A double-acting wave-energy pump with semi-sub caisson is newly developed. The pump consists of a pair of float-piston and cylinder, circular columns, and stabilizers. The float which heaves with up-anddown motions of the sea wave is directly connected to the pressure piston. Four hollow columns act as the float of the caisson. The pump is operated in doubleaction that water is pressurized by both up-and-down motions of the float. The test pump is 370 kg in total weight and is 700 mm in float diameter. The fluid characteristics of the wave-energy pump were investigated varying wave height and wave period with the caisson being fixed and unfixed. The motion of the float-piston and the semi-sub caisson in regular waves was also studied to clarify the performance difference between fixed and floating type. Pumping effect was successfully confirmed in all the experimental conditions. The performance of the semi-sub type decreased in comparison with the fixed one. It was due to the decrement of relative piston stroke caused by the caisson heaving.


One of the methods to accomplish ocean developments, preserving natural environments, is to adopt natural energy as the power source for ocean development systems. Many reports have been demonstrated about the utilization of ocean wave energy. For example, from the latest information, Araki et al (1991) suggested a wave energy converter using an unbalanced rotor. Watanabe et al (1991) experimented an wave energy conversion system with water valves for rectifying oscillating air flow. Gato et al (1991) reported about Wells turbine. Kaneko et al (1991) conducted a study of self-rectifying turbine. Whittaker and McIlwaine (1991) investigated about owe power device. In contrast, there are few papers that suggest a water-pumping system as a heaving wave energy converter.

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