Nearly 40% of the world’s population lives within 100 kilometres of the coast with the risk that this implies in terms of exposure to the effects of climate change. Ocean energy, according to the IPCC (Intergovernmental Panel on Climate Change) in 2019, has been identified as one of the measures for mitigating these effects. In addition, ocean energy can play an essential role in achieving some of the SDGs (Sustainable Development Goals) set at the Paris Climate Summit in 2015, namely SDG 7 (clean and affordable energy) and SDG 13 (climate action) and could have a substantial impact on others such as SDG 1 (poverty eradication), SDG 2 (end hunger), SDG 5 (gender equality), SDG 6 (universal energy access), SDG 8 (promote sustainable economic growth), SDG 9 (build resilient infrastructure), SDG 14 (sustainable conservation of oceans and seas) and SDG 17 (promote sustainable development cooperation). There are several projects under development around the world aimed at extracting energy... [more]

The Central and South Pacific have significant wave energy resources distributed through the region that are currently not being explored. Even though the wave energy resource in the Pacific has been studied, there is limited knowledge on the potential obstacles when inserting this new energy source into a unique and unexplored environment. Pacific Island countries (PICs) have distinctive characteristics that can become barriers to this technology, especially considering that local coastal and marine systems are fundamental for subsistence and local development. Thus, the success of a project relies on local acceptance. The current study developed an integrative conceptual framework for the PICs (ICFPICs) that derived from the integration of the elements of a political, economic, social, technological, environmental and legal (PESTEL) structured approach and further combined with a strengths, weaknesses, opportunities and threats (SWOT) approach to create a matrix that included relevan... [more]

The optimal utilization of renewable energies is a crucial factor toward the realization of sustainability and zero carbon in a future energy system. Tidal currents, waves, and thermal and salinity gradients in the ocean are excellent renewable energy sources. Ocean tidal, osmotic, wave, and thermal energy sources have yearly potentials that exceed the global power demand of 22,848 TWh/y. This paper extensively reviews the technologies related to energy harvesting from waves, tidal, ocean thermals, and the salinity gradient. Moreover, the socio-economic, social, and environmental aspects of the above technologies are also discussed. This paper provides a better picture of where to invest in the future energy market and highlights research gaps and recommendations for future research initiatives. It is expected that a better insight into ocean energy and a deep understanding of various potential devices can lead to a broader adoption of ocean energy. It is also clear that further resear... [more]

One option for converting the energy in sea waves into renewable electricity is the development of floating wave energy converters coupled to electrical generators. For this to work, bespoke slow-speed electrical machines coupled to bidirectional power smoothing power electronic converters are required. This paper reports on the successful design and wave tank validation of an electric machine, power converter and fully controlled direct drive power take-off system coupled to two small scale heaving wave energy converters. The design, development and demonstration of linear generators and power converters is presented including some simulated and laboratory results. Demonstration of wave energy converters with pure electric drives, fully automated control, bidirectional power flow and active force management is almost unique and essential for future wave energy development. The results presented prove that direct-drive power take-off for wave energy devices is technically possible and... [more]

In order to solve the hydrodynamic characteristics of the multi-floater truss-type wave energy convertor (WEC) platform, the mathematical model is established by using the high-order boundary element method based on potential flow theory, in which the floater and the platform are connected by the floating arm based on the lever principle. The mathematical model is applied to study the heave motion response of each floater of the multi-floater truss-type WEC platform, and the effects of the floater number and the floater arrangement on the motion responses of floaters, as well as the power generation of the WEC platform are analyzed. The effect of the hydraulic cylinder on the floater is simulated by linear damping, and then, the work of the hydraulic cylinder is used to generate electricity, so as to achieve the purpose of simulating the multi-floater WEC power generation device. Some useful conclusions are obtained through calculation, which can provide data support for the correspond... [more]

