Tillgänglig från: 2012-01-09 Skapad: 2011-10-14 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
    8. Lysekil Research Site, Sweden: A status update
    Öppna denna publikation i ny flik eller fönster >>Lysekil Research Site, Sweden: A status update
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    2011 (Engelska)Ingår i: 9th European Wave and Tidal Energy Conference, Southampton, UK, 2011, 2011Konferensbidrag, Publicerat paper (Refereegranskat)
    Nationell ämneskategori
    Elektroteknik och elektronik
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-160039 (URN)
    Konferens
    9th European Wave and Tidal Energy Conference, Southampton, UK, 5-9 September 2011
    Tillgänglig från: 2011-10-13 Skapad: 2011-10-13 Senast uppdaterad: 2017-01-25
    9. Offshore wave power measurements: a review
    Öppna denna publikation i ny flik eller fönster >>Offshore wave power measurements: a review
    2011 (Engelska)Ingår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 15, nr 9, s. 4274-4285Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The first wave power patent was filed in 1799. Since then, hundreds of ideas for extraction of energy from ocean waves have surfaced. In the process of developing a concept, it is important to learn from previous successes and failures, and this is not least important when moving into the ocean. In this paper, a review has been made with the purpose of finding wave power projects that have made ocean trials, and that also have reported what has been measured during the trials, and how it has been measured.

    In relation to how many projects have done work on wave power, surprisingly few have reported on such measurements. There can be many reasons for this, but one is likely the great difficulties in working with experiments in an ocean environment. Many of the projects have reported on sensor failures, unforeseen events, and other general problems in making measurements at sea.

    The most common site measurement found in this review was wave height. Such measurements was almost universal, although the technologies used differed somewhat. The most common device measurements were electric voltages and/or currents and system pressures (air and water). Device motion and mooring forces were also commonly measured. The motion measurements differed the most between the projects, and many varying methods were used, such as accelerometers, wire sensors, GPS systems, optical systems and echo sounders.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2011
    Nyckelord
    Wave power, Measurement system, Offshore
    Nationell ämneskategori
    Energiteknik
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-160081 (URN)10.1016/j.rser.2011.07.123 (DOI)000298764400006 ()
    Tillgänglig från: 2012-01-09 Skapad: 2011-10-14 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
    10. Spectral Parameters and Wave Energy Converter Performance
    Öppna denna publikation i ny flik eller fönster >>Spectral Parameters and Wave Energy Converter Performance
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Wave energy converter performance is typically specified for given values of significant wave height Hm0 and energy period T-10, in a matrix. For such a representation to be valid, it must be assumed that two parameters determine the performance of the wave energy converter satisfactorily. However, studying performance data for the wave energy converter L1 at the Lysekil research site, it can be seen that for measurements with similar values of Hm0 and T-10, there are values of relative absorption that range from 5 % to 25 %. It therefore seems probable that the properties of the sea state that are not captured using Hm0 and T-10 have an effect on how a WEC performs. It has been proposed in the literature that the width of the wave spectrum is one such property. In this paper, six parameters that describe spectral width have been tested against performance data to look for correlations. In addition to this, the performance data was tested against peak period and standard deviation of peak frequency, as found through wavelet analysis. Out of the parameters tested, κ and ε1 displayed the strongest correlation with relative absorption. Even this correlation was not very strong however, and did only exhibit an r2-value of 0.39 in a linear fit for L1 connected to a 4.9 Ω load. It was also found that the lowest absorption values were connected to the lowest and highest values for peak period.

    Nationell ämneskategori
    Energiteknik
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-160084 (URN)
    Tillgänglig från: 2011-10-14 Skapad: 2011-10-14 Senast uppdaterad: 2012-01-04
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  • 38. Liu, Yuqi
    et al.
    Liu, Xiaocheng
    Guo, Jingkang
    Lou, Ranran
    Lv, Zhihan
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Historisk-filosofiska fakulteten, Institutionen för speldesign.
    Digital Twins of Wave Energy Generation Based on Artificial Intelligence2022Ingår i: 2022 IEEE Conference on Virtual Reality and 3D User Interfaces Abstracts and Workshops (VRW), Institute of Electrical and Electronics Engineers (IEEE), 2022, s. 718-719Konferensbidrag (Refereegranskat)
    Abstract [en]

    Ocean waves provide a large amount of renewable energy, and Wave energy converter (WEC) can convert wave energy into electric energy. This paper proposes a visualization platform for wave power generation. The platform can monitor various indicators of wave power generation in real time, combined with Long Short-Term Memory (LSTM) neural network to predict wave power and electricity consumption. We make digital twins of a wave power plant in a computer, allowing users to remotely view the factory through VR glasses.

