🌊Tidal and Wave Energy Engineering Unit 14 – Tidal and Wave Energy: Project Case Studies

Key Concepts and Principles

• Tidal and wave energy harness the power of ocean tides and waves to generate electricity
• Tidal energy relies on the predictable rise and fall of tides caused by the gravitational pull of the moon and sun
• Wave energy captures the kinetic energy of ocean surface waves using various technologies (wave energy converters)
• Tidal range, tidal current velocity, and wave height are crucial factors in determining the potential energy output
• Tidal barrages and tidal stream generators are the main technologies used for tidal energy extraction
  • Tidal barrages work by capturing water during high tide and releasing it through turbines during low tide
  • Tidal stream generators use underwater turbines to harness the kinetic energy of tidal currents
• Wave energy converters (WECs) come in various designs (attenuators, point absorbers, oscillating water columns) to capture wave energy
• The intermittent nature of tidal and wave energy requires energy storage solutions for grid integration

Technology Overview

• Tidal barrages are large-scale structures that span across estuaries or bays to create a reservoir for capturing tidal energy
  • They consist of sluice gates, turbines, and embankments to control water flow and generate electricity
  • The La Rance Tidal Power Plant in France is a notable example of a tidal barrage
• Tidal stream generators are submerged turbines that extract energy from tidal currents
  • They can be mounted on the seabed or floating structures and are designed to rotate with the tidal flow
  • Examples include the SeaGen project in Northern Ireland and the MeyGen project in Scotland
• Wave energy converters (WECs) have 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 waves (Pelamis Wave Energy Converter)
  • Point absorbers are buoy-like devices that move up and down with the waves to drive a generator (PowerBuoy by Ocean Power Technologies)
  • Oscillating water columns use the rise and fall of waves to compress air and drive a turbine (Mutriku Wave Energy Plant in Spain)
• Tidal and wave energy technologies are still in the development and demonstration stages, with ongoing research to improve efficiency and reliability

Site Selection and Assessment

• Identifying suitable locations for tidal and wave energy projects is crucial for their success
• Tidal energy sites require a significant tidal range (difference between high and low tide) and strong tidal currents
  • Estuaries, bays, and narrow channels with a tidal range of at least 5 meters are considered suitable for tidal barrages
  • Areas with tidal current velocities exceeding 2 m/s are ideal for tidal stream generators
• Wave energy sites should have consistent and high wave energy flux (power per unit width of wave crest)
  • Offshore locations with deep water and exposure to prevailing winds are preferred for wave energy projects
• Detailed site assessments involve measuring tidal range, tidal current velocity, wave height, period, and direction over an extended period
  • Acoustic Doppler Current Profilers (ADCPs) are used to measure tidal currents
  • Wave buoys and radar systems are employed to collect wave data
• Bathymetry, seabed conditions, and proximity to the electrical grid are also important considerations in site selection
• Environmental impact assessments (EIAs) are conducted to evaluate the potential effects on marine life, coastal processes, and local communities

Project Planning and Design

• Tidal and wave energy projects require comprehensive planning and design to ensure their technical and economic viability
• Conceptual design involves selecting the appropriate technology, determining the project scale, and estimating energy output
  • Numerical modeling and simulation tools are used to optimize the design and predict performance
• Detailed engineering design includes the development of structural, mechanical, and electrical components
  • Tidal barrages require the design of embankments, sluice gates, and turbine housings
  • Tidal stream generators involve the design of turbine blades, support structures, and mooring systems
  • Wave energy converters require the design of hydrodynamic shapes, power take-off systems, and anchoring mechanisms
• Grid connection and transmission infrastructure are critical components of project planning
  • Subsea cables, transformers, and onshore substations are designed to deliver the generated electricity to the grid
• Logistics and installation plans are developed to ensure the efficient deployment of the technology at the project site
  • Specialized vessels and equipment are required for the installation of tidal and wave energy devices
• Maintenance and operation strategies are established to ensure the long-term performance and reliability of the project