Wave energy is a renewable energy source with the potential to contribute to the global electricity demand, but a remaining challenge is the survivability of the wave energy converters in harsh offshore conditions. To understand the system dynamics and improve the reliability, experimental and numerical studies are usually conducted. However, these processes are costly and time-consuming. A statistical model able to provide equivalent results is a promising approach. In this study, the digital twin of the CFD solution is developed and implemented for the prediction of the force in the mooring system of a point-absorber wave energy converter during extreme wave conditions. The results show that the digital twin can predict the mooring force with 90.36% average accuracy. Moreover, the digital twin needs only a few seconds to provide the solution, while the CFD code requires up to several days. By creating a digital analog of a wave energy converter and showing that it is able to predict... [more]

Growing energy demand worldwide and onshore limitations have increased interest in offshore renewable energy exploitation. A combination of offshore renewable energy resources such as wind and wave energy can produce stable power output at a lower cost compared to a single energy source. Consequently, identifying the best locations for constructing combined offshore renewable energy farms is crucial. This paper investigates the technical, economic, social, and environmental aspects of Combined Offshore Wind and Wave Energy Farm (COWWEF) site selection. Past literature was evaluated using a systematic review method to synthesize, criticize, and categorize study regions, dataset characteristics, constraints, evaluation criteria, and methods used for the site selection procedure. The results showed that most studied regions belong to European countries, and numerical model outputs were mainly used in the literature as met-ocean data due to the limited coverage and low spatiotemporal resol... [more]

This paper presents work on a wave energy device with an on-board power take-off based on a magnetostrictively actuated deformable structure. Such devices potentially could be used in low-cost, short-term expeditionary operations. The paper discusses an analytical model that describes the heave oscillations of a buoy with two inclined, overhanging beams with magnetostrictive strips affixed to them. This work comprises the first steps toward an analytical model that would enable potential users to obtain quick power estimates at the planning stage. Here, the fully nonlinear magneto-mechanical-electrical constitutive relations are linearized about a desirable operating point, and a coupled dynamic model is derived using a variational formulation that includes buoy heave, flexural oscillations of the two beams, and the voltage response of the magnetostrictive strips. Energy conversion performance in wind-sea-dominated Pierson−Moskowitz spectra is found to be modest. However, present resul... [more]

Wave energy converters are still a maturing technology and, as such, still face a series of challenges before they can compete with already-established technologies. One of these challenges is optimising the amount of energy extracted from the waves and delivered to the power grid. This study investigates the possibility of increasing the energy output of the existing hydraulic power take-off system of a wave energy converter made by Floating Power Plant during small-scale testing of their hybrid wind and wave energy platform. This system consists of a floater arm that rotates an axle when displaced by the waves. When the axle rotates, two hydraulic cylinders are actuated, displacing oil to run through a hydraulic motor driving an electric generator. The energy extraction is controlled by implementing a control algorithm on a series of on/off valves, which decouples the two hydraulic cylinders driving the hydraulic motor, and by varying the applied torque from the generator to match th... [more]

Ocean energy is one potential renewable energy alternative to fossil fuels that has a more significant power generation due to its better predictability and availability. In order to harness this source, wave energy converters (WECs) have been devised and used over the past several years to generate as much energy and power as is feasible. While it is possible to install these devices in both nearshore and offshore areas, nearshore sites are more appropriate places since more severe weather occurs offshore. Determining the optimal location might be challenging when dealing with sites along the coast since they often have varying capacities for energy production. Constructing wave farms requires determining the appropriate location for WECs, which may lead us to its correct and optimum design. The WEC size, shape, and layout are factors that must be considered for installing these devices. Therefore, this review aims to explain the methodologies, advancements, and effective hydrodynamic... [more]

