Logo: to the web site of Uppsala University

uu.sePublications from Uppsala University
Change search
Link to record
Permanent link

Direct link
Publications (10 of 84) Show all publications
Leijon, J., Engström, J., Göteman, M. & Boström, C. (2024). Desalination and wave power for freshwater supply on Gotland. Energy Strategy Reviews, 53, 101404-101404, Article ID 101404.
Open this publication in new window or tab >>Desalination and wave power for freshwater supply on Gotland
2024 (English)In: Energy Strategy Reviews, ISSN 2211-467X, E-ISSN 2211-4688, Vol. 53, p. 101404-101404, article id 101404Article in journal (Refereed) Published
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-528342 (URN)10.1016/j.esr.2024.101404 (DOI)
Available from: 2024-05-20 Created: 2024-05-20 Last updated: 2024-05-20
Shahroozi, Z., Göteman, M. & Engström, J. (2023). A Neural Network Approach To Minimize Line Forces In The Survivability Of The Point-Absorber Wave Energy Converters. In: Proceedings of ASME 2023 42nd International Conference on Ocean, Offshore & Arctic Engineering (OMAE2023): . Paper presented at International Conference on Ocean, Offshore & Arctic Engineering (OMAE), 11-16 June, 2023, Melbourne, Australia. ASME Press, 8, Article ID OMAE2023-102422.
Open this publication in new window or tab >>A Neural Network Approach To Minimize Line Forces In The Survivability Of The Point-Absorber Wave Energy Converters
2023 (English)In: Proceedings of ASME 2023 42nd International Conference on Ocean, Offshore & Arctic Engineering (OMAE2023), ASME Press, 2023, Vol. 8, article id OMAE2023-102422Conference paper, Published paper (Refereed)
Abstract [en]

One strategy for the survivability of wave energy converters(WECs) is to minimize the extreme forces on the structure by adjusting the system damping. In this paper, a neural network model is developed to predict the peak line force for a 1:30 scaled point-absorber WEC with a linear friction-damping power take-off (PTO). The algorithm trains over the wave tank experimental data and enables an update of the system damping based on the system state (i.e. position, velocity, and acceleration) and information on the incoming waves for the extreme sea states. The results show that the deep neural network (DNN) developed here is relatively fast and able to predict the peak line forces with a correlation of 88% when compared to the true (experimental)data. Then, the optimum damping for survivability purposes is found by minimizing the peak line force. It is shown that the optimum damping varies depending on the system state in each zero up-crossing episode.

Place, publisher, year, edition, pages
ASME Press, 2023
National Category
Control Engineering Marine Engineering Ocean and River Engineering
Identifiers
urn:nbn:se:uu:diva-506611 (URN)10.1115/OMAE2023-102422 (DOI)001216330300065 ()978-0-7918-8690-8 (ISBN)
Conference
International Conference on Ocean, Offshore & Arctic Engineering (OMAE), 11-16 June, 2023, Melbourne, Australia
Funder
Swedish Energy Agency, 47264-1Swedish Research Council, 2020-03634StandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Available from: 2023-06-28 Created: 2023-06-28 Last updated: 2024-06-12Bibliographically approved
Shahroozi, Z., Göteman, M. & Engström, J. (2023). Control of a point absorber wave energy converter in extreme wave conditions using a deep learning model in WEC-Sim. In: OCEANS 2023 - LIMERICK: . Paper presented at OCEANS Conference,JUN 05-08, 2023, Limerick, IRELAND. IEEE
Open this publication in new window or tab >>Control of a point absorber wave energy converter in extreme wave conditions using a deep learning model in WEC-Sim
2023 (English)In: OCEANS 2023 - LIMERICK, IEEE, 2023Conference paper, Published paper (Refereed)
Abstract [en]

The survivability of wave energy converters (WECs) is one of the challenges that have a direct influence on their cost. To protect the WEC from the impact of extreme waves, it is often to over-dimension the components or adopt survivability modes e.g. by submerging or lifting the WEC if it is applicable. Here, a control strategy for adjusting the system damping is developed based on deep neural networks (DNN) to minimize the line (mooring) force exerted on a 1:30 scaled WEC. This DNN model is then implemented in a control system of a numerical WEC-Sim model to find the optimal power take-off (PTO) damping for every zero up-crossing episode of surface elevation which minimizes the peak line force. The WEC-Sim model was calibrated based on a 1:30 scaled wave tank experiment that was designed to investigate the WEC response in extreme sea states with a 50-year return period. It is shown that this survival strategy reduces the peak forces when compared with the response of a system that has been set to a constant PTO damping for the entire duration of the sea state.

