Offshore Farms Research Articles

Genetic parameters and genotype-by-environment interaction estimates for growth and feed efficiency related traits in Chinook salmon, Oncorhynchus tshawytscha, reared under low and moderate flow regimes

BackgroundA genotype-by-environment (G × E) interaction is defined as genotypes responding differently to different environments. In salmonids, G × E interactions can occur in different rearing conditions, including changes in salinity or temperature. However, water flow, an important variable that can influence metabolism, has yet to be considered for potential G × E interactions, although water flows differ across production stages. The salmonid industry is now manipulating flow in tanks to improve welfare and production performance, and expanding sea pen farming offshore, where flow dynamics are substantially greater. Therefore, there is a need to test whether G × E interactions occur under low and higher flow regimes to determine if industry should consider modifying their performance evaluation and selection criteria to account for different flow environments. Here, we used genotype-by-sequencing to create a genomic-relationship matrix of 37 Chinook salmon, Oncorhynchus tshawytscha, families to assess possible G × E interactions for production performance under two flow environments: a low flow regime (0.3 body lengths per second; bl s−1) and a moderate flow regime (0.8 bl s−1).ResultsGenetic correlations for the same production performance trait between flow regimes suggest there is minimal evidence of a G × E interaction between the low and moderate flow regimes tested in this study, for Chinook salmon reared from 82.9 ± 16.8 g (x¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\overline{\ ext{x}}}$$\\end{document} ± s.d.) to 583.2 ± 117.1 g (x¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\overline{\ ext{x}}}$$\\end{document} ± s.d.). Estimates of genetic and phenotypic correlations between traits did not reveal any unfavorable trait correlations for size- (weight and condition factor) and growth-related traits, regardless of the flow regime, but did suggest measuring feed intake would be the preferred approach to improve feed efficiency because of the strong correlations between feed intake and feed efficiency, consistent with previous studies.ConclusionThis new information suggests that Chinook salmon families do not need to be selected separately for performance across different flow regimes. However, further studies are needed to confirm this across a wider range of fish sizes and flows. This information is key for breeding programs to determine if separate evaluation groups are required for different flow regimes that are used for production (e.g., hatchery, post smolt recirculating aquaculture system, or offshore).

Environmental Life Cycle Assessment of multi-use of marine space: A comparative analysis of offshore wind energy and mussel farming in the Belgian Continental Shelf with terrestrial alternatives

The Belgian Continental Shelf is a highly used part of the North Sea, where many different maritime activities thrive, such as shipping, fishing and energy production. Offshore wind energy in particular has gained importance in the region and concessions zones are allowed to be combined with aquaculture activities. It is unclear what the environmental impact of maritime multi-use is, from a life-cycle perspective, where there is potential to create synergies in the value chains, and how similar the impact compares to currently used alternatives. Therefore, this study performs a Life Cycle Assessment on a combination of a full scale existing wind energy farm and a mussel farm design. When analyzing the net environmental impact results of the multi-use offshore farm at the level of three areas of protection, i.e. human health, ecosystem quality and natural resources, it shows that the mussel farm contributes relatively the most to the net impacts, while the majority of the avoided burdens are attributed to the wind farm. Mainly the supply chain of materials required to manufacture its components followed by the operational activities of the multi-use offshore farm contribute to the environmental footprint. Moreover, taking advantage of joint activities, i.e. combined transport between the wind and mussel farm during operational activities (Scenario 1) and at decommissioning phase (Scenario 2) did not show a significant reduction in the overall net impacts of a multi-use farm. The life cycle assessment results of a multi-use offshore farm are furthermore compared with relevant terrestrial benchmarks in Belgium, i.e. nuclear energy and pork meat production. While the benchmarks have a high burden on the area of protection ecosystem quality due water and land use requirements, the multi-use farm mainly impacts the remaining areas of protection, i.e. human health and natural resources, again as a consequence of the burdens of its supply chain. This study reveals the potential of offshore multi-use farms in terms of environmental sustainability, offering valuable insights to policy-makers and value chain actors, and generally contributes to well-informed decision-making.