  • 39.
    Lv, Zhihan
    et al.
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Historisk-filosofiska fakulteten, Institutionen för speldesign. Extended Energy Big Data and Strategy Research Center, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, 266101, China;State Key Laboratory of Media Convergence Production Technology and Systems, Beijing, 100803, China.
    Wang, Nana
    Lou, Ranaran
    Tian, Yajun
    Guizani, Mohsen
    Towards carbon Neutrality: Prediction of wave energy based on improved GRU in Maritime transportation2023Ingår i: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 331, artikel-id 120394Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Efficient use of renewable energy is one of the critical measures to achieve carbon neutrality. Countries have introduced policies to put carbon neutrality on the agenda to achieve relatively zero emissions of greenhouse gases and to cope with the crisis brought about by global warming. This work analyzes the wave energy with high energy density and wide distribution based on understanding of various renewable energy sources. This study provides a wave energy prediction model for energy harvesting. At the same time, the Gated Recurrent Unit network (GRU), Bayesian optimization algorithm, and attention mechanism are introduced to improve the model's performance. Bayesian optimization methods are used to optimize hyperparameters throughout the model training, and attention mechanisms are used to assign different weights to features to increase the prediction accuracy. Finally, the 1-hour and 6-hour forecasts are made using the data from China's NJI and BSG observatories, and the system performance is analyzed. The results show that, compared with mainstream prediction algorithms, GRU based on Bayesian optimization and attention mechanism has the highest prediction accuracy, with the lowest MAE of 0.3686 and 0.8204, and the highest R2 of 0.9127 and 0.6436, respectively. Therefore, the prediction model proposed here can provide support and reference for the navigation of ships powered by wave energy.

    Ladda ner fulltext (pdf)
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  • 40.
    Ning, Dezhi
    et al.
    State Key of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China.
    Liu, Chengguo
    State Key of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China.
    Zhang, Chongwei
    State Key of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China.
    Göteman, Malin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Zhao, Haitao
    State Key of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China.
    Teng, Bin
    State Key of Coastal and Offshore Engineering, Dalian University of Technology, Dalian, China.
    Hydrodynamic performance of an oscillating wave surge converter in regular and irregular waves: an experimental study2017Ingår i: Journal of Marine Science and Technology, ISSN 0948-4280, E-ISSN 1437-8213, Vol. 25, nr 5, s. 520-530Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A series of physical experiments are carried out to investigate the hydrodynamic performance of a bottom-hinged flap-type oscillating wave surge converter (OWSC). The power take-off (PTO) system in the OWSC is achieved with the magnetic powder brake. Both regular and irregular wave conditions are considered. It is observed that the capture width ratio (CWR) of the proposed OWSC is strongly affected by the PTO damping torque, incident wave amplitude, inertia of the structure and wave spectrum etc.

  • 41.
    Peng, Xin
    et al.
    School of Navigation, Wuhan University of Technology, Wuhan, Hubei, China; Key Laboratory of Hubei Inland Shipping Technology, Wuhan, Hubei, China.
    Wen, Yuanqiao
    Intelligent Transportation System Center (ITSC), Wuhan University of Technology, Wuhan, Hubei, China; National Engineering Research Center for Water Transport Safety, Wuhan University of Technology, Wuhan, Hubei, China.
    Wu, Lichuan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Luft-, vatten- och landskapslära.
    Xiao, Changshi
    School of Navigation, Wuhan University of Technology, Wuhan, Hubei, China.
    Zhou, Chunhui
    School of Navigation, Wuhan University of Technology, Wuhan, Hubei, China; Key Laboratory of Hubei Inland Shipping Technology, Wuhan, Hubei, China.
    Han, Dong
    School of Navigation, Wuhan University of Technology, Wuhan, Hubei, China; Key Laboratory of Hubei Inland Shipping Technology, Wuhan, Hubei, China.
    A sampling method for calculating regional ship emission inventories2020Ingår i: Transportation Research Part D: Transport and Environment, ISSN 1361-9209, E-ISSN 1879-2340, Vol. 89, artikel-id 102617Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, we propose a sampling method for calculating ship exhaust emission inventories, which reduces the uncertainties induced by missing ship static data in traditional methods. The stratified random sampling method is utilized to take sample ships based on the ship density, ship type, and main engine power. The exhaust emissions from sample ship are calculated using an activity-based method with 1 s temporal resolution AIS (Automatic Identification System) data. Then the regional ship exhaust emissions are estimated based on the sampling relationship. Sensitivity experiments show that the relative error of the proposed method decreases quickly with the sampling ratio (the ratio between the number of sampled ships and total ships) and it is less than 3.5% when the sampling ratio is higher than 10%. The method is used to estimate the inventories of ship exhaust emissions in the Yangtze river, which can improve the computational accuracy of ship emissions.

