Large-scale types of power plants using thermoelectric effects, such as temperature differences found in ocean waters, may someday generate electricity efficiently at lower costs than solar power plants, a study is predicting.

Such ocean-based plants would resemble huge barges floating in tropical oceans, generating electricity by using shallow water being warmed by sunlight to heat cold water brought up from the depths, researchers said.

Liping Liu of Rutgers University has authored a paper published in the New Journal of Physics analyzing the feasibility of such floating power plants.

They would work, he explained, by using energy provided by ocean waves to pump cold water up from hundreds of feet deep into a heat exchanger near the surface, where it would be heated by warmer surface water.

The tubes of this heat exchanger would be constructed using thermoelectric composite materials that will transfer heat energy through their walls, directly converting the temperature differences of the deep and surface waters into electricity, Liu said.

The surface water acts like a giant storage tank of solar energy that such plants can convert into electricity, he explained, describing potential "large-scale green power plants that make economic use of the largest accessible and sustainable energy reservoir on the earth."

Such plants would provide many advantages compared to other options, he said. Their temperature difference "fuel" is free, easily accessible and unlimited; they require no space on land; their lack of moving parts would mean lower maintenance costs; time of day or season would have no effect on their power output; and a lack of any emissions makes them a completely green option.

The cost of the energy produced by such floating plants compares favorably with other renewable energy sources, Liu said.

The U.S. Department of Energy estimates the current annual cost of one megawatt of electricity is around $0.83 million for conventional coal plants, compared to $1.84 million for solar power plants.

Liu predicts a thermoelectric power plant could provide electricity for less than that annually, assuming such a thermoelectric facility operated for 20 years.

His analysis suggests thermoelectric power plants are promising solutions that could help solve the globe's energy problems, he said.

"We are currently working on experimentally validating the predicted power factor of the thermoelectric composites," Liu said. "Once this is validated, we will seek to fabricate a table-top prototype of the generator that uses ice water and hot water as 'fuel.'"