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The growing global demand for sustainable and environmentally friendly energy has stimulated the rapid adoption of renewable offshore energy. However, infrastructure needed for green energy production ironically impacts upon marine species and biodiversity. Consequently, this positional review paper seeks to comprehensively synthesise the prevailing body of knowledge on the impact of offshore energy development on a broad range of marine species. An interpretivist philosophical stance and inductive reasoning was adopted using scientometric analysis to conduct a rich synthesis of extant literature. From an operational perspective, the Scopus database was utilised to search for key terms on the phenomena under investigation and using the VoS Viewer software for the identification of trends using scientometric maps. The analysis reveals that research in this area of science has increased significantly over the last decade but private sector involvement is conspicuous by its absence. Primary concerns among the research community include the impact of energy development on the abundance of species, pollution and biodiversity behaviour and migration. At present, researchers have extensively focused on the impact of offshore wind farms on fish and marine mammals. However, the literature reveals no significant long-term impact upon energy development on most marine species albeit, short-term interference has raised concerns (from sound, disruption of navigation and foraging patterns, and damage of habitat). To minimise short term disruption, researchers have recommended the use of acoustic deterrence during construction, enforcement of protected areas and continued research.

Nowadays, an increase in energy demand, environmental concerns, and the shortage of fossil fuel resources have made energy management researchers explore alternative resources for clean and renewable energy resources. The simultaneous incorporation of a comprehensive set of technical, economic, environmental, and social attributes in decision-making processes is recommended to improve the efficiency and effectiveness of sustainable decisions on energy resource planning. To tackle this challenge, an efficient method is proposed based on the Simultaneous Evaluation of Criteria and Alternatives (SECA) for the optimal selection of renewable energy resources. In the SECA technique, criteria and alternative evaluations are performed simultaneously. The proposed assessment framework is applied in Iran's electricity industry as a real case study, and a two-round fuzzy-based Delphi technique is also adopted to extract the assessment criteria from the experts' opinions. Moreover, the management insights are inferred from sensitivity analysis. According to the study results, solar, wind, biomass, hydroelectric, hydrogen, geothermal, and marine energy resources are sorted in descending order of priority. Finally, the best composite option of sustainable energies encompassing a combination of solar, wind, and biomass energy resources concludes the study.

The depletion of fossil fuel and their impact on the environment due to continual usage for our ever-increasing power needs has forced us to look pro-actively towards other renewable forms of clean energy like wind, solar, ocean energy, etc. Amongst all renewable sources of energy, solar energy is abundantly available throughout the world and can meet the energy needs of our planet if appropriately harnessed. Solar thermal collectors are used to collect solar thermal energy, and then it is transferred to the fluid. The fluid may be air, water, oil, etc. depending on the application. Many researchers are working towards performance enhancement of solar thermal collectors. This article concentrates on solar air collectors and different types of modifications made in the recent past to improve its efficiency. This study is an attempt to summarize and present solar air heaters and various modifications for performance enhancement. The effect of modifications on the Nusselt number, friction factor, and thermohydraulic performance of the solar thermal collector is reported. The present article also discusses the effect of impingement of air on the device thermal efficiency and the geometric modifications. This paper will enable researchers working in this field to get a summary of important work done related to solar thermal collectors.

In this investigation, instrumented mobile platforms are used to spatially map the turbulent flows in Grand Passage, one of the Bay of Fundy's more energetic tidal channels in Nova Scotia, Canada. The aim is to characterize the flow around the PLAT-I floating tidal energy platform developed by Sustainable Marine Energy Canada (SMEC). GPS-tracked surface drifters equipped with fast-sampling acoustic Doppler current profilers (ADCPs) provide turbulence-resolving vertical profiles of velocity and turbulent kinetic energy dissipation rate along drifter trajectories, while vessel-mounted ADCP transects complement the mean flow velocity measurements. These data are used to construct tridimensional quasi-synoptic maps of mean velocities and turbulence parameters for several stages of the tide around PLAT-I's location including peak ebb and flood currents. The data set includes measurements under natural flow conditions, and while the turbines installed on PLAT-I were both not operational and operational. The measurement techniques and resulting maps successfully capture the spatial and temporal structure of the flow for unsteady conditions for various tidal conditions. The combined wake of the four 6.3 m operational PLAT-I turbines was measured for a single tidal stage. Closer to the turbines, the vertical extent of the wake is about 6 m (approximately one turbine diameter), increasing with distance downstream, while the maximum observed velocity deficit is 26% relative to not operating conditions, decreasing with distance downstream.

Most tidal energy site studies concentrate on resource size; few examine other factors that may be of equal or even greater importance in determining site feasibility for tidal turbine array deployments. These factors include aspects such as electrical grid proximity, water depth, the location of marine protected areas, pre-existing users, environmentally significant regions and other restrictions. Using these factors, a more holistic approach to site selection was conducted for Australian waters using a Multi-Criteria Evaluation (MCE) process. This MCE method uses standardized factors combined with weighted linear combinations to calculate a site suitability index, where each factor is multiplied by a weight of relative importance. A sensitivity analysis on the factor weighting was performed to ensure the suitable selection of weighting factors to reduce conformation bias. The developed MCE model identified three promising locations in Australia, with contiguous areas in regions to the north of Broome Western Australia of 534 km2, the Banks Strait region northeast of Tasmania of 67 km2, and the Clarence Strait located in the Northern Territory of

In this paper, a strategic decision making model for the sustainable development of marine renewable energy is proposed, and a specific application to the United Kingdom (UK) is demonstrated. As an island nation the UK benefits from significant marine energy potential which is providing an increasing contribution to UK's renewable energy portfolio. The paper investigates the question of how decision makers can be aided to reach a decision on which types of marine renewable energy projects should be chosen for development given that strategic energy planning is subject to a number of uncertain parameters and multiple sustainability objectives. In this context, the contribution of this paper lies in the combination of renewable energy portfolio selection and the application of multi-objective methods. Interval coefficient goal programming models are adopted in order to address the impreciseness and uncertainty associated with the goals and coefficients of the models in the context of renewable energy selection. The potential renewable energy projects are clustered in order to aid the decision making process and preferential weight sensitivity methods are employed. Conclusions are drawn for optimistic and pessimistic scenarios in the context of UK marine renewable energy planning.

