Marine Application of Fiber Reinforced Composites: A Review

Rotor blades are critical components of tidal energy converters, typically manufactured from thermoset fibre-reinforced composite (FRC) materials using vacuum infusion processing. High load demands result in thick-section laminates (10–100 mm), particularly at the blade root, posing manufacturing challenges. While tidal and wind turbine blades appear similar in design, the fundamentally different operational conditions result in distinct structural differences and, therefore, manufacturing requirements, offering opportunities for the tidal sector to innovate. Advances in materials and manufacturing technologies provide potential to rethink current practices for improved design and process efficiency. Additionally, the relative immaturity of tidal technology allows for early integration of circularity principles, minimising waste and optimising resources. This paper serves as a comprehensive resource for the tidal turbine blade sector, reviewing current manufacturing practices and exploring alternative techniques. Combining knowledge from academic literature and industrial reports, it outlines blade design, material selection, and current manufacturing processes. The paper evaluates emerging techniques and potential modifications to established methods. Due to the range of turbine designs in the sector, optimal materials and manufacturing combinations will differ. This study offers manufacturers valuable insights to support informed and strategic choices to improve and advance tidal turbine blade production.

After wind and solar energy, tidal energy presents the most prominent opportunity for generating energy from renewable sources. However, due to the harsh environment that tidal turbines are deployed in, a number of design and manufacture challenges are presented to engineers. As a consequence of the harsh environment, the loadings on the turbine blades are much greater than that on wind turbine blades and, therefore, require advanced solutions to be able to survive in this environment. In order to avoid issues with corrosion, tidal turbine blades are mainly manufactured from fibre reinforced polymer composite material. As a result, the main design and manufacture challenges are related to the main structural aspects of the blade, which are the spar and root, and the connection between the blade and the turbine hub. Therefore, in this paper, a range of advanced manufacturing technologies for producing a 1 MW tidal turbine blade are developed. The main novelty in this study comes with the challenges that are overcome due to the size of the blade, resulting in thickness composite sections (> 130 mm in places), the fast changes in geometry over a short length that isn’t the case for wind blades and the required durability of the material in the marine environment. These advances aim to increase the likelihood of survival of tidal turbine blades in operation for a design life of 20 + years.

Water’s natural flowing movements, such as in rivers and reservoirs, can be used in the production of electricity. Furthermore, both the tidal range (the periodic rise and fall of the sea level) and the energy contained in flow and waves can be used in the ocean energy system. Both types of energy conversion are classed as renewable energies. While the typical use of hydropower has been widespread for hundreds of years, using the ocean for energy is in its infancy. Large hydropower turbine-generator technologies are highly optimized, robust, and cost-effective designs, with peak energy conversion efficiencies of more than 93%. However, advancements for small-scale turbine-generators must reduce technology cost and enable more compact support structures and smaller physical and environmental footprints to achieve economic feasibility. The environmental performance of turbine designs continues to improve, in the form of blade shape enhancements to reduce injury to fish and aeration into turbine flow passages to improve the water quality of releases. Therefore, research and development have been focused on advanced materials and manufacturing for powertrain components, innovative hydrodynamic and mechanical concepts to reduce integrated turbine-generator size (diameter and length) and increase speed, embedded condition monitoring sensors, and powertrain design innovations that afford flexibility in selection of design objectives such as initial cost minimization, efficiency over a range of head and flow rates, and durability or ease of replacement. Ocean energy is one of the most promising resources that can be broadly split into tides, waves, tidal or marine currents, temperature gradients, and Salinity gradients. It has potential of the same order as that of the present capacity of electricity generation worldwide. The majority of ocean energy converters are fabricated from metals like steel and composite materials. Steel offers good fatigue and stress limits, while composites possess some cost and weight saving advantages over steel, but the fatigue and stress limits are not yet well understood in comparison to steel. Other wave devices are being designed to use rubber or other flexible materials as the main structural component. Composites provide many advantages for manufacturing underwater structures such as tidal turbine blades, and wave devices, which generally offer strength, fatigue-resistance, corrosion resistance, buoyancy, and cost-effectiveness. New materials are also explored to meet the needs of a wide variety of designs, many engineering and materials options, and the unpredictable environment of subsea and new ocean energy technologies. Next-generation component would drive the costs down for multiple energy conversion system solutions, including advanced controls to tune devices to extract the maximum energy from each sea state, compact high-torque, low-speed generator technologies, and corrosion- and biofouling-resistant materials and coatings. This chapter will give a brief review about state of the art of advanced materials and devices including various components for hydropower and ocean energy.

