Ocean Renewable Energy Research Articles

Fine-tuning ocean energy storages for reservoir-integrated wave energy converters with dynamic activation of mechanical energy storage features

The proportion of renewable energy in the power supply has experienced substantial growth; however, its intermittent nature and inherent uncertainty present notable challenges in its integration. This study aims to explore the significance of energy flexibility in energy management by focusing on a hybrid renewable wave-wind zero-energy system implemented in a coastal building. Specifically, the study investigates various sources of flexibility within the system and introduces a novel energy storage mechanism utilising the in-built reservoir of the wave energy converter. The research provides new insights into the flexibility of control strategies from the generation and storage sides. The cost-responsive controls involved on/off-peak periods and monthly variations. Several attempts have been made to develop cost-responsive controls that depend upon the electricity tariffs; these include energy shift and peak shaving. The lower discharging limits and trigger lines were compared in the simulation environment to improve the cost-saving, energy-matching, and peak-shaving performances. In this study, the first group scheduled discharging; however, only limited improvements (0.5%) were achieved. Consequently, the second group shifted to varying the minimum fraction state of the reservoir under a lower discharging limit, which reduced operational cost by 4.5%. Using different discharging lines by considering the current month and the period, the third group achieved the expected peak shaving and correspondingly reduced the operational cost to 90.3 %. The final group showed that an additional battery could improve the peak-shaving and cost-saving performance but not the net present value, owing to high investment costs. Furthermore, annual savings increased for different battery capacities from 4.5 % to 6.8 % by conducting the energy shift. Peak shaving control with additional battery reduced maximum demand and substantially reduced costs from 6.4 % to 10.8 %. The study recommends focusing on peak shaving with extra batteries for further cost savings during the on-peak period. This research brings novelty by integrating flexibility control for both generation- and storage-sides in ocean renewable energy systems. It proposes using a wave energy converter as a mechanical energy storage reservoir, reducing costs and ensuring adequate capacity. The study emphasises dynamic storage control, adjusting in real time based on conditions and energy demands.

Electrochemical Conversion of Salinity Gradient Energy by Using Acid Surface Modified Activated Carbon Electrode

Salinity gradient energy is a sustainable, clean, and renewable ocean energy source. In this work, we used citric acid, phosphoric acid, and nitric acid to modify the surface of activated carbon. Based on the electrochemical capacitive mixing technology, a salinity gradient energy extraction device was constructed using acid-modified activated carbon as cathode and MoS2/MWCNTs as anode. Surface modification by different acids improves the performance of activated carbon electrodes for salt gradient energy conversion in the salt difference battery. The modification effect of nitric acid was the most pronounced, the specific capacitance of the modified electrode reaches 156 F g−1, and the concentration response voltage reaches 170 mV, with the assembled energy extraction system obtaining an energy density of 10.65 J m−2, an enhancement of 53.0% compared to the unmodified activated carbon electrode.

Mapping Kinetic Energy Hotspots in the Persian Gulf and Oman Sea Using Surface Current Derived by Geodetic Observations and Data Assimilation

Harnessing ocean kinetic energy has emerged as a promising renewable energy solution in recent years. However, identifying optimal locations for extracting this energy remains a significant challenge. This study presents a novel scheme to estimate the total surface current (TSC) as permanent surface current by integrating geodetic data and in-situ measurements. The TSC is typically a combination of the geostrophic current, derived from dynamic topography, and the Ekman current. We utilize NOAA’s Ekman current data to complement the geostrophic current and obtain the TSC. To further enhance the accuracy of the TSC estimates, we employ a 3DVAR data assimilation method, incorporating local current meter observations. The results are verified against two control current meter stations. The data-assimilation process resulted in an improvement of 4 to 15 cm/s in the precision of calculated TSC. Using the assimilated TSC data, we then assess the kinetic energy potential and identify six regions with the most significant promise for marine kinetic energy extraction. This innovative approach can assist researchers and policymakers in targeting the most suitable locations for harnessing renewable ocean energy.

