🌊Tidal and Wave Energy Engineering Unit 11 – Environmental Impact of Tidal & Wave Energy

Key Concepts

• Tidal and wave energy harness the power of ocean tides and waves to generate renewable electricity
• Tidal energy relies on the predictable rise and fall of tides caused by gravitational forces of the moon and sun
• Wave energy captures the kinetic energy of ocean surface waves using various technologies (attenuators, point absorbers, oscillating water columns)
• Environmental impact assessment (EIA) evaluates the potential effects of tidal and wave energy projects on marine ecosystems, biodiversity, and coastal communities
• Ecological effects encompass changes to physical, chemical, and biological processes in marine habitats due to the presence of tidal and wave energy devices
• Mitigation strategies aim to minimize or offset the adverse environmental impacts of tidal and wave energy development through careful planning, design, and monitoring
• Case studies provide real-world examples of the environmental challenges and solutions associated with specific tidal and wave energy projects (MeyGen Tidal Energy Project, Pelamis Wave Power)
• Future outlook considers the potential for tidal and wave energy to contribute to global renewable energy targets while addressing environmental concerns and technological limitations

Environmental Considerations

• Site selection for tidal and wave energy projects must account for sensitive marine habitats, protected species, and potential conflicts with other ocean users (fishing, shipping, recreation)
• Construction and installation of tidal and wave energy devices can disturb seabed sediments, create noise pollution, and introduce artificial structures into the marine environment
• Operation of tidal and wave energy devices may alter local hydrodynamics, sediment transport, and water quality, affecting the distribution and behavior of marine organisms
• Electromagnetic fields generated by subsea cables connecting tidal and wave energy devices to onshore power grids can potentially interfere with the navigation and orientation of sensitive species (sharks, rays, migratory fish)
• Decommissioning and removal of tidal and wave energy infrastructure at the end of its operational life must be carefully planned to minimize further environmental disturbance and ensure proper disposal or recycling of materials
• Cumulative impacts of multiple tidal and wave energy projects in a region must be assessed to understand the broader ecological implications and guide sustainable development strategies
• Climate change adaptation and resilience should be considered in the design and placement of tidal and wave energy devices to withstand future changes in sea levels, storm intensity, and ocean acidification

Technology Overview

• Tidal energy technologies harness the kinetic energy of tidal currents using submerged turbines resembling underwater wind turbines
  • Horizontal axis turbines have a rotor mounted on a horizontal shaft, with blades rotating perpendicular to the tidal flow
  • Vertical axis turbines have a rotor mounted on a vertical shaft, with blades rotating parallel to the tidal flow
• Tidal barrages and lagoons capture the potential energy of tides by creating a dam-like structure across an estuary or bay, allowing water to flow through turbines as the tide rises and falls
• Wave energy converters (WECs) capture the kinetic and potential energy of ocean waves using various designs adapted to different wave conditions and water depths
  • Attenuators are long, floating devices that align perpendicular to the wave direction and flex with the motion of the waves (Pelamis)
  • Point absorbers are compact, buoy-like devices that move up and down with the waves, driving a generator through a hydraulic or mechanical system (PowerBuoy)
  • Oscillating water columns are partially submerged structures that use the rise and fall of waves to compress air and drive a turbine (Limpet)
• Subsea cables transmit the electricity generated by tidal and wave energy devices to onshore substations for integration into the power grid
• Energy storage systems, such as batteries or pumped hydro storage, can help balance the intermittent nature of tidal and wave energy generation and ensure a stable power supply

Impact Assessment Methods

• Baseline studies establish the pre-development state of the marine environment, including physical, chemical, and biological characteristics, to serve as a reference for assessing project impacts
• Hydrodynamic modeling simulates the changes in tidal currents, wave patterns, and sediment transport caused by the presence of tidal and wave energy devices
• Acoustic monitoring measures the underwater noise levels generated by construction, operation, and decommissioning activities to assess potential disturbance to marine mammals and other sensitive species
• Benthic surveys document the abundance, diversity, and distribution of seabed organisms before and after the installation of tidal and wave energy devices to detect any changes in benthic communities
• Fish and marine mammal surveys use various techniques (visual observations, tagging, passive acoustic monitoring) to track the behavior, migration patterns, and population dynamics of key species in the vicinity of tidal and wave energy projects
• Collision risk assessment models the likelihood of marine animals (birds, mammals, fish) colliding with tidal and wave energy devices based on their physical characteristics, location, and animal behavior data
• Stakeholder engagement involves consultation with local communities, fishing organizations, environmental groups, and other ocean users to identify potential conflicts, concerns, and opportunities for collaboration in the planning and management of tidal and wave energy projects

