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United States: Is Ocean Thermal the New Geothermal?

Published at: Feb 17, 2012
source: Cleantech Authority

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Geothermal energy continues to be a primary focal point for renewable energy sources and recent developments by the likes ofLockheed Martin and others are showing potential for oceans to be another viable option for geothermal technologies.

The concept is not new, but the application is. The general field is referred to as Ocean Thermal Energy Conversion (OTEC) and designs are being tested now in tropical areas.

One of the big concerns around tapping into the ocean for energy is that our processes can take away needed heat from the fragile oceanic environment. If not careful, we could upset the delicate balance in the ocean and – in a worst case scenario – wreak havoc. Using new techniques, the technology is now much more safe and requires far less energy to power a turbine.

How Does OTEC Work?

Instead of using water-based steam to drive a turbine, the Lockheed Martin (LMC) version uses ammonia, which evaporates around 20 degrees Celsius. The waters in the tropics are about 75 degrees Fahrenheit on the surface and 3,000 feet below are about 40 degrees Fahrenheit. That 35 degree difference is all that is needed to evaporate ammonia and then re-condense it into liquid form.

This entire process is in a closed loop. What that means is there are no by-products or exhaust. OTEC is a completely clean source of energy.

How Much Energy Are We Talking about?

If all goes as planned, one OTEC facility can generate more than enough energy without affecting the ocean’s ambient temperatures. Estimates are 3 to 5 terawatts with no affect to the ocean and zero emissions, and that’s just using tropical regions as a launching point for OTEC.

With energy production in the range of 15 terawatts per year globally, OTEC can make a significant impact. And these estimates are based on a few OTEC facilities in tropical regions only. When you expand the technology, the energy production opportunities start to get really exciting.

While applying OTEC principles in a different way, even Dayton, Ohio is getting into water-based geothermal energy. The region sits on an aquifier that holds the temperature below the surface at a steady 55 degrees Fahrenheit. During the summer water pumped in to cool the buildings. The winter months use the water for heat. The result is a 40% reduction in heating and cooling costs.

Base Power

Many other types of renewable energy sources are intermittent. When the wind stops blowing, clouds cover the sun, or water levels don’t surge; solar, wind, and hydro systems stop generating power. OTEC may be a huge boon to the base power – energy production 24 hours a day, 7 days a week. While other energy sources can produce more energy during their peak output times, OTEC can keep a steady supply of energy coming to prevent shortages.

Bottom Line

The only cost involved with OTEC is installation and maintenance. James Klett of the Oak Ridge National Laboratory says:

“I think this is a case where if we build it they will come. If we can build a power source that doesn’t require fuel and only requires maintenance, then we won’t have to worry about the price of fuel going up and down. The price of energy generated by an OTEC plant will be tied to the cost of maintenance—and if we come up with cheaper ways of maintaining the plant, the price of the OTEC energy could actually go down, and hopefully be competitive with conventional power plants.” (ORNL.gov)

As the technology hopefully proves to be viable, automated maintenance systems have been discussed requiring human intervention only on a seasonal basis.

Other Applications

And the technology has applications far beyond extracting energy from our oceans. The advances by LMC can be put to use in traditional turbine systems for dramatically improved energy production.

The upcoming months will be exciting to watch as a test center is being built in Hawaii for a full-tilt environmental study of the technology.

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