Applying High-Temperature SuperconducTechnologies into Power Systems

implementing of distribution and transmission power systems for urban areas and for future renewableenergy to meet future demand is a challenging task whenconventional cables and transformers are considered.Therefore, there are several methods, that have applied inconational power systems to reduce power losses, voltage regulator issues , capital cost of whole system and increasingpower delivering in urban areas and from offshore farms,such as carefully sited and operated distributed generation(DG) and distributed control techniques. However, thesetechniques may raise others challenges in networks such as stability, voltage regulators issues and increasing capital costof networks. Since High Temperature Superconductor(HTS) cables exhibit zero resistance when cooled to theboiling point of liquid nitrogen (77Keliven), they have thepotential to be used to address these issues in distribution and transmission networks. Consequently, this paperreviews super-conductor power systems: the workpreviously achieved in the DC and AC superconductorpower systems and describes the materials and methodswhich they used. In addition, it shows how the superconductor technologies can address these issues whenthey are used for distribution and transmission powe r systems.

How do technological choices affect the economic and environmental performance of offshore wind farms?

The ongoing energy transition towards fully sustainable energy systems requires designing wind farms looking beyond the sole levelized cost of energy, in order to concurrently ensure not only the economic profitability but also the environmental friendliness of future plants. Within this new approach to design, it becomes necessary to understand the effects that various possible technological choices have on both the economic and the environmental performance of wind farms. This study presents a framework designed to support these coupled economic-environmental assessments. The capabilities of the code are showcased by analysing the impact of different choices in terms of support structure type, specific power, tower height, powertrain type, and array and export voltage level for an exemplary offshore farm, chosen here as the IEA Wind 740-10-MW Reference Offshore Wind Plant with irregular layout. While the effects of many technological choices on the cost of energy are already well understood by industry, the present analysis shows that — at least in this specific case — climate change impacts are mainly driven by steel production, due to the massive amount of required material, but also, interestingly, by vessel activities. A low specific power, tall towers, and a high export cable voltage appear to offer the greatest potential for the concurrent improvement of the environmental and economic performance of the plant.

Investigating the relationship between microbial network features of giant kelp "seedbank" cultures and subsequent farm performance.

Microbial inoculants can increase the yield of cultivated crops and are successful in independent trials; however, efficacy drops in large-scale applications due to insufficient consideration of microbial community dynamics. The structure of microbiomes, in addition to the impact of individual taxa, is an important factor to consider when designing growth-promoting inoculants. Here, we investigate the microbial network and community assembly patterns of Macrocystis pyrifera gametophyte germplasm cultures (collectively referred to as a "seedbank") used to cultivate an offshore farm in Santa Barbara, California, and identify network features associated with increased biomass of mature sporophytes. We found that [1] several network features, such as clustering coefficient and edge ratios, significantly vary with biomass outcomes; [2] gametophytes that become low- or high-biomass sporophytes have different hub taxa; and [3] microbial community assembly of gametophyte germplasm cultures is niche-driven. Overall, this study describes microbial community dynamics in M. pyrifera germplasm cultures and ultimately supports the development of early life stage inoculants that can be used on seaweed cultivars to increase biomass yield.

Atlantic salmon in chronic turbulence: Effects on growth, behaviour, welfare, and stress

An increasing number of aquaculture companies aim to relocate Atlantic salmon (Salmo salar) farms to offshore locations exposed to large wave action. However, the impact that this environment will have on the fish reared within remains unknown, raising questions about their coping ability and welfare. The purpose of this study was to address this knowledge gap and understand how Atlantic salmon respond to wave-induced turbulence. For 8 weeks, post-smolts were exposed to chronic turbulence created using specially designed wave-generating equipment. During the trial, feed intake, growth, behavioural conditioning, plasma biochemistry and welfare were monitored. At study end, swimming capacities were determined, and vertebral deformities were assessed in a sub-group of fish. Despite both control and turbulence groups doubling their weights, the turbulence group exhibited a 5% reduction in size. A drop- in appetite, 17% across the first five days, and deviant behaviour was observed for the first 3 weeks in the turbulence group. These disparities disappeared in the latter half of the trial, suggesting the fish acclimatized. Welfare scores, haematological parameters, critical swimming speeds and deformity prevalence remained similar across both groups, suggesting the fish were not impacted by chronic turbulence on a physical or physiological level. In conclusion, these findings demonstrate that Atlantic salmon is a robust species with the capacity to adapt to novel more chaotic environments without suffering substantial reductions in welfare or long-term production performance. This suggests that Atlantic salmon will be able to adapt and thrive in wave-exposed turbulent offshore farm environments.

