Marine Renewable Energy Devices Research Articles

Static and Fatigue Characterization of Large Composite T-Bolt Connections in Marine Hygrothermal Environments

Fiber-reinforced polymer composites have been highlighted as ideal candidates for structural applications in marine renewable energy devices, such as tidal turbines and wave energy converters. It is well understood that harsh marine environments can cause strength degradation of composite laminates, which has been extensively researched at the coupon scale; however, no research has investigated how this translates into larger-scale composite structures. This paper presents a subcomponent-scale study which investigates the effects of hygrothermal aging and subsequent static and fatigue characterization of thick composite T-bolt connections as part of a large, multilaboratory materials research effort. Of the glass-reinforced epoxy and vinylester-epoxy matrix composites tested, both showed measurable static strength degradation (4–36%) after being hygrothermally aged, even though the composite specimens were only partially saturated with water. Under tension–tension fatigue loading, the epoxy specimens performed very well in their dry states but exhibited significant degradation after hygrothermal aging. In comparison, the vinylester-epoxy specimens had much shorter fatigue lives in their dry states but exhibited no degradation after hygrothermal aging. Overall, this research demonstrates that hygrothermal aging can have significant effects on the ultimate strengths and fatigue lives of even partially saturated thick composite T-bolt connections, indicating that degradation of the outer plies on thick composite laminates can have pronounced effects on the whole structure. It discusses the challenges of building an understanding of the effects of harsh marine environments in large-scale composite structures.

Red rock crab (Cancer productus) movement is not influenced by electromagnetic fields produced by a submarine power transmission cable

Marine renewable energy (MRE) devices, such as ones that harness offshore wind and wave energy, are an effective supplement to traditional energy sources and can support the energy grid while combating climate change. As MRE development increases pace, it is important to anticipate impacts of these infrastructure projects on the marine environment. One potential impact is a localized change in electromagnetic fields (EMF) produced by energized submarine transmission cables. Though many marine species are sensitive to EMF, primarily for navigation and orientation purposes, strong conclusions about how EMF affects invertebrates are lacking. Organisms that traverse the seafloor close to energized submarine cables, such as crabs, may be subject to stronger EMF currents. The U.S. West Coast is both a hot spot for emerging MRE development as well as home to the largest crab fisheries in the nation, there is an obvious concern on the potential impact development will have on fisheries. Our primary objective was to verify the response of red rock crabs in the presence of energized cables similar to those associated with existing MRE installations while also controlling for environmental conditions. We quantified and mapped local magnetic fields near an energized cable, tested crab responses in cable and control areas using a two-choice experimental cage in situ and described and quantified variables that were most likely to affect crab responses, including water current direction/velocity and magnetic field strength. Our results were remarkably consistent with previous studies: 1) crabs showed no preference for crossing/not crossing the cable; 2) crabs preferred to travel to the west regardless of the presence/absence of an energized cable; 3) while crabs preferred to travel to the west even more frequently in the absence of an energized cable, cable crossing and travel direction preferences were not influenced by EMF; and 4) EMF produced by these cables were consistent over time and decay to background levels at a distance of less than 1 m. This information is critical to making informed and sustainable policy decisions about renewable energy development and ensuring that this technology can coexist with local fisheries as MRE development continues.

