Journal of Marine Science and Engineering

Research

18 pages, 2601 KiB

Open AccessArticle

Optimal Constrained Control of Arrays of Wave Energy Converters

by Habeebullah Abdulkadir and Ossama Abdelkhalik

J. Mar. Sci. Eng. 2024, 12(1), 104; https://doi.org/10.3390/jmse12010104 - 05 Jan 2024

Viewed by 694

Wave Energy Converters (WECs) are designed to be deployed in arrays, usually in a limited space, to minimize the cost of installation, mooring, and maintenance. Control methods that attempt to maximize the harvested power often lead to power flow from the WEC to [...] Read more.

Wave Energy Converters (WECs) are designed to be deployed in arrays, usually in a limited space, to minimize the cost of installation, mooring, and maintenance. Control methods that attempt to maximize the harvested power often lead to power flow from the WEC to the ocean, at times, to maximize the overall harvested power from the ocean over a longer period. The Power Take-Off (PTO) units that can provide power to the ocean (reactive power) are usually more expensive and complex. In this work, an optimal control formulation is presented using Pontryagin’s minimum principle that aims to maximize the harvested energy subject to constraints on the maximum PTO force and power flow direction. An analytical formulation is presented for the optimal control of an array of WECs, assuming irregular wave input. Three variations of the developed control are tested: a formulation without power constraints, a formulation that only allows for positive power, and finally, a formulation that allows for finite reactive power. The control is compared with optimally tuned damping and bang–bang control. Full article

(This article belongs to the Special Issue Tidal and Wave Energy)

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17 pages, 1403 KiB

Open AccessArticle

Experimental Investigation of Surface Waves Effect on a Ducted Twin Vertical Axis Tidal Turbine

by Martin Moreau, Grégory Germain and Guillaume Maurice

J. Mar. Sci. Eng. 2023, 11(10), 1895; https://doi.org/10.3390/jmse11101895 - 29 Sep 2023

Viewed by 554

Abstract

The cost effective design of tidal turbines requires a good estimation of the loading cycles and their extrema that are related to the unsteady fluctuation of the current velocity. Apart from the ambient turbulence, the main source of velocity fluctuation is the presence [...] Read more.

The cost effective design of tidal turbines requires a good estimation of the loading cycles and their extrema that are related to the unsteady fluctuation of the current velocity. Apart from the ambient turbulence, the main source of velocity fluctuation is the presence of surface waves. In the present study, we analyse the effect of waves propagating against the current on the performance and the loads of a twin vertical axis tidal turbine by an experimental approach at a 1/20 scale. Overall, the results show little or no effect of the waves on the average power and loads compared to the conditions with current only, but a significant impact on their standard deviation that rises linearly with the amplitude of the waves. The drag, lift, and pitching moment show extended ranges up to 7.5 times higher and extreme values exceedance by 60 to 100% with irregular waves compared to the conditions without waves. That load and power fluctuation increase is totally due to the presence of waves as the coherence function between the rotor torque or the loads and the velocity spectra exceed 0.5 on the whole wave frequency bandwidth. The results also reveal a rotational sampling of the waves by the rotors that had also been observed on horizontal axis turbines. From a structural design point of view, the authors recommend conducting tests in irregular wave conditions as both the load ranges and extreme values are 1.5 to 2 times higher than those encountered with regular waves of the same significant height and period. Full article

(This article belongs to the Special Issue Tidal and Wave Energy)

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24 pages, 9935 KiB

Open AccessArticle

On the Estimation of the Wave Energy Period and a Kernel Proposal for the Peru Basin

by Dennys De La Torre, Jaime Luyo and Arturo Ortega

J. Mar. Sci. Eng. 2023, 11(6), 1100; https://doi.org/10.3390/jmse11061100 - 23 May 2023

Cited by 2 | Viewed by 1115

Abstract

The energy period is a crucial parameter needed for assessing wave energy. This parameter is regularly approximated using standard wave spectrums that do not always characterise an actual ocean region, even more if this region is far from the Northern Hemisphere, where most [...] Read more.

