Utilization of a hinged-barge wave energy conversion system

A linear analysis of the critically-damped planar motions of a three-hinged-barge wave energy conversion system is presented. The analysis is based on the assumption that the system operates as designed. That is, the forward and after barges pitch only, while the center barge experiences no motion. In addition, the system is assumed to be critically-damped. The analysis is applied to the system called the MWP, a prototype of which was deployed in the Shannon Estuary (Ireland) in August of 1996. That three-raft system is designed to convert the energy of waves for the production of potable water or electricity for remote ocean locations. The theoretically pitching amplitudes of the forward and after power barges are approximately 5.0° and 4.6°, respectively, in design waves (1.5-meter height, 7-second period). In the same waves, the observed respective prototype amplitudes were about 11° and 6°, while operating at under-damped conditions. The theoretical performance analysis of the MWP prototype in design waves yields two significant results. First, the forward and after barges can collectively pump approximately 8.2 X 10 5 (U. S.) gallons of water per day against pressures exceeding the reverse-osmosis (RO) pressure (400 psi, 2.76 X 10 6 N/m 2 ). The potable water production from this varies from 2-to-5 x 10 5 gpd. Second, for the design wave conditions, an electrical power of needy 411 kW is predicted from the critically-damped system.