Life Cycle Assessment of a wave energy device – LiftWEC

The need to move towards a low-carbon economy has brought about the emergence of various renewable energy sectors, including Marine Renewable Energy (MRE). However, after many years of research and development, the MRE industry still faces challenges in achieving commercial viability, especially regarding wave energy. Whilst it remains possible that successful wave energy technologies exist in the traditional research trend, it is also appropriate to explore alternatives that produce energy by different approaches. Wave-induced lift force devices may be the possibility to move beyond traditional wave energy technologies using diffraction and/or buoyancy forces. In this context arises the LiftWEC, a promising configuration of a lift-based wave energy converter. The LiftWEC device couples with the waves through lift forces generated by two hydrofoils that rotate in a single direction aligned orthogonally to the direction of wave propagation.
 To fully evaluate the overall advantages of this new technology, it is necessary to go beyond the techno-economic performance and reliability. While capable of producing electricity from clean sources, MRE devices are not entirely environmentally friendly, since energy is consumed and pollutants are emitted during their various life cycle stages. Accordingly, as the MRE sector expands, it is important to ensure that the technologies prove to be sustainable alternatives in terms of their environmental impact.
 Life Cycle Assessment (LCA) is a widely recognized methodology to evaluate environmental impacts by considering the technology’s performance over its life cycle. This methodology complies with international standards ISO 14040, which specify the general framework, principles, and requirements for conducting and reporting this type of assessment.
 A “cradle to grave” LCA assessment was applied to the LiftWEC device to evaluate the potential cumulative environmental impacts of the system, complete from the extraction of raw materials until decommissioning. Each stage was analysed within the defined system boundaries, and data on the energy, materials, emissions, and waste products associated were gathered. To allow comparison with other MRE technologies and traditional means of electricity generation, carbon dioxide equivalent emissions per produced electricity (gCO2eq/kWh) were calculated for the study.
 Since ocean energy is broadly considered to contribute to a low-carbon energy system, special attention was given to the LCA results on the global warming potential (GWP). Besides a set of 18 impact categories, Cumulative Energy Demand (CED) and Carbon and Energy payback time (CPT and EPT, respectively) were also analysed. The CPT and EPT are important indicators that measure the time required to offset the carbon emission and demanded energy, respectively, accounted across all development phases of the device.
 This work included the comparison of LCA findings for other MRE devices reported in the literature to validate the viability of the LiftWEC in terms of carbon and energy footprint. In addition, the assessment analysed alternative materials, locations, and recyclability allowing the identification of potential improvement opportunities regarding the reduction of environmental impacts.

Empowering Communities to Participate in Marine Energy Planning and Development

To meet community priorities and equitable outcomes, marine renewable energy (MRE) projects, such as those for marine energy and offshore wind, require informed and collaborative marine spatial planning (MSP) to overcome significant cultural, societal, and economic barriers that may limit responsible and accelerated deployment. Effective MSP brings together coastal communities and ocean users to coordinate decision-making for sustainable use of marine resources. The goal of this project is to develop digital tools to enable easy access to information, interactive visualization tools, and feedback mechanisms to empower communities to engage in meaningful communications with other stakeholders in the MSP process.
 In collaboration with community organization partners, the Santa Barbara Maritime Museum and Redwood Community Action Agency, we held community-based workshops to solicit needs for communities to gain knowledge and communicate concerns about MRE development. The key results from initial outreach activities are:
 
 The MRE planning process must incorporate stakeholder feedback starting in its early stages (as early as siting). Community benefits must be clearly articulated and quantified.
 Communities generally distrust offshore energy developers. Communication with regulators and developers together would be useful.
 Community members are eager to learn about MRE. Their biggest knowledge gaps are MRE device and array characteristics (size, extent, location) and effects of MRE development on the viewshed, recreational activities, and on wildlife.
 There is too much information available over disparate sources. Community members do not know where or how to search for answers to questions about MRE development in their communities (or elsewhere).
 Community members want to hit the ‘Easy Button’. Data need to be digestible and tools need to be easy to use with little technical knowledge or experience necessary.
 
 Outreach activities guided the development of the following digital tools:
 
 Interactive infographics to communicate topics of concern (e.g., viewshed impacts and potential interactions with whales) in a visually engaging and interative platform.
 News feed relevant to MRE to quickly digest headlines and read articles in greater detail, sort articles by topic, and react to articles or other comments.
 Artificial intelligence (AI) driven chat bot, which uses the latest in AI, namely GPT-3 (Generative Pre-trained Transformer 3), to produce real-time answers to user questions. Answers are logged, and can be reviewed and revised by marine energy experts to provide human vetting of the results.
 Commenting system to provide feedback on information throughout the site, as well as the tools themselves.
 
 These tools will empower communities with information and feedback mechanisms to promote meaningful stakeholder engagement and communications, and therefore, informed decision-making. These tools represent a major leap forward in ocean multi-use management with MRE.