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  • 42.
    Potapenko, Tatiana
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Parwal, Arvind
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Kelly, James
    Hjalmarsson, Johannes
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Anttila, Sara
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Boström, Cecilia
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Temiz, Irina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Power Hardware in-the-Loop Real Time Modelling using Hydrodynamic Model of a Wave Energy Converter with Linear generator Power Take-Off2019Ingår i: the 29th International Ocean and Polar Engineering Conference (ISOPE), Honolulu, Hawaii, USA, June 16-21, 2019, 2019Konferensbidrag (Refereegranskat)
  • 43.
    Remouit, Flore
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Automation of underwater operations on wave energy converters using remotely operated vehicles2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In the last fifteen years, the Division of Electricity at Uppsala University has been developing a wave energy converter (WEC) concept. The concept is based on a point-absorbing buoy with a directly driven linear generator placed on the seabed. Several units are connected to a marine substation, whose role is to collect and smooth the power absorbed from the waves and then bring it to the shore through one single cable.

    A big challenge in the project is to reduce the costs related to the deployment and maintenance of the WECs and substation. Currently, those operations are performed by divers, which is costly and entail considerable risks. A possibility is to replace divers with automated solutions using small robots called remotely operated vehicles (ROVs). This PhD thesis proposes and analyses a method for deployment and maintenance of underwater devices with no use of diving operations.

    Existing ROVs need additional modules and equipment in order to carry out operations with the required force and precision. Typical missions are inspection, shackles or slings removal, valve closing, and cable connection. The latter demands especially high precision in the positioning: 5 mm in distance and 5◦ in heading angle. In addition, this operation involves forces up to 200 N. This combination power-precision is not reached by existing ROVs. This PhD thesis presents a positioning system for underwater robot to enable autonomous positioning of the vehicle before cable connection.

    The positioning system is composed of two green lasers and a monocular camera, and is based on image processing. Experimental results from laboratory testing show that the mean absolute error in distance measurement is as low as 6 mm at 0.7 m from the target, whereas the heading is minimized to 2◦. The computational time for the image processing is 13.6 ms per image, meaning the possibility of a 30 Hz measurement system. Used together with a closed-loop path-following unit, this positioning system can support autonomous docking. This PhD thesis presents the model of an autopilot and results from docking simulations, showing the performance of the positioning system used in closed-loop.

    Delarbeten
    1. Wave Energy Research at Uppsala University and The Lysekil Research Site, Sweden: A Status Update
    Öppna denna publikation i ny flik eller fönster >>Wave Energy Research at Uppsala University and The Lysekil Research Site, Sweden: A Status Update
    Visa övriga...
    2015 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    This paper provides a summarized status update ofthe Lysekil wave power project. The Lysekil project is coordinatedby the Div. of Electricity, Uppsala University since 2002, with theobjective to develop full-scale wave power converters (WEC). Theconcept is based on a linear synchronous generator (anchored tothe seabed) driven by a heaving point absorber. This WEC has nogearbox or other mechanical or hydraulic conversion systems,resulting in a simpler and robust power plant. Since 2006, 12 suchWECs have been build and tested at the research site located atthe west coast of Sweden. The last update includes a new andextended project permit, deployment of a new marine substation,tests of several concepts of heaving buoys, grid connection,improved measuring station, improved modelling of wave powerfarms, implementation of remote operated vehicles forunderwater cable connection, and comprehensive environmentalmonitoring studies.

