TIDAL POWER. 
events approximately. There is also the possibility that the inter- 
mittent operation of certain electro-chemical processes may be developed 
so as to enable any surplus power to be absorbed as and when available, 
and, if so, power developed tidally will probably prove cheaper in this 
country than that developed from any other source. 
Owing to the relatively large variations in working head in any 
simple scheme, and to the small working heads, the design of hydraulic 
turbines capable of giving constant speed with reasonable efficiencies, 
and of moderately high speeds of rotation, is a matter of considerable 
difficulty. Modern developments, however, promise’much better results 
in both these respects than would have appeared possible only a few 
years ago, and turbines are in existence which are capable of operating 
_ under a variation of head equal to 50 per cent. on each side of the mean, 
with efficiencies which do not fall below 70 per cent. over this range, 
and with reasonably high speeds of rotation under the heads:available. 
Even with. such turbines, the number of technical problems to be 
solved before a tidal scheme of any magnitude can be embarked upon 
‘with confidence is large. The questions of single- versus double-way 
operation, of storage, of the effect of sudden changes of water-level due 
to strong winds, of wave effects, of silting in the tidal basin, and of 
scour on the down-stream side of the sluices, of the best form of turbine © 
and of generator, and of their regulation and of that of the sluice-gates, 
are probably the most important, though not the only, subjects to 
consider. ‘ 
On the other hand, the possibilities of tidal-power, if it can be deve- 
loped commercially, are very great. Assuming a mean tidal! range of 
only 20 feet at springs, and 10 feet at neaps, and adopting the sinegle- 
basin method of development with operation on both rising and falling 
tides, each square mile of basin area would be capable, without storage, 
of giving an average daily output of approximately 110,000 horse-power- 
hours. In such an estuary as the Severn, where an area of 20 square - 
miles could readily be utilized with a spring tidal range of 42 feet, the 
average daily output, without storage, would be approximately 10,000,000 
horse-power-hours. 
At the present time it is difficult to obtain an even rough estimate of 
the total cost of such a scheme, owing to the uncertainty regarding many 
of the factors involved. The whole question would appear to merit 
investigation, especially on matters of detail, by a technical committee 
with funds available for experimental work. _As a result of such an 
investigation, it is at least possible that a definite working scheme could 
be formulated capable of generating power at a cost at least as small as, 
and possibly much smaller than, that of power generated from any coal- 
fired installation. 
AOR 