Offshore wind and wave energy resources are possibly the last significantly untapped renewable energy resource, and could play a significant role in mitigating the impacts of climate change via the generation of renewable electricity. While often considered independently, there are significant technical advantages to co-deployment of wave and offshore wind technologies, and will be future competition for limited marine real estate, so there is a distinct need to development holistic assessments of these offshore resources. Currently, offshore wind and wave energy resource assessments have been conducted as independent parallel processes, with little interaction with regard to best practices, lessons learnt, or opportunities to create compatible methodologies for future utilization by the broader marine energy sector. Based on the latest technical specifications from the International Electrotechnical Commission, and the highest fidelity publicly available datasets, the offshore wind and wave conditions at the PacWave site off Oregon, USA were quantified. At the 70m depth site, the results clearly show a significant untapped energy resource an annual average wave energy flux of ∼35 kW/m and a mean average wind speed of 7.8 m/s; suitable for significant offshore wind (fixed and floating) and wave energy technology deployment The offshore wind and wave energy resources both show significant seasonal variation, with offshore wind also featuring a consistent daily profile during summer. Finally, opportunities and challenges associated with developing a holistic assessment of offshore marine energy resources were discussed and recommendations provided.

Surrogate models maximize information utility by building predictive models in place of computational or experimentally expensive model runs. Marine hydrokinetic current energy converters require large-domain simulations to estimate array efficiencies and environmental impacts. Meso-scale models typically represent turbines as actuator discs that act as momentum sinks and sources of turbulence and its dissipation. An OpenFOAM model was developed where actuator disc k-e turbulence was characterized using an approach developed for flows through vegetative canopies. Turbine-wake data from laboratory flume experiments collected at two influent turbulence intensities were used to calibrate parameters in the turbulence-source terms in the k-e equations. Parameter influences on longitudinal wake profiles were estimated using Gaussian process regression with subsequent optimization minimizing the objective function within 3.1% of those obtained using the full model representation, but for 74% of the computational cost (far fewer model runs). This framework facilitates more efficient parameterization of the turbulence-source equations using turbine-wake data.

Deployment of floating solar photovoltaic installations (floatovoltaics) is advancing, with various designs beginning to appear in a range of marine environments. Insight from freshwater floatovoltaics is not readily transferable offshore, and so lessons from other marine energy infrastructure are used to highlight how the marine environment may impact floatovoltaics, how the floatovoltaics impact the environment (both positively and negatively) and the likely societal response. It becomes clear that research to understand the environmental and societal implications of floating solar in the marine environment must proceed in parallel with investigations of the technical and economic feasibility.

Of current mathematical and physical interest are equatorial waves, in the setting of an azimuthal two-dimensional inviscid flow in a two-layer fluid with a flat bed and a free surface. The Hamiltonian formulation for nonlinear governing equations is adequate for structure-preserving perturbations, at the linear and at the nonlinear level have been derived. Since the ocean energy is concentrated in the long-wave propagation modes, it is of interest to pursue an in-depth analysis of long waves. In the present paper we will consider the process in the absence of vorticity.

Maneuverability is one of the key indicators for the marine power plant. In order to improve the maneuverability, a speed controller using model predictive control (MPC) technique for a marine three-shaft gas turbine is designed in this paper. The linear parameter-varying(LPV) model is established by analyzing the performance of gas turbine. Make use of the LPV model as the prediction model to design a model predictive controller. On that basis, the Kalman filter is combined with MPC algorithm to improve the robustness of the speed controller. The simulation results show that the designed speed controller can effectively improve the maneuverability of marine gas turbine.

This paper provides a feasibility study on a low cost system called Hydrokinetic Wells turbine for surface wave energy conversion without using plenum chambers. The elimination of the plenum chamber and its complicated valve systems can reduce the expenses of wave energy conversion up to 23%.The feasibility process were done for high and low frequency conditions. For the low frequency waves, we offer the 300 rpm angular velocity as an optimum selection for further studies. For the high frequency condition a reliable analytical approach based on validated methods was developed. The analytical results indicate that a wells turbine with 60 cm diameter could produce up to 1600 Watts power in high frequency waves. The efficiency and power coefficient values in high frequency condition are less in compared with low frequency situation, nevertheless the vast usage of the small scale and elimination of the plenum chambers can reduce the total cost of the conversion. The abundant availability of high frequency surface waves is a motivation for developing Hydrokinetic Wells turbine farms to harvest a great source of clean energy with lower cost levels.

Offshore oil exploitation is expanding worldwide in response to the increasing demand for global energy. The long-term acquisition of information on offshore oil production is essential to solve geo-political conflicts and to control marine pollution. However, such information is either dispersed among different authorities or may not even exist. Night-Time Lights (NTL) data has advantages in terms of synoptic coverage and repeatability, providing the opportunity to collect information about marine resources and energy. Until recently, estimating offshore oil production using NTL data was still challenging, largely due to the inability of distinguishing the NTL of oil and gas production. Here, we present an approach for retrieving the spatio-temporal distribution of offshore oil production using DMSP-OLS annual composites. Starting with the geo-locations of offshore platforms, we first propose a Method for Platform Type Classification (MPTC) to discriminate oil platforms from gas platforms. A Model for Oil Production Estimation and Assignment (MOPEA) was then designed by correlating the sum of brightness from oil platforms with offshore oil production. Given worldwide data availability, the offshore regions of the United Kingdom (UK) were used as the initial study area. The principal results are as follows: (i) the overall accuracy of the MPTC and the relative error of the MOPEA were 87.8% and 11.5%, respectively, and the production of each oilfield was in order of magnitude agreement with reality; (ii) there were 365 oil platforms and 258 gas platforms in the UK during 1992–2013, with a distinct spatial distribution north and south of the latitude of 55°N; and (iii) the offshore oil production of the UK declined substantially during 1992–2013, from 9.92 × 107 to 5.63 × 107 sm3, despite an increase in the number of oilfields from 39 to 120 plots; this was mainly because the loss of production in previously highly productive oilfields was too great to be offset by the increased number of low production oilfields. The regional transferability of the MPTC and MOPEA was then validated with reference to three other offshore regions (the Gulf of Guinea of Nigeria, the South China Sea, and the northern Gulf of Mexico of the USA) with satisfactory results. In addition, the MPTC and MOPEA are demonstrated to be capable of extension to the NPP-VIIRS products, paving the way for future applications.

