Aloha, OTEC heat exchangers

Lockheed Martin's advanced ocean thermal energy heat exchanger ready for testing in Hawaii


file An integral component for producing ocean thermal energy, Lockheed Martin’s heat exchanger is the first to use friction stir welding, which minimizes ocean corrosion and ultimately drives down cost.

Hawaii has it all - sandy beaches, tropical breezes, plush resorts and, of course, sparkling ocean.  For Lockheed Martin engineers, the ocean grabs their attraction.

Hawaii's waters are ideal for soaking up rays. And that's why members of Lockheed Martin's Ocean Thermal Energy Conversion (OTEC) team recently packed their sunscreen and first-of- its-kind heat exchanger and headed to the Aloha state.

A critical component of its efforts to generate renewable, clean energy from the world’s oceans, the 20-foot tall and three-foot wide technological wonder will be tested at the Natural Energy Laboratory of Hawaii Authority in Kona over the next six months by Makai Ocean Engineering, Lockheed Martin's OTEC partner.

Heat exchangers generate steam by vaporizing an ammonia working fluid with warm surface seawater. The steam drives a turbine to generate electricity. Once the steam transfers its energy, a condenser cools the ammonia vapor and turns it back into a liquid. The process then repeats itself.

Lockheed Martin's heat exchanger is the first to use friction stir welding, a technique that minimizes ocean corrosion. This process has been used successfully on other products, such as the space shuttle external tank, the Orion Crew Module and the Littoral Combat Ship.

The team expects this unique design to reduce the cost of manufacturing the heat exchanger by as much as 50 percent, making ocean thermal energy more affordable.

"Low-cost, reliable heat exchangers are essential to commercialize OTEC," said John Nagurny, OTEC heat exchanger lead.  "The testing in Hawaii will help validate the design, and we can use the information to develop a more advanced prototype, bringing us close to large-scale production."

The temperature difference between deep and shallow ocean waters offers enormous potential for producing energy. On an average day, 60 million square kilometers of tropical seas absorb an amount of solar radiation equivalent to the energy produced by approximately 250 billion barrels of oil.

Since 2009, the U.S. Naval Facilities Engineering Command has awarded Lockheed Martin $12.5 million to advance the design for the OTEC pilot plant off the coast of Hawaii.


Speaking of the Future: Energy