Environmental Impact and Mitigation

• Tidal and wave energy projects can have both positive and negative environmental impacts
• Tidal barrages can alter the natural tidal regime and sediment transport patterns in estuaries
  • Changes in water levels and salinity can affect marine habitats and species
  • Fish passage facilities and ecological flow management are implemented to mitigate the impact on aquatic life
• Tidal stream generators may pose risks to marine mammals and fish due to collision with turbine blades
  • Careful site selection and the use of protective screens or deterrent devices can reduce the risk of collisions
• Wave energy converters may interfere with marine navigation and fishing activities
  • Proper siting and marking of the devices, along with stakeholder engagement, can minimize conflicts with other ocean users
• Underwater noise generated by tidal and wave energy devices can disturb marine life
  • Mitigation measures include the use of noise-reducing materials and operational strategies to minimize noise levels
• The construction and decommissioning phases of the projects can temporarily disturb seabed habitats and coastal areas
  • Environmental management plans are developed to minimize the impact and ensure proper restoration of the affected areas
• Regular environmental monitoring is conducted throughout the project lifecycle to assess and address any unforeseen impacts

Economic Feasibility and Funding

• The economic viability of tidal and wave energy projects depends on various factors, including capital costs, operation and maintenance costs, and energy output
• Capital costs for tidal and wave energy projects are currently high compared to conventional energy sources
  • Tidal barrages require significant upfront investment in civil works and turbine technology
  • Tidal stream generators and wave energy converters have high manufacturing and installation costs
• Operation and maintenance costs are also considerable due to the harsh marine environment and the need for regular servicing
• Energy output and capacity factors are critical in determining the revenue potential of the projects
  • Tidal energy projects have relatively predictable output, while wave energy projects are subject to seasonal variations
• Government support and incentives play a crucial role in the economic feasibility of tidal and wave energy projects
  • Feed-in tariffs, renewable energy credits, and grants can help offset the high costs and encourage investment
• Public-private partnerships and innovative financing mechanisms are explored to attract private capital and share the financial risks
• Cost reduction through technology advancement, economies of scale, and supply chain development is essential for the long-term competitiveness of tidal and wave energy

Implementation Challenges

• Tidal and wave energy projects face various technical, environmental, and social challenges during implementation
• Technical challenges include the reliability and survivability of the technology in the harsh marine environment
  • Tidal and wave energy devices are exposed to corrosion, biofouling, and extreme weather events
  • Robust design, materials selection, and regular maintenance are crucial for ensuring the long-term performance of the technology
• Grid integration and energy storage are significant challenges due to the intermittent nature of tidal and wave energy
  • Developing efficient and cost-effective energy storage solutions is essential for maximizing the utilization of the generated electricity
• Environmental challenges involve minimizing the impact on marine ecosystems and complying with environmental regulations
  • Comprehensive environmental impact assessments and monitoring programs are required to address concerns and obtain necessary permits
• Social acceptance and stakeholder engagement are critical for the successful implementation of tidal and wave energy projects
  • Addressing the concerns of local communities, fishing industries, and other ocean users through transparent communication and consultation is essential
• Regulatory and permitting processes can be complex and time-consuming, requiring coordination with multiple agencies and stakeholders
  • Streamlining the permitting process and establishing clear guidelines can facilitate the development of tidal and wave energy projects

Lessons Learned and Future Outlook

• The tidal and wave energy industry has gained valuable insights from pilot projects and demonstrations worldwide
• Lessons learned include the importance of robust technology design, comprehensive site assessment, and stakeholder engagement
  • Collaboration between technology developers, research institutions, and industry partners is crucial for advancing the state of the art
• Pilot projects have highlighted the need for cost reduction and improved reliability to make tidal and wave energy commercially viable
  • Standardization of components, manufacturing processes, and installation techniques can help drive down costs
• Environmental monitoring and adaptive management strategies are essential for minimizing the impact on marine ecosystems
  • Sharing best practices and knowledge among projects can accelerate the learning curve and improve environmental performance
• Successful projects have demonstrated the potential of tidal and wave energy to contribute to the renewable energy mix and support coastal communities
  • The MeyGen project in Scotland has achieved significant milestones in tidal stream energy deployment
  • The Mutriku Wave Energy Plant in Spain has been operating successfully since 2011, providing clean energy to the local grid
• The future outlook for tidal and wave energy is promising, with increasing global interest and investment in the sector
  • Governments are setting ambitious targets for ocean energy deployment and providing support through policies and funding programs
  • Ongoing research and development efforts focus on improving the efficiency, reliability, and cost-effectiveness of tidal and wave energy technologies
• As the industry matures, it is expected to create new employment opportunities and contribute to the sustainable development of coastal regions worldwide