    Nyckelord
    Wave energy, point absorber, experiments, arrays, generators, ROVs
    Nationell ämneskategori
    Elektroteknik och elektronik Havs- och vattendragsteknik
    Identifikatorer
    urn:nbn:se:uu:diva-265218 (URN)
    Konferens
    Proceedings of the 11th European Wave and Tidal Energy Conference. Nantes, France, September 2015
    Tillgänglig från: 2015-10-26 Skapad: 2015-10-26 Senast uppdaterad: 2019-08-19Bibliografiskt granskad
    2. Variability Assessment and Forecasting of Renewables: A Review for Solar, Wind, Wave and Tidal Resources
    Öppna denna publikation i ny flik eller fönster >>Variability Assessment and Forecasting of Renewables: A Review for Solar, Wind, Wave and Tidal Resources
    Visa övriga...
    2015 (Engelska)Ingår i: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 44, s. 356-375Artikel i tidskrift (Refereegranskat) Published
    Nationell ämneskategori
    Energiteknik Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära; Teknisk fysik med inriktning mot fasta tillståndets fysik
    Identifikatorer
    urn:nbn:se:uu:diva-225870 (URN)10.1016/j.rser.2014.12.019 (DOI)000351324300025 ()
    Tillgänglig från: 2014-06-09 Skapad: 2014-06-09 Senast uppdaterad: 2018-08-01
    3. Automation of subsea connections for clusters of wave energy converters
    Öppna denna publikation i ny flik eller fönster >>Automation of subsea connections for clusters of wave energy converters
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    2015 (Engelska)Ingår i: The Proceedings of the Twenty-fifth (2015) International Ocean and Polar Engineering Conference, 2015Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    To make wave power a viable energy source, large clusters of wave energy converters should be deployed. For most of the farms the output power of the WECs should be aggregated in a marine substation and then transmitted to the grid. The need for cost effective underwater cable connection operations is one of the main issues in offshore operations. Underwater connections can be conducted with wet- or dry-mateable connectors, performed by divers or ROVs. Although there are existing solutions used by the oil and gas industry that could be employed, the capital expenditure needed is not compatible with the offshore renewable energy industry.

     

    The objective of this research is to decrease costs and minimize working hazards associated with sub-sea work when performing these underwater electrical connections. This article presents a solution using small ROV’s instead of divers to execute the task. The main idea is to perform the connection underwater, but using dry-mateable connectors. A solution to make this possible is to install air pockets at the substation enclosing the connectors. These boxes are meant to be filled with air and hence create a dry environment in which to perform the connections. This is achieved with help of two tools. First a docking system allows the operator to fix the ROV at the substation before doing the connection. Then a gripper tool added to the ROV grasps the cable and connects it to the substation in the air pocket. The procedure and design of this low-cost solution are described, and the different prototypes that have been tested for offshore operation are also shown.

    Nyckelord
    Wave energy, ROV, subsea connection, gripper, substation
    Nationell ämneskategori
    Teknik och teknologier
    Forskningsämne
    Teknisk fysik med inriktning mot elektricitetslära
    Identifikatorer
    urn:nbn:se:uu:diva-259835 (URN)978-1-880653-89-0 (ISBN)
    Konferens
    The Twenty-fifth International Ocean and Polar Engineering Conference, June 21-26, Kona, Hawaii, USA
    Projekt
    Lysekil project
    Tillgänglig från: 2015-08-12 Skapad: 2015-08-12 Senast uppdaterad: 2018-08-01Bibliografiskt granskad
    4. Review of Electrical Connectors for Underwater Applications
    Öppna denna publikation i ny flik eller fönster >>Review of Electrical Connectors for Underwater Applications
    2018 (Engelska)Ingår i: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691, Vol. 43, nr 4, s. 1037-1047Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The history of underwater electrical connectors is relativelynew: In 1858, the first transatlantic communication cable was created. Sincethen, the need for subsea electrical connectors has been growing very fastin the offshore industry. Today numerous companies offer a large choiceof underwater connectors and assemblies, and it can be intricate to distinguish the different technologies employed for each of them. However theuse, deployment, maintenance, and lifetime of any subsea equipment, froma simple sonar to a wave energy converter, relies on its connectors. Hencethe design of an underwater electrical connector is to be carefully lookedat, and especially for tailor-made applications that have more specific requirements. To produce a good connector, it is necessary to account for thermal, electrical, and mechanical properties, as well as to determine thebest materials that should be used for the application. Finally, connector issues go hand in hand with the deployment and operation of any electrical equipment, and it is of interest to review the different techniques for cable connection, as well as the challenges related to cable layout. Those challenges can be of different nature, but they should all be taken into account for any subsea connection.