Fusing heterogeneous tri-dimensional information for reconstructing submerged structures in harsh sub-sea environments

Exploiting stronger winds at offshore farms leads to a cyclical need for maintenance due to the harsh maritime conditions. While autonomous vehicles are the prone solution for O&M procedures, sub-sea phenomena induce severe data degradation that hinders the vessel’s 3D perception. This article demonstrates a hybrid underwater imaging system that is capable of retrieving tri-dimensional information: dense and textured Photogrammetric Stereo (PS) point clouds and multiple accurate sets of points through Light Stripe Ranging (LSR), that are combined into a single dense and accurate representation. Two novel fusion algorithms are introduced in this manuscript. A Joint Masked Regression (JMR) methodology propagates sparse LSR information towards the PS point cloud, exploiting homogeneous regions around each beam projection. Regression curves then correlate depth readings from both inputs to correct the stereo-based information. On the other hand, the learning-based solution (RHEA) follows an early-fusion approach where features are conjointly learned from a coupled representation of both 3D inputs. A synthetic-to-real training scheme is employed to bypass domain-adaptation stages, enabling direct deployment in underwater contexts. Evaluation is conducted through extensive trials in simulation, controlled underwater environments, and within a real application at the ATLANTIS Coastal Testbed. Both methods estimate improved output point clouds, with RHEA achieving an average RMSE of 0.0097m - a 52.45% improvement when compared to the PS input. Performance with real underwater information proves that RHEA is robust in dealing with degraded input information; JMR is more affected by missing information, excelling when the LSR data provides a complete representation of the scenario, and struggling otherwise.

Interactive effects of multiple stressors with significant wave height exposure on farmed Atlantic salmon (Salmo salar) welfare along an inshore-offshore gradient

Fish farming is the fastest growing food production sector worldwide and now accounts for most human fish consumption. Expansion of finfish aquaculture to exposed offshore marine environments is appealing where additional sheltered areas are unavailable. While more energetic environments may reduce waste accumulation and parasite exposure, effects on fish health and wellbeing are largely speculative. The multiple stressors faced by fish on offshore farms may interact synergistically and increase their cumulative impact. We used 20 months of health and welfare data from eight Atlantic salmon (Salmo salar) sea pen farms in Scotland along a wave exposure gradient to assess the effects of, and interactions between, environmental variables and management treatments on fish mortality and parasite loads. While farms showed high variability in mortality rate and sea lice infections, multi-level Bayesian modelling indicated that wave exposure primarily modulated effects of other variables. Higher exposure farms showed steeper increases in mortality with time and with extreme temperatures. Similarly, sea lice infections tended to increase with time, with higher exposure farms seeing steeper increases at higher Amoebic Gill Disease (AGD) scores and at high temperatures. The effect of AGD was greater at slow water speeds. Treatments against parasites were more frequent at low exposure farms, leading to uncertainty in their impact on welfare across farms. The support for interactive effects of wave exposure with other variables rather than strong direct effects suggests an accumulation of chronic and acute stressors. Expansion of aquaculture to more energetic offshore environments may have negative impacts on fish health in some circumstances, requiring adaptation of practices. In particular, the stronger increase in mortality over time may have implications for cycle length in different environments, and the more dramatic impacts of the warmest temperatures at high exposure farms call for consideration of the change in water temperature both inshore and offshore.

Cost and financial evaluation model for the design of floating offshore wind farms

A cost and financial evaluation model is proposed for floating wind farm designs. The model evaluates the cost of the offshore farms depending on the required capacity, technical aspects, and technology implemented, among other aspects. The costs involved in the different phases of the farm construction are studied. The main equations developed for the model construction are simplified and presented in this document. This study presents a comparison of several financial indicators for the following floating concepts: Spar-Buoy (TELWIND), Tension-Leg-Platform (CENTEC-TLP) and Semi-Submersible (SATH). The model is applied to a farm composed of thirty-four 10 MW floating turbines in a Life Cycle Analysis perspective. The model allows the determination of the optimal floating platform for a site and identifies the optimal solution for a floating farm depending on the economic and financial aspects associated.

