Ocean Thermal Energy Conversion (OTEC)
untapping the potential of the tropical ocean
by Al Binger
The oceans cover 70.8 percent of the world and act as solar irradiative energy collector and heat storage on earth, especially in the tropic region. This huge available thermal energy, which is replenished every day by the sun, represents a tremendous pollution-free natural energy resource for human progress and civilization. Ocean Thermal Energy Conversion (OTEC) technology refers to a mechanical system that utilizes the natural temperature gradient that exists in the tropical ocean between the warm surface layer and the deep cold water, to generate electricity and produce other economically valuable by-products from its Deep Ocean Water Applications (DOWA). These DOWA include producing large quantities of drinking water, supporting aquaculture and fish farming, making fertilizer and hydrogen, and cooling or air conditioning, among others. The science and engineering behind OTEC has been studied and experienced for decades in many countries such as Britain, France, Japan, Netherlands and the United States. OTEC electric power generations have been demonstrated and many DOWA sub-systems have been individually designed, tested, advanced and reported with fruitful results. The Scientific and Technical Advisory Panel (STAP) of the Global Environment Facility (GEF) reviewed a proposed OTEC project for the Caribbean states in 2000, concluded that, “OTEC is too promising to be ignored, particularly for the small island states, and that the potential multi-purpose benefits of the technology deserve recognition.”
Generally OTEC is a low temperature, low speed and low pressure energy conversion machine, hence it requires relatively low operation and maintenance costs, and NO fossil fuel consumption. In addition, the oceanic thermal resource in not intermittent, OTEC systems can be operated at full capacity around the clock and consequently make maximum use of its capital investment. The tropical ocean thermal reservoir is the largest natural renewable energy resource in the world. It is large enough to have the potential to serve as the alternate for the much expensive and rapidly exhausting fossil fuel in future. It would be possible that OTEC will supply all of human energy needs in perpetuity, after its advanced development and supporting infrastructure are available. But, so far, there is not yet one successful OTEC field demonstration of an integrated system over the world.
In the previous US national policy review on energy in the 1990s, there were few sentences, mentioned in the US Report of the Energy Research and Development Panel, which commented that based mostly on the 1980s field experimental results, “OTEC’s prospective (at the time) was poor.” This advisory statement has been quoted as guidelines for eliminating all OTEC funding in the U.S., ever since. Until today, there has been no recent systematic evaluation of this potentially important OTEC technology and its DOWA systems. Technical advances as well as global climate and economic developments make it a suitable time to take a fresh look at OTEC systems both as appropriate for tropical island-based multi-product installations and as large scale energy base for liquid hydrogen production floating platforms.
As petroleum consumption continue to outstrip new discoveries and the future forecast is for continuation of this trend, the world needs to seriously look at the vast untapped potential of the tropical ocean and not continue on the path of carbon energy and its negative economic, social and environmental consequences. I wonder? Is anyone out there listening?