Place, publisher, year, edition, pages
IEEE, 2023
National Category
Marine Engineering Ocean and River Engineering Control Engineering
Identifiers
urn:nbn:se:uu:diva-506599 (URN)10.1109/OCEANSLimerick52467.2023.10244529 (DOI)001074614700227 ()979-8-3503-3227-8 (ISBN)979-8-3503-3226-1 (ISBN)
Conference
OCEANS Conference,JUN 05-08, 2023, Limerick, IRELAND
Funder
Swedish Energy Agency, 47264-1Swedish Research Council, 2020-03634StandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Available from: 2023-06-28 Created: 2023-06-28 Last updated: 2024-03-12Bibliographically approved
Zhu, G., Shahroozi, Z., Zheng, S., Göteman, M., Engström, J. & Greaves, D. (2023). Experimental study of interactions between focused waves and a point absorber wave energy converter. Ocean Engineering, 287, Article ID 115815.
Open this publication in new window or tab >>Experimental study of interactions between focused waves and a point absorber wave energy converter
Show others...
2023 (English)In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 287, article id 115815Article in journal (Refereed) Published
Abstract [en]

Predicting the response of point absorber wave energy converters (WECs) in extreme sea states is crucial for assessing their survivability. However, data are scarce and hydrodynamic understanding is limited. In order to simulate extreme wave conditions, laboratory-scale focused waves based on NewWave theory have been utilized. To investigate the interactions between focused waves and a point absorber WEC, a wave basin experiment has been conducted. Various parameters, including focusing amplitude and peak frequency have been examined across three different damping conditions. The motion response of the point absorber WEC and the corresponding mooring force have been measured over time. The experimental findings reveal that both the focused wave parameters and the damping values have a significant influence on the motion response and mooring force. It is shown that an increase in the focusing amplitude leads to a more intense motion response, while the mooring force is relatively insensitive to the focused amplitude/peak frequency when the end-stop spring is not compressed. The force in the connection line is maximized when the upper end-stop spring is compressed. As the peak frequency increases, the heave and surge responses decrease, whereas the maximum mooring force increases with peak frequency for a locked power take-off (PTO) system. Finally, the results indicate that optimizing the design of the power take-off system, including selecting appropriate damping values and stroke lengths for the translator, can significantly reduce the mooring load for extreme wave conditions.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Wave energy converter, Point absorber, Focused wave, Wave-structure, Mooring force
National Category
Ocean and River Engineering Marine Engineering Energy Engineering
Identifiers
urn:nbn:se:uu:diva-512165 (URN)10.1016/j.oceaneng.2023.115815 (DOI)001077334900001 ()
Available from: 2023-09-22 Created: 2023-09-22 Last updated: 2024-04-04Bibliographically approved
Shahroozi, Z., Göteman, M. & Engström, J. (2023). Investigation on the extreme peak mooring force distribution of a point absorber wave energy converter with and without a survivability control system. Paper presented at 15th European Wave and Tidal Energy Conference (EWTEC 2023), 3–7 September, 2023, Bilbao, Spain. Proceedings of the European Wave and Tidal Energy Conference (EWTEC), 15, Article ID 161.
Open this publication in new window or tab >>Investigation on the extreme peak mooring force distribution of a point absorber wave energy converter with and without a survivability control system
2023 (English)In: Proceedings of the European Wave and Tidal Energy Conference (EWTEC), ISSN 2706-6932, Vol. 15, article id 161Article in journal (Refereed) Published
Abstract [en]

To determine the optimal design of the wave energy converter (WEC) that can withstand extreme waveconditions, the short- and long-term extreme responses of the system need to be determined. This paper focuses on the extreme peak force distribution of the mooring force for a 1:30 scaled point absorber WEC. The basis of this analysis is the mooring force response obtained from a WEC-Sim model calibrated by wave tank experimental data. The extreme sea states have been chosen from a50-year environmental contour. Here, first, the long-term extreme response using the full sea state approach is obtained for three constant damping cases of the power take-off (PTO) system. Then, using a contour approach, the expected value of the extreme peak line (mooring) force distribution is computed for the sea states along an environmental contour. Further, for the most extremesea state, the extreme peak line force distribution is also computed where a survivability control system, based on a deep neural network (DNN), changes the PTO damping to minimize the peak mooring force in each zero up-crossing episode of surface elevation. The results show that in the absence of a control system, the zero PTO damping case is a conservative choice in the analysis of the long-term response and the design load. For the most extreme sea state along the environmental contour, the survivability control system slightly reduces the expected value of the extreme peak force distribution when compared with lower constant PTO damping configurations.