As a way of exploitation and utilization of ocean energy, the waterjet pump is used in a wide range of high-speed marine vessels over 30 knot. This paper aims to investigate the mechanism of the energy loss and pressure fluctuations caused by the non-uniform inflow for a waterjet pump. Unsteady internal flows inside the waterjet pump are simulated using the Reynolds-averaged Navier-Stokes equations with the SST k-ω turbulence model. The predicted pump head and efficiency are in reasonable accordance with the experimental data. The inflow non-uniformity would decrease the hydraulic head, efficiency and increase the axial force fluctuations in the impeller, causing large pulsations in the unsteady energy performance. Based on analyses of the energy loss, the turbulent kinetic energy production and the diffusion of the Reynolds stress are major sources of the energy loss in the waterjet pump. The non-uniform inflow induces a dramatic energy loss in the intake duct and diffuser with an apparent flow separation observed near the trailing edge of the diffuser blade. Due to the inflow non-uniformity, the pressure fluctuates violently at the impeller rotating frequency (fn) in the intake duct, impeller and near the diffuser inlet, but a dominant frequency of 2fn is generated by the unsteady flow separation near the diffuser outlet.

Ocean waves are a huge and largely untapped resource of green energy. In order to extract energy from waves, a novel wave energy converter (WEC) consisting of a floating, hollow cylinder capped by a roof with a variable aperture is presented in this paper. The power take-off (PTO) system is composed of a linear generator attached to the seabed, driven by the heave motion of the floating cylinder through a tether line. The air pressure within the cylinder can be modified by adjusting the roof aperture. The hydrodynamic characteristics of this WEC are investigated through an analytical model based on potential flow theory, in which the wave diffraction/radiation problems are coupled with the air pressure fluctuation and PTO system. Analytical expressions are derived for the maximum power absorbed by the WEC under different optimization principles, revolving around the PTO damping, roof aperture damping and non-negative mooring stiffness. We find that the best power absorption is obtained when the aperture is either completely open or entirely closed, depending on the wave conditions. Intermediate values of the aperture are useful to minimize the heave motion and thus ensure survivability under extreme sea states.

Deep ocean water (DOW) is a renewable alternative to the many sustainability challenges that the Caribbean faces today. DOW can provide seawater air conditioning (SWAC) for buildings and greenhouses, provide electricity through an ocean thermal energy conversion plant (OTEC), and provide nutrients for aquaculture and cosmetic industries. However, today the implementation of DOW technologies in the Caribbean is inexistent, and studies about DOW potential in the Caribbean are limited. We present a methodology for estimating the practical potential of a city while considering constraints in ocean currents, temperature, and salinity. We applied the methodology to five cities in the Caribbean and found that the average potential is about 50 m3/s per city, enough to supply more than 100% of a city’s demand for air conditioning and 60% of its demand for electricity. We also estimated the monthly availability of DOW resource, with maximum extraction potentials between December to March, and minimum values between August to October. These estimations serve as input for future feasibility and design studies on DOW technologies in the Caribbean. Given the assumptions, the found potential may be underestimated; thus, the results of this study can be considered as a minimum reference value, complementary to the maximum theoretical potential found in previous studies.

A near-shore oscillating water column (OWC) device with a surging front-wall, which can be conveniently mounted on various cliff-like shores or coastal structures, is proposed to improve the pneumatic efficiency of wave energy extraction. Based on linear potential theory, the interaction between ocean waves and the OWC device is solved by the matched eigenfunction expansion method (MEEM). Auxiliary functions, expanded in orthogonal polynomials, are introduced to approximate the singular behaviors of fluid field in the vicinity of the salient corner. The effects of the dimensions of lip-wall and the stiffness of the spring on the hydrodynamic performances, such as the response amplitude operator (RAO), average inside free-surface elevation, phase difference between the motions of lip-wall and inside free-surface, and optimum conversion efficiency are taken into consideration. The numerical results show that the existence of a freely surging lip-wall can considerably improve the performance of the device over a wider bandwidth, especially for the intermediate and short wavelength regimes, compared with the fixed one.

Morocco has an exceptional maritime potential especially on its two 500-km Mediterranean and 300-km Atlantic coastlines. The assessment of this potential for marine currents, wind and temperature is largely necessary for the various activities related to the coastline: fishing, exploitation of aggregates, tourism, transport services, desalination and marine renewable energies. Morocco is engaged in a policy of preservation of the environment, the fight against global warming and reducing the emission of greenhouse gases. It is reviewing its 'electric mix' and promoting all renewable energies including marine energy. The results of this study show clearly that Morocco can boast of the potential of its Atlantic and Mediterranean coasts, thanks to the strong winds that blow in the North Atlantic and around the city of Dakhla, at sea currents speeds in vicinity of the Strait of Gibraltar and the difference in temperature between the surface and deep sea. We are particularly interested in the study of the behavior of the marine current, temperature and wind. This is based on monthly data provided by a credible website with free access and statistics from the MATLAB Software.

As one of the largest energy-consumption nations, the South Korean government has recently invested in the deployment and commercialization of various renewable energy sources to reduce the environmental impacts of fossil fuel-based energy sources. Thus, in order to investigate the likelihood the government will default on the investment of research and development (R&D) in the renewable energy industry, this study utilizes a system-dynamics approach to develop a default-prediction model based on the Black-Scholes-Merton model, while investigating the interactions of uncertainty factors and the impacts of the probability of default (PD) on renewable energy production and carbon emission reduction amounts from 2017 to 2030. The results of this study indicate that R&D investments in marine energy (2.64%) has a high default risk, while the use of waste energy (46.95 B kg CO2) results in the largest reduction in the amount of carbon emissions. In addition, the results show that the PD of the R&D investment decreases when the uncertainty of the unit price, the R&D investment amount, and the renewable energy production amount have increased. Further, the results of a Monte Carlo simulation indicate that the PD of the R&D investment is not greatly affected by the risk-free interest rate.

A call for flexible power generation for a wide range of applications is gradually increasing, making Small Modular Reactor (SMR) a heat topic, especially for marine power. Unlike normal reactors, marine reactors demand a long lifetime up to 15 years without refueling, a high power-density and also a higher reliability and security. The standard PWR cannot achieve this goal. Here, a new 13 × 13 assembly loaded with Accident Tolerant Fuels (ATFs): U3Si2 – FeCrAl system, is proposed and analyzed on an assembly-level. U3Si2 is one kind of ATFs with high heavy metal density and thermal conductivity. It has a lower parasitic absorption. FeCrAl has a great radiation resistance, corrosion resistance and thermodynamic properties although with serious neutron penalties. It is currently the fastest researched accident tolerant cladding material. The fuel enrichment of this assembly is raised to 13%, prolonging the burnup to up to 95,000 MWD/tU, which means that the reactor can survive for more than 15 years at its rated power density. Using 15 B4C control rods can help achieve the beginning-of-life cool shutdown (K

Indonesia has many archipelagos with long and complex coastlines that connect to the Pacific Ocean in the northeast and to the Indian Ocean in the southwest. Several species of fish in this area are easily attracted to fish aggregating devices (FADs), which are a type of environmentally friendly artificial ocean infrastructures. We investigated characteristics of tidal currents in the Indonesia archipelagos and suitably designed a small-scale tidal-current turbine with an FAD to independently supply electric power to the archipelagos. Moreover, we estimated the amount of electric power generated by the setup. The results indicate that the tidal currents in narrow straits are considerably higher in archipelagos, such as the Maluku and Nusa Tenggara Islands including Bali Strait. Lombok Strait also exhibited the maximum tidal-current velocity of 4 m/s. The small-scale tidal-current turbine was theoretically and numerically designed to utilize the tidal current specific to the Indonesian archipelagos. We estimated the amount of electric power generated by the 2.2-m-diameter turbine with 10-kW class to adjust to the specific archipelagos.

