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Waters, Rafael
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Publications (10 of 61) Show all publications
Ayob, M. N., Castellucci, V., Abrahamsson, J., Svensson, O. & Waters, R. (2018). Control Strategy for a Tidal Compensation System for Wave Energy Converter Device. In: : . Paper presented at The 28th International Ocean and Polar Engineering Conference, 10-15 June, Sapporo, Japan.
Open this publication in new window or tab >>Control Strategy for a Tidal Compensation System for Wave Energy Converter Device
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2018 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Ocean and River Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-363349 (URN)978-1-880653-87-6 (ISBN)
Conference
The 28th International Ocean and Polar Engineering Conference, 10-15 June, Sapporo, Japan
Available from: 2018-10-17 Created: 2018-10-17 Last updated: 2019-04-05Bibliographically approved
Ayob, M. N., Castellucci, V., Göteman, M., Widén, J., Abrahamsson, J., Engström, J. & Waters, R. (2018). Small-Scale Renewable Energy Converters for Battery Charging. Journal of Marine Science and Engineering, 6(1), Article ID 26.
Open this publication in new window or tab >>Small-Scale Renewable Energy Converters for Battery Charging
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2018 (English)In: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 6, no 1, article id 26Article in journal (Refereed) Published
Abstract [en]

This paper presents two wave energy concepts for small-scale electricity generation. In the presented case, these concepts are installed on the buoy of a heaving, point-absorbing wave energy converter (WEC) for large scale electricity production. In the studied WEC, developed by Uppsala University, small-scale electricity generation in the buoy is needed to power a tidal compensating system designed to increase the performance of the WEC in areas with high tides. The two considered and modeled concepts are an oscillating water column (OWC) and a heaving point absorber. The results indicate that the OWC is too small for the task and does not produce enough energy. On the other hand, the results show that a hybrid system composed of a small heaving point absorber combined with a solar energy system would be able to provide a requested minimum power of around 37.7W on average year around. The WEC and solar panel complement each other, as the WEC produces enough energy by itself during wintertime (but not in the summer), while the solar panel produces enough energy in the summer (but not in the winter).

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
small wave energy converter, oscillating water column, heaving point absorber
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-357765 (URN)10.3390/jmse6010026 (DOI)000428558900025 ()
Funder
Swedish Energy AgencySwedish Research Council, 2015-04657ÅForsk (Ångpanneföreningen's Foundation for Research and Development)StandUpCarl Tryggers foundation
Available from: 2018-08-22 Created: 2018-08-22 Last updated: 2019-04-05Bibliographically approved
Göteman, M., Mathew, J., Engström, J., Castellucci, V., Giassi, M. & Waters, R. (2018). Wave energy farm performance and availability as functions of weather windows. In: : . Paper presented at RENEW 2018, 3rd International Conference on Renewable Energies Offshore, Pct 8-10, 2018, Lisbon, Portugal.
Open this publication in new window or tab >>Wave energy farm performance and availability as functions of weather windows
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2018 (English)Conference paper, Published paper (Refereed)
National Category
Energy Systems Other Engineering and Technologies
Identifiers
urn:nbn:se:uu:diva-363294 (URN)
Conference
RENEW 2018, 3rd International Conference on Renewable Energies Offshore, Pct 8-10, 2018, Lisbon, Portugal
Available from: 2018-10-16 Created: 2018-10-16 Last updated: 2019-03-14Bibliographically approved
Sjökvist, L., Göteman, M., Rahm, M., Waters, R., Svensson, O., Strömstedt, E. & Leijon, M. (2017). Calculating Buoy Response for a Wave Energy Converter - a Comparsion Between Two Computational Methods and Experimental Results [Letter to the editor]. Theoretical and Applied Mechanics Letters, 7(3), 164-168
Open this publication in new window or tab >>Calculating Buoy Response for a Wave Energy Converter - a Comparsion Between Two Computational Methods and Experimental Results
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2017 (English)In: Theoretical and Applied Mechanics Letters, ISSN 2095-0349, Vol. 7, no 3, p. 164-168Article in journal, Letter (Refereed) Published
Abstract [en]

When designing a wave power plant, reliable and fast simulation tools are required. Computational fluid dynamics (CFD) software provides high accuracy but with a very high computational cost, and in operational, moderate sea states, linear potential flow theories may be sufficient to model the hydrodynamics. In this paper, a model is built in COMSOL Multiphysics to solve for the hydrodynamic parameters of a point-absorbing wave energy device. The results are compared with a linear model where the hydrodynamical parameters are computed using WAMIT, and to experimental results from the Lysekil research site. The agreement with experimental data is good for both numerical models.

