Ocean Energy Devices Research Articles

SEASNAKE: Impact - Marine operations modelling for evidence-based results detailing the impact of using a new fully dynamic cable design for ocean energy devices.

The SEASNAKE project - an OceanERA-NET project – is aiming for developing fully dynamic cables for ocean energy. Through new design and application of novel coatings the project is designing a dynamic cable that better suits the conditions and user requirements. In order to fully understand the benefits, the Wave Venture TEMPEST™ techno-economic analysis software will be used to simulate the performance of a proposed wave energy farm with a special focus on the contribution of the dynamic cable subsystem. The results obtained from the simulations will not only provide a deep understanding of the reliability and cost-risk areas regarding the use of dynamic cables, but will also allow a comparison with a baseline scenario consisting of a more traditional cabling system. The latter will be key to identify the advantages of the SEASNAKE project and its commercial viability. KPIs (Key Performance Indicators) will include farm availability and power production downtime as a direct result of cable related issues. The reliability, maintainability and survivability of the cabling subsystem will be tested and the KPIs will give clear indication on the performance benefits and ultimately the impact on the LCOE will be of greatest consideration.

Towards increased social acceptability of marine renewable energy

The development and deployment of novel technologies, including those associated with marine renewable energy, are vital for the ongoing decarbonisation of our energy system. However, technology on its own is not sufficient to realise the energy transition away from fossil fuels. Non-technical barriers – such as regulatory, economic, environmental or social aspects – can be a substantial impediment to widespread adoption of renewable energy technologies. One such impediment, is public opposition to specific deployments of renewable energy and/or indeed to the use of particular technologies. Within the SafeWAVE project, we are cognisant of the importance of good community relations and the need to develop two-way communication with stakeholders to facilitate the successful scaling up of ocean energy device deployments. Accordingly we have worked to co-develop and demonstrate a framework for education and public engagement (EPE), specifically aimed at ocean literacy for communities in France, Ireland, Portugal and Spain. This EPE framework aims to go beyond social acceptance, which is often equated to acquiescence to a fait accompli, and is designed to contribute to the development of projects which exhibit inherent social acceptability.
 This paper presents the work within SafeWAVE project to develop the EPE framework with input from the communities. The first part of the paper reports on critical review of selected EPE programmes associated with marine energy test sites and infrastructure deployments, with methods adopted in each case analysed, key challenges faced identified, and best practices documented. Next a framework for public education and engagement is presented, which builds on this review and draws from literature across multiple disciplines – including sociology, psychology, political science, education. Finally, leveraging this developed knowledge the collaborative process of deriving tailored EPE programmes on ocean literacy around marine renewables for the four focal communities is outlined and described. These programmes are intended to reach out to, and engage with, local communities, interested stakeholders and the wider public on issues surrounding the deployment of ocean energy devices, including but not limited to: effects on local communities, implications for marine life, potential impacts for water users, etc.
 The paper concludes by discussing the experience of developing the bespoke programmes, outlining emergent feedback from trialling of key elements of the programmes, discussing experiences and proffering guidance based on lessons learned.

Propulsion characteristics of self-pitching flapping foil

As a promising form of oscillating hydrofoil propulsion, self-pitching flapping foil (SPFF) has been widely used in ocean engineering applications such as ships, underwater vehicles and ocean energy devices. Due to the complexity of its mass spring system, it is still a lack of comprehensive parametric analysis to conclude the theoretical maximum efficiency of SPFF up to now. Particular interest of this work is centered on the influence of frequency ratio (r), spring stiffness ratio (K′), advance coefficient (J) and pitch axis (c0/c) on the propulsive performance of self-pitching flapping foil (SPFF), including induced propulsion force, propulsive efficiency and related wake structure. The analysis covers the range of full advance coefficient, which starts around 0 and ends at a thrust drop of 0. The influence of stiffness ratio (K’) on the SPFF performance was discussed in the large range of 0.1–100. Special attention is also paid to the impact of system resonance on performance. By employing an appropriate combination of various parameters, the highest efficiency of SPFF could reach 87.6%, which shows it could perform a satisfactory propulsion performance as a marine propulsion. This study is expected to provide guidance on both academics and industries in relevant fields.