This work focuses on the geometry effects over the performance of oscillating water column (OWC)-type wave energy converter (WEC) systems and searches for the OWC geometries that enhance the energy efficiencies under the same wave conditions. To analyze the hydrodynamic performances of the WEC systems, an in-house smoothed particle hydrodynamics (SPH) code based on weakly compressible fluid approach is utilized. The energy efficiency enhancement studies of the determined OWC device are carried out with a two-step geometry modification procedure. The first step starts with the validation of the free-surface elevation and orbital velocity time histories. Then, a three-by-three simulation matrix that depends on the geometrical design parameters of chamber length and front wall draft is run at three different wave conditions, and the OWC geometry that produces the maximum energy efficiency is determined. In the second step, the corner regions of the obtained optimal geometry are chamfered,... [more]

Electrifying off-grid and isolated islands in the Philippines remains one of the challenges that hinders community development, and one of the solutions seen to ensure energy security, energy access and promote a low-carbon future is the use of renewable energy sources. This study determines the nearshore wave energy resource during monsoon seasons in Cuyo Island using a 40-year wave hindcast and 8-year on-site wind speed data as inputs to develop a high-resolution wave energy model using SWAN and assesses its annual energy production through matching with wave energy devices. The results show that the average significant wave height (Hs), peak period (Tp) and wave power density (Pd) during a northeast monsoon are Hs = 1.35 m, Tp = 4.79 s and Pd = 4.05 kW/m, respectively, while a southwest monsoon, which is sheltered by the mainland, results in Hs = 0.52 m, Tp = 3.37 s and Pd = 0.34 kW/m. While the simulated model was observed to overestimate the significant wave height (bias = 0.398,... [more]

The combination of an offshore wind turbine and a wave energy converter on an integrated platform is an economical solution for the electrical power demand in coastal countries. Due to the expensive installation cost, a prediction should be used to investigate whether the location is suitable for these sites. For this purpose, this research presents the feasibility of installing a combined hybrid site in the desired coastal location by predicting the net produced power due to the environmental parameters. For combining these two systems, an optimized array includes ten turbines and ten wave energy converters. The mathematical equations of the net force on the two introduced systems and the produced power of the wind turbines are proposed. The turbines’ maximum forces are 4 kN, and for the wave energy converters are 6 kN, respectively. Furthermore, the comparison is conducted in order to find the optimum system. The comparison shows that the most effective system of desired environmenta... [more]

Tupperwave is a wave energy device based on the Oscillating-Water-Column (OWC) concept. Unlike a conventional OWC, which creates a bidirectional air flow across the self-rectifying turbine, the Tupperwave device uses rectifying valves to create a smooth unidirectional air flow, which is harnessed by a unidirectional turbine. This paper deals with the development and validation of time-domain numerical models from wave to pneumatic power for the Tupperwave device and the conventional OWC device using the same floating spar buoy structure. The numerical models are built using coupled hydrodynamic and thermodynamic equations. The isentropic assumption is used to describe the thermodynamic processes. A tank testing campaign of the two devices at 1/24th scale is described, and the results are used to validate the numerical models. The capacity of the innovative Tupperwave OWC concept to convert wave energy into useful pneumatic energy to the turbine is assessed and compared to the correspon... [more]

For over three decades the “Pendulor” wave energy device has had a significant influence in this field, triggering several research endeavours. It includes a top-hinged flap propelled by the standing waves produced in a caisson with a back wall on the leeward side. However, one of the main disadvantages which impedes its progress is the enormous expense involved in the construction of the custom made typical caisson structure, about a little more than one-quarter of the wave length. In this study, the influence of such design parameters on the performance of the device is investigated, via numerical modelling for a device arranged in an array configuration, for irregular waves. The potential wave theory is applied to derive the frequency-dependent hydrodynamic parameters by making a distinction in the fluid domain into a separate sea side and lee side. The Cummins equation was utilised for the development of the time domain equation of motion while the transfer function estimation meth... [more]