Understanding the Dynamics of Ocean Wave-Current Interactions Through Multivariate Multi-Step Time Series Forecasting

ABSTRACT Understanding ocean wave-current interactions’ complex dynamics is crucial for coastal engineering, marine operations, and climate research applications. This study introduces a pioneering data-driven approach by employing advanced deep learning techniques, specifically Long Short-Term Memory (LSTM), and Bidirectional LSTM (BiLSTM) models, to forecast both wave and current parameters at varying depths. The models are designed to capture the complex temporal relationships inherent in ocean dynamics, considering wave speed and direction, current speed, and direction as multivariate time series inputs. Two comprehensive experiments are conducted, one utilizing historical values of all parameters and another focusing on using wave parameters to forecast current parameters. Model performance is rigorously evaluated across forecast horizons of 5, 12, and 24 hours ahead using metrics such as Mean Absolute Error (MAE), Mean Squared Error (MSE), and Root Mean Squared Error (RMSE). BiLSTM emerges as the superior model, demonstrating lower errors, particularly at higher depths, while nearshore predictions reveal challenges in shallower waters. Furthermore, the methodology incorporates hyperparameter optimization and cross-validation techniques to enhance the model’s robustness. Ultimately, this work represents a transformative leap toward smarter oceans, emphasizing the fusion of fluid dynamics and bathymetry to advance our understanding of coupled wave-current dynamics. The results showcase high accuracy and reliability across various forecast horizons and depths, signifying the method’s potential applications in oceanography, hydrodynamics, coastal engineering, and ocean renewable energy.

Development of Savonius Rotor Based on Bezier Curve for Vertical Axis Marine Current Turbine at Sunda Strait, Hindia Ocean

Due to its strategic location and ocean currents, the Sunda Strait has the potential to produce energy that might be used as a source of electricity. As a result, this strait area urgently needs a suitable turbine design. This strait's most significant sea current speed is 1 (one) m/s. The Savonius rotor is one of the rotor kinds of turbines that can operate in the slow sea current—modifying the rotor from semi-circular to use the Bezier curve for the shape to optimize the performance. This paper will discuss the design of the Savonius rotor using the Bezier curve, that have improved performance. The rotor with double stacking will also enhance the performance of the rotor. This design is a novelty for vertical marine current turbine applications in ocean renewable energy.

Electric vehicle-based distant energy sharing between zero-emission coastal office and hotel buildings

With the rapid growth of distributed renewable energy systems, energy sharing brings a practical solution to mitigate mismatching between intermittent electricity generation and building demand. In past research, energy sharing was designed mostly for onshore energy integrated systems and is commonly realised with the assistance of microgrids, distributed battery storage, or peer-to-peer energy trading. This research innovatively proposed a distant energy sharing between the ocean energy-supported coastal office building and hotel building by ten electric vehicles, enabling the circulation of ocean renewable energy between two buildings. This project aims to accomplish maximum technical, environmental and economic benefits for the stakeholder. Using bidirectional vehicle-building interaction, advanced control algorithms, including shifting vehicle batches, sizing renewable capacity, and involving stationary batteries, are implemented successively in the TRNSYS simulation as analysis groups to enhance the current system's performance. According to the results, the vehicle-based bidirectional energy sharing between these two buildings can attain a relative net present value of 49.18 million HKD and a weighted matching index of 0.63. After implementing advanced controls with stationary batteries, the system achieved a relative net present value of 62.15 million HKD with an improved matching index of 0.70. Both batteries contributed to increase the matching performance of the system, but the increase in battery capacity reduces the benefit due to their replacement cost. This research developed an energy management system for effectively utilising electric vehicles and coastal renewable energy for distant energy sharing. It elucidated the technological, environmental, and economic benefits to the stakeholders for effective decision-making.

Energy flux variations and safety assessment of offshore wind and wave resources during typhoons in the northern South China Sea

Extreme ocean conditions during typhoons pose significant challenges to the sustainable utilization of ocean renewable energy. This study focuses on analyzing the wind and sea states within typhoon systems and the variations in offshore wind & wave energy flux during typhoons passing over the northern South China Sea (SCS) from 2000 to 2022. The trajectories and intensities of 769 typhoons in the Western Pacific, along with wind & wave energy flux variations during 155 instances of typhoons making landfall in the SCS, are isolated for comprehensive analysis. Specifically, the safety of energy exploitation during severe typhoon Hato (2017) is assessed considering the local met-ocean condition during typhoon passing and the survival ocean conditions of Offshore Wind Turbines (OWTs) and Wave Energy Converters (WECs). The WRF model and FVCOM-SWAVE model are used to provide necessary winds and waves during the passage of Hato with simulations validated against observations for reliable safety assessments. The results show that, over the past 22 years, the regions spanning from northern Guangdong to the Luzon Strait have been subjected to robust winds and formidable waves. The average values of Wind Power Density (WPD) and Wave Power Flux (WPF) during typhoons have exceeded 1500 W/m2 and 20 kW/m, respectively. In the Hato typhoon system, the maximum wind speed surpasses 60 m/s, while the significant wave height is about 10 m. Moreover, the survival capabilities of current OWTs (MySE5.5-155, SWT-6.0-154, SWT-7.0-154, SG 8.0–167 DD and D10000-185) and WECs (Sea Power and CycWEC) are assessed, demonstrating their ability to withstand the entire typhoon lifetime. Therefore, OWTs and WECs exhibit robust survival capabilities through comprehensive assessments based on the validated numerical simulation results, facing extreme typhoon conditions.

