It is possible to derive ancillary benefits from both the warm and cold water cycled through OTEC plants. In an open-cycle plant, the warm water, after being vaporized, can be recondensed while keeping separated from the cold seawater, leaving behind the salt and providing a source of desalinated water fresh enough for municipal or agricultural use. The cold-water effluent can be applied to mariculture (the cultivation of marine organisms such as algae, fish, and shellfish), air conditioning and other applications. At the National Energy Laboratory of Hawaii (NELHA), once the locus of OTEC research and pilot programs, there are no longer any functioning, net energy-producing OTEC plants, but research into uses for deep seawater pumped to the surface using OTEC technology continues.
Cold, deep seawater brought up by OTEC pipes is nutrient-rich-parasite and free, and can be pumped into onshore ponds producing algae or other products in a controlled system [6]. At NELHA, private companies have already profited from raising lobsters, flounder, and high-protein algae in mariculture ponds fed by the cold water. Additionally, this cold water has been used to grow temperate crops such as strawberries in Hawaii's tropical climate [7]. Air conditioning and industrial cooling may be the most lucrative of all ancillary benefits of OTEC plants. Currently, both of the two main buildings at the NELHA lab are effectively air conditioned by cold seawater pumped through OTEC pipes [8].