National Category
Marine Engineering
Identifiers
urn:nbn:se:uu:diva-328498 (URN)10.1016/j.taml.2017.05.004 (DOI)000416966800008 ()
Funder
Natural‐Disaster ScienceSwedish Research Council, 2015-04657
Available from: 2017-08-24 Created: 2017-08-24 Last updated: 2018-03-07Bibliographically approved
Castellucci, V., García-Terán, J., Eriksson, M., Padman, L. & Waters, R. (2017). Influence of Sea State and Tidal Height on Wave Power Absorption. IEEE Journal of Oceanic Engineering, 42(3), 566-573
Open this publication in new window or tab >>Influence of Sea State and Tidal Height on Wave Power Absorption
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2017 (English)In: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691, Vol. 42, no 3, p. 566-573Article in journal (Refereed) Published
Abstract [en]

The wave energy converter developed at Uppsala University (Uppsala, Sweden) consists of a linear generator placed on the seabed and driven by the motion of a buoy on the water surface. The buoy is connected to the moving part of the linear generator, the translator, which is made of ferrite magnets. The translator moves vertically inducing voltage in the windings of a fixed component, the so-called stator. The energy conversion of the linear generator is affected by the sea state and by variations of mean sea level. The sea state influences the speed and the stroke length of the translator, while the variation of tidal level shifts the average position of the translator with respect to the center of the stator. The aim of this study is to evaluate the energy absorption of the wave energy converter at different locations around the world. This goal is achieved by developing a hydromechanic model which analyses the optimum generator damping factor for different wave climates and the power absorbed by the generator, given a fixed geometry of the buoy and a fixed stroke length of the translator. Economic considerations regarding the optimization of the damping factor are included within the paper. The results suggest a nominal damping factor and show the power absorption losses at various locations, each of them characterized by a different wave climate and tidal range. The power losses reach up to 67% and in many locations a tidal compensation system, included in the design of the wave energy converter, is strongly motivated.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-295597 (URN)10.1109/JOE.2016.2598480 (DOI)000405673800007 ()
Funder
Swedish Energy AgencyÅForsk (Ångpanneföreningen's Foundation for Research and Development)Carl Tryggers foundation
Available from: 2016-06-08 Created: 2016-06-08 Last updated: 2017-10-24Bibliographically approved
Ayob, M. N., Castellucci, V. & Waters, R. (2017). Wave energy potential and 1-50 TWh scenarios for the Nordic synchronous grid. Renewable energy, 101, 462-466
Open this publication in new window or tab >>Wave energy potential and 1-50 TWh scenarios for the Nordic synchronous grid
2017 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 101, p. 462-466Article in journal (Refereed) Published
Abstract [en]

This study estimates the wave energy potential along the coasts of the Nordic countries with the Nordicsynchronous grid as a chosen boundary. A model for wave farm allocation was developed and applied to achieve annual energy production targets of 1 TWh, 3 TWh, 10 TWh and 50 TWh. The study is based on 10 years of data, from 2005 to 2014, from the European Center for Medium-Range Weather Forecasts. Data from a total of 728 coordinate points along the Nordic countries, with a 0.125° x 0.125° spatial resolution, were considered. An algorithm was developed to generate the scenarios, to estimate the installed capacity of wave farms at different locations along the coasts, and to measure the physical space required by the farms. This analysis of the four energy target scenarios resulted in a required installed capacity of 337 MW, 1.02 GW, 3.42 GW and 17.09 GW, covering a stretch of the total coast of 0.4, 1.2, 3.8 and 18.9% respectively. The total annual wave energy resource for the Nordic countries is determined at 590 TWh, most of which is available along the Norwegian coast.