Place, publisher, year, edition, pages
European Wave and Tidal Energy Conference, 2023
Keywords
Wave energy converter, Deep neural network, Control system, Design load, Long-term extreme response
National Category
Marine Engineering Ocean and River Engineering Reliability and Maintenance Energy Engineering Control Engineering
Identifiers
urn:nbn:se:uu:diva-511367 (URN)10.36688/ewtec-2023-161 (DOI)
Conference
15th European Wave and Tidal Energy Conference (EWTEC 2023), 3–7 September, 2023, Bilbao, Spain
Available from: 2023-09-13 Created: 2023-09-13 Last updated: 2024-03-12Bibliographically approved
Engström, J., Shahroozi, Z., Katsidoniotaki, E., Stavropoulou, C., Johannesson, P. & Göteman, M. (2023). Offshore Measurements and Numerical Validation of the Mooring Forces on a 1:5 Scale Buoy. Journal of Marine Science and Engineering, 11(1), Article ID 231.
Open this publication in new window or tab >>Offshore Measurements and Numerical Validation of the Mooring Forces on a 1:5 Scale Buoy
Show others...
2023 (English)In: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 11, no 1, article id 231Article in journal (Refereed) Published
Abstract [en]

Wave energy conversion is a renewable energy technology with a promising potential. Although it has been developed for more than 200 years, the technology is still far from mature. The survivability in extreme weather conditions is a key parameter halting its development. We present here results from two weeks of measurement with a force measurement buoy deployed at Uppsala University’s test site for wave energy research at the west coast of Sweden. The collected data have been used to investigate the reliability for two typical numerical wave energy converter models: one low fidelity model based on linear wave theory and one high fidelity Reynolds-Averaged Navier–Stokes model. The line force data is also analysed by extreme value theory using the peak-over-threshold method to study the statistical distribution of extreme forces and to predict the return period. The high fidelity model shows rather good agreement for the smaller waves, but overestimates the forces for larger waves, which can be attributed to uncertainties related to field measurements and numerical modelling uncertainties. The peak-over-threshold method gives a rather satisfying result for this data set. A significant deviation is observed in the measured force for sea states with the same significant wave height. This indicates that it will be difficult to calculate the force based on the significant wave height only, which points out the importance of more offshore experiments.

Place, publisher, year, edition, pages
MDPI, 2023
Keywords
wave energy conversion, point absorber, line force, offshore measurements
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:uu:diva-494290 (URN)10.3390/jmse11010231 (DOI)000917599500001 ()
Funder
Swedish Energy Agency, 47264-1Swedish Research Council, 2015-04657Lars Hierta Memorial Foundation
Available from: 2023-01-17 Created: 2023-01-17 Last updated: 2024-04-04Bibliographically approved
Crespo, A. J., Tagliafierro, B., Martınez-Estevez, I., Domınguez, J. M., deCastro, M., Gómez-Gesteira, M., . . . Stansby, P. (2023). On the state-of-the-art of CFD simulations for wave energy converters within the open-source numerical framework of DualSPHysics. In: Proceedings of the 15th European Wave and Tidal Energy Conference, Bilbao, 3-7 September 2023: . Paper presented at 15th European Wave and Tidal Energy Conference (EWTEC), September 3-7, 2023, Bilbao, Spain. European Wave and Tidal Energy Conference
Open this publication in new window or tab >>On the state-of-the-art of CFD simulations for wave energy converters within the open-source numerical framework of DualSPHysics
Show others...
2023 (English)In: Proceedings of the 15th European Wave and Tidal Energy Conference, Bilbao, 3-7 September 2023, European Wave and Tidal Energy Conference , 2023Conference paper, Published paper (Refereed)
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.

Place, publisher, year, edition, pages
European Wave and Tidal Energy Conference, 2023
Series
Proceedings of the European Wave and Tidal Energy Conference, ISSN 2706-6932, E-ISSN 2706-6940 ; 15
Keywords
CFD, SPH, WEC, open-source, PTO, numerical modelling
National Category
Marine Engineering Energy Systems
Identifiers
urn:nbn:se:uu:diva-512045 (URN)10.36688/ewtec-2023-145 (DOI)
Conference
15th European Wave and Tidal Energy Conference (EWTEC), September 3-7, 2023, Bilbao, Spain
Available from: 2023-09-20 Created: 2023-09-20 Last updated: 2023-09-25Bibliographically approved
Göteman, M., Shahroozi, Z., Stavropoulou, C., Katsidoniotaki, E. & Engström, J. (2023). Resilience of wave energy farms using metocean dependent failure rates and repair operations. Ocean Engineering, 280, Article ID 114678.
Open this publication in new window or tab >>Resilience of wave energy farms using metocean dependent failure rates and repair operations
Show others...
2023 (English)In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 280, article id 114678Article in journal (Refereed) Published
Abstract [en]