Ecological Effects

• Alteration of hydrodynamics due to the presence of tidal and wave energy devices can modify local current patterns, wave heights, and sediment transport, potentially affecting the distribution and behavior of marine organisms
• Noise pollution generated by construction, operation, and decommissioning activities can disrupt the communication, navigation, and foraging of marine mammals, fish, and invertebrates
• Habitat loss or modification may occur due to the installation of tidal and wave energy devices and associated infrastructure, particularly in sensitive areas such as coral reefs, seagrass beds, or spawning grounds
• Electromagnetic fields emitted by subsea cables can potentially interfere with the orientation, migration, and hunting behavior of elasmobranchs (sharks, rays) and other electromagnetically sensitive species
• Collision risk with tidal and wave energy devices is a concern for marine mammals, fish, and diving seabirds, particularly in areas with high animal density or migration routes
• Changes in biodiversity and community structure may result from the introduction of artificial structures (foundations, anchors, cables) that can act as new habitats for colonizing organisms and attract fish and invertebrates
• Invasive species may be introduced or spread through the attachment of organisms to tidal and wave energy devices or support vessels, potentially altering local ecosystem dynamics

Mitigation Strategies

• Careful site selection that avoids ecologically sensitive areas, critical habitats, and migration routes can minimize the impact of tidal and wave energy projects on marine life
• Design modifications to tidal and wave energy devices, such as improved blade shapes, protective screens, or acoustic deterrents, can reduce the risk of animal collisions and entanglement
• Seasonal or temporal restrictions on construction and maintenance activities can be implemented to avoid disturbing marine life during sensitive periods (breeding, spawning, migration)
• Noise reduction measures, such as using sound-absorbing materials, bubble curtains, or slow start-up procedures, can minimize the impact of underwater noise on marine animals
• Electromagnetic field shielding of subsea cables through proper insulation and burial can reduce the potential effects on sensitive species
• Adaptive management strategies involve monitoring the environmental impacts of tidal and wave energy projects and adjusting operations or mitigation measures as needed based on the findings
• Ecosystem-based management approaches consider the cumulative impacts of multiple human activities (tidal and wave energy, fishing, shipping) on marine ecosystems and aim to balance economic, social, and environmental objectives

Case Studies

• MeyGen Tidal Energy Project in Scotland, the world's largest tidal stream array, has implemented extensive environmental monitoring and mitigation measures to minimize impacts on marine life and local communities
  • Detailed baseline studies and hydrodynamic modeling were conducted to assess potential changes in tidal flows, sediment transport, and marine habitats
  • Turbine designs were optimized to reduce collision risk for marine mammals and fish, and operational speeds were adjusted based on animal presence
  • A comprehensive environmental management plan was developed in consultation with stakeholders, including local fisheries, conservation groups, and regulatory agencies
• Pelamis Wave Power in Portugal, one of the first commercial wave energy projects, faced challenges related to the ecological effects of its attenuator devices on the marine environment
  • Concerns were raised about the potential entanglement of marine mammals and the impact of electromagnetic fields on sensitive species
  • The project implemented a range of mitigation measures, including acoustic deterrents, cable shielding, and regular monitoring of marine life interactions
  • Lessons learned from the Pelamis project have informed the design and environmental management of subsequent wave energy developments worldwide
• The Roosevelt Island Tidal Energy (RITE) Project in New York, USA, has focused on minimizing the ecological impact of its tidal turbines on the East River estuary
  • Extensive fish and benthic surveys were conducted to establish baseline conditions and monitor changes in species abundance and distribution
  • Turbine designs incorporated fish-friendly features, such as slow rotational speeds and wide blade spacing, to reduce the risk of injury or mortality
  • The project collaborated with local universities and research institutions to study the effects of tidal energy on estuarine ecosystems and inform adaptive management strategies

Future Outlook

• Technological advancements in tidal and wave energy devices are expected to improve efficiency, reliability, and environmental performance, making them more competitive with other renewable energy sources
• Continued research and monitoring of the ecological effects of tidal and wave energy projects will enhance our understanding of the long-term impacts on marine ecosystems and guide the development of more sustainable practices
• Increased stakeholder engagement and public participation in the planning and decision-making processes for tidal and wave energy projects will help to address concerns, build trust, and foster a sense of shared ownership in the sustainable development of ocean resources
• Integration of tidal and wave energy into broader marine spatial planning frameworks will enable a more holistic and ecosystem-based approach to ocean management, balancing the needs of energy production, conservation, and other human activities
• International collaboration and knowledge sharing among tidal and wave energy developers, researchers, and regulators will accelerate the adoption of best practices and standards for environmental impact assessment and mitigation
• As the global demand for renewable energy grows, tidal and wave energy have the potential to make a significant contribution to the decarbonization of the power sector, particularly in coastal regions with abundant ocean energy resources
• Overcoming the environmental challenges associated with tidal and wave energy development will require ongoing innovation, adaptive management, and a commitment to sustainable and equitable ocean governance