ENERGY FROM THE TIDES.

Auckland Star, Volume LIX, Issue 237, 6 October 1928, Page 7 (Supplement)

ENERGY FROM THE TIDES.

~- : METHODS OF STORAGE. The possibility that tidal power developments on a large scale may become economically feasible in the near future renders it desirable that more detailed and accurate data should be available regarding certain problems, which, although not peculiar to tidal-power installations, are yet o£ special importance in this connection. One of the most important problems 5s that of storage, for owing to the Ihourly and daily, variation in the rate of output of any such installation, some form of storage may be essential if energy, has to be available when required for satisfying the normal--demands ot Industry. Various systems of storage hare been suggested for this purpose from time to. time. Thus it has been ■'proposed to utilise the energy at times •when'this is in excess of the-demand . to:—(a) Operate a* system of thermal storage tanks working in conjunction with low-pressure steam turbines; (b) compress air to be stored in suitable air .chambers. for use with reciprocating engines or turbines; (c)-produce electrolytic hydrogen for 'use in internal combustion engines and (tl) to pump water into an elevated reservoir, .from which jt may be taken to operate a series of secondary turbines, as required. So far the last of these systems would appear to offer most promise, ■■ where the eonfiguration of the ground is such as to " give an elevated reservoir site within a reasonable distance of the tidal barrage, ■ but reliable data concerning the probable cost of other systems when operated on -'euch a. scale, as to be capable of storing Eay. 10. million to 20 million Horse-power hours of energy would be of great value in enabling a final decision to be made. . - It ■ is possible that certain electrochemical processes might be so operated as to enable the output from a tidal station to be absorbed, as and when; generated, sufficient energy being, obtain-' . ed from existing steam stations to keep "■■ the furnaces hot when tidal energy is not. available. There is also the possi- •_ bility, that it might be practicable to iOpcrate without storage, delivering- all the energy into a ring transmission line also fed by a number of large steam --- stations, which would be operated in conjunction with the tidal station. * These possibilities are worthy of'serious consideration, in view of the fact that, - if the necessity for storage can be 'eliminated, the cost per unit' of output of a tidal-power installation will be little 'more, than one-third of it's cost with storage. ' '...'.' .■■■■'■>.■

Another problem is that of the best size an°d type of turbine and turbinesetting, for use in a tidal scheme. In .such a'scheme, with a' reasonably largt

tidal range at springs, the mean heat ~ would bo of the order of 14ft, while the maximum and minimum working

heads would be about 22.5 ft and 75ft. The recent developments of the turbint of high specific speed have greatly, iin proved the prospects of economically developing tidal power, but there is Hack.of definite data as to the relative, merits and possibilities of the competitive tj'pes of turbine . when required to operate under such difficult conditions. ' Data would i be of great value regarding (1) the output and efficiency at constant speed, under such a variable head; (2) the maximum specific speeds attainable with reasonably high efficiency; and (3) the minimum size of setting required for efficient operation. —Professor A. H. Gibson in "Engineering." .