of sea waves, as there is a spectrum of electromagnetic waves. They 

 range from the shortest of ripples to the very long waves which we 

 call tides. 



Although it is mainly the long waves of the tides that are of 

 interest for power generation, there have been many attempts to 

 harness the energy of the shorter waves. The most promising scheme 

 to date, one tested on the Algerian coast, is a relatively simple 

 device consisting of a V-shaped concrete structure open to the sea. 

 The waves approaching the coast are funneled into the open end of 

 the V, and as the water is crowded by the tapering sides, the level 

 rises until it becomes high enough to spill over a dam at the apex 

 and flow into a reservoir. Power can then be derived from turbines 

 operated by the steady outflow of water from the reservoir. Al- 

 though sound in principle, to be economically sound the device 

 must have large enough waves of a sufficiently uniform size through- 

 out the year to keep it running continuously, and this has been the 

 difficulty. 



The tides, which are much longer waves, can be relied upon 

 throughout the year. Their amplitude varies with the relative 

 positions of the Sun and Moon, but in contrast to the short waves 

 tides exhibit a fairly regular fluctuation and can be harnessed 

 during given periods of the tidal cycle. Coastal areas with high 

 tides obviously are the best sites. Because some of the highest tides 

 in the world occur in European waters near highly industrialized 

 areas that could well make use of the power developed, it was in 

 Europe that the first large schemes were thought out. 



In 1933 British engineers proposed a plan for the River Severn 

 estuary which has a tidal range of some forty feet, the so-called 

 Severn Barrage, but the project was abandoned. Since then it has 

 been reviewed from time to time. Initially the plan was to trap 

 water of the incoming tide in a single basin, the power being 

 generated on the outflowing tide. Later, two basins were proposed 

 to give continuous power output, but this project, Uke the first, 

 was not approved, and now it seems doubtful that anything will 

 ever be done. The general opinion seems to be that if the scheme 

 had been undertaken when it was first proposed, it would have 

 been successful, but expensive labor costs today make it unattrac- 

 tive financially. However, when the British come to appreciate the 

 irreplaceable nature of the coal they so happily burn today, tidal 

 energy projects may again be considered in Great Britain to supple- 

 ment the demand with which nuclear power production will be 

 hard put to keep pace. 



In contrast to the fate of the Severn Barrage, the French have 

 begun construction of a plant to harness the tides in the Ranee 

 estuary at St. Malo. In principle the power station consists of a 

 dam with two-way turbines capable of being worked by both the 

 incoming and outgoing tides. In addition, the turbines can operate 

 as pumps. The critical point about this scheme is that turbine 

 generators require a certain head of water to operate them efficiently, 

 so by virtue of their ability to pump, the turbines can also quickly 

 adjust the water levels in the estuary and behind the dam at the end 

 of each tidal period so that power generation can be resumed 

 quickly. When completed, the Ranee project will feed about 565 

 million kilowatt hours annually into France's electricity system, yet 

 the Ranee scheme is looked upon as a pilot experiment for a much 



A scheme proposed by the French to utilize 

 the thermal energy of the sea depends on 

 avaiiabiiity of deep, cold water near the 

 coast. This diagram shows details of the 

 system to be used for raising cold water 

 to the surface. It is then pumped to a 

 generating station, where it is used 

 to condense low-pressure steam coming 

 from turbines. 



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