Development and Application of a GIS for Identifying Areas for Ocean Energy Deployment in Irish and Western UK Waters

Ireland and the UK possess vast ocean energy resources within their respective maritime areas. However, not all offshore areas are suitable for deployment of ocean energy devices. This article describes the development of a multitude of geospatial data relating to ocean energy site suitability, as well as a Web-GIS tool for hosting and performing analysis on this data. A validation of wave, water depth and seabed character data used in the study revealed good correlation between modelled and in situ data. The data is mapped, and the spatial patterns are discussed with relevance to ORE sector implications. A site selection model, which included much of this data, was developed for this study and the Web-GIS tool. A survey conducted with ocean energy technology developers revealed their desired site criteria. The responses were applied in a case study using the site selection model to uncover potential and optimum areas for deployment of both wave and tidal energy devices. The results reveal extensive areas of the Atlantic Ocean and Celtic Sea appropriate for wave energy deployment and less extensive areas for tidal energy deployment, in the Irish Sea and Inner Seas off the West Coast of Scotland.

An unsteady RANS simulation of the performance of an oscillating hydrofoil at a high Reynolds number

The oscillating hydrofoil has been widely used in ocean engineering applications such as ships, underwater vehicles and ocean energy devices. However, Reynolds number of existing research are lower than real ocean applications.This study reports our recent numerical effort in studying a sinusoidally oscillating hydrofoil under unsteady conditions by solving the Reynolds-averaged Navier–Stokes equations. By using experimental test data, the numerical method is well validated. Three wake patterns are identified to fundamentally affect the propulsive performance of the oscillating hydrofoil. Only the wake in the reverse von Kármán vortex street pattern is found to generate thrust for purely oscillating motion. The leading-edge vortex is demonstrated todirectly influence the pressure distribution over the foil’s surface but not the thrust.Furthermore, impact of 3D effect on vortex shedding on the hydrodynamic performance of the hydrofoil is presented. This study is expected to provide guidance on both academics and industries in relevant fields.

A Review of SPH Techniques for Hydrodynamic Simulations of Ocean Energy Devices

This article is dedicated to providing a detailed review concerning the SPH-based hydrodynamic simulations for ocean energy devices (OEDs). Attention is particularly focused on three topics that are tightly related to the concerning field, covering (1) SPH-based numerical fluid tanks, (2) multi-physics SPH techniques towards simulating OEDs, and finally (3) computational efficiency and capacity. In addition, the striking challenges of the SPH method with respect to simulating OEDs are elaborated, and the future prospects of the SPH method for the concerning topics are also provided.

On the Dimensionless Absorption Heat Pump Widespread

Climate change has a huge challenge to 2050. Some renewable energies can be installed to reduce CO2 production. Unfortunately, the photovoltaic systems, wind energy, and ocean energy devices do not have direct thermal applications. These systems are useful for people’s electricity consumption. Absorption heat pumps (AHP) are thermal devices for increasing the temperature level from an energy source at medium temperature level, such as plane solar collectors, to another energy sink. The main problem with design, power calculations and device construction is a lack of education about this technology, which is more complex than compression heat pumps but with 90 % less electric energy consumption that would be supplied by photovoltaic cells. This paper shows an approximation for future engineers designing several absorption heat pumps to avoid global warming beyond the Paris Agreement. Future engineers should be encouraged to analyze this technology with this first and basic approach.

Renewable energy production in a Mexican biosphere reserve: Assessing the potential using a multidisciplinary approach

In Mexico, the CEMIE-Océano (Mexican Center for Ocean Energy Innovation) is exploring potential locations for marine energy production while assessing social perception and protecting the environment. The goals of this study were to: a) calculate potential renewable energy production in the north of the Yucatan Peninsula; b) understand the perception of the local inhabitants towards the installation and operation of ocean energy devices and c) estimate the potential environmental impacts in the Río Lagartos Biosphere Reserve, considering keystone or unique/endemic species. Our results indicate that energy harvesting through salinity gradient would be the most feasible among renewable energy production alternatives that would reduce emissions of CO2 into the atmosphere thus helping mitigate global warming. The maximum recorded salinity was 90 psu, in February and April, which would provide 1.39 kWh/m3. This would not be sufficient to fully meet the local demands for electricity. Our findings show that the local people are not well informed regarding renewable energies. They appreciate their natural environment and would be very reluctant to see drastic changes in their surroundings. Finally, if saline gradient energy production were to be implemented here, the changes in the gradient and hydrosedimentary flows would probably induce undesirable alterations to the natural ecosystems: (mangroves), food webs (plankton), and threatened species (flamingos and horseshoe crabs). In conclusion, our findings indicate that salinity gradient energy production is unlikely to be viable in the Ria Lagartos Biosphere Reserve mostly because of the reluctance of local inhabitants to changes in their environment and the potential environmental impacts.