Performance of European oysters (Ostrea edulis L.) in the Dutch North Sea, across five restoration pilots

IntroductionThe European flat oyster (Ostrea edulis) is a biogenic reef former, internationally recognised as threatened and declining in the NE Atlantic by OSPAR and one of the focal species in nature inclusive designs in offshore windfarms in The Netherlands. Oyster reefs offer habitat to many other benthic hard substrate and fish species and provide ecosystem functions such as shelter and feeding grounds. European flat oyster reefs have disappeared from the Dutch North Sea in the early 1900s due to overfishing and diseases but are now subject of nature restoration under the Dutch Marine Strategy.MethodSince 2018, pilot projects have started in the Dutch North Sea to restore European flat oysters at suitable locations, such as offshore windfarms or natural reefs, which are protected from bottom trawling. We compared European flat oyster performance in five pilot projects, using translocated adult oysters sourced from Ireland, Norway, and the Netherlands. The aim of this research was to assess the performance of translocated oysters between pilots, to assess the installation and monitoring techniques, and to come forward with recommendations for future pilot projects.ResultsWe found that translocation of both foreign sourced flat oyster populations (Ireland and Norway in nearshore and offshore areas) and local oysters (in nearshore areas) result in good oyster performance. Oysters were able to grow (max 3.67 mm/month) and reproduce (larvae present) in their new environment. We found that growth rate was explained by origin and average water temperature, to a lesser extent by number of months, location and salinity and not to other environmental factors such as pH and O2. Correlations between growth and environmental conditions need to be considered with caution, since not all pilots were sampled just before and after the growing season. Oysters were Bonamia-negative at the start and end of the pilots, indicating that the offshore Dutch North Sea is still Bonamia-free.Discussion, conclusions, recommendationsBy the year 2050 more than ten new offshore farms will be constructed in the Dutch North Sea and some sites will be suitable for oyster restoration. We conclude that local and foreign sourced oysters performed well at all locations. Based on the success and failure of the different outplacement and monitoring techniques, we provide recommendations on good practice for the future, including developing standardized monitoring protocols. This will enable better inter-site comparisons in upcoming oyster restoration pilots.

Economic Risk of Wind Farm Investments in UAE: Evaluation through Real Options Approach

This study examines the potential of business investments in wind offshore farm in the United Arab Emirates through projection of five different possible scenarios. The evaluation was done by using real option approach and Monte Carlo simulation imbibing the potential risk on investment with the source of funds used. Our analysis indicates that the return on investments and the risk on delay option remain at the highest degree if the project is financed with 50% government support and 50% investor’s own equity. On the contrary, a 100% bank-financed project yields lowest investments return and lowest risk option to delay. This implies that the financial leverage and the high bank interest rate are significant factors in influencing the economic risk and return of the wind farm project. This research contributes to the existing literature by highlighting the significance of real options application in the most-sought energy sector – wind farm. Moreover, this will pave way for small and medium enterprises (SMEs) in the UAE to invest in this energy field.