    Nyckelord
    Cable, connector, electrical, review, subsea, underwater
    Nationell ämneskategori
    Teknik och teknologier Elektroteknik och elektronik Signalbehandling
    Identifikatorer
    urn:nbn:se:uu:diva-334294 (URN)10.1109/JOE.2017.2745598 (DOI)000448542200017 ()
    Forskningsfinansiär
    EU, FP7, Sjunde ramprogrammet, 607656
    Tillgänglig från: 2017-11-22 Skapad: 2017-11-22 Senast uppdaterad: 2019-01-24Bibliografiskt granskad
    5. Deployment and Maintenance of Wave Energy Converters at the Lysekil Research Site: A Comparative Study on the Use of Divers and Remotely-Operated Vehicles
    Öppna denna publikation i ny flik eller fönster >>Deployment and Maintenance of Wave Energy Converters at the Lysekil Research Site: A Comparative Study on the Use of Divers and Remotely-Operated Vehicles
    Visa övriga...
    2018 (Engelska)Ingår i: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 6, nr 2, artikel-id 39Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Ocean renewable technologies have been rapidly developing over the past years. However, current high installation, operation, maintenance, and decommissioning costs are hindering these offshore technologies to reach a commercialization stage. In this paper we focus on the use of divers and remotely-operated vehicles during the installation and monitoring phase of wave energy converters. Methods and results are based on the wave energy converter system developed by Uppsala University, and our experience in offshore deployments obtained during the past eleven years. The complexity of underwater operations, carried out by either divers or remotely-operated vehicles, is emphasized. Three methods for the deployment of wave energy converters are economically and technically analyzed and compared: one using divers alone, a fully-automated approach using remotely-operated vehicles, and an intermediate approach, involving both divers and underwater vehicles. The monitoring of wave energy converters by robots is also studied, both in terms of costs and technical challenges. The results show that choosing an autonomous deployment method is more advantageous than a diver-assisted method in terms of operational time, but that numerous factors prevent the wide application of robotized operations. Technical solutions are presented to enable the use of remotely-operated vehicles instead of divers in ocean renewable technology operations. Economically, it is more efficient to use divers than autonomous vehicles for the deployment of six or fewer wave energy converters. From seven devices, remotely-operated vehicles become advantageous.

    Nationell ämneskategori
    Marin teknik
    Identifikatorer
    urn:nbn:se:uu:diva-348816 (URN)10.3390/jmse6020039 (DOI)000436558500011 ()
    Forskningsfinansiär
    StandUpEU, FP7, Sjunde ramprogrammet, 607656Energimyndigheten
    Tillgänglig från: 2018-04-17 Skapad: 2018-04-17 Senast uppdaterad: 2022-02-02Bibliografiskt granskad
    6. Optical System for Underwater Positioning of Observation Class Remotely Operated Vehicle
    Öppna denna publikation i ny flik eller fönster >>Optical System for Underwater Positioning of Observation Class Remotely Operated Vehicle
    2016 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    To make wave power a viable energy source, large clusters of wave energy converters (WECs) will be deployed into large farms. For most of these farms, the output power of the WECs will be aggregated in a marine substation and then transmitted to the grid. The need for cost effective underwater connection operations is one of the main challenges with this kind of offshore installation. Our research is related to underwater connection with help of Observation Class Remotely Operated Vehicles (OC ROVs). The main idea is to use a docking system in order for the small and light ROV to perform the connection, using the reaction force from its docking point instead of the motors propulsion, the latter being too little. This docking operation has to be very accurate and needs both an autopilot and a good positioning tool. In this paper we present an optical positioning system made of green lasers that together with the ROV’s camera measure the distances to the docking point. This is obtained by tracking the laser beams on the images captured from the camera and using triangulation of the points extracted. The tool has been implemented into an OCROV and tested in a tank.

    Nyckelord
    ROV, positioning, underwater connections, wave energy converters
    Nationell ämneskategori
    Annan elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:uu:diva-302641 (URN)
    Externt samarbete:
    Konferens
    3rd Asian Wave and Tidal Energy Conference, AWTEC, Singapore
    Tillgänglig från: 2016-09-07 Skapad: 2016-09-07 Senast uppdaterad: 2018-08-01Bibliografiskt granskad
    7. Laser-based relative positioning system for underwater remotely operated vehicle
    Öppna denna publikation i ny flik eller fönster >>Laser-based relative positioning system for underwater remotely operated vehicle
    (Engelska)Ingår i: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691Artikel i tidskrift (Refereegranskat) Submitted
    Abstract [en]

    This paper addresses the development, testing and verification of a relative positioning system for underwater vehicles. The position and orientation of the vehicle relative to a plane based target is estimated through a laser-based optical system. The sensor package consists of two green line-lasers and a camera. The image processing algorithm is built on the probabilistic Hough transform and a light but robust filtering method. This decreases the computational time to 13.6 ms per image. Experimental results from laboratory testing show that the mean absolute error in distance measurement is as low as 6 mm at 0.7 m from the target, whereas in heading is 2°.