The energy period is a crucial parameter needed for assessing wave energy. This parameter is regularly approximated using standard wave spectrums that do not always characterise an actual ocean region, even more if this region is far from the Northern Hemisphere, where most of the energy period approximations have been developed. In this work, diverse approximations for the energy period were evaluated using spectral data from a region of the Peru Basin. It included the assessment of a proposed Kernel “coefficient” curve. They were assessed regarding their time series, wave climate, and temporal variability. The time series analysis showed that the approximations based on the peak period do not have a realistic physical representation of ocean waves. On the other hand, the proposed Kernel correlation gave the best results for computing the energy period and the monthly/seasonal variability indexes for temporal variability analysis. Additionally, the correlations based on the zero-up-crossing period generated the best results for computing the coefficient of variation. Conversely, the highest errors were calculated for the correlations based on the traditional Bretschneider and JONSWAP spectrums. The wave climate indicated an annual average energy period equal to 9.8 s, considered stable due to its low variability. Full article

(This article belongs to the Special Issue Tidal and Wave Energy)

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18 pages, 3362 KiB

Open AccessArticle

Scenario Analysis of Cost-Effectiveness of Maintenance Strategies for Fixed Tidal Stream Turbines in the Atlantic Ocean

by Mitra Kamidelivand, Peter Deeney, Fiona Devoy McAuliffe, Kevin Leyne, Michael Togneri and Jimmy Murphy

J. Mar. Sci. Eng. 2023, 11(5), 1046; https://doi.org/10.3390/jmse11051046 - 13 May 2023

Cited by 1 | Viewed by 1303

Abstract

This paper has developed an operation and maintenance (O&M) model for projected 20 MW tidal stream farm case studies at two sites in the northeast Atlantic in France and at EMEC’s Fall of Warness site in the UK. The annual energy production, number [...] Read more.

This paper has developed an operation and maintenance (O&M) model for projected 20 MW tidal stream farm case studies at two sites in the northeast Atlantic in France and at EMEC’s Fall of Warness site in the UK. The annual energy production, number of incidents, and downtimes of the farms for corrective and planned (preventive) maintenance strategies are estimated using Monte Carlo simulations that vary weather windows, repair vessel availabilities, and mean annual failure rates modelled by Weibull distributions. The trade-offs between the mean annual failure rates, time availability, O&M costs, and energy income minus the variable O&M costs were analysed. For all scenarios, a 5-year planned maintenance strategy could considerably decrease the mean annual failure rates by 37% at both sites and increase the net energy income. Based on a detailed sensitivity analysis, the study has suggested a simple decision-making method that examines how the variation in the mean annual failure rate and changes in spare-part costs would reduce the effectiveness of a preventive maintenance strategy. This work provides insights into the most important parameters that affect the O&M cost of tidal stream turbines and their effect on tidal energy management. The output of the study will contribute to decision-making concerning maintenance strategies. Full article

(This article belongs to the Special Issue Tidal and Wave Energy)

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15 pages, 3242 KiB

Open AccessArticle

Hydrokinetic Power Potential in Spanish Coasts Using a Novel Turbine Design

by Mahmoud I. Ibrahim and María José Legaz

J. Mar. Sci. Eng. 2023, 11(5), 942; https://doi.org/10.3390/jmse11050942 - 28 Apr 2023

Viewed by 939

Abstract

Nowadays, there is great concern about obtaining clean energy. Governments around the world are boosting renewable energy resources. Oceans provide abundant renewable energy resources, including tidal, wave, and current energy. It seems that ocean currents are one of the most promising ways to [...] Read more.