High-fidelity modelling of a six-turbine tidal array in the Shetlands

Micro-siting tidal stream turbines in a confined seabed area requires a extensive understanding of the flow dynamics over the water column at turbine deployment locations so that operating conditions are assessed, wake effects can be estimated to infer the energy yield [1], or bathymetry effects can be quantified. Tidal currents have the advantage of being highly predictable and mostly bidirectional but the uneven bathymetry found at most of sites introduces a high variability to the flow conditions within relatively short distances. Considering future tidal turbine arrays will comprise dozens of devices, deploying ADCPs at each turbine position would be very expensive or very time consuming, outlining the need for accurate modelling tools to be used as digital twins in micro-siting. Shallow-water models are widely adopted in preliminary design of tidal arrays but fail to capture the three dimensional nature of the flow and predict deflected wakes whose streamwise length is also over-predicted [2]. Thus, eddy-resolving method are required to fully capture the turbulence from the free-stream flow, induced by turbines and from bathymetry. \\
 This study provides a real-project application of the state-of-the-art large-eddy simulation (LES) code DOFAS (Digital Offshore Farms Simulator) [3] to the six 100kW-turbine array deployed by NOVA Innovation Ltd. in the Shetlands, UK [4]. The bathymetry data has been obtained from EMODnet database with the velocity profiles set at the inlet condition of both ebb and flood tides imported from Macleod et al. (2019) [4]. The deployment site is characterised by steep slopes with a maximum depth of 45 m at the cross-section where turbines are located. The bathymetry has a downwards slope when the flow goes in the ebb tide direction whilst upstream during flood tide. The tidal rose indicated a slight deviation of about 20$^{\circ}$ between ebb and flood directions. The turbines have a diameter ($D$) of 9 m attached to a 10 m long hub whose diameter is 1 m. Three array configurations have been studied: (i) single row of three turbines, (ii) two rows of turbines spaced 8$D$, and (iii) two rows of turbines spaced 12$D$. The computational domain extends over 600 m by 300 m in the horizontal plane yielding 540 million cells, requiring 32,500 CPU hours to compute 30 min of physical time.\\
 Results show that bathymetry effects at this site play a larger role when designing the location of the secondary row of turbines compared to wake effects from upstream turbines. During the ebb tide, the increase in water depth reduces the wake recovery far downstream so that the array with 12$D$ row spacing has a lower performance than the 8$D$ one with approx. 30\% decrease in energy yield. Conversely, the uphill shape of the bathymetry during the flood enables a fast wake recovery so that the downstream row experiences almost no energy yield loss due to wakes.

Large-eddy simulations of interaction between surface waves and a tidal turbine wake in a turbulent channel

Tidal stream turbines are now being developed for array deployments, largely at sites with relatively shallow water depths on either bed-supported, or floating support structures. Proximity to the free-surface presents design challenges with increased exposure to wave-induced kinematics leading to potential for increased peak- and fatigue-loads. Free surface proximity can also alter wake recovery rates which can influence the siting, and operation, of further turbines. To-date the impact of waves on turbine loading and on wake recovery has receivedlimited attention, generally for specific combinations of conditions reproducible in experimen tal facilities [1-2] or numerical models [3]. Improved understanding of how waves affect both turbine loading, and wake dynamics is necessary to inform the development of appropriate load prediction and mitigation methods and to further parameterise wake recovery to inform array siting.
 This work presents CFD analysis of the loading and wake of a three-bladed horizontal axis tidal turbine within a wide, shallow channel with a turbulent inflow developed using a synthetic eddy method and free surface waves modelled using a Level-Set Method (LSM). The turbine and wave conditions considered are based on prior experimental studies [1] within a channel depth h = 0.45 m and mean flow U = 0.47 m/s. The simulated channel is width 3.67h and length 88h and long-crested regular waves are imposed, with the focus of this study on waves with non-dimensional wavenumber kh = 2.8, comparable with experimental conditions. Simulations are accomplished using the in-house large-eddy simulation (LES) code DOFAS(Digital Offshore Farms Simulator) [4], which adopts an Actuator Line Method (ALM) to resolve the turbine blades. LSM is used to model the air-water interface in an accurate manner [5] with waves can be generated in DOFAS using linear or second-order Stokes theories with an absorption layer placed at the outlet of the domain to avoid wave reflections. At the inlet a mean logarithmic velocity profile is imposed over which artificial turbulence is added. Simulations were run for 400 s of physical time on 8,000 cores using ARCHER2.
 The waves studied are shown to alter the rate of wake recovery, increasing the rate in the near-wake of the turbine and slightly reducing the rate beyond eight diameters downstream. Analysis of turbulence characteristics indicates a significant variation across the water column due to wave action. Propagation over the turbine wake also introduces directionality to the wave field, which is associated with the change of wave-speed over the wake region. Modal decomposition analysis of the velocity fluctuations with Proper Orthogonal Decomposition(POD) reveals that the wake dynamics behind the turbine change due to the waves.