New trends and future prospects for small capacity systems of Renewable Energy-driven DESalination (REDES) are reviewed and assessed in this paper over a nominal desalination capacity range of 3−1000 m3/d. A thorough literature review is reported in order to evaluate current research and developing activities. Outstanding commercial prospects in the near future are identified for two off-grid REDES technologies under development. First, wave energy converters with direct coupling to seawater desalination. Second, solar micro gas turbines with biofuel backup coupled to reverse osmosis (RO) desalination and/or zero liquid discharge water treatment. These systems, as well as mature REDES plants (namely PV/RO and wind turbines/RO), will benefit from forthcoming advances in energy efficiency in the RO process itself. The Closed Circuit RO desalination (CCROTM) concept may be a key configuration for enhancing RE-driven RO desalination. Additionally, opportunities for innovation in seawater R... [more]

The key market drivers for marine energy are to reduce carbon emissions, and improve the security and sustainability of supply. There are other technologies that also meet these requirements, and therefore the marine energy market is dependent on the technology being cost effective, and competitive. The potential UK wave and tidal stream energy market is assessed using ETI’s energy systems modelling environment (ESME) which uses a multi-vector approach including energy generation, demand, heat, transport, and infrastructure. This is used to identify scenarios where wave and tidal energy form part of the least-cost energy system for the UK by 2050, and will assess what Levelised Cost of Energy (LCOE) reductions are required to improve the commercialization rate. The results indicate that an installed capacity of 4.9 GW of wave and 2.5 GW of tidal stream could be deployed by 2050 if the LCOE is within 4.5 and 7 p/kWh for each respective technology. If there is a step reduction to the LCO... [more]

With about a 7% average annual economic growth rate in Vietnam, the demand for electricity production is increasing, and, with more than 3000 km of coastline, the country has great potential for developing wave energy sources to meet such electricity production. This energy source, also known as renewable energy, comes from tides, wind, heat differences, flows, and waves. Both wind and wave energy are considered to have the most potential for energy sources in Vietnam. Just as hydropower projects are controversial due to depleting water resources and regulating floods, nuclear power projects cause safety concerns. To overcome this problem, Vietnamese scientists are considering using abundant wave energy resources for electricity. Nowadays, the ocean energy sector offers many new technologies to help minimize carbon dioxide emissions (CO2) in the living environment. Further, many countries already have wave power plants. In this research, an integrated model, combining the fuzzy analyti... [more]

Linear wave energy converters generate intrinsically intermittent power with variable frequency and amplitude. A composite energy storage system consisting of batteries and super capacitors has been developed and controlled by buck-boost converters. The purpose of the composite energy storage system is to handle the fluctuations and intermittent characteristics of the renewable source, and hence provide a steady output power. Linear wave energy converters working in conjunction with a system composed of various energy storage devices, is considered as a microsystem, which can function in a stand-alone or a grid connected mode. Simulation results have shown that by applying a boost H-bridge and a composite energy storage system more power could be extracted from linear wave energy converters. Simulation results have shown that the super capacitors charge and discharge often to handle the frequent power fluctuations, and the batteries charge and discharge slowly for handling the intermit... [more]

The main purpose of this paper is to analyze the energy production in the Maltese islands, focusing on the employment of renewable energies in order to increase their energy independence. The main renewable source here proposed is wave energy: thanks to a strategic position, Malta will be able to produce electrical energy using an innovative type of Wave Energy Converter (WEC) based on the prototype of a linear generator realized by University of Palermo. The use of this new technology will be able to cut down the electrical energy production from traditional power plants and, consequently, the greenhouse gas emissions (GHG). Wave energy source and off-shore photovoltaic (PV) technology are here proposed. Particularly, the installation of 12 wave farms, for a total installed capacity of 86 MW, will generate about 9.5% of Malta’s energy requirement in 2025, while the installation of 9.6 MW of off-shore PV will generate about 0.73%.