The performance assessment of industrial marine energy converters involves the integrated treatment of their hydrodynamic design and the optimization of their device hulls. Nowadays, such tasks require extensive experimental work and simulation plans, consuming considerable resources and time. In this comprehensive review of integrated approaches to numerical and experimental testing, the advantages and disadvantages of existing tools, from full-scale prototype and wave tank models to Computational Fluid Dynamics (CFD) and potential flow simulations, are all analysed. Likewise, current challenges such as experimental scale effects, numerical viscosity, and turbulence treatment are all studied. The novelty of this research is an integrated approach that employs experimental wave tank tests to validate a numerical wave tank model based on CFD that serves to calibrate a fast potential flow solver with Morison's correction terms. The model allows running, on tight resources, the necessary simulation for the design and optimisation of marine energy converters under multiple sea state conditions. Given the operating regimes of conventional marine energy converters, the results show that the influence of turbulence may be small, due to the unsteady nature of the oscillatory boundary layer flows.

Variability in the predicted cost of energy of an ocean energy converter array is more substantial than for other forms of energy generation, due to the combined stochastic action of weather conditions and failures. If the variability is great enough, then this may influence future financial decisions. This paper provides the unique contribution of quantifying variability in the predicted cost of energy and introduces a framework for investigating reduction of variability through investment in components. Following review of existing methodologies for parametric analysis of ocean energy array design, the development of the DTOcean software tool is presented. DTOcean can quantify variability by simulating the design, deployment and operation of arrays with higher complexity than previous models, designing sub-systems at component level. A case study of a theoretical floating wave energy converter array is used to demonstrate that the variability in levelised cost of energy (LCOE) can be greatest for the smallest arrays and that investment in improved component reliability can reduce both the variability and most likely value of LCOE. A hypothetical study of improved electrical cables and connectors shows reductions in LCOE up to 2.51% and reductions in the variability of LCOE of over 50%; these minima occur for different combinations of components. The research leading to this publication is part of the DTOceanPlus project which has received funding from the EuropeanUnion's Horizon 2020 research and innovation programme under grant agreement No 785921. Funding was also received from the European Community's Seventh Framework Programme for the DTOcean Project (grant agreement No. 608597). The contribution of Sandia National Laboratories was funded by the U.S. Department of Energy's Water Power Technologies Office. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. The image of the RM3 device, in Fig. 7, was reproduced with the permission of Sandia National Laboratories

Ocean energy technologies are still at an early stage of development; only a handful of concepts are being invented and tested worldwide. The environmental impact of these devices is not always taken into account, mainly because of the prevailing uncertainty regarding its assessment. It is vital that attention is paid to the mitigation of potential negative impacts on physical and biotic marine systems. In this study, the direct and indirect effects of ocean energy projects on biophysical systems, and their interactions, are identified from an analysis of current literature on the subject. A tool that could be applied to any ocean energy project at any stage of an EIA is then proposed from a framework designed to evaluate the widely varying impacts of devices. This framework uses a categorisation of the environmental impacts of MRE devices (biophysical, chemical and socio-economic), based on the technology used and the device location. It is hoped that this tool will facilitate the identification of the potential environmental impacts of MRE devices and thus serve as a guide to quantitatively assess these impacts.

Owing to the depletion of oil reserves and the low efficiency of traditional deep-water semi-submersible drilling platforms, the application of photovoltaic generation and energy storage systems in marine power systems has been increasingly attracting attention. However, the intermittent and uncertain nature of solar energy brings crucial challenges in maintaining stable and sustainable operations. Furthermore, unlike land-based power systems, the deep-water semi-submersible drilling platform depends on a dynamic positioning system to be fixed in an area of deep water for producing oil, but irregular and stochastic waves make the outputs of a dynamic positioning system uncertain, increasing the difficulty and complexity of energy management. This paper develops a novel hybrid day-ahead probabilistic scheduling method to reduce the total fuel cost of the whole system and improve the energy efficiency; the method combines Taguchi's orthogonal algorithm with particle swarm optimization and a probabilistic load flow method. A detailed model of the deep-water semi-submersible drilling platform is established to validate the proposed method, which is compared with various classical methods. With the help of the proposed method, the total operation cost and greenhouse gas emissions are reduced from $7562.52 to $7333.68, and from 18.95 tons to 16.81 tons, respectively. Furthermore, compared to the two-point estimation method, the experimental times drops by half, which minimizes the computational burden. The simulation results clearly demonstrate the necessity for day-ahead energy scheduling, and the advantages of the proposed method.

Wave energy development continues to advance in order to capture the immense ocean energy available globally. A large number of wave energy conversion concepts have been developed and researched to date but we are still not able to see a convergence of technologies. This provides the requirement and additional opportunity for further research. This paper provides a review and discusses the development of the OWC concept of wave energy converters in general and the evolved variation of the M-OWC more specifically. The review outlines the increased potential of the M-OWC concept and its current state through its advancement in recent years. Although still under development the M-OWCs have the potential to provide promising results, through the various innovative concepts under consideration, and support the progression and further development of wave energy as another serious contender in the renewables energy mix.

Developing design tools to make more information available sooner is desirable because decisions of the greatest impact are made in early stages of ship design. Moreover, there is still room for improvement in the optimisation of energy system selection considering an integrated approach. Therefore, the present work aims to provide a comprehensive early-stage approach to optimise the design, synthesis and operation of a marine energy system for liquified gas carriers, considering their economic and technical aspects, and also weather along the route. Constraints are used to avoid propellers that could present issues concerning strength, cavitation and vibration. Various propellers, engines and operational profiles can be assessed with this approach. A differential evolution optimisation algorithm that maximises the net present value is applied. This part of the study details the approach that we have developed, while the case study, results and discussion, and the main conclusions are given in Part B. Different parameters can be set up in each route-track, which enables various operational profiles and sea conditions to be considered to seek the highest net present value. The proposed approach is expected to be able to automatically search a broad range of possible alternatives and then make small refinements to achieve the optimal arrangement.