The accumulation characteristics of surface chloride in concrete in different zones are different in the marine environment. A series of laboratory experiments were conducted to investigate the surface chloride and permeation characteristics of concrete in a simulated marine environment. The experimental results indicated that the surface chloride and chloride profiles of concrete in different zones of marine environment decreased in the following order: tidal zone > splash zone > submerged zone > atmospheric zone. The width of the ascent zone of Cl− concentration at tidal and splash zones was far less than that of the influential depth of moisture transport (IDMT), and the range of convection zone was dependent on the IDMT. Cl− at splash and tidal zones penetrated into concrete as a bulk liquid by non-saturated permeation driven by a humidity gradient. The change of chloride profiles in concrete along the altitudinal gradient was consistent with that of the cyclic water absorption amount (CWAA). The transport rate of chloride was the highest at the highest point of the tide.

This study developed a sensor to monitor the corrosion of reinforced concrete structures. Concrete pile specimens with embedded sensors were used to obtain data on corrosion and cathodic protection for bridge columns in a real marine environment. Corrosion potential, cathodic protection current density, concrete resistivity, and the degree of depolarization potential were measured with the embedded sensors in concrete pile specimens. The cathodic protection (CP) state was accurately monitored by sensors installed in underwater, tidal, splash, and atmospheric zones. The protection potential measurements confirmed that the CP by Zn-mesh sacrificial anode was fairly effective in the marine pile environment. The protection current densities in the tidal, splash zones were 2–3 times higher than those in underwater and atmospheric zones. The concrete resistivity in the tidal and splash zones was decreased through the installation of both mortar-embedded Zn-mesh (sacrificial anode) and outside an FRP jacket (cover). Considering the CP, the cathodic prevention was more effective than cathodic protection.

A novel powder-epoxy towpregging line for wind and tidal turbine blades

Summary1. Viruses are a pervasive component of microbial food webs in both marine and freshwater systems. The abundance of viruses in individual aquatic systems appears to be independent of salinity but related to the biomass of primary and secondary producers as well as seasonal effects. Burst size, virus production rate and the percentage of microbial cells carrying a viral burden also appear to be more closely correlated to trophic status than to salinity.2. In marine environments, the roles of planktonic viruses as regulators of carbon and nutrient cycling as well as microbial community structure have been a focus of numerous studies, yet the roles of freshwater virioplankton remain much less studied. Nevertheless, a survey of published freshwater studies demonstrates that virioplankton recycle important quantities of growth‐limiting nutrients from hosts via generation of dead particulate and dissolved organic matter during cell lysis, and suggests that both the chemical speciation and concentration of these organic compounds and nutrients may have important influences on the microbial community.3. Parallel observations on the spatial patterns and dynamics of microbial mortality due to viruses or grazing are more advanced in freshwaters than in marine environments. However, the constraints that determine whether virus‐ or grazer‐mediated mortality dominates are not yet understood in either environment.4. Application of molecular approaches has facilitated the examination of the diversity and ecological dynamics of specific viral populations and entire communities. The depth of detail achieved in marine environments towards characterizing these populations and communities is just beginning to be matched in freshwater systems. The few available data suggest that viruses targeting‐related hosts in freshwater and marine systems may be genetically distinct.5. Although the role of viruses in aquatic systems is complex and remains insufficiently studied, our survey of the literature indicates that, despite some differences, many of the controls on virioplankton activity and diversity are similar in marine and freshwater environments.