    Nyckelord
    Optical positioning, Green lasers, Image processing, Relative positioning, Remotely operated vehicle
    Nationell ämneskategori
    Robotteknik och automation
    Identifikatorer
    urn:nbn:se:uu:diva-356535 (URN)
    Tillgänglig från: 2018-07-31 Skapad: 2018-07-31 Senast uppdaterad: 2018-08-07
    8. Autonomous docking based on optical positioning system for remotely operated vehicle
    Öppna denna publikation i ny flik eller fönster >>Autonomous docking based on optical positioning system for remotely operated vehicle
    (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    Underwater docking is of high interest as it could be used to chargeunderwater robots while on a mission, thus extending their range of ac-tion, or to upload data without retrieving the vehicle, thus increasing itsmemory capacity. In this paper, the purpose of the docking system is toperform cable connections using remotely operated vehicles. The modelof an autopilot for autonomous docking is presented and the performancesof its components are analysed. This autopilot is based on measurementsfrom an optical positioning system which localizes the vehicle based onfeature detection from image processing. It shows that this positioning system could be integrated to the modelled autopilot and used in closed-loop for autonomous docking.

    Nyckelord
    Optical positioning; closed-loop; Image processing; Remotely operated vehicle; Autonomous docking.
    Nationell ämneskategori
    Elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:uu:diva-356562 (URN)
    Tillgänglig från: 2018-08-01 Skapad: 2018-08-01 Senast uppdaterad: 2018-08-01
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    presentationsbild
  • 44.
    Remouit, Flore
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Chatzigiannakou, Maria-Angeliki
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Bender, Anke
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Temiz, Irina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Sundberg, Jan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Engström, Jens
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Deployment and Maintenance of Wave Energy Converters at the Lysekil Research Site: A Comparative Study on the Use of Divers and Remotely-Operated Vehicles2018Ingår i: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 6, nr 2, artikel-id 39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ocean renewable technologies have been rapidly developing over the past years. However, current high installation, operation, maintenance, and decommissioning costs are hindering these offshore technologies to reach a commercialization stage. In this paper we focus on the use of divers and remotely-operated vehicles during the installation and monitoring phase of wave energy converters. Methods and results are based on the wave energy converter system developed by Uppsala University, and our experience in offshore deployments obtained during the past eleven years. The complexity of underwater operations, carried out by either divers or remotely-operated vehicles, is emphasized. Three methods for the deployment of wave energy converters are economically and technically analyzed and compared: one using divers alone, a fully-automated approach using remotely-operated vehicles, and an intermediate approach, involving both divers and underwater vehicles. The monitoring of wave energy converters by robots is also studied, both in terms of costs and technical challenges. The results show that choosing an autonomous deployment method is more advantageous than a diver-assisted method in terms of operational time, but that numerous factors prevent the wide application of robotized operations. Technical solutions are presented to enable the use of remotely-operated vehicles instead of divers in ocean renewable technology operations. Economically, it is more efficient to use divers than autonomous vehicles for the deployment of six or fewer wave energy converters. From seven devices, remotely-operated vehicles become advantageous.

    Ladda ner fulltext (pdf)
    fulltext
  • 45.
    Salar, Dana
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper.
    Miniature Wave Energy Converter (WEC)2018Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Abstract

     

     

    In this project, I present a design of a scale model of a linear generator (LG) similar to a full size Wave Energy Converter (WEC) being developed at Uppsala University since 2002 and commercialized by Seabased AB. The purpose of a WEC is to convert the energy from ocean waves into electrical energy.

    In order to implement the behaviour of the prototype design, a preliminary study has been done to further build it for use in education, laboratory tests and research. The challenge with this project is to scale down the WEC but maintain the shape, appearance and characteristics of the generator for educational purposes.

    A miniature version of a WEC, previously developed by Uppsala University in collaboration with Seabased Industry AB, has been designed with scaling rate 1:14 of the linear dimensions. In this case, the value of the output power is not important- it has simply been calculated. The electrical rated parameters of the three phase generator are power  26 W,  peak line-line voltage  13 V and  rated armature current  2 A. The mechanical parameters utilized in the design are the total length and the diameter of the miniature WEC, 50 cm and 25 cm, respectively.

    The simulated prototype model (described in Section 5.4) has been validated with an experimental setup comprising translator and stator (described in Section 5.1), where the translator is moved by a programmed industrial robot. The experimental results have shown good agreement with the simulations.