Environmental Effects of MRE: Advancing the Industry through Broad Outreach and Engagement

Marine renewable energy (MRE) can benefit from broad outreach and engagement with a wide variety of audiences to raise awareness, address concerns about potential environmental impacts, generate public support, build a future workforce, share progress on research and development, and succeed within the larger blue economy. OES-Environmental is an international initiative of 16 countries that brings together the MRE community to increase understanding of environmental effects of MRE. OES-Environmental has focused on sharing research outcomes and knowledge to broad audiences that are best addressed with a variety of learning formats. Throughout these diverse outreach efforts, several important lessons have been learned. These include the importance of clarifying the main message for each audience and for each resource created; finding the best venue to deliver materials to different audiences; using language, complexity, and context that suits audience requirements and is age-appropriate; utilizing a variety of methods to share messages; and leveraging creative ideas to produce an assortment of engaging, accurate products. Creating materials tailored for specific groups has made outreach efforts more effective and has allowed for the information and findings from OES-Environmental to increase awareness of environmental effects of MRE by reaching new audiences.
 Based on OES-Environmental’s 2020 State of the Science Report – a comprehensive technical report providing the most up-to-date review of scientific information on environmental effects of MRE – and additional research to date, products have been designed to engage with different audiences, mainly: the MRE community (which includes regulators and advisors, project and device developers, consultants, and researchers); science, technology, engineering, and math (STEM) students; and the interested public. For the MRE community, a brochure that provides a high-level overview of environmental effects and a series of guidance documents which provide in-depth information to aid application of scientific evidence for consenting have been developed. In addition to these new resources, webinars, workshops, and Tethys – an online knowledge platform – have been used to share information and collaborate with the MRE community to advance the state of understanding. For STEM students, an animated MRE video series and a coloring book were created to offer a visual format to learn about environmental interactions with MRE devices and current research. For the interested public, an open-access magazine article and several podcast episodes were developed to expand general understanding of MRE. OES-Environmental also engages the public through ongoing content creation on various social media platforms.
 As OES-Environmental continues to synthesize current scientific knowledge around environmental effects of MRE, outreach and engagement will continue to be a focus to ensure important findings are communicated to diverse audiences. Sharing lessons learned by OES-Environmental around outreach and engagement can help other researchers and the MRE community broadly to communicate more effectively and accelerate industry progress.

ITSASDRONE, an autonomous marine surface drone for fish monitoring around wave energy devices

The ocean energy development is one of the main pillars of the EU Blue Growth strategy. However, while the technological development of devices is growing fast, their potential environmental effects are not well-known. The nascent status of the Marine Renewable Energy (MRE) sector and Wave Energy (WE) in particular, yields many unknowns about its potential environmental pressures and impacts, some of them still far from being completely understood. Wave Energy Converters’ (WECs) operation in the marine environment is still perceived by regulators and stakeholders as a risky activity, particularly for some groups of species and habitats. The SafeWAVE project aims to improve the knowledge on these impacts trough an Environmental Research Demonstration Strategy based on the collection, processing, modelling, analysis and sharing of environmental data collected in WE sites from different European countries where WECs are currently operating (Mutriku power plant and BIMEP in Spain, Aguçadoura in Portugal and SEMREV in France) representing different types of technology, different types of locations and different types of project scales, therefore, different types and/or magnitudes of environmental impacts. As part of SafeWAVE project, environmental monitoring plans relative to electromagnetic fields, acoustics (noise), seafloor integrity and fish communities need to be put in place. In the case of fish communities, generally speaking, any artefact located in the sea may cause an attraction effect on fish communities, especially if it is floating. In the case of Marine Renewable Energy Devices, during the operation phase, in general, the placement of any artefact in the sea can result in an attracting effect on fish communities, especially if it is floating. In order to study this possible effect, fish communities monitoring around the Penguin WEC-2 of WELLO-Oy localized in BiMEP test site with the ITSASDRONE surface drone developed by AZTI was planned. The study was designed to carry out the tunning and conditioning of the ITSASDRONE and to discover the associations between WECs and fish aggregations. Penguin WEC-2 of WELLO was removed from BiMEP test site due to an alarm of leakage. Consequently, we decided to carry out the monitoring work around the HarshLab, a floating laboratory device constructed by Tecnalia and localized also in BiMEP test site. The study allows us to validate the ITSASDRONE as a viable autonomous vehicle for fish school monitoring. It still needs some technological improvement related to navigation system, but in general, the ITSADRONE meets the objectives for which it was conceived and could be an excellent monitoring technique due to its capacity to work remotely and in near shore areas. Schools of unidentified small pelagic fish were observed distributed throughout the water column, predominantly near the bottom in the device area. But, future studies are needed to further explore the association between WECs and fish aggregations. The aim of this communication is to show the work done by an autonomous marine surface drone, ITSASDRONE, in relation to fish monitoring in BiMEP area.

