Wave Power for U.S. Coast Guard First District Lighthouses

Lighthouses and other navigational aids are situated near tumultuous seas and thus may be good candidates for early applications of wave energy conversion technologies. The U.S. Coast Guard First District is converting lighthouses’ electrical systems to solar power to divest itself of electrical submarine cables and overhead costs associated with cable maintenance. However, in some lighthouses solar conversion is impractical or may compromise historic preservation. Unless alternative energy sources become available for these locations, they will continue to use submarine cables to run on shore power. Lighthouse sites for which shoreline and wave characteristics are suitable would be good candidates for a wave energy demonstration project. This paper describes gravity wave physics and the characteristics of mechanical radiation (growth, propagation, diffraction, and shoaling). A simple expression for energy content of a wave train with a two-parameter Bretschneider spectrum is applied to spectral wave density data collected from 15 buoys to evaluate wave energy resource potential at 31 candidate lighthouse sites in New England. Annual average wave power per meter of wavecrest varied from 3.9 to 21.7 kW/m at the buoys, and from 3.9 to 9.2 kW/m (with an average of 5.0 kW/m) at the lighthouses (buoys with maximum wave power are far out to sea, but still influence the correlation). The performance characteristics of two types of wave energy conversion technologies are used to calculate annual energy delivery by way of example. The paper concludes with a discussion of economics and environmental and permitting issues. It identifies Seguin Island light off a point in Maine and Nauset Beach, Chatham, Nantucket, and Sankaty Head lights (on Nantucket Island and along the outer shore of Cape Cod) as the best sites to begin more detailed evaluations, based on a comparison of wave power and utility rates. Subsequent studies would include demand profile for lighthouses, supply profiles, and resulting storage requirements.