Ocean Thermal Energy Conversion: Lockheed Martin Hopes to Bring It Closer to Financial Viability

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We've written about generating power through ocean thermal energy conversion on a couple of occasions, and though it's currently just a small niche in the marine power world, the New York Times is highlighting work being done by Lockheed Martin to more widely, and economically, develop the procedure:In case you haven't hear of ocean thermal energy conversion (OTEC), most basically it works by using the difference in water temperatures between the ocean surface and in deeper water to generate electricity.

Procedure Dates to 1880s
The procedure was first proposed in the 1880s by a French physicist, a student of whom developed the first working OTEC plant in 1930, in Cuba. After several projects failed in the first half of the 20th century, OTEC has languished, and currently OTEC is an expensive procedure.

Warmer Water Heats Ammonia to Gas, Turns Turbine
Here's how Lockheed Martin's take on OTEC works:

In the approach that Lockheed is pursuing (with another company, Makai Ocean Engineering), the water on the ocean’s surface is used to heat a pressurized liquid, usually ammonia, which boils at a temperature slightly below that of warm seawater. That liquid becomes gas, which powers a turbine generator. Cold water is then pumped from the ocean’s depths through a giant pipe to condense the gas back into a liquid, and the cycle is repeated.

OTEC Needs Warm Ocean Water to Work
The main advantage of an OTEC plant is that it can run all the time, with none of the intermittency problems associated with solar power or wind power. But the technology is really only appropriate for warm tropical waters, where there is a substantial enough temperature gradient for the procedure to work.
Lockheed Martin is trying to address this limitation by developing a pipe (13' in diameter by 40' long) that could work in cold water, which would obviously expand the potential places at which an OTEC plant would be feasible.