Energy generation from sea waves

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Abstract
In comparison with the direct use of wind energy exploitation of wave energy offers great advantages. By the interaction of wind and free water surface an energy concentration takes place. Wind energy which is interchanged through wide surface areas of the oceans is stored in sea waves as a mechanical oscillation. A simple system will be described which enables the conversion of this energy of oscillation into high pressure water and electric power. It is possible to use this wave-driven generator for power supply of buoys for 1 kW or more as well as for big stationary power plants of several hundred kilowatts of electric power. The function consists in the transformation of a big volume of the low pressure water of the waves into a small volume of corresponding high pressure water which can be stored in hydraulic accumulators or in elevated water basins. Due to the periodic pressure changes in the inside of the submerged wave energy generator a piston of large diameter is moved up and down thereby driving a much smaller pump piston. With a diameter ratio between the two pistons of 2 m to 0.4 m the wave pressure is increased 25 times. An effective wave altitude of 2 m therefore will provide a water pressure of 50 m which with a wave period of 7 s easily can be converted into 1 kW of electric power by a Pelton turbine which is directly coupled to the shaft of a generator. The efficiency of such a small wave-driven hydroelectric power plant is about 80%. A basic requirement for operating the wave-driven hydroelectric generator with a high total efficiency over long periods consists in low friction seals for the pistons which additionally must be air-tight. A special type of rolling diaphragm seal accomplishes these requirements. The seals can be used for large diameters up to 20 m and more and don't require a smooth surface so that pistons and cylinders can be made of fibre-reinforced epoxy or ferro concrete. A prototype of the hydroelectric wave generator for buoys of 1 m in diameter, with an electric power of 500 W, is now in construction. If possible, first test results will be reported.

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