Marine environments are increasingly under threat from the direct impacts of human activity, such as resource extraction and over-exploitation, and indirect threats from land-based activities that lead to pollution, increased nutrients and sedimentation. The need for mitigation of these impacts alongside the continued drive for economic growth has led to policy responses that attempt to build the cost of biodiversity losses into the cost of development. One such policy mechanism is biodiversity offsetting, whereby impacts are sequentially avoided, minimized, restored, and finally offset through the use of the mitigation hierarchy. Biodiversity offsets are increasingly used to mitigate the residual impacts of development on threatened species and ecosystems, in theory allowing development without the associated loss of biodiversity. Most biodiversity offset policy and theory has concentrated on offsetting in the terrestrial environment, while offsets in the marine environment have received little focus.In this thesis, I investigate the extent to which marine and coastal biodiversity offset policies occur globally and examine the complexities and challenges associated with their application. I discuss opportunities for offsets to achieve better outcomes for marine biodiversity, and evaluate the risks involved. Using a mixed method approach, I first identify the most relevant differences between marine and terrestrial environments and the implications of those differences for biodiversity offsetting. I then review the literature on biodiversity offsets to develop a database of offset policies globally that could include marine environments and determine their stage of development (Chapter 2). I find that many countries have policies that could potentially include marine environments. I explore several important practical differences when offsetting in the marine environment, for example greater connectivity both within marine ecosystems and between marine and terrestrial systems, and limited finely-resolved marine data. While these differences have significant implications for offset feasibility and effectiveness, I also identify potential opportunities afforded by the nature of marine systems for offsets to mitigate impacts more effectively, such as allowing more spatial ‘flexibility’ in offset locations. Using the database developed in Chapter 1, I next evaluate the way in which marine environments are included in offset policies globally. I explore the extent to which policies are specifically focussed on or apply to marine environments and their stage of development (from Chapter 2), and identify correlations between these factors and marine biodiversity, as well as political and economic variables, to determine what might be driving this policy differentiation (Chapter 3). I find that while few countries had policies specifically tailored to marine environments, many explicitly state that their offset policy can apply to the marine environment. I find that wealthier countries with more stable governance, but a lower density of threatened marine birds and mammals, were more likely to have better-developed and more marine-specific offset policies.I then further explore the global distribution of pressures on the marine environment, specifically from metals and minerals mining, and identify how these relate to whether current offset policies account for impacts at the land-sea boundary. To do this, I summarise information on the types of mines that occur in coral reef catchments globally currently, and those likely to be developed in the future, and then develop a spatially explicit model of the potential for sediment impacts from terrestrial mining on adjacent coral reefs (Chapter 4). I simulate how existing environmental governance in countries with reef-draining catchments could mitigate risks to coral reefs and find that countries with the highest sediment risk also have relatively poor environmental governance, and less-developed offset policies.Spatial flexibility in offsetting means allowing offset actions to occur far from an impact site, and has been controversial because the requirement for ecological equivalence is often met partly through requiring close proximity between the biodiversity lost from development and the biodiversity gained by an offset. In Chapter 5, I discuss the circumstance where spatially flexible offsets could be more effective for marine biodiversity values than offsetting near to the site of impact, and attempt to model the relative benefits of more or less spatial flexibility in offset location for migratory shorebirds. I find that key data were missing to enable confident estimation of the relative benefits of locating offsets near to and far from the impact sites, even in this relatively well-known system. Further, the risks of allowing flexible offsets, such as reduced ecological equivalence and the challenges of working across geopolitical borders, must be weighed against the potential benefits of offshoring biodiversity.This thesis concludes that the development of offset policies in the marine environment has moved faster than the scientific evidence underpinning their application. It is therefore unlikely that offsets occurring in the marine environment can achieve no net loss without significant changes in the way they are applied. This includes a more rigorous application of the first three stages of the mitigation hierarchy, offset policies that account explicitly for the challenges posed by offsetting in the marine environment, strategic environmental assessments that incorporate indirect and cumulative impacts at a wider geographic scale, and the integration of land-sea planning with biodiversity offset policies to mitigate complex impacts more effectively.

Many marine energy systems designers and developers are beginning to implement composite materials into the load-bearing structures of their devices, but traditional mold-making costs for composite prototyping are disproportionately high and lead times can be long. Furthermore, established molding techniques for marine energy structures generally require many manufacturing steps, such as secondary bonding and tooling. This research explores the possibilities of additively manufactured internal composite molds and how they can be used to reduce costs and lead times through novel design features and processes for marine energy composite structures. In this approach, not only can the composite mold be additively manufactured but it can also serve as part of the final load-bearing structure. We developed a conceptual design and implemented it to produce a reduced-scale additive/composite tidal turbine blade section to fully demonstrate the manufacturing possibilities. The manufacturing was successful and identified several critical features that could expedite the tidal turbine blade manufacturing process, such as single-piece construction, an integrated shear web, and embedded root fasteners. The hands-on manufacturing also helped identify key areas for continued research to allow for efficient, durable, and low-cost additive/composite-manufactured structures for future marine energy systems.

Fatigue life of pitch- and stall-regulated composite tidal turbine blades

Work at local biodiversity checklists in nature reserves is essential for the preservation of this diversity, which is the principal aim of establishing nature reserves. Such work is also important for understanding biocenotic connections in marine systems. Crustaceans are among the most numerous and functionally important groups of organisms dwelling in the zones along the coastline. We studied this group in the splash zone and on algal thalli and stems of marine plants in the littoral zone of the Black Sea in and around the Opukskii Nature Reserve, the fauna of which is not sufficiently known. Nineteen crustacean species were found, most of these being members of the order Isopoda. Some of the recorded species have not been observed recently in other areas of the Black Sea. The species composition of crustaceans is peculiar to the reserve and its environs.