A review of geographic information system (GIS) and techno economic (TE) software tools for renewable energy and methodology to develop a coupled GIS-TE software tool for marine renewable energy (MRE)

Accurate and up-to-date Geographic Information System (GIS) and Techno Economic (TE) tools are pertinent to helping to develop the renewable energy sector. This paper reviews the state of the art in existing GIS and TE tools for renewable energy and proposes a methodology to develop a coupled GIS-TE software tool that is geared specifically to Marine Renewable Energy (MRE) applications and bespoke to Irish and Western UK waters. Methods for approaching GIS and TE analysis within existing tools for renewable energy are presented and compared. Many existing tools of this nature have some interesting functionalities, but most are unsuitable for MRE; are limited by a lack of information on both the technology and the site; and focus solely either on GIS or TE aspects of analysis. Additionally, almost all of those with a TE focus are not open access. The proposed tool aims to incorporate increased resolution and site relevance of resource data; the most up-to-date geospatial data for site selection; and will provide site specific TE indicators and recommendations for contemporary MRE devices. The result will be the development of an open-access GIS-TE software tool for MRE.

Commercial cuttlefish exposed to noise from offshore windmill construction show short-range acoustic trauma

The installation of marine renewable energy devices (MREDs, wind turbines and converters of wave, tidal and ocean thermal energy) has increased quickly in the last decade. There is a lack of knowledge concerning the effects of MREDs on benthic invertebrates that live in contact with the seabed. The European common cuttlefish (Sepia officinalis) is the most abundant cephalopod in the Northeast Atlantic and one of the three most valuable resources for English Channel fisheries. A project to build an offshore wind farm in the French bay of Saint-Brieuc, near the English Channel, raised concern about the possible acoustic impact on local cuttlefish communities. In this study, consisting of six exposure experiments, three types of noise were considered: 3 levels of pile-driving and 3 levels of drilling. The objectives were to assess possible associated changes in hatching and larva survival, and behavioural and ultrastructural effects on sensory organs of all life stages of S. officinalis populations. After exposure, damage was observed in the statocyst sensory epithelia (hair cell extrusion) in adults compared to controls, and no anti-predator reaction was observed. The exposed larvae showed a decreased survival rate with an increasing received sound level when they were exposed to maximum pile-driving and drilling sound levels (170 dB re 1 μPa2 and 167 dB re 1 μPa2, respectively). However, sound pressure levels's lower than 163 dB re 1 μPa2 were not found to elicit severe damage. Simulating a scenario of immobile organisms, eggs were exposed to a combination of both pile driving and drilling as they would be exposed to all operations without a chance to escape. In this scenario a decrease of hatching success was observed with increasing received sound levels.

Influence of coating type, colour, and deployment timing on biofouling by native and non-native species in a marine renewable energy context

Biofouling on marine renewable energy devices presents engineering challenges for this developing sector, and has implications for the spread of marine non-native species (NNS) in coastal waters. This is particularly true at sites with abundant energy resource, little existing infrastructure, and few established NNS. Device coatings, such as antifouling paints, could reduce the risk of NNS spread. Settlement on coatings of various types and colours, representing those likely to be used on renewable energy devices, was assessed in the Orkney Islands, northern Scotland. Assemblage composition, but not overall biofouling cover, varied initially among different coloured surfaces, although differences decreased over time. Different coating types (an anticorrosive paint, a biocidal paint and a fouling-release coating) differed in biofouling abundance and composition for the full duration of the experiment. NNS were mostly, but not completely, absent from antifouling surfaces. These results can help informing antifouling strategies for the marine renewable energy industry.

Practical Approaches for Providing Empirical Data on Seabird Behavior and Prey Assemblages in Tidal Channels

