Ps Frog: a Point-absorber Wave Energy Converter Working in a Pitch/surge Mode

In studies of wave energy, notably those made under contract to the U.K. Department of Energy, capital costs have generally been _found too high to compete with other sources It has been shown elsewhere (1) that the large structural element in these costs can be avoided by using point-absorbers reacting against an internal moving mass. This early proposal (2) suffers from the disadvantage that over most of the frequency band capture can only be a fraction of the ideal capture unless some means is adopted of modifying the dynamics to ensure 'resonance' at all frequencies and with irregular waves. Budal and Falnes (3) have used'latching',or holding the mass when it stops until the judicious moment, and have achieved excellent results with their heaving buoy, which, however, ultimately reacts against the sea bed. The authors used latching in early experiments -with a free-floating buoy reacting against an internal mass, but the results were disappointing, although in earlier work with buoys moving in surge on a cable they had had good results with latching (Flounder (4)).