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Eriksson, Mikael
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Publications (10 of 30) Show all publications
Hong, Y., Temiz, I., Pan, J., Eriksson, M. & Boström, C. (2021). Damping Studies on PMLG-Based Wave Energy Converter under Oceanic Wave Climates. Energies, 14(4), Article ID 920.
Open this publication in new window or tab >>Damping Studies on PMLG-Based Wave Energy Converter under Oceanic Wave Climates
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2021 (English)In: Energies, E-ISSN 1996-1073, Vol. 14, no 4, article id 920Article in journal (Refereed) Published
Abstract [en]

Wave energy converters (WECs), which are designed to harvest ocean wave energy, have recently been improved by the installation of numerous conversion mechanisms; however, it is still difficult to find an appropriate method that can compromise between strong environmental impact and robust performance by transforming irregular wave energy into stable electrical power. To solve this problem, an investigation into the impact of varied wave conditions on the dynamics of WECs and to determine an optimal factor for WECs to comply with long-term impacts was performed. In this work, we researched the performance of WECs influenced by wave climates. We used a permanent magnet linear generator (PMLG)-based WEC that was invented at Uppsala University. The damping effect was first studied with a PMLG-type WEC. Then, a group of sea states was selected to investigate their impact on the power production of the WEC. Two research sites were chosen to investigate the WEC's annual energy production as well as a study on the optimal damping coefficient impact. In addition, we compared the WEC's energy production between optimal damping and constant damping under a full range of sea states at both sites. Our results show that there is an optimal damping coefficient that can achieve the WEC's maximum power output. For the chosen research sites, only a few optimal damping coefficients were able to contribute over 90% of the WEC's annual energy production. In light of the comparison between optimal and constant damping, we conclude that, for specific regions, constant damping might be a better choice for WECs to optimize long-term energy production.

Place, publisher, year, edition, pages
MDPIMDPI, 2021
Keywords
wave energy converter, permanent magnet linear generator, wave climate, damping coefficient, optimal
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-440428 (URN)10.3390/en14040920 (DOI)000623469300001 ()
Funder
StandUpSwedish Research Council, 2015-03126Carl Tryggers foundation
Available from: 2021-04-21 Created: 2021-04-21 Last updated: 2024-01-15Bibliographically approved
Hong, Y., Eriksson, M., Boström, C., Pan, J., Liu, Y. & Waters, R. (2020). Damping Effect Coupled with the Internal Translator Mass of Linear Generator-Based Wave Energy Converters. Energies, 13(17), Article ID 4424.
Open this publication in new window or tab >>Damping Effect Coupled with the Internal Translator Mass of Linear Generator-Based Wave Energy Converters
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2020 (English)In: Energies, E-ISSN 1996-1073, Vol. 13, no 17, article id 4424Article in journal (Refereed) Published
Abstract [en]

The damping effect, induced inside the linear generator, is a vital factor to improve the conversion efficiency of wave energy converters (WEC). As part of the mechanical design, the translator mass affects the damping force and eventually affects the performance of the WEC by converting wave energy into electricity. This paper proposes research on the damping effect coupled with translator mass regarding the generated power from WEC. Complicated influences from ocean wave climates along the west coast of Sweden are also included. This paper first compares three cases of translator mass with varied damping effects. A further investigation on coupling effects is performed using annual energy absorption under a series of sea states. Results suggest that a heavier translator may promote the damping effect and therefore improve the power production. However, the hinder effect is also observed and analyzed in specific cases. In this paper, the variations in the optimal damping coefficient are observed and discussed along with different cases.

Place, publisher, year, edition, pages
MDPI AG, 2020
Keywords
wave energy converter, linear generator, damping, translator mass
National Category
Energy Engineering Ocean and River Engineering
Identifiers
urn:nbn:se:uu:diva-423064 (URN)10.3390/en13174424 (DOI)000569679900001 ()
Funder
Swedish Research Council, 2015-03126
Available from: 2020-10-21 Created: 2020-10-21 Last updated: 2023-08-28Bibliographically approved
Engström, J., Göteman, M., Eriksson, M., Bergkvist, M., Nilsson, E. O., Rutgersson, A. & Strömstedt, E. (2020). Energy absorption from parks of point-absorbing wave energy converters in the Swedish exclusive economic zone. Energy Science & Engineering, 8(1), 38-49
Open this publication in new window or tab >>Energy absorption from parks of point-absorbing wave energy converters in the Swedish exclusive economic zone
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2020 (English)In: Energy Science & Engineering, ISSN 2050-0505, Vol. 8, no 1, p. 38-49Article in journal (Refereed) Published
Abstract [en]

In a future energy system based on renewable energy sources, wave energy will most likely play a role due to its high energy potential and low intermittency. The power production from parks of wave energy converters of point absorber type has been extensively studied. This is also the case for the wave energy resource at many coastal areas around the globe. Wave energy has not yet reached a commercial level, and a large variety of technologies exist; therefore, an established method to calculate the technical potential for wave energy has still not been established. To estimate the technical potential of wave energy conversion, some approximations inevitably need to be taken due to the systems high complexity. In this study, a detailed mapping of the wave climate and simulation of large arrays of hydrodynamically cross‐coupled wave energy converters are combined to calculate the technical potential for wave energy conversion in the Swedish exclusive economic zone. A 16‐year wave data set distributed in a 1.1 km × 1.1 km grid is used to calculate the absorbed energy from a park of 200 generic point absorbers. The areas with best potential have an average annual energy absorption of 16 GWh for the selected wave energy park adapted to 1 km2 when using a constant damping, while the theoretical upper bound is 63 GWh for the same area.