Utilization of Multi-Mission Satellite Altimetry for Wave Energy with Site Suitability Analysis using the Analytic Hierarchy Process

Space technology advancements have enabled the acquisition of marine data that support the research on wave energy as an alternative to reduce fossil fuel dependency and mitigate climate change. Malaysia's ocean renewable energy potential lacks attention from local authorities due to insufficient in-situ data, posing challenges in investigating ocean characteristics, such as wave heights. This study investigated Malaysia's wave energy potential using extensive significant wave height data from multiple altimetry missions. The former assessed site suitability using the Analytical Hierarchy Process (AHP) multicriteria analysis, incorporating marine constraints, namely socioeconomic, physical, and environmental factors. The multicriteria findings were integrated into a Geographical Information System (GIS) to improve the site suitability analysis and generate a localized suitability index for wave energy. Validation of satellite altimeter data with in-situ measurements showed a strong correlation and low RMSE. AHP analysis indicated good consistency in the criteria analysis, with a consistency ratio of 0.045, which falls below the limit of 0.1. The coastal and offshore regions of the Malaysian seas are suitable for harnessing wave energy with energy ranges up to 4.21 kW/m. Therefore, this study provides valuable information to stakeholders and the government to increase their interest in wave energy.

Wave Height Forecasting Over Ocean of Things Based on Machine Learning Techniques: An Application for Ocean Renewable Energy Generation

Wave Height Forecasting Over Ocean of Things Based on Machine Learning Techniques: An Application for Ocean Renewable Energy Generation

A short review of marine renewable energy: Generation, storage, and applications

Renewable energy is a sustainable and green energy converted from renewable energy resources in the nature. There is a huge amount of renewable energy resources in the ocean that can be changed into useful energy like electricity, store for long time use, or apply in the daily energy consumption. These marine renewable energies (MRE) include wave energy, ocean thermal energy, tidal energy, ocean current energy, salinity gradient energy, and offshore energy. With a big area, the oceans have been prospected that it brings endless renewable energy sources for social development and human demand. The renewable ocean energy shows many advantages of sustainable energy, clean energy, and non-carbon dioxide emissions by generating from wave and water in the ocean with an enormous amount of natural energy resources. The MRE can service at many areas of off-shore, on-shore, and remote areas where need energy to drive daily living demands. The MRE reveals some disadvantages such as the influence of daily, monthly, season, and period of time. The solutions have been developed to solve the limitations of the MRE such as developing the storage method to store energy for long time use or making the balance of the output performance to improve quality of the renewable energy. The MRE has also received many concerns from countries by promulgating policies, strategies, and plans to develop the renewable ocean energy such as green economy development, blue economy strategy, carbon dioxide emission reduction, and encouragement of using marine renewable energy. This paper reviews current marine renewable energy with its generation, storage, and application. The work also mentioned some advantages, disadvantage, policies, strategies, and solutions to encourage the development of the renewable ocean energy in over the world. The results hope that it will be spread development, exploitation, and application of marine renewable energy in the near future. Keywords: Marine renewable energy, energy storage, generation, application, sustainable energy

Numerical Study of an Innovative Concept for a Multibody Anti-Pitching Semi-Submersible Floating Wind Turbine

The floating offshore wind turbine provides a feasible solution for the development of renewable ocean energy. However, the sizeable rotor diameter of the wind turbine results in large wind heeling moments and pitch amplitude. It will increase the structural loads and cause safety problems. Additionally, the contradictory nature between the stability and the sea-keeping of the floating structure requires that the more flexible method should be adopted to reduce the motion response of the floating offshore wind turbine. Therefore, an innovative concept of a multibody anti-pitching semi-submersible floating offshore wind turbine, named the MBAPSF, is proposed in this paper. The MBAPSF consists of a 5 MW braceless semi-submersible wind turbine and three wave energy converters. The multibody coupled numerical model is established by using an F2A tool, and the dynamic performance of the MBAPSF is compared with that of the traditional semi-submersible wind turbine named the TSSF. The results show that the innovative concept proposed in this paper can reduce pitch motion up to approximately 27% under different load cases, and the maximum bending moment and shearing force at the tower base are also reduced by more than 10%. Meanwhile, WECs are beneficial for increases in the total power generation capacity.