With the development of marine energy in full swing, an increasing number of pipelines are being installed in deep-sea areas, which inevitably pass through extremely complex topographic conditions, to form natural sections of suspension over submarine canyons. The seabed is easily eroded and shaped by active deep-sea bottom currents and watercourses, resulting in different span heights for pipelines originally laid on the seabed. In particularly, deep-sea geological hazards frequently occur, and submarine landslides seriously threaten the safe operation of the pipelines. To address these problems, an improved numerical analysis method combined with low-temperature rheological models of landslides and the optimization design method of the geometric model, is developed to simulate the landslides’ impacts on pipelines. Based on these, the effect of the span heights on the pipelines’ impact forces induced by deep-sea landslides is systematically investigated, and three modes of the forces on pipelines under the impact of landslides and related mechanism are proposed. Further, the span height ratio is put forward, and four formulas for evaluating the forces on pipeline are established. Through the analysis of calculation results, the lift force coefficient even increases nearly 20 times considering different span heights. This research provides a theoretical basis for the design and protection of deep-sea pipelines.

This work discusses and provides a critical expose of some of the newly emerging renewable energy technologies with special concentration on marine energy generation. The work shows that there are several promising new developments in harvesting marine energy and it examines some of these technologies and discusses their advantages and some of the obstacles that are impeding the commercialization of these emerging technologies. This includes wave energy harvesting, tidal energy harvesting, ocean thermal energy and the utilisation of salinity gradients for electricity generation. The work emphasises the fact that these new emerging technologies are currently at the developing stages and has a long way to go before successful commercialization and wide adoption become the norm. The work stresses the need for more research and developmental work to address several of the technical issues that need to be addressed including devices designs, their installation and maintenance, the infrastructure which includes the grid and power transmission as well as losses, their use in arrays, and their longevity. This work underlines the lack of reliable studies on the long term impacts of these technologies on both the marine environment and nearby habitations and highlights the need for proper environmental and social impact assessments of these technologies. The work concludes that combination of technical, policy and economic advances will enable marine energy technologies to play a large role in combination with currently adopted non-pollution renewable energy resources to provide the world population with their energy needs and contribute to affecting significant reduction in the use of non-renewable and other polluting fuels worldwide.

The offshore renewable energy sector has challenging requirements related to the physical simulation of the ocean environment for the purpose of evaluating energy generating technologies. In this paper the demands of the wave and tidal energy sectors are considered, with measurement and characterisation of the environment explored and replication of these conditions described. This review examines the process of advanced ocean environment replication from the sea to the tank, and rather than an exhaustive overview of all approaches it follows the rationale behind projects led, or strongly connected to, the late Professor Ian Bryden. This gives an element of commonality to the motivations behind marine data acquisition programmes and the facilities constructed to take advantage of the resulting datasets and findings. This review presents a decade of flagship research, conducted in the United Kingdom, at the interfaces between physical oceanography, engineering simulation tools and industrial applications in the area of offshore renewable energy. Wave and tidal datasets are presented, with particular emphasis on the novel tidal measurement techniques developed for tidal energy characterisation in the Fall of Warness, Orkney, UK. Non-parametric wave spectra characterisation methodologies are applied to the European Marine Energy Centre's (EMEC) Billia Croo wave test site, giving complex and highly realistic site-specific directional inputs for simulation of wave energy sites and converters. Finally, the processes of recreating the resulting wave, tidal, and combined wave-current conditions in the FloWave Ocean Energy Research Facility are presented. The common motivations across measurement, characterisation, and test tank are discussed with conclusions drawn on the strengths, gaps and challenges associated with detailed site replication.

Energy is currently the basis for development in different areas worldwide. Traditional sources of energy such as coal, oil, and nuclear energy have serious repercussions on the environment and are non-renewable energies. Therefore, renewable energy, like solar, wind, and marine energy, are alternatives. Egypt is considered an important country that has climatic averages allowing the exploitation of renewable energy. Solar energy is available in Egypt, especially in Upper Egypt, throughout the year. Different models have been created to estimate and predict the global solar radiation intensity due to the shortage of measuring stations. This study presents a mathematical model to estimate and predict the global solar radiation intensity in Egypt. This model is compared and validated against published measurements of global solar radiation intensity. Furthermore, this study introduces a hybrid system used to produce hydrogen (photovoltaic generator–PEM electrolyzer). Modelling and simulating methods is done by running a flowchart in MATLAB to minimize the losses in the system and increase the quantity of hydrogen produced. The simulation includes the global solar radiation estimation and the photovoltaic generator–PEM electrolyzer. The experiment was conducted in March in Suez city, Egypt. The results obtained showed that the model of global solar radiation gives a good prediction for estimating the intensity of global solar radiation in Egypt. Furthermore, they concluded that there is a significant improvement in system performance that signifies an increase in the volume of hydrogen produced by the system. The whole model is simulated, and the simulation results fit the experimental data very well. The electrolyzer is powered by a PV panel and is modelled, sized, and experimentally validated.

Wave energy is one of the most promising marine energy resources in terms of the scale of the resource, but there remains little technology convergence and costs remain at near- prohibitive levels. Of many wave energy converter (WEC) concepts that have been developed over the years, the oscillating water column (OWC) stands out for its simplicity and low maintenance cost. Quite some experience of actual OWC operation has been gained to date from small, stand-alone pilot schemes. One way to reduce costs is the integration of an OWC-WEC into a breakwater, enabling some degree of cost-sharing between energy and harbour or coastal defence functions. A major problem encountered during the design of an OWC-WEC scheme remains the uncertainty in the wave loads, with their critical influence upon capital cost. A model to estimate forces acting on an OWC chamber in a caisson breakwater is proposed in this paper. Horizontal forces on the front (curtain) wall and the rear (in-chamber) wall are predicted. In addition, and unlike a conventional caisson breakwater, vertical forces acting on the caisson chamber ceiling will have considerable effect on sliding and overturning characteristics of the breakwater structure. The proposed model enables the prediction of chamber pressures which in turn influence the chamber vertical force. The new model has been compared with results from large scale physical model measurements from tests carried out in the very large wave channel, GWK, in Hannover (Germany). Forces under both regular and irregular wave conditions were measured. The comparisons show that the model fits well with the test results to the factor of 1 ± 0.2 for the regular wave cases and to the factor of 0.8 ± 0.2 for irregular wave cases. This model will enable the structural design of caisson breakwater-integrated OWCs to be approached with uncertainties reduced to those comparable with conventional caisson design.