Electromagnetic design method for a TLSRG with application in ocean wave energy conversion

The tubular linear switched reluctance machine (TLSRM) has shown potential for applications as generator in direct drive conversion of ocean wave energy devices. However, the design of this type of machine is a difficult task and there is no methodology to provide an explicit solution. This work aims to contribute for the solution of this problem with the proposal of a new procedure to design tubular linear switched reluctance generators (TLSRG). With the proposed procedure the TLSRG can be designed to develop a given linear force and to achieve better generation efficiency. The design is defined as a minimization problem where an optimization process is used to find the optimal solution for the dimensional parameters. Finite element method (FEM) analysis is applied to compute the relevant electromagnetic characteristics. The mathematical model of the generator conversion system is formulated to evaluate its dynamic performance. An H-Bridge asymmetric converter is adopted to control the energy flow in the generator. The electric currents in the generator phases are adjusted with a hysteresis controller. A TLSRG with a maximum mean force of 120 kN is designed by applying the proposed procedure, implemented in Matlab® and combined with MagNet® (FEM commercial software) to compute the electromagnetic characteristics of the machine. The system mathematical model is solved in Simulink®. The dynamic simulations are performed for a constant velocity of 1.3 m/s. For these operating conditions, the generator is characterised with an output power of 126.2 kW and an efficiency of 82.1%. The control proposed to drive the TLSRG is experimentally tested on a small-scale prototype. The experimental results show the effectiveness of the controller in keeping the phase current near the reference value.

Use of the Mps method to estimate the energy conversion efficiency of the owc-wec (first report)

In recent years, ocean renewable energy has been increasingly in the spotlight due to global warming and energy issues etc. Research on ocean renewable energy devices is being carried out by many researchers, companies and countries. Additionally, many sea tests are being carried out by countries with real sea test sites. Ocean renewable energy devices still need to research about a power generation method, an energy conversion efficiency and costs etc. In this paper, Authors focus on the oscillating water column type wave energy converter (called below OWC-WEC). It is considered that the OWC-WEC is useful because a movable part which becomes a cause of trouble is few and can also be used as a breakwater device. In this study, the MPS (Moving Particle Semi-implicit) method is applied to the performance analysis of the OWC-WEC. It is because the performance analysis by various parameters and the reduction of an experimental cost is needed. In this paper, these following items are shown; 1) the development of analysis program code which can simulate the multiphase flow by three phases of gas, liquid and solid, 2) the development of air duct model, 3) verification of the usefulness of the improved MPS program code and 4) verification of the applicability to the performance analysis of the OWC-WEC. This program code was applied to the simulation of the fixed type OWC-WEC. Following this, the reproducibility of the primary conversion efficiency of the fixed type OWC-WEC by this program code was verified and discussed. Finally, the usefulness and applicability of this program code were discussed and recommendations for future work were made.

A framework to evaluate the environmental impact of OCEAN energy devices

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.

Assessment of Energy Production Potential from Tidal Stream Currents in Morocco

Energy extracted from the ocean can provide a source of regular and foreseeable electrical production at higher energy densities than any other renewable energy resource. The marine current resource is potentially great and is focused in several sites around the world. The knowledge of the energy potential, its constraints and availability are all prerequisites to determine the possibilities for the implementation of infrastructure to produce energy. They are also required to anticipate the structuring of energy routes and to respond to increasing technological needs. Several Moroccan regions want to take advantage by their coastal domain and play a role in the development of the tidal energy sector. They also want to benefit from the associated economic advantages knowing that the Mediterranean coast length is 550 km and the Atlantic length is 3000 km, respectively. The Copernicus Marine Service ocean products provide key input for such technologies, as they can be employed to help evaluate the accessible ocean energy devices and choose the most attractive sites to exploit the tidal energy projects in Morocco. The goal of this research was to evaluate and analyze the tidal marine current resource at the sites which are potentially suitable for the installation of Horizontal Axis Marine Current Turbines in Morocco. Distributions of available power of tidal energy in the Moroccan region are provided, and three possible areas are suggested for installing tidal energy conversion systems.

