The first at-sea ocean thermal energy conversion (OTEC) power was produced by Mini-OTEC on Aug. 2, 1979. The powerplant was mounted on a barge located approximately 2.2 km off Keahole Point on the Kona Coast of Hawaii. Ammonia was employed as the working fluid in a closed-cycle (Rankine) powerplant, which produced approximately 50 kW of gross electrical power at an average seawater temperature difference of 21°C. Parasitic pumping power requirements for seawater and ammonia resulted in a net electrical power of approximately 15 kW. Cold seawater was drawn from a depth of approximately 670 m through a 0.61 m dia polyethylene pipe, which formed part of a single-point tension leg mooring system. The longest period of continuous operation was 10 days, terminated by the conclusion of the program on Nov. 18, 1979.