Review on Ocean Thermal Energy Conversion

Abstract

Renewable energy technology, OTEC harnesses the difference in temperature between the surface and deep ocean to generate useful electricity. Unlike solar PV and wind energy, the feedstock can be supplied continuously for day and night. The basic concept, main types, how they work, key components, advantages, uses and challenges are discussed in this paper. In a closed cycle system, a secondary fluid is processed in a loop of evaporator, turbine, condenser and pump which has a low boiling point. Open cycle systems involve the flashing of the heated seawater to generate desalinated water. Hybrid system generates both electricity and water. Thermodynamics are discussed as there is little temperature difference causing low theoretical efficiency. Important design considerations are heat exchanger performance and pumping power. The different plant designs are reviewed ranging from land based, shelf mounted and offshore floating. The pipe work in deep water, working over and under materials that resist corrosion, the prevention of biofouling and mooring and working in a marine environment are all key areas. The benefits of OTEC are the continuous low carbon electricity, freshwater production, cold seawater for air conditioning, cold seawater for aquaculture and other applications. The challenges are high capital costs, high volume of seawater, and unpredictable environmental factors with few commercial demonstrations in the long run. Ultimately, OTEC should be considered as a site-specific solution when considering marine energy solutions. Accurate net power calculations, reliable marine infrastructure, careful environmental considerations, and utilizing the electricity and seawater products together, will help the technology. The quality of resource, net power, reliability and environmental issues need to be considered. Research opportunities are discussed to allow for responsible demonstrations and deployment if the resource and the local need align.