Keywords
wave energy, wave farm, installed power, scenarios, Nordic synchronous grid
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Environmental Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-307177 (URN)10.1016/j.renene.2016.09.004 (DOI)000388775700044 ()
Funder
Swedish Energy AgencyÅForsk (Ångpanneföreningen's Foundation for Research and Development)StandUpCarl Tryggers foundation
Available from: 2016-11-10 Created: 2016-11-10 Last updated: 2019-04-05Bibliographically approved
Castellucci, V., Eriksson, M. & Waters, R. (2016). Impact of Tidal Level Variations on the Wave Energy Absorption at Wave Hub. Energies, 9(10), Article ID 843.
Open this publication in new window or tab >>Impact of Tidal Level Variations on the Wave Energy Absorption at Wave Hub
2016 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 9, no 10, article id 843Article in journal (Refereed) Published
Abstract [en]

The energy absorption of the wave energy converters (WEC) characterized by a limited stroke length - like the point absorbers developed at Uppsala University-depends on the sea level variation at the deployment site. In coastal areas characterized by high tidal ranges, the daily energy production of the generators is not optimal. The study presented in this paper quantifies the effects of the changing sea level at the Wave Hub test site, located at the south-west coast of England. This area is strongly affected by tides: the tidal height calculated as the difference between the Mean High Water Spring and the Mean Low Water Spring in 2014 was about 6.6 m. The results are obtained from a hydro-mechanic model that analyzes the behaviour of the point absorber at the Wave Hub, taking into account the sea state occurrence scatter diagram and the tidal time series at the site. It turns out that the impact of the tide decreases the energy absorption by 53%. For this reason, the need for a tidal compensation system to be included in the design of the WEC becomes compelling. The economic advantages are evaluated for different scenarios: the economic analysis proposed within the paper allows an educated guess to be made on the profits. The alternative of extending the stroke length of the WEC is investigated, and the gain in energy absorption is estimated.

Keywords
wave energy converter (WEC), tides, Wave Hub, energy absorption, economic analysis
National Category
Ocean and River Engineering
Identifiers
urn:nbn:se:uu:diva-295599 (URN)10.3390/en9100843 (DOI)000388578800084 ()
Funder
Swedish Research CouncilÅForsk (Ångpanneföreningen's Foundation for Research and Development)Carl Tryggers foundation
Available from: 2016-06-08 Created: 2016-06-08 Last updated: 2017-11-30Bibliographically approved
Hong, Y., Eriksson, M., Castellucci, V., Boström, C. & Waters, R. (2016). Linear generator-based wave energy converter model with experimental verification and three loading strategies. IET Renewable Power Generation, 10(3), 349-359
Open this publication in new window or tab >>Linear generator-based wave energy converter model with experimental verification and three loading strategies
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2016 (English)In: IET Renewable Power Generation, ISSN 1752-1416, E-ISSN 1752-1424, Vol. 10, no 3, p. 349-359Article in journal (Refereed) Published
Abstract [en]

Within the Lysekil wave energy research project at the Swedish west coast, more than ten Wave Energy Converters (WECs) prototypes have been developed and installed in an ocean based test site. Since 2006 various experiments have been conducted and the generated electricity was delivered to shore at a nearby island. While experiments are essential for the development of wave energy converters, theoretical studies and simulations are an important complement – not only in the search for advanced designs with higher efficiency, but also for improving the economic viability of the studied concepts. In this paper a WEC model is presented. The model consists of three subsystems: i) the hydrodynamic source, ii) the linear generator model, and iii) the electrical conversion system. After the validation with the experimental results at the research site, the generator model is connected to three passive load strategies – linear resistive load, passive rectification and resonance circuit. The paper focuses on analysing the operation of the model coupled with three load cases. The results prove that the WEC model correctly simulates the linear generator developed in the Lysekil Project. Moreover, the comparison among different load cases is made and discussed. The results gives an indication of the efficiency of energy production as well as the force ripples and resulting mechanical loads on the wave energy converters.