    Ladda ner fulltext (pdf)
    Miniature Wave Energy Converter (WEC)
  • 46.
    Savin, Andrej
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Temiz, Irina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Strömstedt, Erland
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Leijon, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Statistical analysis of power output from a single heaving buoy WEC for different sea states2018Ingår i: Marine Systems & Ocean Technology, ISSN 1679-396X, Vol. 2-4, s. 103-110Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Output power fluctuations from a wave energy converter (WEC) utilizing the principle of an oscillating body are unavoidable due to the reciprocating movement of the translator inside the generator. Moreover, the wave energy flux largely varies with time and propagates with the wave group velocity. Making use of the oscillating output power is a challenge for many wave energy conversion concepts. Therefore, estimation of the output power from a WEC solely by the mean power does not fully reflect the process of energy conversion, especially, by a direct drive linear generator. In the present paper, the output power from the WEC with a linear generator power take-off (PTO) is considered as a stochastic process, and the WEC performance is evaluated from the statistical point of view and related to the linear generator’s (LG) stroke length. Statistics as mean, standard deviation, relative standard deviation, maximum, and mode are found for different sea states. All statistics have shown an expected overall tendency with a rising significant wave height of incoming waves. As the significant wave height increases, statistics of the power output such as mean, standard deviation, maximum, and quantile are increasing, and the mode is decreasing beside the mode for the sea state C. It has been noted that for a significant wave height equal to the LG’s stroke length, the mode is greater than the same values for sea states of other significant wave heights. The results are based on a full-scale offshore experiment and may be used for the design of energy conversion systems based on a linear generator PTO.

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  • 47. Shahroozi, Zahra
    Force Prediction and Estimation for Point Absorber Wave Energy Converter2019Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
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  • 48.
    Shahroozi, Zahra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för elektroteknik.
    Prediction horizon requirement  in control and extreme load analyses for survivability: Advancements to improve the performance of wave energy technologies2021Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The main objective of wave energy converters (WECs) is to ensure reliable electricity production at a competitive cost. Two challenges to achieving this are ensuring an efficient energy conversion and offshore survivability.        

    This thesis work is structured in three different sections: Control and maximum power optimization, forces and dynamics analysis in extreme wave conditions, and statistical modeling of extreme loads in reliability analysis.       

    The need for prediction and future knowledge of waves and wave forces is essential due to the non-causality of the optimal velocity relation for wave energy converters. Using generic concepts and modes of motion, the sensitivity of the prediction horizon to various parameters encountered in a real system is elaborated. The results show that through a realistic assumption of the dissipative losses, only a few seconds to about half a wave cycle is sufficient to predict the required future knowledge for the aim of maximizing the power absorption.         

    The results of a 1:30 scaled wave tank experiment are used to assess the line force and dynamic behaviour of a WEC during extreme wave events. Within the comparison of different wave type representations, i.e. irregular, regular and focused waves, of the same sea state, the results show that not all the wave types deliver the same maximum line forces. As a strategy of mitigating the line forces during extreme wave events, changing the power take-off (PTO) damping may be employed. With consideration of the whole PTO range, the results indicate an optimum damping value for each sea state in which the smallest maximum line force is obtained. Although wave breaking slamming and end-stop spring compression lead to high peak line forces, it is possible that they level out due to the overtopping effect. Waves with a long wavelength result in large surge motion and consequently higher and more damaging forces.        

    On the investigation of reliability assessment of the wave energy converter systems, computing the return period of the extreme forces is crucial. Using force measurement force data gathered at the west coast of Sweden, the extreme forces are statistically modelled with the peak-over-threshold method. Then, the return level of the extreme forces over 20 years for the calm season of the year is computed.

    Delarbeten
    1. Considerations on prediction horizon and dissipative losses for wave energy converters
    Öppna denna publikation i ny flik eller fönster >>Considerations on prediction horizon and dissipative losses for wave energy converters
    2021 (Engelska)Ingår i: IET Renewable Power Generation, ISSN 1752-1416, E-ISSN 1752-1424, IET Renewable Power Generation, Vol. 15, nr 14, s. 3434-3458Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    The non-causal optimal control law for wave energy converters leads to a requirement of predicting waves and wave forces over a future horizon.  Using examples of generic body shapes and oscillation modes, we show through computations of the velocity reference trajectory how the length of prediction horizon required to reach the maximum power output depends on the level of dissipative losses in the conversion chain. The sensitivity to noise is discussed, and so is the use of filtering to improve performance when the available prediction horizon is short or predictions are inaccurate. Considerations are also made for amplitude constraints and other effects encountered in a real system.  With realistic assumptions for the level of dissipative losses, results indicate that the prediction horizon needed to approach the maximum achievable power output for real systems ranges from only a few seconds up to about half a wave period, which is shorter than has generally been assumed earlier.

