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Engström, Jens
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Publications (10 of 50) Show all publications
Göteman, M., McNatt, C., Giassi, M., Engström, J. & Isberg, J. (2018). Arrays of Point-Absorbing Wave Energy Converters in Short-Crested Irregular Waves. Energies, 11(4), Article ID 964.
Open this publication in new window or tab >>Arrays of Point-Absorbing Wave Energy Converters in Short-Crested Irregular Waves
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2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 4, article id 964Article in journal (Refereed) Published
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.

National Category
Energy Systems Marine Engineering
Identifiers
urn:nbn:se:uu:diva-349295 (URN)10.3390/en11040964 (DOI)000434703400275 ()
Funder
Swedish Research Council, 2015-04657Swedish Energy Agency, 40421-1
Available from: 2018-04-25 Created: 2018-04-25 Last updated: 2018-09-19Bibliographically approved
Remouit, F., Chatzigiannakou, M.-A., Bender, A., Temiz, I., Sundberg, J. & Engström, J. (2018). Deployment and Maintenance of Wave Energy Converters at the Lysekil Research Site: A Comparative Study on the Use of Divers and Remotely-Operated Vehicles. Journal of Marine Science and Engineering, 6(2), Article ID 39.
Open this publication in new window or tab >>Deployment and Maintenance of Wave Energy Converters at the Lysekil Research Site: A Comparative Study on the Use of Divers and Remotely-Operated Vehicles
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2018 (English)In: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 6, no 2, article id 39Article in journal (Refereed) 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.

National Category
Marine Engineering
Identifiers
urn:nbn:se:uu:diva-348816 (URN)10.3390/jmse6020039 (DOI)000436558500011 ()
Funder
StandUpEU, FP7, Seventh Framework Programme, 607656Swedish Energy Agency
Available from: 2018-04-17 Created: 2018-04-17 Last updated: 2018-09-17Bibliographically approved
Thomas, S., Giassi, M., Göteman, M., Hann, M., Ransley, E., Isberg, J. & Engström, J. (2018). Performance of a Direct-Driven Wave Energy Point Absorber with High Inertia Rotatory Power Take-off. Energies, 11(9), Article ID 2332.
Open this publication in new window or tab >>Performance of a Direct-Driven Wave Energy Point Absorber with High Inertia Rotatory Power Take-off
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2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 9, article id 2332Article in journal (Refereed) Published
Abstract [en]

An alternating rotatory generator using an eddy current break is developed as a physicalscale model of a direct-driven floating point absorber power take-off (PTO) for wave tank tests. It isshown that this design is a simple and cost-effective way to get an accurate linear damping PTO. Thedevice shows some beneficial characteristics, making it an interesting option for full scale devices:For similar weights the inertia can be significantly higher than for linear generators, allowing it tooperate with natural frequencies close to typical wave frequencies. The influence of the higher inertiaon the power absorption is tested using both a numerical simulation and physical wave tank tests.With the increased inertia the PTO is able to absorb more than double the energy of a comparabledirect-driven linear generator in some sea states. Moreover, the alternating rotatory generator allowsthe absorption characteristic to be tuned by changing the inertia and the generator damping.

Keywords
wave energy; power take-off; direct-driven; wave tank test; physical scale model; natural frequency tuning; floating point absorber
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics; Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-359690 (URN)10.3390/en11092332 (DOI)
Funder
Swedish Energy Agency, 40421-1Swedish Research Council, 2015-04657
Available from: 2018-09-04 Created: 2018-09-04 Last updated: 2018-09-06Bibliographically 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: 2018-08-22Bibliographically 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
Engineering and Technology 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: 2018-10-18
Francisco, F., Leijon, J., Boström, C., Engström, J. & Sundberg, J. (2018). Wave Power as Solution for Off-Grid Water Desalination Systems: Resource Characterization for Kilifi-Kenya. Energies, 11(4), Article ID 4.
Open this publication in new window or tab >>Wave Power as Solution for Off-Grid Water Desalination Systems: Resource Characterization for Kilifi-Kenya
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2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 4, article id 4Article in journal (Refereed) Published
Abstract [en]