Persisting knowledge gaps relating to the ecological context and potential environmental impacts of marine renewable energy (MRE) devices continue to add substantial costs and uncertainty to MRE projects globally. Increasingly sophisticated technological approaches to environmental monitoring can have fundamental non-trivial shortcomings for environmental impact assessment (EIA), whilst substantial practical and financial costs of deployments can prevent their application. For the tidal stream energy (TSE) sector, there is a need for practical and cost-effective methods that can provide site-specific information on predator behavior and associated prey assemblages. Considering existing knowledge of animal communities in tidal channel environments, a proportional approach using shore-based observation and baited fish trap methods was developed. During April 2021, a trial of these methods was conducted in tidal channel environments in Shetland, UK. The practical application of the proposed approach is demonstrated here with results from three tidal channels including Bluemull Sound, the site of active TSE installations (the Shetland Tidal Array). Observation of predator behavior across the study sites are reported for great cormorant Phalacrocorax carbo and European shag Phalacrocorax aristotelis. Seabird diving data calculated from the shore-based observations provided metrics relevant to informing EIA and collision risk modelling including dive duration, dives per minute, and % time underwater. Fish trap deployments targeted the benthic and demersal prey of these predators in the three study sites and across a range of depths and hydrodynamic conditions. A variety of fish and invertebrate species known to be important components of benthic-foraging seabird diet were successfully captured by the traps, providing basic biological information on the prey assemblages observed in each site. The fish species observed in the highest abundance were saithe Pollachius virens and cod Gadus morhua. Benefits, limitations, and applications of this approach are discussed along with various factors relating to the performance of both methods. The shore-based observations rapidly identified relevant patterns in predator foraging activity which informed the targeted deployment of fish traps to provide complementary prey data. This novel combined approach has potential to reduce costs and uncertainty in EIA and for supporting the responsible development of the MRE industry.

Environmental impacts on marine energy: collision risks for marine animals and priority species for monitoring in Brazil

ABSTRACT Brazil has great potential for the development of technologies for the conversion of marine energy from waves and tides, which raises the discussion about the possible environmental impacts of these projects. This article seeks to synthesize knowledge about the risks of collision of marine animals, such as mammals, fish and birds, with marine renewable energy (MRE) devices, as well as to identify priority species for environmental monitoring along the Brazilian coast. The risk of marine mammals colliding with MRE devices is influenced by regional and behavioral factors. The risk of collision in a fish community is influenced by the avoidance behavior, the distribution of fish in the MRE sites and the stages of the enterprise (installation, operation and maintenance). Seabird collision risk is influenced by species behavior (geographical distribution, seasonal habitat use, diving time and depth) and the location of MRE structures (surface and/or water column). The survey of priority species for monitoring the risk of collision with MRE devices in Brazil consisted of 5 species of marine mammals, 13 taxa of seabirds, 5 species of endangered sea turtles and 18 species or groups of species of fish of economic importance to the country. The research review did not record the occurrence of collisions with marine animals. However, this does not mean that they did not occur, but that they may not have been observed due to monitoring challenges. The study concluded that research on the interaction of marine animals with MRE devices should be encouraged, even in prototypes and non-commercial projects, in order to reduce knowledge gaps and support the development of MRE in an environmentally sound manner. Keywords: Marine renewable energy, Collision risk, Species, Marine animals.

Underwater Acoustic Impact of a Marine Renewable Energy Device

Underwater Acoustic Impact of a Marine Renewable Energy Device

Insights into the behavioural responses of juvenile thornback ray Raja clavata to alternating and direct current magnetic fields.

As part of energy transition, marine renewable energy devices (MRED) are currently expanding in developed countries inducing the deployment of dense networks of submarine power cables. Concern has thus raised about the cable magnetic emissions (direct or alternating current) because of potential interference with the sensorial environment of magneto-sensitive species, such as sharks and rays. This study sought to assess the short-term behavioural responses of juvenile thornback rays (Raja clavata) (n = 15) to direct and alternating (50 Hz) uniform 450-μT artificial magnetic fields using 1 h focal-sampling design based on a detailed ethogram. Careful control of magnetic fields' temporal and spatial scales was obtained in laboratory conditions through a custom-made Helmholtz coil device. Overall, qualitative or quantitative behavioural responses of juvenile rays did not significantly vary between control vs. exposed individuals over the morning period. Nonetheless, rays under direct current magnetic field increased their activity over the midday period. Synchronisation patterns were also observed for individuals receiving alternating current exposure(chronologic and qualitative similarities)coupled with a high inter-individual variance. Further studies should consider larger batches of juveniles to address the effect of long-term exposure and explore the sensitivity range of rays with dose-response designs.