Nowadays, there is great concern about obtaining clean energy. Governments around the world are boosting renewable energy resources. Oceans provide abundant renewable energy resources, including tidal, wave, and current energy. It seems that ocean currents are one of the most promising ways to obtain energy from the oceans. The goal of this paper is to assess the hydrokinetic power potential in three different areas of the Spanish coast using a novel turbine design, named the fin-ring turbine. The patented turbine was previously power tested in 2014 in the Gulf of Mexico and numerically validated in the literature. A three-dimensional computational fluid dynamics (CFD) simulation of the novel current turbine is presented, including mesh sensitivity and turbulence studies. The turbine’s performance represented in TSR-Cp is discussed. The turbine was simulated in different regions with several current speeds, focusing on the Spanish coast. The results are very promising, with upper limit power coefficients of 37.5%, and 36.5% as a lower limit. Also, the comparisons with power test data available in the literature show very satisfactory agreement. The results highlight the superiority of the turbine in lower currents and present the suitability of the turbine’s applicability. Full article

(This article belongs to the Special Issue Tidal and Wave Energy)

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22 pages, 8067 KiB

Open AccessArticle

Control Parameters Optimization of Accumulator in Hydraulic Power Take-Off System for Eccentric Rotating Wave Energy Converter

by Gang Xue, Zhenquan Zhang, Jian Qin, Shuting Huang and Yanjun Liu

J. Mar. Sci. Eng. 2023, 11(4), 792; https://doi.org/10.3390/jmse11040792 - 06 Apr 2023

Cited by 2 | Viewed by 1438

Abstract

To improve the efficiency and stability of an eccentric rotating wave energy converter (ERWEC), the adaptive hydraulic power-take-off (PTO) system with an accumulator is designed and developed. Experiments are performed to analyze the effects of trigger pressure, delay time, and open state duration [...] Read more.

To improve the efficiency and stability of an eccentric rotating wave energy converter (ERWEC), the adaptive hydraulic power-take-off (PTO) system with an accumulator is designed and developed. Experiments are performed to analyze the effects of trigger pressure, delay time, and open state duration on average output power and power fluctuation index. The results show that the effects of those three control parameters of accumulator on output power are strongly coupled. The experimental examples are designed based on the optimal Latin hypercube sampling (OLHS) method, and the nonparameterized agent models of control parameters to output power indices are established based on the Gaussian process regression (GPR) method. With the help of sensitivity analysis, it is found that the coupled effect of delay time and open state duration on the power fluctuation index is greater than that on the average output power. Furthermore, the optimal combination of control parameters is obtained by non-dominated sorting genetic algorithm-III (NSGA-III), which improves the amount and stability of output power from a hydraulic PTO system. This paper is of important significance for parameter setting of hydraulic PTO systems with an accumulator for wave energy converter, and provides the basis for the real-time adjustment of control parameters under complex sea conditions. Full article

(This article belongs to the Special Issue Tidal and Wave Energy)

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18 pages, 16489 KiB

Open AccessArticle

Study of the Performance of Deep Learning Methods Used to Predict Tidal Current Movement

by Kai Zhang, Xiaoyong Wang, He Wu, Xuefeng Zhang, Yizhou Fang, Lianxin Zhang and Haifeng Wang

J. Mar. Sci. Eng. 2023, 11(1), 26; https://doi.org/10.3390/jmse11010026 - 26 Dec 2022

Cited by 1 | Viewed by 1777

Abstract

To predict tidal current movement accurately is essential in the process of tidal energy development. However, the existing methods have limits to meet the need for accuracy. Recently, artificial intelligence technology has been widely applied to solve this problem. In this paper, a [...] Read more.