An overview of marine renewables in the UK: a synopsis of Michael Hay's presentation

Additive manufacturing (AM) is a rapidly growing technology space, not only for prototyping, but is also becoming more feasible at larger scales and increasing component quantities. There are a large variety of AM processes and materials available to users and effectively applying those processes and materials to a specific use case can be challenging. One specific area where AM could be particularly beneficial is marine renewable energy (MRE). Not only is MRE a relatively nascent industry with a near-term need for rapid deployments and prototype testing, but developers could also see long-term benefits from the broad variety of environmentally resistant materials available and the ability to manufacture complex geometries that AM technologies offer. Over the past 4 years, AM materials have played an increasing role in the Advanced Materials project; a multi-year, multi-laboratory research project funded by the U.S. Department of Energy's Water Power Technologies Office, with the main goal of reducing barriers to the adoption of complex materials in the MRE industry. The primary focus of this project is to develop test methods and generate datasets to understand the long-term performance of advanced materials in marine environmental and address specific material challenges as they arise. This report provides an extensive overview of the research that has been performed specific to AM polymers as part of the Advanced Materials project. The intention of this document is to provide recommendations of best practices with regards to material selection, mechanical test method development, and design practices, lessons learned along the way, current research trends, and ongoing challenges with regards to AM polymers in marine environments. In particular, this report focuses on several key aspects: Material and process selection, Environmental conditioning and subsequent degradation quantification through mechanical characterization, Composite reinforcements on AM polymer substrates, Adhesion of instrumentation for mechanical characterization and loads measurements, Protective coatings for preventing biofouling and water ingress, Other MRE case studies where AM has proved particularly useful. Ultimately, we hope that the test methods that have been developed, data generated, and lessons learned from this research will be valuable to the MRE community (researchers and developers alike), as well as other industries, and can be used as a reference point as the respective MRE and AM industries continue to grow and mature.

Floating Offshore Wind Turbines (FOWT), Current and Tidal Turbines (CTT), Wave Energy Converters (WEC) and Ocean Thermal Energy Converters (OTEC) are promising Marine Renewable Energy (MRE) technologies. Considering the emerging stage of development of MRE technologies, no dedicated certification scheme has been developed so far by international organizations. Technical specifications are under development in the framework of the International Electrotechnical Commission (IEC) Technical Committee (TC) 114 and IEC Renewable Energy (IECRE) has been recently created. Within IECRE, the Marine Energy Operational Management Committee (ME OMC) is in charge of the development of a conformity assessment system dedicated to MRE. In this context, Bureau Veritas (BV) has issued a Guidance Note NI631 Certification Scheme for Marine Renewable Energy Technologies to support technology developers and speed up commercial phases. The note NI631 covers different types of technology for energy conversion from wind, wave, tidal or temperature gradients at sea. This paper presents the Guidance Note NI631, which purpose is to provide an overview of the certification schemes applicable to MRE technologies, addressing prototype, component, type and project certification. Main objective, scope, intermediary steps to be completed and resulting certificates will be detailed for each certification scheme, as well as their interactions. Finally, focus will be made on a riskbased approach developed by Bureau Veritas to define the reference set of standards used as a basis for certification. A methodology relying on the qualification of new technology process will be detailed when no guidelines or standards are available for the most innovative parts of any MECs, or when existing standards from related sectors, such as wind energy, shipping or offshore Oil&Gas, require adaptations to fit their requirements to the specific MRE conditions.

The combination of Marine Renewable Energy (MRE) technologies such as wave or current devices with offshore wind, a more mature technology, could enable pooling of R&D efforts and reducing costs (grid connection, moorings, maintenance activities…). Moreover, the different characteristics of the wind, wave and current resources could be complementary and provide a smoothing effect on the power production. Therefore, the EU FP7 project -MARINA Platform- aims at studying concepts of combined platforms integrating different types of MRE devices. Many challenges are induced by these innovative platforms and guidelines and standards will be required to ensure safety, reliability and quality. However, as the concepts are only at the development stage, no standards have been written for these combined platforms so far. This paper presents a new approach proposed by Bureau Veritas within the scope of the MARINA project for the development of guidelines and standards dedicated to combined MRE platforms. Existing literature on standards about MRE and related sectors, like shipping, wind energy and offshore oil & gas, forms a good basis to be exploited. In addition, risk assessment and qualification of new technology might be considered as a complement to standards to support the design of novel offshore concepts. Therefore, the presented methodology combines the use of existing standards from MRE and related sectors with a risk-based approach for the most innovative and unknown parts of the platform. A global risk assessment is performed in parallel for a whole review of the system.