Numerical Modeling of the Micromechanics Damage of an Offshore Electrical High-Voltage Phase

Due to the strong growth of offshore renewable energies, research and engineering in this field is constantly expanding. One of the centerpieces of these technologies is the high-voltage electrical cable, generally made of copper, to transport the energy produced from the offshore farm to the onshore station. The critical nature of these cables lies in the proven resistance that they must demonstrate during stays underwater for several years, even decades, in difficult environmental conditions, which begin at the handling, shipping and underground burial stage. The marine environment can lead to deformation of the copper wires well beyond the limit of proportionality and, consequently, to breakage. Copper, although being an exceptional electrical conductor, has very poor mechanical properties. The plasticity generated by the excessive deformation of copper wires affects all of the physical properties of copper. When plasticity develops, electrical transport is affected and the heat within copper increases, but care should be given to not exceed 90 °C, as this would result in the shutdown of the cable with dramatic economic consequences. The work carried out in this article, which is part of the National Project EMODI as well as the European Project FLOW-CAM, aims at studying the mechanical behavior of the phase in order to correlate the deformation levels reached to the phase geometry as well as operating mechanisms of damage which reflect the proliferation of microstructural defects within the conductor. To do this, we propose a numerical model using Abaqus. Correct description of the effects of several parameters (geometry of the phase) and plasticity development on the performance of the phase were simulated and discussed.

Natural variation of Macrocystis pyrifera gametophyte germplasm culture microbiomes and applications for improving yield in offshore farms.

With national interest in seaweed-based biofuels as a sustainable alternative to fossil fuels, there is a need for tools that produce high-yield seaweed cultivars and increase the efficiency of offshore farms. Several agricultural studies have demonstrated that the application of microbial inoculants at an early life stage can improve crop yield, and there is an opportunity to use similar techniques in seaweed aquaculture. However, there is a critical knowledge gap regarding host-microbiome associations of macroalgae gametophytes in germplasm cultures. Here, we investigate the microbial community of Macrocystis pyrifera gametophyte germplasm cultures that were used to cultivate an offshore farm in Santa Barbara, California and identify key taxa correlated with increased biomass of mature sporophytes. This work provides a valuable knowledge base for the development of microbial inoculants that produce high-biomass M. pyrifera cultivars to ultimately be used as biofuel feedstocks.

Citizen Science and Expert Judgement: A Cost-Efficient Combination to Monitor and Assess the Invasiveness of Non-Indigenous Fish Escapees

Mapping the distribution and evaluating the impacts of marine non-indigenous species (NIS) are two fundamental tasks for management purposes, yet they are often time consuming and expensive. This case study focuses on the NIS gilthead seabream Sparus aurata escaped from offshore farms in Madeira Island in order to test an innovative, cost-efficient combined approach to risk assessment and georeferenced dispersal data collection. Species invasiveness was screened using the Aquatic Species Invasiveness Screening Kit (AS-ISK), and revealed a high invasion risk. Occurrences of S. aurata were assessed involving citizens in GIS participatory mapping and data from recreational fishing contests. A probability map showed that S. aurata is well dispersed around Madeira Island. This assessment proved to be a cost-efficient early warning method for detecting NIS dispersal, highlighting the urgent need for additional surveys that should search for sexually mature individuals and assess the direct and indirect impacts in the native ecosystem.

Comparative study of the impacts of fish cage culture on some environmental factors and Macrobenthic communities in offshore farms in the southern Caspian Sea

The aim of this study was to investigate the effects of fish cage culture on Macrobenthic in the southern Caspian Sea. Samples were collected in two offshore farms with four floating polyethylene cages with a production of 60 tons for 5 months in 2015. Sampling was performed of macrobenthos, physicochemical, and sediment in January, March, May, and August at the depths of shade, 50, 100, and 1000 m in three geographical directions (east, west, and south) of the farm. Macrobenthic analysis showed Hypaniola kowalewskii and Streblospio gynobranchiata were predominant, which resulted in an unusual condition due to the effectiveness of the marine farm. There was a linear relationship between environmental factors and macrobenthos communities under the RDA analysis test and the water temperature was the most crucial factor in the density of the dominant species in both fish farm sites. The dominant Macrobenthic species were subjected to environmental conditions in addition to the influence of temperature, salinity, pH, dissolved oxygen, nitrogen, and phosphorus compounds. This situation can be attributed to the hydrological conditions of the studied area; low production of fish, a short period of fish farming, suitable depth of cages established and different water flow directions.

