Ocean thermal energy conversion

Abstract

Ocean Thermal Energy Conversion (OTEC) is a process that employs the natural temperature difference between the surface and the depths of the ocean. First introduced in 1881, OTEC has been described as an effective and renewable energy source. OTEC systems must be designed with regard to potential efficiency issues. These issues should be properly researched in order to design OTEC systems that are effective. OTEC plants can be a feasible source of cost effective renewable energy in tropical costal regions that have high shipping costs for fuels and foods. I. Introduction Covering over 70% of the planet's area, the Earth's oceans could potentially be utilized as a source of virtually inexhaustible renewable energy. Ocean Thermal Energy Conversion (OTEC) is a method that employs naturally occurring temperature differences between warm surface water and colder deep seawater (Thomas, 1993). To be effective a minimum temperature difference between the ocean surface layers is 20 o C. These temperature gradients exist primarily in specific tropical regions near the equator (Takahashi and Trenka, 1996). Originally proposed by French Engineer Jacques Arsene d'Arsonval in 1881, OTEC is not a new technology. Since then many advancements have been made in the development of this technology. The three most common OTEC systems are: open-cycle, closed-cycle and hybrid cycle, all requiring a working fluid, condenser and evaporator within the system. These three systems all employ the thermodynamics of a working heat exchanger and use the temperature differences naturally occurring in the ocean as the driving force. Concerns with efficiency losses due to biofouling, system power requirements and heat exchanging systems have lead to exploration through case studies and analysis. While OTEC systems have been studied since 1881 there have been few full-scale implementations. There are still, however, a number of studies being conducted, especially in Japan, regarding the implementation of this renewable large scale technology.