Marine renewable energy devices and their control: An overview

Marine renewable energy (MRE) is a label that embraces a range of technologies used to harness ocean energy, including wave, tidal stream, tidal barrage, ocean thermal energy conversion (OTEC) and salinity gradient, as well as offshore wind (floating and fixed). For the current analysis, floating solar is omitted from the MRE set. With an increasing drive towards zero-carbon energy provision, and the need for complementarity with increasing penetration of wind and solar, the need to tap the vast available MRE resources has never been greater. Ultimately, the adoption of MRE energy harnessing technology is contingent on the cost of MRE being competitive with other renewable, and conventional, energy sources, in terms of Levelised Cost of Energy (LCoE). The value of appropriate control systems, which can maximise the energy conversion capability of MRE and give added value to the capital investment, has been identified as an important modulator of LCoE. This paper examines the range of control problems within the gamut of MRE technologies and documents commonality and contrasts, as well as the emergence of control problems that are unique to aspects of MRE

Standardising Marine Renewable Energy Testing: Gap Analysis and Recommendations for Development of Standards

Marine renewable energy (MRE) is still an emerging technology. As such, there is still a lack of mature standards and guidance for the development and testing of these devices. The sector covers a wide range of disciplines, so there is a need for more comprehensive guidance to cover these. This paper builds on a study undertaken in the MaRINET2 project to summarise recommendations and guidance for testing MRE devices and components, by reviewing the recently published guidance. Perceived gaps in the guidance are then discussed, expanding on the previous study. Results from an industry survey are also used to help quantify and validate these gaps. The main themes identified can be summarised as: the development progression from concept to commercialisation, including more complex environmental conditions in testing, accurately modelling and quantifying the power generated, including grid integration, plus modelling and testing of novel moorings and foundation solutions. A pathway to a standardised approach to MRE testing is presented, building on recommendations learnt from the MaRINET2 round-robin testing, showing how these recommendations are being incorporated into the guidance and ultimately feeding into the development of international standards for the marine renewable energy sector.

Modeling Small Scale Impacts of Multi-Purpose Platforms: An Ecosystem Approach

Aquaculture and marine renewable energy are two expanding sectors of the Blue Economy in Europe. Assessing the long-term environmental impacts in terms of eutrophication and noise is a priority for both the EU Water Framework Directive and the Marine Strategy Framework Directive, and cumulative impacts will be important for the Maritime Spatial Planning under the Integrated Maritime Policy. With the constant expansion of aquaculture production, it is expected that farms might be established further offshore in more remote areas, as high-energy conditions offer an opportunity to generate more power locally using Marine Renewable Energy (MRE) devices. A proposed solution is the co-location of MRE devices and aquaculture systems using Multi-Purpose Platforms (MPPs) comprising offshore wind turbines (OWTs) that will provide energy for farm operations as well as potentially shelter the farm. Disentangling the impacts, conflicts and synergies of MPP elements on the surrounding marine ecosystem is challenging. Here we created a high-resolution spatiotemporal Ecospace model of the West of Scotland, in order to assess impacts of a simple MPP configuration on the surrounding ecosystem and how these impacts can cascade through the food web. The model evaluated the following specific ecosystem responses: (i) top-down control pathways due to distribution changes among top-predators (harbor porpoise, gadoids and seabirds) driven by attraction to the farming sites and/or repulsion/killing due to OWT operations; (ii) bottom-up control pathways due to salmon farm activity providing increasing benthic enrichment predicated by a fish farm particle dispersal model, and sediment nutrient fluxes to the water column by early diagenesis of organic matter (recycled production). Weak responses of the food-web were found for top-down changes, whilst the results showed high sensitivity to increasing changes of bottom-up drivers that cascaded through the food-web from primary producers and detritus to pelagic and benthic consumers, respectively. We assessed the sensitivity of the model to each of these impacts and the cumulative effects on the ecosystem, discuss the capabilities and limitations of the Ecospace modeling approach as a potential tool for marine spatial planning and the impact that these results could have for the Blue Economy and the EU’s New Green Deal.

Sea-trial verification of a novel system for monitoring biofouling and testing anti-fouling coatings in highly energetic environments targeted by the marine renewable energy industry

A novel system was developed to deploy settlement panels to monitor biofouling growth in situ and evaluate antifouling coatings at depths representative of operational conditions of full-scale marine renewable energy devices. Biofouling loading, species diversity, and succession were assessed at depths ranging from 25-40 m at four tests sites in Orkney (UK) featuring extreme wave and tidal current exposure to more sheltered conditions. Evaluations were carried out over a period of 8 months with intermediate retrieval of samples after 3 months. Early pioneer fouling communities, comprised of colonial hydroids, were succeeded by tube-forming amphipods across sites while solitary tunicates dominated in greater shelter. The highest biofouling loading was observed on high-density polyethylene (HDPE) panels (6.17 kg m−2) compared with coated steel (3.34 kg m−2) panels after 8 months. Distinct assemblages were present at exposed vs sheltered sites. Better understanding of fouling and antifouling strategies may provide guidance to more effectively manage biofouling impacts in this sector.