Galway Bay – The 1/4 scale wave energy test site? A detailed wave energy resource assessment and investigation of scaling factors

Ireland offers a complete testing pathway for wave energy devices from small-scale testing in laboratory wave tanks to the Galway Bay Test Site (GBTS), located in a sheltered bay, and the full-scale Atlantic Marine Energy Test Site (AMETS) exposed to the Atlantic Ocean on its west coast. This research investigates the scaling relationships between the GBTS and the AMETS, and also with the Westwave commercial demonstration site. The paper presents (i) detailed wave resource assessments at GBTS and Westwave (ii) a scaling analysis methodology suitable for determining the scale relationships between two sites, and (iii) the appropriate scaling factors for wave energy test sites in Ireland which can be used by developers for prototype testing and commercial deployment. The assessment and scaling analyses were performed using 12-year model outputs from two high resolution wave models from January 2004–December 2015. The models were well-validated using available measured data. The resource assessments determined (1) mean and maximum conditions and (2) operational, high and extreme event conditions for significant wave height, energy period and power. Both annual and seasonal analyses are presented. The 12-year annual mean power was 3 kW/m at GBTS and 50 kW/m at Westwave. Three scaling approaches have been analysed to identify the appropriate scale ratios to be used to upscale GBTS to AMETS for wave height, energy period and power. The distribution fittings method was found to be the most accurate method for resource scalability between GBTS and both AMETS and Westwave sites. The scaling result shows GBTS, although often termed a ¼-scale test site, is not actually ¼-scale proportionate to AMETS or Wavewave. Scaling factors are presented in tabular format, which are based on the Froude scaling method, for seasonal windows that could be used to determine the scale of ocean energy device models for testing in the benign site of GBTS in Ireland to ensure it adequately upscales to the open sea exposed sites of AMETS and Westwave in Ireland.

Life cycle assessment of ocean energy technologies

Purpose Oceans offer a vast amount of renewable energy. Tidal and wave energy devices are currently the most advanced conduits of ocean energy. To date, only a few life cycle assessments for ocean energy have been carried out for ocean energy. This study analyses ocean energy devices, including all technologies currently being proposed, in order to gain a better understanding of their environmental impacts and explore how they can contribute to a more sustainable energy supply.

High performance ocean energy harvesting turbine design–A new casing treatment scheme

Delaying a stall improves the performance of any turbomachinery system. TC (tip clearance), which is used in a bi-directional flow Wells turbine of an ocean wave energy device, changes the flow pattern on the turbine blade suction surface, while changing or modifying the TC zone can help obtaining a delayed stall. In the present work, a new tip grooving scheme is introduced and the performance is compared for different tip groove depths and TCs of a Wells turbine. The performance is defined in terms of wider operating range or stall delay, power production and efficiency. The problem was solved by a numerical analysis technique. A multi-block meshing scheme was employed to generate structured and hexahedral elements in the computational domain and the flow was solved in ANSYS CFX® v14.5 by solving Reynolds-averaged Navier Stokes equations. It was found that the grooves improve the turbine operating range and power production as compared to those of the turbine without a groove. The groove depth of 3% of the chord length produced highest power and widest operating range. Using the circumferential groove, 26% increase in turbine power output for a particular operating point is achieved.

Model Scaling of Ocean Hydrokinetic Renewable Energy Systems

Numerical simulations are performed to validate a nondimensional dynamic scaling procedure that can be applied to subsurface and deeply moored systems, such as hydrokinetic ocean renewable energy devices. The prototype systems are moored in water 400 m deep and include: subsurface spherical buoys moored in a shear current and excited by waves; a subsurface ocean current turbine excited by waves; and a deeply submerged spherical buoy in a shear current excited by strong current fluctuations. The corresponding model systems, which are scaled based on relative water depths of 10 and 40 m, are also studied. For each case examined, the response of the model system closely matches the scaled response of the corresponding full-sized prototype system. The results suggest that laboratory-scale experimentation of complete ocean current renewable energy systems moored in a current is possible.

Damping of unwanted turbulence in wave–current experiments

Laboratory testing of structures placed in combined wave–current flows is a valuable source of information for the fulfillment of offshore engineering related tasks and the development of ocean energy devices. In recirculating wave–current flumes, one of the problems encountered during such experimental studies is the occurrence of undesirable current induced velocity fluctuations. These fluctuations often result in significant disturbances of the generated wave profiles. In this paper, a physical flow filter is introduced that significantly reduces fluctuations in the current profile while permitting wave passage. This is achieved by passing the wave–current flow through a setup of perforated net tubes that allows for both horizontal and vertical flow motions. An in depth investigation of the properties of different filter configurations is presented, focusing on the reduction of turbulence intensities in the flow field as well as the influence of the setup on waves. The filter characteristics are quantified in terms of its deflection, absorption, and transmission properties. It is shown that the overall setup effectively reduces velocity fluctuations, resulting in stable wave–current conditions and allowing for high quality laboratory testing.

