Ocean Thermal Energy Conversion – Renewable Energy from the Sea

According to OTEC International LLC (OTI), in 1870, Jules Verne introduced the concept of ocean thermal energy conversion (OTEC) in his book, Twenty Thousand Leagues Under the Sea. Within a decade, American, French and Italian scientists are said to have been working on the concept but the Frenchman, physicist Jacques-Arsene d’Arsonval, is generally credited as the father of the concept for using ocean temperature differences to create power.

“I owe it all to the ocean; it produces electricity, and electricity gives heat, light, motion, and, in a word, life to the Nautilus.” Jules Verne, Twenty Thousand Leagues Under the Sea.

D’Arsonval’s student, Georges Claude, built the first OTEC power plant in 1930 in Cuba, which produced 22 kilowatts of electricity. This led to an on-shore open cycle plant, with a pipe extending out to sea. Despite initial problems, power was generated. French research continued in earnest through the 1940s and into the 1950s. Research also began in California in the 1940s. In all cases, work was slowed or halted by cheaper alternatives to power generation. In the 1960s, J. Hilbert Anderson and his son James Anderson designed a closed-cycle OTEC power plant, aimed to be more practical, compact, and economic. This cycle pumps warm surface water through heat exchangers to boil a working fluid into a vapor. The vapor expands to power turbines and drive generators. Cold water pumped from the deep ocean condenses the vapor back into its liquid state. The Arab Oil Embargo and the skyrocket of oil prices in the mid 1970s drove high interest to the Andersons’ and other OTEC models. Japan and India each have done research on smaller scale OTEC power plants and both continue to pursue the technology. In 1979 and 1980, closed-cycle Mini-OTEC and OTEC-1 were built at the Natural Energy Laboratory of Hawai‘i Authority (NELHA) to demonstrate the concept. The U.S. Department of Energy deemed OTEC was a viable energy source following the Hawaii projects. The Andersons, using personal resources, continued to advance their innovative technology. In 2000, the Andersons granted an exclusive worldwide license to The Abell Foundation to their lifetime work of OTEC research and development. The Abell Foundation established OTEC International LLC in 2001.

OTEC makes use of the vast solar energy stored in the upper layers of the oceans. The concept is based on heat from the warm surface water being used to vaporize ammonia, which turns a turbine to drive a generator to produce electricity. Deep, cold ocean water cools the ammonia back to its liquid state to be heated again in a continuous cycle. OTI has earned an AIP (Approval-in-principle) from ABS (American Bureau of Shipping) for a floating power plant. They are negotiating with the Hawaiian Electric Company for a power purchase agreement that would install a 100 MW offshore power plant in the island of Oahu and a 25 MW facility with the Caribbean Utilities Company, Ltd. A small 1MW power plant will be built ashore in Hawaii to demonstrate the OTEC power cycle functionality before OTI sets up a production floating platform.