The cost effective utilisation of shoreline wave energy is still an unsolved problem. Recently, overtopping devices with stacked water reservoirs and a slotted inclined front wall have been proposed; their rather complex construction and the utilisation of specially developed Kaplan turbines will however affect their cost-effectiveness. So-called composite seawalls have been developed and constructed in Japan. These are walls with a row of cylindrical obstacles in front, which reduce wave loadings and overtopping by breaking up the incoming wave and dissipating its energy. At Southampton University, this concept was modified by replacing the row of obstacles with a ramp, creating a reservoir between wall and ramp with a level above MWL. The recent development of a cost-effective energy converter for very low head differences allows to utilise this potential, which may have a head difference of less than 1m. Exploratory model tests of the modified seawall and the energy converter confirmed theory and assumptions. For average (scaled up) wave heights of lm and a head difference of 0.9 m, a hydraulic power of 1.2 to 2 kW per m wall can be expected; the energy converter has an estimated overall efficiency of 65% (hydraulic to electric), giving the concept an overall efficiency of 17 to 28%.
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