Representation of the marine environment is key for reliable coastal hydrodynamic models. This study investigates the implications of common depth-averaged model configuration choices in sufficiently characterising seabed geometry and roughness. In particular, applications requiring a high level of accuracy and/or exhibiting complex flow conditions may call for greater detail in marine environment representation than typically adopted in coastal models. Ramsey Sound, a macrotidal strait in Pembrokeshire, Wales, UK is considered as a case study. The site contains various steeply inclined bathymetric features, including a submerged pinnacle named Horse Rock and a rocky reef called “The Bitches”. The available energy in Ramsey Sound's tidal currents has attracted attention from tidal energy developers. There is interest in accurately modelling the energetic hydrodynamics surrounding its pronounced bathymetry. The coastal flow solver Thetis is applied to simulate the flow conditions in Ramsey Sound. It is shown that notable prominent bathymetric features in the strait influence localised and, most importantly, regional hydrodynamic characteristics. “The Bitches” consistently accelerate flow in the strait while Horse Rock induces a notable wake structure and flow reversals. The model is calibrated against bed- and vessel-mounted Acoustic Doppler Current Profiler (ADCP) observations, by altering seabed roughness parameterisations. A spatially variable and locally scaled Manning coefficient based on diverse seabed classification observations is found to improve model performance in comparison to uniformly applied constants, the latter a more common approach. The local impact of altering the Manning coefficient configuration is found to be greatest during spring flood periods of high velocity currents. Meanwhile, the effect of coarsening the computational mesh around bathymetric features towards values more typically applied in coastal models is investigated. Results indicate severe misrepresentation of seabed geometry and subsequent wake hydrodynamics unless refined to a mesh element size that adequately represents Horse Rock and “The Bitches”.

According to the actual situation of China’s oil imports and transportation, the Middle East route was selected as the research object. Based on Multi-Agent modeling and simulation method, this paper is going to start at the micro level to simulate the energy transport process. Select oil carrier, pirate and hurricane as the agents after analyzing the security factors influencing China’s marine energy channel; build a multi-agent model of China’s marine energy channel (Middle East route) with agents’ attributes and interaction rules; design and conduct simulation program on NetLogo platform. Three experimental schemes are designed to verify the model validity and study the inherent and actual safety factors’ impact on China’s marine oil imports. The result shows the simulation model is validity; the quantity of China’s VLCC is far from carring all the oil transportation on the Middle East route; the increase in the number of tankers is usually lower than that in the total amount of oil imports, while the raise of pirates and hurricanes will cause a greater reduction on oil imports.

This article investigates whether Maritime Spatial Planning (MSP) –which promotes the integrated planning and management of seas and oceans– can play a role in creating increased integration between the EU's renewable energy policy and the potentially conflicting rules on the protection of habitats, species and water. The article focuses on innovative ocean energy (tidal stream, wave and salinity gradient energy). It can be said that there is a possible lack of integration between the Renewable Energy Directive and the EU rules on the protection of habitats, species and water: the Habitats Directive, the Birds Directive, the Water Framework Directive and the Marine Strategy Framework Directive. The role that MSP could play in solving this is assessed with regard to the following two legal issues that reflect the said lack of integration: 1) while there are derogation clauses, there is no obligation for Member States to apply these clauses and to undertake a balancing act between ocean energy, on the one hand, and the protection of habitats, species and water, on the other; 2) even if these clauses are applied, it remains unclear how much weight Member States should attach to ocean energy under a subsequent balancing act. The concept of Maritime Spatial Planning in theory is very suitable for guaranteeing that the interests of both renewable energy policy and environmental policy are duly taken into account in licensing procedures and management measures. The contribution that MSP can make towards increased integration is, however, strongly dependent on the way MSP is interpreted on the Member State level. This is illustrated by a discussion of the differences in the current MSP approaches in Scotland and the Netherlands. This article concludes that Maritime Spatial Planning may –if certain conditions are fulfilled– be a suitable way to create a necessity to balance the EU's habitats, species and water protection rules with (ocean) renewable energy projects, on different levels of governance. Nevertheless, it also concludes that MSP alone cannot guarantee a balancing act that represents the goals of the Renewable Energy Directive and those of the aforementioned environmental directives in an equal manner. This article proposes to link MSP to detailed renewable energy plans per Member State in order to solve this issue.

The present work aims to provide a comprehensive early-stage approach to optimise the design, synthesis and operation of a marine energy system for liquified gas carriers, considering their economic and technical aspects, and also weather along the route. Part A of this work details the approach that we have developed while Part B will summarise the first part, it will then describe the case study, results and discussion, as well as the conclusion. Various propellers, 16 engines and 4 operational profiles are assessed. In this part, we will apply a differential evolution optimisation algorithm, whose objective function will be maximised as the net present value. The case study is designed to use a liquefied natural gas carrier of 175,000 m3 sailing between Lake Charles (USA) and Tokyo Bay (Japan), via the Panama Canal. All of the suitable matchings for 15,023 propellers are found. This approach shows a gain of 22% between the worst individual of the initial population and the worst individual of the final population. The required brake power is approximately 22% higher for rough weather than for still water. A difference of over 120% was found by comparing varied matchings of economic scenarios and fuel profiles. Our approach shows a significant gain and highlights the value of exploring a broad range of energy system configurations in an integrated manner, especially considering the weather conditions.

Ocean Energy (OE) industry would contribute to the sustainable development in China. However, Chinese OE industry is still in early stage. Effective policy system is needed to accumulate the industrialization. This article mainly focuses on OE policies and is intended to render constructive suggestions for the establishment and reform of Chinese OE policy system. An overview of current policy status both in the nations possessing relatively mature OE industry and in China is given. Based on the overview, the corresponding policy improvement measures are commended, including launching an accurately long-termed national OE development roadmap and special law, polishing up feed-in tariffs and subsidy system, introducing renewable tradable renewable certificate system.

