Tests On The Wave Power Generator "Kaimei"

1. INTRODUCTION Although the possibility of utilizing wave energy has long been considered, the only wave power generator put to practical use in the world today is a navigation lite buoy. Thus, the utilization of wave energy is still limited to a small scale. The Japan Marine Science and Technology Center (JAMSTEC) has been carrying out a five-year developmental research project on a large-output wave power generator since 1976. Since the objective of the research is the conversion of wave energy into electricity, a wave power generator, " Kaimei", was constructed in order to perform two stages open-sea tests during two years. From these tests, technical data on the wave power generation system was obtained and will contribute to the realization of actual harnessing of wave power. Below is a portion of the data from the open-sea tests. 2. PRINCIPLE OF CONVERTING WAVE POWER INTO ELECTRICAL POWER Various applicable methods for the conversion of wave power into electrical power have been proposed by experts in the world. However, JAMSTEC has been concentrating its efforts on the research of a wave power generator employing air turbines. In this type of generator, a bottomless box is floated on the surface of the sea, and an entering or exiting flow of air is actuated by the upward and downward movement of the water in the box. An air turbine driving a generator are installed on the box and utilize these air currents, to generate electricity. After various types of model tests, the steelmade 80-m long, l2-m wide Kaimei was constructed. The body of the Kaimei consists of four buoyancy rooms and a number of air pump rooms where wave energy is converted into air flow. The following are its characteristics.As a floating structure, the Kaimei is moored with chain and anchors.Since it is a ship-like buoy, always heading to the waves in order to reduce mooring force.The model tests have proven that wave energy can be absorbed sufficiently, even when the waves are received on the bow.The absorption of wave energy is related to the wave length, and maximum efficiency is achieved when wave length is 8O% of the buoy length.Calculation of the hull strength is facilitated by the design of the Kaimei as a ship-shape structure.There was no observable affect on output caused by differences in mooring systems.No mobile apparatus were installed at areas exposed in the water.The slow movements of the waves are transformed into high-speed movements by the use of air turbines.The energy converting apparatus does not directly receive the shocks from the waves.The Kaimei is not affected by the marine fouling to its surface. 3. OPEN-SEA TESTS The open-sea tests were performed twice. The first tests, from August 1978 to May 1979, employed three generator units. The second, from August 1979, is a joint research project involving five countries as part of an IEA undertaking.