Keywords
linear machines; electric generators; wave power generation; ocean waves; power convertors; power grids; power generation economics; hydrodynamics; rectifying circuits; circuit resonance; load (electric); power generation planning; linear generator-based wave energy converter model; experimental verification; loading strategy; ocean-based test site; grid connection; WEC model; economic viability; hydrodynamic source; electrical conversion system; passive load strategy; linear resistive load; passive rectification; resonance circuit; Lysekil Project; energy production efficiency; force ripples; mechanical load
National Category
Energy Systems Ocean and River Engineering
Identifiers
urn:nbn:se:uu:diva-283546 (URN)10.1049/iet-rpg.2015.0117 (DOI)000371789100008 ()
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy StorageSwedish Research CouncilSwedish Energy AgencyVINNOVAGöran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologySwedish Research Council, 621-2009-3417
Available from: 2016-04-13 Created: 2016-04-13 Last updated: 2017-11-30Bibliographically approved
Li, W., Isberg, J., Waters, R., Engström, J., Svensson, O. & Leijon, M. (2016). Statistical Analysis of Wave Climate Data Using Mixed Distributions and Extreme Wave Prediction. Energies, 9(6), Article ID 396.
Open this publication in new window or tab >>Statistical Analysis of Wave Climate Data Using Mixed Distributions and Extreme Wave Prediction
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2016 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 9, no 6, article id 396Article in journal (Refereed) Published
Abstract [en]

The investigation of various aspects of the wave climate at a wave energy test site is essential for the development of reliable and efficient wave energy conversion technology. This paper presents studies of the wave climate based on nine years of wave observations from the 2005-2013 period measured with a wave measurement buoy at the Lysekil wave energy test site located off the west coast of Sweden. A detailed analysis of the wave statistics is investigated to reveal the characteristics of the wave climate at this specific test site. The long-term extreme waves are estimated from applying the Peak over Threshold (POT) method on the measured wave data. The significant wave height and the maximum wave height at the test site for different return periods are also compared. In this study, a new approach using a mixed-distribution model is proposed to describe the long-term behavior of the significant wave height and it shows an impressive goodness of fit to wave data from the test site. The mixed-distribution model is also applied to measured wave data from four other sites and it provides an illustration of the general applicability of the proposed model. The methodologies used in this paper can be applied to general wave climate analysis of wave energy test sites to estimate extreme waves for the survivability assessment of wave energy converters and characterize the long wave climate to forecast the wave energy resource of the test sites and the energy production of the wave energy converters.

Keywords
wave climate, wave energy converter, ocean wave modelling, mixed-distribution model, extreme wave
National Category
Ocean and River Engineering
Identifiers
urn:nbn:se:uu:diva-300069 (URN)10.3390/en9060396 (DOI)000378854400009 ()
Funder
StandUpSwedish Energy Agency
Available from: 2016-08-02 Created: 2016-08-02 Last updated: 2017-11-28Bibliographically approved
Lejerskog, E., Boström, C., Hai, L., Waters, R. & Leijon, M. (2015). Experimental results on power absorption from a wave energy converter at the Lysekil wave energy research site. Renewable energy, 77, 9-14
Open this publication in new window or tab >>Experimental results on power absorption from a wave energy converter at the Lysekil wave energy research site
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2015 (English)In: Renewable energy, ISSN 0960-1481, E-ISSN 1879-0682, Vol. 77, p. 9-14Article in journal (Refereed) Published
Abstract [en]

Power generation from wave power has a large potential to contribute to our electric energy production, and today, many wave power projects are close to be commercialized. However, one key issue to solve for many projects is to decrease the cost per installed kW. One way to do this is to investigate which parameters that have a significant impact on the wave energy converters (WEC) performance. In this paper, experimental results on power absorption from a directly driven point absorbing WEC are presented. The experiments have been carried out at the Lysekil research site in Sweden. To investigate the performance of the WEC, the absorbed power and the speed of the translator are compared. The result confirms that the buoy size and the translator weight have a large impact on the power absorption from the generator. By optimizing the buoy size and translator weight, the WEC is believed to produce power more evenly over the upward and downward cycle. Moreover, to predict the maximum power limit during normal operation, a simulation model has been derived. The results correlates well with experimental data during normal operation. 

National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-238267 (URN)10.1016/j.renene.2014.11.050 (DOI)000349504800002 ()
Available from: 2014-12-11 Created: 2014-12-11 Last updated: 2017-12-05Bibliographically approved
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