Ocean energy

This article presents the principles and technologies for converting the main renewable ocean energy resources (ocean thermal energy, wave energy and tidal energy) into electricity. Their energy production potential is put into perspective in terms of the challenges of the energy transition.

A systematic methodology to assess local economic impacts of ocean renewable energy projects: Application to a tidal energy farm

Ocean renewable energy (ORE) is one of the most important clean sources of energy and a major player towards the EU ambitions of being net zero emission by 2050. However, at present, there are few examples of commercially viable ORE technologies and no large-scale projects currently under implementation. Together with social and environmental analyses, the assessment of economic impacts is one of the key elements to help policy makers build a compelling case to gain local community acceptance and implement ORE projects. This paper presents a systematic methodology to assess local economic impacts of renewable energy projects, including jobs creation and impacts on gross value added and income. By combining the use of Location Quotients – which are indexes informing on local industrial specialisation – with the Input-Output multipliers the method can be used to map the supply-chain potential of a local economy and estimate local impacts compared to global ones. The method has been applied to a tidal project carried out in Orkney, Scotland. The research demonstrates the merit of early economic assessments for understanding the economic benefit of ORE projects, particularly for the local communities in which they are located, and it provides a methodological framework to be tested in other case studies.

Performance analysis of a novel small-scale radial turbine with adjustable nozzle for ocean thermal energy conversion

Ocean thermal energy is acknowledged as one of the most promising ocean renewable energy sources in low latitude sea areas. In the ocean thermal energy conversion system, the turbine plays a significant role, and it is responsible for converting the working medium enthalpy into the shaft output power. The present study is focused on the performance analysis of a novel radial inflow turbine with an adjustable nozzle in the OTEC system in order to adapt to the changing operating conditions of the turbine, which vary with the change in seawater temperature. At the design point, the predicted overall isentropic efficiency is 86.5%, and the shaft output power is 15.3 kW, slightly higher than the expected 15 kW. Furthermore, a parametric study is performed, respectively, for the nozzle vane stagger angle and the nozzle-impeller radial clearance to explore the favorable geometric parameters for different conditions. The turbine’s overall efficiency increases slightly with deceasing nozzle-impeller radial clearance, and the variation of the nozzle vane stagger angle is much more influential on the turbine shaft power and overall efficiency. The optimum stagger angle point moves from 32° to 36° gradually with the increase in nozzle-impeller clearance. Finally, the feasibility of an adjustable nozzle for the turbine under off-design conditions was verified by combining the radial clearance and nozzle stagger angle.

Enhancing Islanded Power Systems: Microgrid Modeling and Evaluating System Benefits of Ocean Renewable Energy Integration

The energy transition hinges on the effective integration of renewable energy sources into the power grid. Islands can provide invaluable insights into the challenges and opportunities of integrating variable renewable energy into the grid due to their relatively small power systems, isolated grids, and diverse availability of renewable energy resources. This paper presents a study on the system benefits and challenges of marine energy integration in insular power systems, focusing on the Orkney Islands as a case study. A microgrid modeling approach that optimizes the mix of renewable sources and energy storage systems for future scenarios considering strategic time horizons (2030, 2040, and 2050) was employed. Results suggest that integrating ocean energies, namely, wave and tidal energy, yields notable benefits compared to traditional renewable energy sources exclusively. These benefits encompass reduced installed capacity, minimized energy storage requirements, lower excess generation, and overall cost-saving.

Modelling the impacts of a large marine turbine array in the Cozumel Channel

Ocean renewable energies are a promising alternative to meet the growing energy demand. Due to the intense, persistent and relatively constant unidirectional flow, the Cozumel Channel (CC) in the Caribbean Sea is considered one of the most favorable global sites for the potential exploitation of ocean current energy. In this paper we use the Regional Ocean Modelling System (ROMS) to simulate the effects of a large number of individual turbines (5277) on the marine environment at a regional scale. A couple of two-way nested grids were used to extend the horizontal resolution from 30 m to ∼3600 m. The impacts of the turbines on circulation, water temperature, sea surface high (SSH), sediment transport and upwelling events, were analyzed. An improved estimate of the average power generated was also performed, which includes the disruption of the currents by the turbines. The results suggest that the installation of a large number of marine turbines would cause severe flow disturbances in the CC and neighboring regions, changing several aspects of the ecosystem. While the number and characteristics of the marine turbines might seem excessive, this study could serve as a benchmark to determine thresholds in the size of future turbine farms in the region.