Potential Environmental Effects of Marine Renewable Energy Development—The State of the Science

Marine renewable energy (MRE) harnesses energy from the ocean and provides a low-carbon sustainable energy source for national grids and remote uses. The international MRE industry is in the early stages of development, focused largely on tidal and riverine turbines, and wave energy converters (WECs), to harness energy from tides, rivers, and waves, respectively. Although MRE supports climate change mitigation, there are concerns that MRE devices and systems could affect portions of the marine and river environments. The greatest concern for tidal and river turbines is the potential for animals to be injured or killed by collision with rotating blades. Other risks associated with MRE device operation include the potential for turbines and WECs to cause disruption from underwater noise emissions, generation of electromagnetic fields, changes in benthic and pelagic habitats, changes in oceanographic processes, and entanglement of large marine animals. The accumulated knowledge of interactions of MRE devices with animals and habitats to date is summarized here, along with a discussion of preferred management methods for encouraging MRE development in an environmentally responsible manner. As there are few devices in the water, understanding is gained largely from examining one to three MRE devices. This information indicates that there will be no significant effects on marine animals and habitats due to underwater noise from MRE devices or emissions of electromagnetic fields from cables, nor changes in benthic and pelagic habitats, or oceanographic systems. Ongoing research to understand potential collision risk of animals with turbine blades still shows significant uncertainty. There has been no significant field research undertaken on entanglement of large animals with mooring lines and cables associated with MRE devices.

Applying Two Active Acoustic Technologies to Document Presence of Large Marine Animal Targets at a Marine Renewable Energy Site

Coastal regions are highly used by humans. The growing marine renewable energy (MRE) industry will add to existing anthropogenic pressures in these regions. Regulatory bodies require animal risk assessment before new industrial activities can progress, and MRE is no exception. Preliminary data of marine mammal use of an MRE device deployment location could be informative to permitting. A combination of downlooking hydroacoustics using an echosounder and acoustic camera (imaging sonar) was used to provide a number of large targets (proxy for large fish and marine mammals) in an area of interest for MRE tidal turbine deployment in Western Passage, Maine, USA. Data were collected in May, June, August, and September of 2010 and 2011. Of the nine large targets confirmed to be animals, eight were porpoises and one was a shark. Few large targets were observed in May and June, with the majority (90%) being present in August and September of both years. The most large targets were observed when tidal current speed was less than 1 m·s−1. These data provide a preliminary assessment of large targets in a single location over sixteen 24-h surveys. The aforementioned methodology could be used for future pre- and post-installation assessments at MRE device deployment locations. Their use in concert with visual and passive acoustic monitoring can provide water depth usage by marine mammals, which is a metric that is difficult to assess with passive acoustic and visual techniques.

Wave loads on a land-based dual-chamber Oscillating Water Column wave energy device

Wave energy is one of renewable energy resources with great potential. Due to the mechanical and structural simplicity, Oscillating Water Column (OWC) Wave Energy Converter (WEC) is considered to be one of the most promising marine renewable energy devices. However, OWC remains not commercialized mainly due to its complex hydrodynamic performance and uncertainty in wave loads. In the present study, based on potential flow theory and time-domain higher-order boundary element method (HOBEM), a fully nonlinear numerical model is developed and used to investigate the wave-induced force and bending moment on a land-fixed dual-chamber OWC device. The Bernoulli equation is used to calculate the wave force and bending moment. The equation is modified by accounting for the pneumatic pressure in the air chamber and the viscosity effect and then solved using an acceleration-potential method. The numerical model was compared with the experiment carried out in a wave-current flume at the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, China, and good agreement between the simulation and experimental results was observed. The horizontal components of wave forces on the two curtain walls of the dual-chamber OWC WEC were found to be much larger than the corresponding vertical components. The seaside curtain wall suffered much larger wave loads in comparison with the inner curtain wall. Therefore, the wave force on the seaside curtain wall is the dominant force. The largest wave-induced bending moment occurs at the joint of device and seabed. The effects of the sub-chamber width ratio and curtain-wall draft on the wave-induced force and bending moment are investigated. The dominant wave force and moment increase with curtain wall draft. And the peak wave loads can be reduced by moving the internal curtain wall close to the seaside curtain wall.