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Ocean Thermal Energy Conversion: Technological Fruit Ripe for Harvest
Mar 26 2014 3:11PM Posted by David Ludwig, Ph.D.
 


Decades ago, I was involved in a project establishing the engineering, economic, and environmental bounding conditions for a large Ocean Thermal Energy Conversion [OTEC] System power generating station. We were preparing a conceptual planning guide for a group of investors interested in innovating electric power production via non-fossil fuel technologies.

OTEC is an interesting, important, and (conceptually, at least) simple technology. You pump cold water from oceanic depths to the surface, where you condense a thermal exchange fluid vaporized by the warm surface waters. If sea water temperatures are stable, and your thermal exchange infrastructure efficient, you can run power-generating turbines with the vapor phase and recondense with the cold deep water in cyclical fashion. If you want to be bit more expansive, you can run an open (or hybrid) system in which the warm surface water is vaporized in a partial vacuum. With this open-cycle technology, you can generate desalinated water by collecting the vapor phase as it recondenses. 

In the 1980s, the federal Department of Energy made elaborate, pro-active preparations for the emergence of OTEC and its integration in the global power grid. Environmental impact assessment concepts were developed and published and pilot programs explored the engineering and cost parameters associated with deep water acquisition. Over time, however, the momentum of fossil-fuel exploitation overran the innovation of fledgling OTEC efforts, and the concept slipped back into obscurity. 

Today’s Washington Post (3 March 2014), in a story under the byline of Marjorie Censer, reports a revival of interest in OTEC. As large defense contractors adapt to shrinking military budgets, energy generation is an attractive buffering sector. Technological similarities—energy shares with military a foundation in hard metal and large scale—offer a pre-adapted environment for transition. According to Ms. Censer, Lockheed Martin and Chinese partners are in planning phases for an OTEC power generating station to be sited on the southern coast of China. 

Progress in OTEC is interesting and important. Environmental impacts are generally much lower than for comparable fossil fuel infrastructure. Opportunities for innovative affiliated activities—ranging from desalination to aquaculture and marine environmental restoration—abound. Effectively designed and operated OTEC facilities have the potential to not only be sustainable, but to yield clear and quantifiable net environmental benefits over their operational life (30 plus years or more, depending largely on the conformation of the condensers).

Environmental engineering in the coming decades faces incredible challenges. Global warming, fossil fuel reserves, water management, agriculture, and constraints associated with human population shifts are among the most prominent. Ocean Thermal Energy Conversion technology has real potential to not only minimize such constraints, but (if carefully planned and designed from a whole-systems perspective) to actually help resolve some of the negative outcomes usually associated with electric power generation. A rare and important focus for optimism in the complex relationship between humans and the environment. Let’s hope much more grows from this technology as we gain experience with it. It has real potential to be a multifaceted winner, a big step toward leaving our children, and their children, a cleaner, more functional biosphere.

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