Freshwater scarcity is one of humanity's reoccurring problems that hamper socio-economic development in many regions across the globe. In coastal areas, seawater can be desalinated through reverse osmosis (RO) and transformed into freshwater for human use. Desalination requires large amounts of energy, mostly in the form of a reliable electricity supply, which in many cases is supplied by diesel generators. The objective of this work is to analyze the wave power resource availability in Kilifi-Kenya and evaluate the possible use of wave power converter (WEC) to power desalination plants. A particular focus is given use of WECs developed by Uppsala University (UU-WEC). The results here presented were achieved using reanalysis-wave data revealed that the local wave climate has an approximate annual mean of 7 kW/m and mode of 5 kW/m. Significant wave height and wave mean period are within 0.8-2 m and 7-8 s respectively, with a predominant wave mean direction from southeast. The seasonal cycle appeared to be the most relevant for energy conversion, having the highest difference of 6 kW/m, in which April is the lowest (3.8 kW/m) and August is the peak (10.5 kW/m). In such mild wave climates, the UU-WEC and similar devices can be suitable for ocean energy harvesting for water desalination systems. Technically, with a capacity factor of 30% and energy consumption of 3 kWh/m(3), a coastal community of about five thousand inhabitants can be provided of freshwater by only ten WECs with installed capacity of 20 kW.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
wave power resource, desalination, freshwater, wave energy converter, Kilifi, Kenya
National Category
Energy Engineering Ocean and River Engineering
Identifiers
urn:nbn:se:uu:diva-358565 (URN)10.3390/en11041004 (DOI)000434703400315 ()
Funder
EU, FP7, Seventh Framework Programme, 607656Swedish Research Council, 2015-03126
Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2018-10-15Bibliographically approved
Giassi, M., Göteman, M., Thomas, S., Engström, J., Eriksson, M. & Isberg, J. (2017). Multi-parameter optimization of hybrid arrays of point absorber Wave Energy Converters. In: Proceedings of the 12th European Wave and Tidal Energy Conference: . Paper presented at 12th European Wave and Tidal Energy Conference (EWTEC), Cork, Ireland, August 27-31, 2017..
Open this publication in new window or tab >>Multi-parameter optimization of hybrid arrays of point absorber Wave Energy Converters
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2017 (English)In: Proceedings of the 12th European Wave and Tidal Energy Conference, 2017Conference paper, Published paper (Refereed)
Series
European Wave and Tidal Energy Conference Series, ISSN 2309-1983
National Category
Marine Engineering Energy Engineering
Identifiers
urn:nbn:se:uu:diva-329393 (URN)
Conference
12th European Wave and Tidal Energy Conference (EWTEC), Cork, Ireland, August 27-31, 2017.
Available from: 2017-09-14 Created: 2017-09-14 Last updated: 2018-01-08Bibliographically approved
Sjökvist, L., Wu, J., Ransley, E., Engström, J., Eriksson, M. & Göteman, M. (2017). Numerical models for the motion and forces of point-absorbing wave energy converters in extreme waves. Ocean Engineering, 145, 1-14
Open this publication in new window or tab >>Numerical models for the motion and forces of point-absorbing wave energy converters in extreme waves
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2017 (English)In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 145, p. 1-14Article in journal (Refereed) Published
Abstract [en]

Reliable simulation tools are necessary to study the performance and survivability of wave energy devices, since experiments are both expensive and difficult to implement. In particular, survivability in nonlinear, high waves is one of the largest challenges for wave energy, and since the wave loads and dynamics are largely model dependent, each device must be studied separately with validated tools. In this paper, two numerical methods based on fully nonlinear computational fluid dynamics (CFD) are presented and compared with a simpler linear method. All three methods are compared and validated against experimental data for a point-absorbing wave energy converter in nonlinear, high waves. The wave energy converter consists of a floating buoy attached to a linear generator situated on the seabed. The line forces and motion of the buoy are studied, and computational cost and accuracy are compared and discussed. Whereas the simpler linear method is very fast, its accuracy is not sufficient in high and extreme waves, where instead the computationally costly CFD methods are required. The OpenFOAM model showed the highest accuracy, but also a higher computational cost than the ANSYS Fluent model.

National Category
Marine Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-328485 (URN)10.1016/j.oceaneng.2017.08.061 (DOI)000414886600001 ()
Funder
Natural‐Disaster ScienceSwedish Research Council, 2015-04657
Available from: 2017-08-24 Created: 2017-08-24 Last updated: 2018-02-22Bibliographically approved
Remouit, F., Ruiz-Minguela, P. & Engström, J. (2017). Review of Electrical Connectors for Underwater Applications. IEEE Journal of Oceanic Engineering
Open this publication in new window or tab >>Review of Electrical Connectors for Underwater Applications
2017 (English)In: IEEE Journal of Oceanic Engineering, ISSN 0364-9059, E-ISSN 1558-1691Article in journal (Refereed) Accepted
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.

Keywords
Cable, connector, electrical, review, subsea, underwater
National Category
Engineering and Technology Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-334294 (URN)10.1109/JOE.2017.2745598 (DOI)
Available from: 2017-11-22 Created: 2017-11-22 Last updated: 2018-08-01
Wang, L., Göteman, M., Engström, J., Eriksson, M. & Isberg, J. (2016). Constrained Optimal Control of Single and Arrays of Point-Absorbing Wave Energy Converters. In: : . Paper presented at Marine Energy Technology Symposium.
Open this publication in new window or tab >>Constrained Optimal Control of Single and Arrays of Point-Absorbing Wave Energy Converters
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2016 (English)Conference paper, Published paper (Refereed)
National Category
Ocean and River Engineering
Identifiers
urn:nbn:se:uu:diva-297190 (URN)
Conference
Marine Energy Technology Symposium
Available from: 2016-06-21 Created: 2016-06-21 Last updated: 2017-04-26Bibliographically approved
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