A spatial-temporal clustering for low ocean renewable energy resources using K-means clustering

Advancements in space technology have enabled the acquisition of reliable marine data, facilitating research on the potential of ocean renewable energy as an alternative source that can reduce dependency on fossil fuels, subsequently mitigating climate change. However, the ocean renewable energy development in Malaysia has not received adequate attention from local authorities and communities due to low resources in this area. Insufficient in-situ data, both in spatial and temporal dimensions, poses challenges in investigating the characteristics of ocean parameters, hindering a thorough study of the potential for ocean renewable energy development. Hence, this paper aims to identify potential ocean renewable energy development locations using the altimetry data and spatial-temporal clustering using the K-means technique. Theoretically, Malaysian seas are suitable for harnessing wind and waves with energy density ranges of up to 104.69 kW/m2 and 4.21 kW/m, respectively. This study enhances the understanding of Malaysian potential for ocean renewable energy, providing valuable information to stakeholders and the government to increase their interest in ocean renewable energy as a sustainable source for electricity generation in the future.

Bias correction techniques for uncertainty reduction of long-term metocean data for ocean renewable energy systems

The design of effective and reliable solutions for Offshore Renewable Energy (ORE) technologies greatly relies on accurate metocean data. Uncertainties can significantly impact the design process. This paper presents a thorough evaluation of different bias-correction (BC) techniques applied to re-analysis datasets from diverse locations along the Spanish coast, presenting a multi-level evaluation procedure including novel, more appropriate statistical metrics beyond the traditional assessment techniques. First, the quality of raw ERA5 datasets is demonstrated to be rather poor, especially under extreme events, confirming the need for BC. Once the need is identified, results show that only the most sophisticated distribution-mapping BC techniques present the capacity to significantly improve the quality of the datasets, with the linearly-spaced Quantile-mapping (QM) showing the best overall performance for power production conditions (PP), reducing the bias by over an order of magnitude. In contrast, the Gumble Quantile-Mapping (GQM) outperforms the QM in survivability conditions (Surv). However, when computing overall performance of BC techniques, the predominance of PP hinders the relevance of Surv. Hence, adapted metrics with a more realistic balance between the PP and Surv regions are suggested, which show a better suitability of GQM providing more accurate estimations of the average power density and variability.

Assessment of offshore wind-solar energy potentials and spatial layout optimization in mainland China

Developing offshore wind and solar energy presents a promising solution to reduce carbon emissions. Yet, there has been little focus on the co-location of offshore wind and solar energy, and an absence of methods for optimizing their spatial layout for regional integration. To this end, this study introduces a framework to assess both the technical and economic potential using geographic information system technology, and to seek the optimal spatial layout by combining electricity dispatch simulation and multi-objective optimization. Our results reveal that China's offshore wind-solar generation potential amounts to ∼15.7 × 103 TWh/year, half of which is accessible at a cost of less than €86/MWh. This potential could satisfy 100% of the coastal electricity demands, but the proportion of offshore generation delivered to the grid and the share of load addressed are contingent on specific constraints. We demonstrate that co-located wind-solar farms diminish generation variability and that energy storage markedly reduces PV curtailment during dispatch. Our study underscores the importance of site selection in distant offshore and decentralized placement among locations with varying characteristics. Our study serves as a foundation for offshore wind-solar energy endeavors and offer crucial considerations for the spatial layout optimization of ocean renewable energy utilization.

DEVELOPMENT OF OCEAN RENEWABLE ENERGY MODEL IN INDONESIA TO SUPPORT ECO-FRIENDLY ENERGY

Abstract. Renewable energy is a solution for reducing environmental damage caused by greenhouse gas emissions from fossil fuels. Energy consumption in Indonesia involves sectors such as industry, households, transportation, and agriculture, which still heavily rely on non-renewable energy sources. Indonesia possesses significant maritime potential, boasting the second longest coastline in the world, a water area covering 71%, and abundant marine biological resources that can contribute to maritime economic growth. This research aims to leverage remote sensing technology and geographic information science to harness Indonesia's maritime potential. In the realm of renewable energy, this study emphasizes the potential of wave energy and current energy in Indonesia, with the objective of establishing an Ocean Renewable Energy (ORE) model. Additionally, the research will consider marine habitat suitability to mitigate any negative impact on biodiversity from power generation activities. Based on the research findings, the ocean current energy in Lombok Strait has a high energy potential reaching 1,035 Watts and Maluku Sea has 1,536 Watts, while the southwest region exhibits wave energy potential of Panaitan Island has a wave energy potential of 23,051 kW/m, while Sangiang Island has a potential of 12,842 kW/m. Furthermore, potential energy locations will be identified through the overlaying of potential fish zones. The ultimate goal of this research is to fulfill sustainable energy needs, decrease dependence on fossil fuels, and promote sustainable economic growth in Indonesia.