    Ort, förlag, år, upplaga, sidor
    Institution of Engineering and TechnologyInstitution of Engineering and Technology (IET), 2021
    Nyckelord
    Wave energy converter, prediction horizon, dissipative losses, optimal velocity, useful power
    Nationell ämneskategori
    Energisystem Marin teknik Reglerteknik Havs- och vattendragsteknik
    Identifikatorer
    urn:nbn:se:uu:diva-457294 (URN)10.1049/rpg2.12290 (DOI)000703141600001 ()
    Forskningsfinansiär
    Forskningsrådet Formas, 2020-03634Energimyndigheten
    Tillgänglig från: 2021-10-27 Skapad: 2021-10-27 Senast uppdaterad: 2024-03-12Bibliografiskt granskad
    2. Experimental investigation of a point-absorbing wave energy converter response in different wave types of extreme sea states
    Öppna denna publikation i ny flik eller fönster >>Experimental investigation of a point-absorbing wave energy converter response in different wave types of extreme sea states
    (Engelska)Ingår i: Artikel i tidskrift, Editorial material (Övrigt vetenskapligt) Submitted
    Nationell ämneskategori
    Energisystem Marin teknik Havs- och vattendragsteknik Energiteknik
    Identifikatorer
    urn:nbn:se:uu:diva-457326 (URN)
    Tillgänglig från: 2021-10-27 Skapad: 2021-10-27 Senast uppdaterad: 2021-10-27
    3. Experimental results of force measurements from a scaled point absorbing wave energy converter subjected to extreme waves
    Öppna denna publikation i ny flik eller fönster >>Experimental results of force measurements from a scaled point absorbing wave energy converter subjected to extreme waves
    2021 (Engelska)Ingår i: Proceedings of the Fourteenth European Wave and Tidal Energy Conference, European Wave and Tidal Energy Conference (EWTEC) , 2021Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    To achieve a high reliability and durability for wave energy technologies, the effect of extreme wave conditions on the system must be understood. Wave tank experiments are an essential tool to evaluate this, and provide also a foundation for validation of numerical and analytical methods. However, it is not straight-forward how to design such small scale experiments so that they realistically represent wave energy converters in the ocean. In this paper, wave tank experiments of a 1:30 scaled friction damping linear power take-off (PTO) and cylindrical buoy with ellipsoidal bottom are presented. The linear PTO includes a rod that moves vertically against a Teflon block which introduces friction damping. The damping can be adjusted by changing the spring length that provides the compressive force between the Teflon block and the rod. To study extreme forces and snap loads, two load cells measure the line force both directly beneath the buoy, and at the top of the PTO. The motion of the PTO and the buoy are measured with a wire draw line position sensor and Qualysis system, respectively, and a data acquisition system collects and synchronizes the data. The extreme wave conditions used in the experiments are sea states with 50 years return period at the Dowsing site, North Sea. The waves are modelled as regular, irregular and focused waves. Here, the experimental setup and dry testing experiments are presented, and results of the wave tank test experiment for extreme forces are evaluated and further compared with WEC-SIM, to evaluate the agreement of the numerical and experimental model.

    Ort, förlag, år, upplaga, sidor
    European Wave and Tidal Energy Conference (EWTEC), 2021
    Serie
    Proceedings of the European Wave and Tidal Energy Conference, ISSN 2706-6932, E-ISSN 2706-6940
    Nationell ämneskategori
    Marin teknik Havs- och vattendragsteknik
    Identifikatorer
    urn:nbn:se:uu:diva-457301 (URN)
    Konferens
    Fourteenth European Wave and Tidal Energy Conference (EWTEC), 5-9 September, 2021, Plymouth, UK
    Tillgänglig från: 2021-10-27 Skapad: 2021-10-27 Senast uppdaterad: 2024-03-12
    4. Design and evaluation of linear and rotational generator scale models for wave tank testing
    Öppna denna publikation i ny flik eller fönster >>Design and evaluation of linear and rotational generator scale models for wave tank testing
    2019 (Engelska)Konferensbidrag, Publicerat paper (Refereegranskat)
    Ort, förlag, år, upplaga, sidor
    CRC Press, 2019
    Nationell ämneskategori
    Energisystem Havs- och vattendragsteknik Marin teknik Annan elektroteknik och elektronik
    Identifikatorer
    urn:nbn:se:uu:diva-457307 (URN)9780429505324 (ISBN)9781138585355 (ISBN)
    Konferens
    3rd international conference on renewable energies offshore (renew 2018), 8–10 october 2018, Lisbon, Portugal
    Tillgänglig från: 2021-10-27 Skapad: 2021-10-27 Senast uppdaterad: 2024-03-12Bibliografiskt granskad
    5. Wave Energy Converter Power Take-Off System Scaling and Physical Modelling
    Öppna denna publikation i ny flik eller fönster >>Wave Energy Converter Power Take-Off System Scaling and Physical Modelling