To predict tidal current movement accurately is essential in the process of tidal energy development. However, the existing methods have limits to meet the need for accuracy. Recently, artificial intelligence technology has been widely applied to solve this problem. In this paper, a tidal current prediction model combining numerical simulation with deep learning methods is proposed. It adopts three deep learning algorithms for comparative investigations: multilayer perceptron (MLP), long-short term memory (LSTM) and attention-ResNet neural network (AR-ANN). The numerical simulation was carried out using ROMS, and the observation collected in the Zhoushan region were used to validate the results. Compared with the numerical simulations, deep learning methods can increase the original correlation coefficient from 0.4 to over 0.8. In comparison, the AR-ANN model shows excellent performance in both the meridional and zonal components. This advantage of deep learning algorithms is extended in the tidal energy resource assessment process, with MLP, LSTM and AR-ANN models reducing the root mean square error by 32.9%, 34.4% and 42%, respectively. The new method can be used to accurately predict the hydrodynamic of tidal flow in the process of tidal energy extraction, which contributes to determine the suitable location for energy generation and tidal turbine design. Full article

(This article belongs to the Special Issue Tidal and Wave Energy)

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18 pages, 2360 KiB

Open AccessArticle

A BEM-Based Model of a Horizontal Axis Tidal Turbine in the 3D Shallow Water Code SHYFEM

by Micol Pucci, Chiara Di Garbo, Debora Bellafiore, Stefania Zanforlin and Georg Umgiesser

J. Mar. Sci. Eng. 2022, 10(12), 1864; https://doi.org/10.3390/jmse10121864 - 02 Dec 2022

Cited by 3 | Viewed by 1363

Abstract

We present a novel 3D implementation of a horizontal axis tidal turbine (HATT) in the shallow water hydrostatic code SHYFEM. The uniqueness of this work involves the blade element momentum (BEM) approach: the turbine is parameterized by applying momentum sink terms in the [...] Read more.

We present a novel 3D implementation of a horizontal axis tidal turbine (HATT) in the shallow water hydrostatic code SHYFEM. The uniqueness of this work involves the blade element momentum (BEM) approach: the turbine is parameterized by applying momentum sink terms in the x and y momentum equations. In this way, the turbine performance is the result of both the flow conditions and the turbine’s geometric characteristics. For these reasons, the model is suitable for farm-layout studies, since it is able to predict the realistic behavior of every turbine in a farm, considering the surrounding flow field. Moreover, the use of a shallow water code, able to reproduce coastal morphology, bathymetry wind, and tide effects, allows for studying turbine farms in realistic environments. Full article

(This article belongs to the Special Issue Tidal and Wave Energy)

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19 pages, 7663 KiB

Open AccessArticle

Experimental Investigation of Mooring Performance and Energy-Harvesting Performance of Eccentric Rotor Wave Energy Converter

by Gang Xue, Jian Qin, Zhenquan Zhang, Shuting Huang and Yanjun Liu

J. Mar. Sci. Eng. 2022, 10(11), 1774; https://doi.org/10.3390/jmse10111774 - 18 Nov 2022

Cited by 2 | Viewed by 1267

Abstract

To obtain the optimal mooring mode and the best-matching wave condition of an eccentric rotor wave energy converter (ERWEC), a physical model of the ERWEC was developed. Ten mooring modes and eight wave conditions were set up. Several experiments were carried out to [...] Read more.

To obtain the optimal mooring mode and the best-matching wave condition of an eccentric rotor wave energy converter (ERWEC), a physical model of the ERWEC was developed. Ten mooring modes and eight wave conditions were set up. Several experiments were carried out to analyze the influence of mooring modes and wave conditions on the mooring and energy-harvesting performances of the ERWEC. The results showed that the mooring and energy-harvesting performances changed significantly for the same mooring mode under various regular wave conditions, but the opposite situation was found under irregular wave conditions. The wave-facing direction of the buoy was a critical factor affecting the mooring and energy-harvesting performances, while the number of anchor lines had little effect on them. In addition, a method to evaluate the motion response of the buoy based on the number of effective excitations and a method to evaluate the comprehensive performance based on the cloud chart are proposed. The mooring mode and wave condition combination that obtained the optimal mooring and energy-harvesting performances for the ERWEC was determined. This paper provides a novel perspective on how to balance the efficiency and reliability of wave energy converters. Full article

(This article belongs to the Special Issue Tidal and Wave Energy)

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