From Science Daily:
NASA, U.S. Navy and university researchers have successfully demonstrated the first robotic underwater vehicle to be powered entirely by natural, renewable, ocean thermal energy.
The Sounding Oceanographic Lagrangrian Observer Thermal RECharging (SOLO-TREC) autonomous underwater vehicle uses a novel thermal recharging engine powered by the natural temperature differences found at different ocean depths. Scalable for use on most robotic oceanographic vehicles, this technology breakthrough could usher in a new generation of autonomous underwater vehicles capable of virtually indefinite ocean monitoring for climate and marine animal studies, exploration and surveillance.Researchers at NASA's Jet Propulsion Laboratory, Pasadena, Calif.; and the Scripps Institution of Oceanography, University of California, San Diego, completed the first three months of an ocean endurance test of the prototype vehicle off the coast of Hawaii in March.
Read more: NASA Demonstrates Novel Ocean-Powered Underwater Vehicle | Science Daily