A Tank Experimental Research on a Horizontal Wave Flow Turbine Generating Device

Used a new type horizontal wave flow turbine ocean energy device as a prototype for the tank experiment, theoretically analyzed the fluid dynamics and energy capacitation of its key component turbine. Through analyzing the data of the tank experimental of the key component turbine, we found the feasibility of this kind of power device. Besides, the experiment proved a particular characteristics of the turbine of maintaining the same rotational direction whatever the directions of the incoming flow of this kind of turbine. The feature of the turbine can eliminate the complicated steering mechanism, which helped the whole device with the advantage of simple structure. The tank experiment not only provided a practical foundation for optimizing the generating device, but also gave a reference method to solve the similar engineering problems.

Environmental Risk Evaluation System—an Approach to Ranking Risk of Ocean Energy Development on Coastal and Estuarine Environments

The pressure to develop new and renewable forms of energy to combat climate change, ocean acidification, and energy security has encouraged exploration of sources of power generation from the ocean. One of the major challenges to deploying these devices is discerning the likely effects those devices and associated systems will have on the marine environment. Determining the effects each device design and deployment system may have on specific marine animals and habitats, estimating the extent of those effects upon the resiliency of the ecosystem, and designing appropriate mitigation measures to protect against degradation all pose substantial challenges. With little direct observational or experimental data available on the effects of wave, tidal, and offshore wind devices on marine animals, habitats, and ecosystem processes, researchers have developed the Environmental Risk Evaluation System (ERES) to provide preliminary assessments of these risks and to act as a framework for integrating future data on direct interactions of ocean energy devices with the environment. Using biophysical risk factors, interactions of marine animals and seabirds, with ocean energy devices and systems, are examined; potential effects on habitats, and changes in processes such as sedimentation patterns and water quality, are also considered. The risks associated with specific interactions for which data are more readily available are explored including interactions between ocean energy devices and surface vessels, toxicity of anti-biofouling paints, and potential for harm to animals from turbine blade strike. ERES also examines the effect that environmental regulations have on the deployment and operation of ocean energy devices.

FP7 EU funded CORES wave energy project: a coordinators' perspective on the Galway Bay sea trials

The present paper gives an overview of the lessons learnt from the project called Components for Ocean Renewable Energy Systems (CORES). In the context of this European funded 7th Framework Programme research project, new components and systems for ocean energy devices were developed and trialed. The present paper also details the work packages, major achievements, significant impacts, summary results and the outcomes of the sea trials. 1. Introduction Components for Ocean Renewable Energy Systems (CORES) was an EU funded FP7 Collaborative Research Project and was coordinated by the Hydraulics and Maritime Research Centre in University College Cork (UCC). The Hydraulics and Maritime Research Centre is now integrated into UCC Beaufort Research since 2013. The CORES project was intended to further develop components and systems required by the wave energy sector such as grid interface technology, power generators, moorings, instrumentation, telemetry and power control systems. The project started in 2008 and spanned over 3.5 years. It culminated with a three-month sea trial of the systems integrated onto the quarter-scale OEBuoy Hull in Ireland's Galway Bay Wave Test Site. This test site, which is operated jointly by Sustainable Energy Authority Ireland (SEAI) and the Marine Institute (MI), was made available at no cost to the project. Thirteen partners from across seven European countries participated in the project. Although it concentrated on new concepts and components based on floating oscillating water column (OWC) systems, the majority of developments have relevance to most other wave device types. The project finished successfully on budget, but was extended by six months owing to issues concerning weather conditions and vessel availability. How this was achieved, the lessons learnt and what pitfalls need to be avoided are addressed in the present paper. Techniques and tools developed to reduce the risk involved in prototype sea trials and planning, as well as resourcing methods, are discussed. Finally, the present paper details the intellectual property (IP) generated from the project that will be available to the wider ocean energy community. The ultimate objective of the CORES project was to create a wave-to-wire modelling 'toolbox'. This toolbox would allow developers to evaluate the effect of changes in device components on the performance and economics of their devices. It was to consist of a number of numerical models or 'tools' developed within individual work packages and validated at bench scale and through laboratory scale testing at sea. Further information on these tools can be found in a number of detailed technical papers (CORES, 2011; Thiebaut, 2011) as well as on the CORES website (www.fp7-cores.eu).