Place, publisher, year, edition, pages
John Wiley & Sons, 2020
Keywords
point absorber, Swedish exclusive economic zone, technical potential, wave energy conversion, wave energy park
National Category
Geosciences, Multidisciplinary Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-399934 (URN)10.1002/ese3.507 (DOI)000492721800001 ()
Funder
StandUpSwedish Energy Agency, 42256‐1
Available from: 2019-12-17 Created: 2019-12-17 Last updated: 2023-09-14Bibliographically approved
Shahroozi, Z., Eriksson, M., Göteman, M. & Engström, J. (2019). Design and evaluation of linear and rotational generator scale models for wave tank testing. In: : . Paper presented at 3rd international conference on renewable energies offshore (renew 2018), 8–10 october 2018, Lisbon, Portugal. CRC Press
Open this publication in new window or tab >>Design and evaluation of linear and rotational generator scale models for wave tank testing
2019 (English)Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
CRC Press, 2019
National Category
Energy Systems Ocean and River Engineering Marine Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-457307 (URN)9780429505324 (ISBN)9781138585355 (ISBN)
Conference
3rd international conference on renewable energies offshore (renew 2018), 8–10 october 2018, Lisbon, Portugal
Available from: 2021-10-27 Created: 2021-10-27 Last updated: 2024-03-12Bibliographically approved
Thomas, S., Giassi, M., Eriksson, M., Göteman, M., Isberg, J., Ransley, E., . . . Engström, J. (2018). A model free control based on machine learning for energy converters in an array. Big Data and Cognitive Computing, 4(2), Article ID 36.
Open this publication in new window or tab >>A model free control based on machine learning for energy converters in an array
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2018 (English)In: Big Data and Cognitive Computing, ISSN 2504-2289, Vol. 4, no 2, article id 36Article in journal (Refereed) Published
Abstract [en]

This paper introduces a model-free, "on-the-fly" learning control strategy for arrays of energy converters with adjustable generator damping. The devices are arranged so that they are affected simultaneously by the energy medium. Each device uses a different control strategy, of which at least one has to be the machine learning approach presented in this paper. During operation all energy converters record the absorbed power and control output; the machine learning device gets the data from the converter with the highest power absorption and so learns the best performing control strategy for each state. Consequently, the overall network has a better overall performance than each individual strategy. This concept is evaluated for wave energy converter (WEC) with numerical simulations and experiments with physical scale models in a wave tank. In the first of two numerical simulations, the learnable WEC works in an array with four WECs applying a constant damping factor. In the second simulation, two learnable WECs were learning with each other. It showed that in the first test the WEC was able to absorb as much as the best constant damping WEC, while in the second run it could absorb even slightly more. During the physical model test, the ANN showed its ability to select the better of two possible damping coefficients based on real world input data.

Place, publisher, year, edition, pages
MDPI, 2018
Keywords
machine learning; wave energy; power take-off; artificial neural network; wave tank test; physical scale model; floating point absorber; damping; control; collaborative
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-364093 (URN)10.3390/bdcc2040036 (DOI)
Projects
SUPERFARMS
Funder
Swedish Energy Agency, 40421-1Swedish Research Council, 2015-04657
Available from: 2018-10-24 Created: 2018-10-24 Last updated: 2022-10-17Bibliographically approved
Thomas, S., Eriksson, M., Göteman, M., Hann, M., Isberg, J. & Engström, J. (2018). Experimental and numerical collaborative latching control of wave energy converter arrays. Energies, 11(11), Article ID 3036.
Open this publication in new window or tab >>Experimental and numerical collaborative latching control of wave energy converter arrays
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2018 (English)In: Energies, E-ISSN 1996-1073, Vol. 11, no 11, article id 3036Article in journal (Refereed) Published
Abstract [en]

A challenge while applying latching control on a wave energy converter (WEC) is to find a reliable and robust control strategy working in irregular waves and handling the non-ideal behavior of real WECs. In this paper, a robust and model-free collaborative learning approach for latchable WECs in an array is presented. A machine learning algorithm with a shallow artificial neural network (ANN) is used to find optimal latching times. The applied strategy is compared to a latching time that is linearly correlated with the mean wave period: It is remarkable that the ANN-based WEC achieved a similar power absorption as the WEC applying a linear latching time, by applying only two different latching times. The strategy was tested in a numerical simulation, where for some sea states it absorbed more than twice the power compared to the uncontrolled WEC and over 30% more power than a WEC with constant latching. In wave tank tests with a 1:10 physical scale model the advantage decreased to +3% compared to the best tested constant latching WEC, which is explained by the lower advantage of the latching strategy caused by the non-ideal latching of the physical power take-off model.

Keywords
wave energy, power take-off, artificial neural network, machine learning, wave tank test, 14 physical scale model, floating point absorber, latching, control, collaborative
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Electronics
Identifiers
urn:nbn:se:uu:diva-364095 (URN)10.3390/en11113036 (DOI)000451814000174 ()
Projects
SUPERFARMS
Funder
ÅForsk (Ångpanneföreningen's Foundation for Research and Development), 16-591Swedish Energy Agency, 40421-1Swedish Research Council, 2015-04657StandUp
Available from: 2018-10-24 Created: 2018-10-24 Last updated: 2023-08-28Bibliographically 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
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: 2020-09-30Bibliographically 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
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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