Control of wave energy converters (WECs) has been very often limited to hydrodynamic control to absorb the maximum energy possible from ocean waves. This generally ignores or significantly simplifies the performance of real power take-off (PTO) systems. However, including all the required dynamics and constraints in the control problem may considerably vary the control strategy and the power output. Therefore, this paper considers the incorporation into the model of all the conversion stages from ocean waves to the electricity network, referred to as wave-to-wire (W2W) models, and identifies the necessary components and their dynamics and constraints, including grid constraints. In addition, the paper identifies different control inputs for the different components of the PTO system and how these inputs are articulated to the dynamics of the system. Examples of pneumatic, hydraulic, mechanical or magnetic transmission systems driving a rotary electrical generator, and linear electric g... [more]

This paper establishes a general methodology to calculate the life-cycle cost of floating offshore renewable energy devices, applying it to wave energy and wind energy devices. It is accounts for the contributions of the six main phases of their life-cycle: concept definition, design and development, manufacturing, installation, exploitation and dismantling, the costs of which have been defined. Moreover, the energy produced is also taken into account to calculate the Levelized Cost of Energy of a floating offshore renewable energy farm. The methodology proposed has been applied to two renewable energy devices: a floating offshore wave energy device and a floating offshore wind energy device. Two locations have been considered: Aguçadoura and São Pedro de Moel, both in Portugal. Results indicate that the most important cost in terms of the life-cycle of a floating offshore renewable energy farm is the exploitation cost, followed by the manufacturing and the installation cost. In additi... [more]

A novel tuned heave plate energy-harvesting system (THPEH) is presented for the motion suppressing and energy harvesting of a semi-submersible platform. This THPEH system is designed based on the principle of a tuned mass damper (TMD) and is composed of spring supports, a power take-off system (PTO) and four movable heave plates. The permanent magnet linear generators (PMLG) are used as the PTO system in this design. A semi-submersible platform operating in the South China Sea is selected as the research subject for investigating the effects of the THPEH system on motion reduction and harvesting energy through numerical simulations. The numerical model of the platform and the THPEH system, which was established based on hydrodynamic analysis, is modified and validated by the results of the flume test of a 1:70 scale model. The effects of the parameters, including the size, the frequency ratio and the damping ratio of the THPEH system, are systematically investigated. The results show t... [more]

Wave energy converter (WEC) arrays deployed in coastal regions may create physical disturbances, potentially resulting in environmental stresses. Presently, limited information is available on the nature of these physical disturbance or the resultant effects. A quantitative Spatial Environmental Assessment Tool (SEAT) for evaluating the potential effects of wave energy converter (WEC) arrays on nearshore hydrodynamics and sediment transport is presented for the central Oregon coast (USA) through coupled numerical model simulations of an array of WECs. Derived climatological wave conditions were used as inputs to the model to allow for the calculation of risk metrics associated with various hydrodynamic and sediment transport variables such as maximum shear stress, bottom velocity, and change in bed elevation. The risk maps provided simple, quantitative, and spatially-resolved means of evaluating physical changes in the vicinity of a hypothetical WEC array in response to varying wave co... [more]

An analysis of the variability of wave climate and energy within the Black Sea for the period 1960⁻2011 was made using field data from the Voluntary Observing Ship Program. Methods using wavelet analysis were applied. It was determined that the power flux of wave energy in the Black Sea fluctuates: the highest value is 4.2 kW/m, the lowest is 1.4 kW/m. Results indicate significant correlations among the fluctuations of the average annual wave heights, periods, the power flux of wave energy, and teleconnection patterns of the North Atlantic Oscillation (NAO), the Atlantic Multi-decadal Oscillation (AMO), the Pacific Decadal Oscillation (PDO) and the East Atlantic/West Russia (EA/WR). It was revealed that, in positive phases of long-term periods of AMO (50⁻60 years) as well as PDO, NAO, and AO (40 years), a decrease of wave energy was observed; however, an increase in wave energy was observed in the positive phase of a 15-year period of NAO and AO. The positive phase of changes of EA/WR... [more]