🌊Tidal and Wave Energy Engineering Unit 1 – Ocean Energy Resources: An Introduction

What's This Unit About?

• Explores the potential of oceans as a renewable energy source
• Covers the various types of ocean energy resources (tidal, wave, ocean thermal, and salinity gradient)
• Examines the principles behind harnessing energy from the ocean
• Discusses the current state of ocean energy technologies and their future potential
• Investigates the environmental impacts and considerations associated with ocean energy systems
• Highlights real-world applications of ocean energy and the challenges and opportunities in this field

Key Ocean Energy Concepts

• Ocean energy refers to the energy carried by ocean waves, tides, salinity, and ocean temperature differences
• Tidal energy is generated through the use of tidal stream generators or by capturing the potential energy in tides
• Wave energy is harnessed using floating or fixed devices that convert the motion of waves into electrical energy
• Ocean thermal energy conversion (OTEC) utilizes the temperature difference between deep cold ocean water and warm surface waters to generate power
• Salinity gradient energy is obtained from the difference in salt concentration between freshwater and saltwater, using techniques like reverse electrodialysis (RED) or pressure retarded osmosis (PRO)
• Renewable energy sources are crucial for reducing greenhouse gas emissions and combating climate change
• Predictability of tides and waves makes ocean energy a reliable and consistent source of renewable energy

Types of Ocean Energy Resources

• Tidal energy
  • Tidal stream systems capture kinetic energy from moving masses of water in tidal currents
  • Tidal range systems harness potential energy by capturing water at high tide and releasing it at low tide
• Wave energy
  • Point absorbers capture energy from the up and down motion of waves at a single point
  • Attenuators are long, floating devices that generate energy as waves move along their length
  • Oscillating water columns use the rise and fall of waves to compress air and drive a turbine
• Ocean thermal energy conversion (OTEC)
  • Closed-cycle systems use a working fluid (ammonia) that is vaporized and condensed repeatedly to drive a turbine
  • Open-cycle systems use the warm surface water directly to produce vapor, which then drives a turbine
• Salinity gradient energy
  • Pressure retarded osmosis (PRO) uses the osmotic pressure difference between freshwater and saltwater to generate power
  • Reverse electrodialysis (RED) employs ion-selective membranes to create an electrical potential difference between freshwater and saltwater

How Ocean Energy Systems Work

• Tidal stream generators
  • Underwater turbines are placed in areas with high tidal current velocities
  • The flow of water rotates the turbine blades, which drive a generator to produce electricity
• Tidal range systems (tidal barrages)
  • A dam or barrage is built across an estuary or bay with a high tidal range
  • Water is captured at high tide and released through turbines at low tide, generating electricity
• Wave energy converters (WECs)
  • Point absorbers use the vertical motion of waves to drive a hydraulic pump or linear generator
  • Attenuators have hinged segments that flex and bend as waves pass, driving hydraulic pumps or generators
  • Oscillating water columns funnel waves into a chamber, compressing the air and driving a turbine
• OTEC systems
  • Warm surface water is used to vaporize a working fluid (closed-cycle) or produce vapor directly (open-cycle)
  • The vapor drives a turbine, which powers a generator to produce electricity
  • Cold deep ocean water is used to condense the vapor back into a liquid, completing the cycle
• Salinity gradient systems
  • PRO uses the osmotic pressure difference to drive freshwater through a semi-permeable membrane into a pressurized saltwater chamber, powering a turbine
  • RED uses ion-selective membranes to separate freshwater and saltwater, creating an electrical potential difference that drives a current through an external circuit

Environmental Impacts and Considerations

• Tidal energy systems
  • May affect marine life and habitats due to changes in water flow and sediment transport
  • Tidal barrages can impact fish migration and estuarine ecosystems
• Wave energy converters
  • Floating devices may pose a collision risk for marine mammals and seabirds
  • Underwater noise from WECs could disturb marine life
• OTEC systems
  • Discharge of cold, nutrient-rich deep ocean water may impact local marine ecosystems
  • The intake of large volumes of seawater could harm marine organisms
• Salinity gradient systems
  • Brine discharge from PRO and RED systems may affect local marine environments
  • Careful site selection and environmental impact assessments are essential for all ocean energy projects
• Visual impact of ocean energy infrastructure on coastal landscapes and seascapes
• Potential conflicts with other marine activities (fishing, shipping, recreation)

Current Tech and Future Innovations

• Advancements in materials science for more efficient and durable ocean energy devices
  • Improved corrosion resistance and biofouling prevention
  • Lighter, stronger materials for reduced costs and increased performance
• Development of advanced control systems and power electronics for optimized energy capture and grid integration
• Integration of ocean energy with other renewable sources (offshore wind, solar) for hybrid systems
• Exploration of alternative designs and concepts for ocean energy converters
  • Oscillating wave surge converters (OWSCs) that harness the horizontal motion of waves
  • Submerged pressure differential devices that use the pressure difference above and below a submerged device
• Research into energy storage solutions to address the intermittency of ocean energy resources
• Improvements in installation, operation, and maintenance techniques for reduced costs and increased reliability

Real-World Applications

• Powering remote coastal communities and islands with limited access to conventional energy sources
• Desalination plants powered by ocean energy for freshwater production in water-scarce regions
• Offshore aquaculture facilities using OTEC cold water discharge for enhanced productivity
• Integration with offshore wind farms for shared infrastructure and grid connection
• Charging stations for electric vessels and underwater vehicles
• Providing power for offshore oil and gas platforms, reducing their reliance on fossil fuels
• Supporting scientific research and monitoring equipment in remote ocean locations

Challenges and Opportunities

• High upfront costs and long payback periods for ocean energy projects
• Need for improved reliability and survivability of ocean energy devices in harsh marine environments
• Lack of established supply chains and infrastructure for ocean energy technologies
• Regulatory and permitting challenges for ocean energy projects
• Need for increased public awareness and acceptance of ocean energy technologies
• Opportunities for job creation and economic development in coastal communities
• Potential for ocean energy to contribute significantly to global renewable energy targets
• Collaboration between industry, academia, and government to accelerate the development and deployment of ocean energy technologies
• Attracting investment and funding for research, development, and demonstration projects
• Establishing international standards and best practices for ocean energy projects