Diverse responses of coastal communities to offshore wind farming development in Southern Spain

Abstract Despite having one of the fastest rates of wind power growth in Europe, offshore wind power development in Spain has been relatively slow. One of the factors affecting its deployment is strong local opposition. In this paper, we explore the main factors affecting local perceptions of offshore wind farms in the coastal regions of Southern Spain. We also compare local opinions of on-land and offshore farms, their impacts on local landscapes/seascapes, and their compatibility with local practices and values. To this end, a multi-phase research approach was applied, based on several stages of data collection and analysis and on surveys conducted between 2012 and 2022. Our study shows that the conflicts surrounding offshore wind farms are linked to the perception of the sea and the wind as important local resources and the perceived right of the coastal region to use these resources to generate wealth for their communities. The coastal communities’ values, perceptions, and practices regarding the sea have a fundamental influence on their opinions. Our research indicates that local people are more likely to accept offshore wind farms if they provide socioeconomic benefits for their communities and if joint use of marine resources can be guaranteed.

The power balancing benefits of wave energy converters in offshore wind-wave farms with energy storage

With many countries planning to significantly increase grid renewable energy penetration levels, we consider the role of wave energy in supply–demand matching. We investigate how incorporating wave power into an offshore wind farm affects farm power predictability, smoothness, required energy storage capacity, and cost. In this paper, we do a first-order cost analysis of an offshore farm comprised of floating wind turbines and wave energy converters that are both standalone and combined and onshore compressed air energy storage. Then, we do a parameter sweep investigation of an isolated power network supplied by varied grid renewable energy penetration levels supplemented by natural gas, varied distribution of renewable energy between wind and wave power, and varied power capacity of a compressed air energy storage system supplying power to a shoreline community. For each parameter set, we consider the historical hourly electricity demand and wind-sea data of a coastal California community over a year, and optimize the energy storage schedule to reduce curtailed power, stored energy, and base gas plant operational cost. We show that a co-located wind-wave farm has smoother power supply, less energy curtailment, and higher farm-to-grid efficiency than a solely wind farm. That is, a 50%–50% wind-wave farm has a 15% smaller coefficient of variation in the power supply, 6% less curtailed power, and 2% higher farm-grid efficiency than a 100% wind farm when the grid is 100% renewable energy. These benefits of wave power potentially decrease the need for interconnecting regional transmission lines to match power supply with demand. The intent of this paper is to provide baseline system technical results to help future researchers and policy makers make decisions about offshore hybrid wind-wave-storage farms.

Toward an environmentally responsible offshore aquaculture industry in the United States: Ecological risks, remedies, and knowledge gaps

There is growing interest in cultivating fish, shellfish, and seaweeds in offshore waters. Existing pilot and commercial facilities demonstrate that offshore aquaculture is technically feasible, and that it can improve growing conditions and farmed animal health under some conditions. Many of the advances that have improved the ecological outcomes of nearshore aquaculture are likely to apply to offshore facilities as well. However, some ecological risks will likely persist in the near term. The vulnerability of offshore farm site infrastructure to weather events and vessel collisions could be similar to nearshore sites and result in escape events, and the farming of finfish will likely require feeds that include fishmeal and fish oil, ingredients derived from finite marine resources, and terrestrial-origin ingredients whose embodied carbon footprint may be high. Moreover, because offshore aquaculture occurs in ecological contexts that differ significantly from nearshore contexts, different kinds of ecological risks may also arise as the sector grows. Existing claims on marine space and conflicts with other uses could result in clustering of farms in favorable sites, posing a risk of cumulative impact. The transport, deployment, operation, and decommissioning of infrastructure associated with offshore farms may also pose ecological risks related to harmful interactions with marine wildlife (e.g., entanglement, vessel strikes, and habitat exclusion). Here we synthesize information on the ecological risks posed by offshore aquaculture and how to mitigate them. We also use this synthesis to identify knowledge gaps to inform the development of a research agenda and effective policies that can allow an offshore aquaculture industry to grow in the federal waters of the United States while minimizing environmental impact.