Emerging offshore renewable energy technologies are expected to become an important part of the futureenergy system, and reliability for these new technologies in different metocean scenarios must be guaranteed.This poses a challenge in extreme weather scenarios like storms, in particular for less mature technologiessuch as wave energy. Not only the offshore survivability must be controlled; the restoration after disruptiveevents and failures should be addressed and optimized. Offshore operations are costly and cannot be carriedout if the weather is too harsh, and the resulting downtime after failures may be financially devastating forprojects. In this paper, the resilience of large wave energy systems is studied with respect to wave conditions,metocean dependent failure rates, and weather windows available for offshore repair operations. A metocean-and time-dependent failure rate is derived based on a Weibull distribution, which is a novelty of the paper.The performance of the farm is assessed using the varying failure rates and metocean data at different offshoresites. Critical metocean thresholds for different offshore vessels are considered, and the resilience is quantifiedusing relevant measures such as unavailability and expected energy not supplied. The resilience analysis iscoupled to an economic assessment of the wave farm and different repair strategies. Our results show thatthe commonly used assumption of constant failure rates is seen to overestimate the annual energy productionthan when a more realistic varying failure rate is used. Two offshore sites are compared, and the availabilityis found to be higher at the calmer site. Most of the evaluated repair strategies cannot be considered to beeconomically justified, when compared to the cost of the energy not supplied.

Place, publisher, year, edition, pages
Elsevier, 2023
National Category
Energy Engineering Fluid Mechanics and Acoustics Reliability and Maintenance
Identifiers
urn:nbn:se:uu:diva-501652 (URN)10.1016/j.oceaneng.2023.114678 (DOI)001019734300001 ()
Funder
Swedish Research Council, 2020-03634
Available from: 2023-05-10 Created: 2023-05-10 Last updated: 2024-04-04Bibliographically approved
Stavropoulou, C., Engström, J. & Göteman, M. (2023). Two-body, time domain model for a heaving point absorber. In: J. W. Ringsberg;C. Guedes Soares (Ed.), Advances in the Analysis and Design of Marine Structures: Proceedings of the 9th International Conference on Marine Structures (MARSTRUCT 2023, Gothenburg, Sweden, 3-5 April 2023). Paper presented at MARSTRUCT, 9th International Conference on Marine Structures, Gothenburg, Sweden, 3-5 April 2023. London: CRC Press
Open this publication in new window or tab >>Two-body, time domain model for a heaving point absorber
2023 (English)In: Advances in the Analysis and Design of Marine Structures: Proceedings of the 9th International Conference on Marine Structures (MARSTRUCT 2023, Gothenburg, Sweden, 3-5 April 2023) / [ed] J. W. Ringsberg;C. Guedes Soares, London: CRC Press, 2023Conference paper, Published paper (Other academic)
Abstract [en]

Place, publisher, year, edition, pages
London: CRC Press, 2023
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-501820 (URN)9781003399759 (ISBN)
Conference
MARSTRUCT, 9th International Conference on Marine Structures, Gothenburg, Sweden, 3-5 April 2023
Available from: 2023-05-15 Created: 2023-05-15 Last updated: 2023-10-25Bibliographically approved
Katsidoniotaki, E., Shahroozi, Z., Eskilsson, C., Palm, J., Engström, J. & Göteman, M. (2023). Validation of a CFD model for wave energy system dynamics in extreme waves. Ocean Engineering, 268, Article ID 113320.
Open this publication in new window or tab >>Validation of a CFD model for wave energy system dynamics in extreme waves
Show others...
2023 (English)In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258, Vol. 268, article id 113320Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Extreme waves, CFD, OpenFOAM, Validation model, Wave energy, Point-absorber
National Category
Energy Engineering Marine Engineering
Identifiers
urn:nbn:se:uu:diva-491092 (URN)10.1016/j.oceaneng.2022.113320 (DOI)000905510100001 ()
Funder
Swedish Research Council, 2015-04657Swedish Energy Agency, 47264-1Swedish National Infrastructure for Computing (SNIC)
Available from: 2022-12-16 Created: 2022-12-16 Last updated: 2024-04-04Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2031-8134

Search in DiVA

Show all publications