Ocean Thermal Energy Conversion Aloha!

Geothermal energy uses the heat differential between atmospheric and subterranean air to heat and cool buildings. Why not use similar principles to generate energy with the deep, cold water in ocean? That’s the idea behind ocean thermal energy conversion (OTEC)–a technology that  researchers at the University of Hawaii at Manoa are saying would be ideal for the Leeward side of the Hawaiian Islands.

OTEC technology dates back more than a half century. It involves placing a heat engine between warm water collected at the ocean’s surface and cold water pumped from the ocean deep. Obeying the laws of physics, heat flows from the warm reservoir to the cool one, spinning a turbine and generating electricity. The greater the temperature difference, the stronger the flow of heat and the greater the potential electricity.

OTEC Power Plant

image via PhysOrg

Why hasn’t OTEC taken off before now? Largely because fossil fuels have remained so cheap. Also, because OTEC technology depends on areas where temperature differentials in ocean water are strategically located enough to make it worth the infrastructure investment.  Hawaii still currently holds the world’s record for OTEC power production with the 250 KW and more than 100 KW of net power exported to the grid by a land-based experimental open-cycle OTEC plant that operated between 1993 and 1998 on the Big Island.

Analyzing data from the National Oceanic and Atmospheric Administration’s National Oceanographic Data Center, the University of Hawaii’s Gérard Nihous said, in a statement, that the warm-cold temperature differential is about one degree Celsius greater on the leeward (western) side of the Hawaiian Islands than that on the windward (eastern) side, making it the ideal location for a new, modernized OTEC plant with a greater potential for electricity output. “Testing that was done in the 1980s clearly demonstrates the feasibility of this technology,” he said, in a statement. “Now it’s just a matter of paying for it.”

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Susan DeFreitas has covered all manner of green technology for EarthTechling since 2009. She is a graduate of Prescott College for the Liberal Arts and the Environment, and has a background in marketing green businesses. Her work on green living has been featured in Yes! Magazine, the Utne Reader and Natural Home.