The incorporation of ancillary renewable energy sources into ocean thermal energy conversion (OTEC) plants promises to radically expand their geographic range of operation.

While experiments with OTEC have persisted in fits and starts ever since the late 19th century, they have been continually hampered by a number of debilitating factors, including the difficulty of pumping huge amounts of cold water from the ocean's depth and the fact that the process requires a temperature gap of at least 20 degrees Celsius to work, confining it to a thin belt of tropical and sub-tropical areas around the equator.

Recent scientific advances promise to overcome these hurdles however, and make OTEC a more economic and practical source of renewable energy.

Scientists are focusing in particular on combining OTEC with other forms of renewable energy, such as solar power or geo-thermal power, to enhance its potential and render it effective in a broader range of environmental conditions.

Paola Bombarda of the Polytechnic University of Milan has used computer models to prove that solar collectors have the potential to radically increase the power output of OTEC plants, by heating up warm ocean water to increase the temperature gap.

In a paper published by Bombarda in the Journal of Engineering for Gas Turbines and Power, she found that even cheap and rudimentary solar collectors, consisting of a mechanism as simple as lenses or tubes for trapping heat, are capable of tripling the daytime electricity output of OTEC plants.

In South Korea, where during the winter temperature disparities in adjacent sea waters slip below the key 20 degree threshold, engineers from the Korean Ocean Research & Development Institute (KORDI) in Goseong-gun are experimenting with the use of multiple forms of renewable energy to pre-heat incoming water.

A 20-kilowatt demonstration plant developed by KORDI is using solar power, as well as energy generated by wind farms and waste-incineration plants to heat up surface water, thus restoring the temperature disparity to a level which makes OTEC viable.

The engineers at KORDI are also investigating the possibility of adding geothermal energy to the mix, which would enable them to heat up water for OTEC usage on a 24-hour basis.

The incorporation of these measures could radically increase the potential deployment area for OTEC plants, expanding its size by a factor of as much as two.