Storing Energy from the Sea


5.22.13   Eric Hahn P.E., Civil Engineer Corps officer and Acquisition Corps member, U.S. Navy



In February of this year the U.S. Army Corps of Engineers’ Engineer Research and Development Center - Coastal Hydraulics Lab (ERDC-CHL) reported that it had deployed the largest Wave Energy Converter (WEC) in the US at their Field Research Facility in Duck, NC. According to their posting, their facility hosted a wave surge actuated device (a system in the "onshore systems" category of pendulor devices, as described by the Department of Energy). The Navy has also tested a wave energy device (more in the general DOE category of "offshore systems") at Marine Corps Base Kaneohe (MCBH). According to a Navy Times posting of last year, the intent is to provide wave produced power to Marine Corps Base Kaneohe, HI by 2014.
 
The suitability of onshore or offshore wave energy conversion systems, as harvesters of the intermittent wave energy resource, is highly dependant on the particulars of wave climate, bathymetry, and topography of the locale with respect to the proximity of facilities power requirements. Synchronizing the delivery of this energy to the facilities’ demand is another important consideration germane to the overall suitability of wave energy conversion systems for a given locale.
 
As with other forms of intermittent renewable energy, commercializing and providing converted wave energy to local shore facilities, like those at MCBH, requires systems designed to provide the energy to facilities or a distribution network, as demanded.  Enter the concept of Energy Storage Systems (ESS). Some examples of land-based ESS are;  large scale battery storage, flywheel, and underground Compressed Air Energy Storage (CAES). Are ESS alternatives necessarily limited to dry-land based options? No. The hydrostatic pressure and/or thermal resources of the sea present other technical possibilities.

One technical possibility is locating a CAES off-shore. The international maritime classification society Det Norske Veritas has presented this ESS concept as a complementary system with offshore windPumped storage as a complementary system with desalination and/or seawater cooling systems, as introduced in my July of 2012 posting, is another technical possibility. The presence of secondary freshwater markets, like the market for recycled water in San Diego, represents one of the additional utility revenue streams for the latter concep

What ESS may be most appropriate for WEC applications you are familiar with? Why? Please share your thoughts.

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