USING THE TIDES

King Country Chronicle, Volume XXV, Issue 3278, 12 March 1931, Page 2

USING THE TIDES

POWER FROM THE SEA. AN EXPERIMENT UNDER WAY. An interesting experiment in the production of electricity from tidal power is being tried at Avonmouth Dock, where a demonstration plant working on a system devised by Mr. Paul Shiskoff has been erected by Hydro Thermal Power, Limited, says the Morning Post. One great difficulty in the utilisation of the tides by means of water impounded from the sea in a reservoir is that for some hours before and after high tide the difference between the level of the water in the reservoir and that of the sea outside it does not give sufficient fall to work a turbine, so that there is an interval during which no power can be generated. Under the Shiskoff system this difficulty is met, and continuity of supply obtained by the aid of thermal storage. Part of the power produced by the turbine during its working period is used to drive an electrical generator, but part is converted into heat. For the latter purpose a waterfriction brake is employed, the water heated by it being stored under pressure in a steam accumulator. When the level of the tide runs too high to permit the turbine to be run, steam is taken from the accumulator and used to drive a turbo-alternator which generates electricity during the time the water turbine is out. of action, so that there is no interruption of the supply. The tidal range at Avonmouth is some 30ft. and of this about 10ft. cannot be utilised by the waterturbine, which must, therefore, be idle for about one-third of the tidal cycle. This turbine, which is supplied with water from the dock through its actual output, of course, varies with the state of the tide. Its vertical shaft carries on the top, a 32 k.w. alternator, and, lower down, a modified Heenan and Froude hydraulic dynamo-meter, or brake, which absorbs the surplus power not converted into electricity. The brake is connected with a Ruths steam accumulator having a capacity of about 25,0001 b. of water, and the temperature of this water by circulating through the brake is gradually raised to 380 deg. F., corresponding to a steam pressure of 2001 b. per square inch. In absorbing the varying surplus power the brake also acts as a governor to maintain the speed of the water-turbine constant at 500 revolutions a minute, and thus avoids the expense of a separator governor. When, on account of the rise of the tide the water turbine ceases to be usable, steam is taken from the accumulator to a de Laval turboalernator which supplies current un-

til, with the falling tide, the water turbine can again be put into service.

This system is not confined to the harnessing of the tides, but is applicable also to hydro-electric stations depending on rivers. In cases, for example, where the flow is larger than is necessary to supply the demand at some portion of the day, it could be used to store the surplus against the time when the demand was heavier, and it would enable a station to be fitted with a smaller amount of machinery than would be required to meet directly the maximum load coming upon it. The cost of electrical power under the Shiskoff method of operation has been calculated for many specific cases and under favourable conditions might, it is claimed, be as low as 0.2 d per unit, an average figure for a large installation being one farthing. Applied to the Severn Barrage, the method, it sponsors estimate, would enable power to be generated at 0.2 d. per unit, or about half the cost estimated under the original scheme.