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US Navy Awards Lockheed Martin $8 Million Contract to Advance Ocean Thermal Energy Conversion Technology (OTEC)

The US Naval Facilities Engineering Command (NAVFAC) recently awarded Lockheed Martin an $8.12 million contract to further develop Ocean Thermal Energy Conversion (OTEC) technology, which the leverages ocean’s natural thermal gradient between warmer water at the ocean’s surface and colder water below to produce renewable and reliable power.

In geographical areas with warm surface water and cold deep water, the temperature difference can be leveraged to drive a steam cycle that turns a turbine and produces power. Warm surface sea water passes through a heat exchanger, vaporizing a low boiling point working fluid to drive a turbine generator, producing electricity. This process can serve as a baseload power generation system that produces a significant amount of renewable, non-polluting power, available 24/7.

Additionally, OTEC power can be used to produce energy carriers such as hydrogen and ammonia, which can be shipped to areas not close to OTEC resources. The system can also include fresh-water production by flash evaporating the warm sea water and condensing the subsequent water vapor using cold sea water.

The Department of Energy’s National Renewable Energy Laboratory (NREL)  describes three types of OTEC designs: closed-cycle, open cycle, and hybrid.

  • Closed-cycle OTEC. Warm seawater vaporizes a working fluid, such as ammonia, flowing through a heat exchanger (evaporator). The vapor expands at moderate pressures and turns a turbine coupled to a generator that produces electricity. The vapor is then condensed in another heat exchanger (condenser) using cold seawater pumped from the ocean’s depths through a cold-water pipe. The condensed working fluid is pumped back to the evaporator to repeat the cycle. The working fluid remains in a closed system and circulates continuously.

  • Open-cycle OTEC. Warm seawater is the working fluid. The warm seawater is “flash”-evaporated in a vacuum chamber to produce steam at an absolute pressure of about 2.4 kilopascals (kPa). The steam expands through a low-pressure turbine that is coupled to a generator to produce electricity. The steam exiting the turbine is condensed by cold seawater pumped from the ocean's depths through a cold-water pipe. If a surface condenser is used in the system, the condensed steam remains separated from the cold seawater and provides a supply of desalinated water.

  • Hybrid OTEC. In a hybrid OTEC system, warm seawater enters a vacuum chamber where it is flash-evaporated into steam, which is similar to the open-cycle evaporation process. The steam vaporizes the working fluid of a closed-cycle loop on the other side of an ammonia vaporizer. The vaporized fluid then drives a turbine that produces electricity. The steam condenses within the heat exchanger and provides desalinated water.

In 2008, Lockheed Martin was awarded a US Department of Energy contract to demonstrate a modern fabrication approach for a cold water pipe, a key component of an OTEC system. (Earlier post.)

Under the new contract, a Lockheed Martin-led industry team will develop critical OTEC system components and further mature its design for an OTEC pilot plant, an incremental step in developing large-scale utility plants. A key part of maturing the plant design includes developing an interface between the system’s cold water pipe and the platform.

Lockheed Martin’s experience with OTEC technology dates back to the 1970s when the heritage Lockheed Martin Ocean Systems Division, based in Sunnyvale, California, developed a mini-OTEC plant, which ran for three months and successfully generated 50 kW of electricity. This early prototype remains the world’s only floating OTEC system to generate power in excess of what is required for self-sustainment.

Since that time, Lockheed Martin has continued to mature and validate the critical technologies necessary for an OTEC system that could generate a utility-scale power supply.

Comments

ejj

This is really incredible research...I love the desalination & renewable power benefits. Florida Atlantic University established a program to research ocean energy conversion (including thermal energy conversion) a couple years back when gas prices were going through the roof (http://coet.fau.edu/?p=oceanres) but they haven't done a whole lot since. It would be nice if Lockheed could further refine the technology & get a utility scale project figured out.

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