International audience; Ocean Energy Europe has estimated that 100 GW of ocean energy capacity (wave and tidal) could be deployed in Europe by 2050. Along with the European targets it is expected that large farms of Wave Energy Converters (WECs) will be installed in the sea and, as part of the consenting process for their installation, it will be necessary to quantify their impact on the local environment. The objective of this study is to improve the assessment of WEC farms impact on the surrounding wave field (wake effect) through the use of a numerical coupling methodology. The methodology consists of a Boundary Element Method (BEM) solver to obtain the wave perturbation generated by the WEC farm for the near-field accounting for the wave-body interactions within the farm whilst a Wave Propagation Model (WPM) based on the mild-slope equations determines the wave transformation in the far-field. The near-field solution obtained from the BEM solver is described as an internal boundary condition in the WPM and then it is propagated throughout the WPM numerical domain. The internal boundary is described by imposing the solution of the surface elevation and velocity potential at the free-surface at each instant of time along a line surrounding the WEC farm.As a case study the methodology was applied to flap type WECs that are deployed in shallow water conditions. The validation of the technique was done first for a single flap and then for a farm of 5 flaps. Once validated, a realistic scenario was assessed by quantifying the impact of irregular sea states composed of long crested waves on a large WEC farm composed of 18 flaps and located on a real bathymetry. The irregular waves were obtained by superposing the regular wave field solutions for all wave frequencies represented in the considered sea state based on the linear water wave theory. Within the limits of this theory these simulations demonstrate the versatility of the methodology to accurately represent the impact of a WEC farm on the surrounding wave climate. The influence of the peak period and the spacing between flaps on the WEC farm wake effect was assessed as well.

New floating devices are emerging thanks to a highly active marine renewable energy sector. These concepts, featuring floating offshore wind installations as well as other projects in the wave energy sector require innovative mooring systems. Therefore, a complete analysis of this element is required to achieve a successful design. This paper investigates the behaviour of mooring systems based on catenary configuration thanks to a detailed experimental program. Tests to characterize the properties of the mooring lines, and geotechnical and hydrodynamic trials were also performed on a 1:40 laboratory scale. Mooring truncation problem is normally faced by the researchers working on model testing of mooring lines in deep water, because the depth of the lab is typically small. However, it does not seem to be a problem for offshore floating renewable energy devices which are usually in relatively shallow water. The influence of catenary weight, imposed displacements at the fairlead, wave-current loads and different types of sea bottom friction on the mooring systems were analysed in terms of tensions, movements and shape of force-displacement curve. However, scaling of the sea bottom and the mooring line interaction is a challenge. Although the damping effect was investigated and compared under different movement conditions, the conclusions achieved can be upscale to real scale but it must be noticed that there are limitations due to scale effect issues. A total of 111 test were performed. The influence of the hydrodynamic inertia and drag is negligible on long wave and slow motions, while they have more importance during shorter waves and quick motions. The results reveal the importance of acceleration in the movement being possible to distinguish dynamic and quasi-static performance depending on the acceleration of the mooring line.

The effect of an upstream bluff body on energy harvesting performance of a heaving and pitching hydrofoil is investigated numerically using a two-dimensional immersed boundary method at R e = 1000 . The presence of the upstream body changes flow structure around the hydrofoil and enhances efficiency significantly by two mechanisms. Mutual interaction of the vortex shed from the upstream body and the leading-edge vortex of the hydrofoil precipitates the separation of the leading-edge vortex from the hydrofoil and its streamwise transport. The incoming flow deflected by the upstream body changes the effective angle of attack for the hydrofoil. These phenomena significantly increase heaving force and pitching moment during stroke reversal, and major contribution to efficiency enhancement is from the change in pitching moment. 30% increase in efficiency, relative to a hydrofoil without an upstream body, can be achieved for same kinematics. However, the upstream body may be disadvantageous in some configurations. If the hydrofoil is placed closely to the body in transverse direction, the leading-edge vortex formation is suppressed after stroke reversal. When flapping frequency does not match with vortex shedding frequency of the upstream body, non-periodic flow structure formed around the hydrofoil can cause efficiency drop and irregular power generation.

Since the ocean energy field has a wide variety range of frequencies and amplitude, applying energy harvesters such as a piezoelectric generator (PEG) with a triboelectric generator (TEG) has been required for maximum result. Generally, energy harvesters can perform well due to the feature mechanism generation and the surface modification. However, few studies explain the relationship between characteristics of power generation with the device’s key factors. This study proposed/developed a TEG into a multi-layered model, combined it with a PEG to form a PEG-TEG hybrid harvester, and demonstrated the improvement of the output voltage by modifying the key factors (i.e., acceleration amplitude, vibration amplitude, initial distance). We found that our hybrid harvester with the multi-layered TEG can improve the electrical energy output in linear terms under a comparatively small device. Furthermore, the key factors have much influence to generate electrical energy instead of compression force, suggesting that a small force is enough to produce a good result. Our result also showed that this linear improvement is possible due to the increase of vibration amplitude, indicating that amplitude adjustment is important, but it is not directly related to a good electrical performance for initial distance. Finally, the complementary relationship between devices was investigated, and it shows good compatibility. The study could be an essential finding and understanding for PEG-TEG hybrid energy harvesters to produce more efficient and sustainable harvesters in the ocean energy utilization.

The concern for climate change and energy consumption has increased the demand for renewable energy production considerably. Marine energy sources attract attention because of their high energy den ...

This paper proposes a generic PTO (power-take-off) simulation platform which can be used to predict how devices perform in wave conditions when a simulated real-time linear or non-linear PTO damping forces is employed. The experimental platform could be used to investigate the maximum power output of wave converters(WECs) without constructing a physical PTO system and complex control strategies at the design stage of a WEC, thus making it efficient and inexpensive to explore different PTO solutions. For this purpose, a software-in-the-loop (SIL) simulation method is adopted which uses an innovative control loop running on an inexpensive real-time controller coupled to a DC motor which simulates the PTO damping torque. To calibrate the proposed PTO simulation platform, 1349 drop tests are carried out. A series of relationship curves and corresponding equations are drawn for both the linear and non-linear PTO cases. Moreover, correlation curves for input gains and the produced damping force coefficients are provided. The correlation indicates the PTO simulation platform's capacity of simulating linear PTO can reach 40–220 and can reach 10–70 for quadratic damping in terms of damping force coefficient. To investigate the accuracy of the platform, uncertainty analyses are also carried out in good details. The calibrating tests and uncertainty analyses indicate that the proposed experimental platform can be used to overcome many of the limitations in modelling PTO systems at laboratory scale to simulate both real-time linear and quadratic PTO damping forces.

The global development of the offshore renewable energy sector has been driven by extensive investment and research in the utilization of offshore renewable energies, mainly at the regional level. However, for mid to long-term marine energy development planning, a comprehensive assessment of the global potential for the exploitation of the main offshore resources is required. This work developed and implemented an innovative methodological approach to identify potential zones for wind and wave energy exploitation at the global level, using long-term data series with fine spatial and temporal resolution. The proposed methodology was based on a five-step approach comprised of: (i) a resource assessment, to identify the zones with favorable conditions for energy exploitation; (ii) a structural survivability assessment, to identify feasible areas which would likely ensure the integrity and durability of the wind and wave devices; (iii) a logistics assessment, to evaluate the possibility of carrying out installation, operations, and maintenance activities; (iv) an assessment of the distance to consumer centers, to estimate the feasibility of transmission to the main urban areas; and (v) an estimate of the extractable power of the identified potential zones. For wind power, the United Kingdom (with 1470 TWh/month using a 10-MW turbine) and the United States (1079 TWh/month) were the countries with the highest estimated energy output of the identified potential zones. For wave energy, Brazil and New Zealand presented good opportunities for the development of the wave energy industry, with an estimated extractable power of 372 TWh/month and 286 TWh/month, respectively. The unique preliminary global analysis presented in this work provides guidelines to assist in the development of wave and offshore wind industries, in addition to supporting the management of marine spaces. Moreover, the methodologies can be replicated for other marine activities.

Australia has considerable wave and tidal ocean energy resources. Development of the emerging ocean renewable energy (ORE) industry in Australia offers opportunities to build Australia's blue economy, while actively contributing to committed carbon mitigation measures. Many interdisciplinary challenges are currently hampering development of the industry in Australia, and globally, including technology, cost reduction, policy and regulations, potential for environmental effects, awareness and investment, amongst others. In October 2016, ORE technology and project developers, researchers, academics, policy makers and other stakeholders in Australia's emerging ORE industry came together to identify these challenges and develop possible pathways to grow ocean energy in Australia. Four themes were identified: Technology Development; Education and Awareness; Policy and Regulation; and Finance and Investment. This paper documents the outcomes of the meeting identifying challenges and a way forward against each theme. A key element identified across all themes was the need for stronger coordination across the sector, and the need for a representing body to lead necessary initiatives to support growth and management of the ORE industry in Australia, as one element of a burgeoning blue economy.

Conversion of the ocean’s vertical thermal energy gradient to electricity via Ocean Thermal Energy Conversion (OTEC) has been demonstrated at small scales over the past century, and represents one of the largest (and growing) potential energy sources on the planet. Here we describe how OTEC could be modified to provide a large source of CO2-emissions-negative energy while also allowing heat removal from the surface ocean, helping to directly counter ocean/atmosphere warming. Most OTEC energy potential is far offshore, thus the conversion of the produced electricity to a chemical energy carrier such as H2 or derivatives is required. This can be achieved by employing a method of electrochemically generating H2 that also consumes CO2, converting the carbon to a common form of ocean alkalinity. The addition of such alkalinity to the ocean would provide high-capacity carbon storage while countering the chemical and biological effects of ocean acidification. For each gigawatt (GW) of continuous electric power generated over one year by the preceding negative-emissions OTEC (NEOTEC), roughly 13 GW of surface ocean heat would be directly removed to deep water, while producing 1.3 × 105 tonnes of H2/yr (avoiding 1.1 × 106 tonnes of CO2 emissions/yr), and consuming and storing (as dissolved mineral bicarbonate) approximately 5 × 106 tonnes CO2/yr. The preceding CO2 mitigation would result in an indirect planetary cooling effect of about 2.6 GW. Such negative-emissions energy production and global warming mitigation would avoid the biophysical and land use limitations posed by methods that rely on terrestrial biology.

Waves and ocean currents have been widely researched worldwide as possible renewable energy sources. Recent findings related to viable energy sites with high power output focus on local dynamic impacts and disregard long-term viability. This study underlines the importance of resource assessment performed through long-term simulations and attempts to improve the understanding of how spatial-temporal variability controls the dynamic patterns of feasible sites for oceanic renewable energy. Hydrodynamic and spectral wave models Telemac-3d and TOMAWAC were performed over a 10-year period from 2003 to 2012. Sources of high current intensity and wave height were found in five sites around the Southern Brazilian Shelf (SBS) and the Southeast Brazil Bight (SBB) and were further analyzed for frequency of high occurrence, variability over months and seasons, and spatial and temporal variability. The results indicate that renewable energy from ocean currents has more stability for conversion in the SBS, while waves present better conditions in the SBB. The weaker seasons for energy conversion were autumn and summer, with the stronger seasons varying. Wave variability demonstrates a high correlation with atmospheric dynamics regarding the passage of frontal systems as opposed to currents that are mainly forced by local wind-driven conditions.

The booming developments of coastal/offshore renewable energies in recent years call for a powerful numerical code, ideally open-source packaged, to accelerate the researches in the spotlight. This paper presents such an efficient software package for evaluating the performance of floating renewable energy systems in the coastal and offshore regions. It aims to contribute an open-source effort in numerical simulations for ocean energy converters. Though computation of the free-surface effect in moderate depth region is extremely troublesome due to the singularities, the software package proposed in the present paper gives a satisfactory solution to keep the balance of accuracy and efficiency. In the present paper, the interface and structure of the package are introduced in detail so as to be well understood by the reader. Benchmark tests for various types of converters have confirmed the accuracy and efficiency of the package which can be incorporated easily with a frequency domain solver for efficient analysis. By contributing as one of the pioneer works in the open-source effort of evaluating the moderate-depth free-surface Green’s function, with its advantages of a reliable accuracy and a relatively low cost, the authors are hoping that the publication of the present software package will promote the continuous researches in developing robust and reliable coastal and offshore renewable energy systems.

Co-located wave-wind farms enhance the competitiveness of marine energy in a number of ways, and in particular through their benefits in terms of Operation and Maintenance (O&M) – the subject of this work. The objective is to investigate how the reduction in significant wave height within a co-located farm caused by the extraction of wave power by the wave energy converters (WECs), also known as the shadow effect, results in enlarged weather windows for O&M tasks. This investigation is carried out through a case study of four wind farms in the North Sea, including a sensitivity analysis in terms of: (i) location (depth and distance from the coast), (ii) sea climate, and (iii) wind farm layout. Real (observed) sea conditions are considered, and a third-generation wave model (SWAN) is implemented on a high-resolution grid. It is found that the combination of wave and offshore wind energy increases the accessibility for O&M tasks over 13% in all the cases considered, leading to accessibility values of up to 82%. The best results are obtained for wind farms with square-like geometries, where the co-located WECs intercept both the prevailing and secondary wave directions, and with small spacings between converters. Besides, proximity to land is found to not be a favourable factor for exploiting this synergy between wave and offshore wind power.