May 6, 1922] 



NATURE 



571 



plant in large stations. This necessitates having a 

 large supply of circulating water in the neighbourhood 

 and it follows that capital stations are not necessarily 

 situated near a pit's mouth. The most economical 

 engines for driving dynamos are steam-turbines, 

 provided they are worked at a very high vacuum, and 

 in order to secure this we must have a supply of cold 

 water equal to seventy times that required by the 

 boilers. It is this consideration that rules out practi- 

 cally all the conier\' sites in this country. 



The author thinks that there should be at least 

 two main generating stations to supply a large district. 

 In addition he says that it generally would be found 

 economical to generate part of the load at the points 

 where the demand is greatest. It seems to us that 

 the author does not lay sufficient stress on the fact 

 that the cost of the network of cables required in a 

 large distributing scheme may be 70 or 80 per cent, 

 of the total cost of the undertaking. The main factor 

 in determining the sites, therefore, will be the cost 

 of the cables required. The cost of fuel transport 

 and of the arrangements for circulating water may 

 not vary much for different sites, but in general for 

 a given supply the cost of the requisite cables will 

 var>' largely with the position of the power station. 

 For commercial success it is very important that the 

 capital cost of the cables should be as small as possible, 

 and this can only be secured by a close study of the 

 nature of the load required for industrial, domestic, 

 and transport purposes, and then choosing the sites 

 so that the cost of the cables is as small as possible. 

 If the undertaking is to be a success, it is also necessary 

 that the power-houses be capable of continual extension, 

 so that the power available need never be much in 

 excess of the demand. In the early days of the in- 

 dustry many of the stations built were much too large 

 for the demand, and consequently years had to pass 

 before they could pay dividends. It was difficult, 

 therefore, to finance new schemes. 



The following interesting comparison is made 

 between the relative value of steam-engine and gas- 

 engine plant. A boiler can easily evaporate 7-5 lb. 

 of steam per lb. of coal consumed ; a ton of coal will 

 therefore yield 16.800 lb. of steam. A modem steam- 

 turbine requires 8-2 lb. of steam per brake horse power 

 hour developed. Hence a ton of coal will produce 

 2049 B.H.P. hours. With a gas producer operating 

 on an average at a thermal efficiency of 75 per cent., 

 a ton of coal of the same calorific value will yield power 

 gas capable of producing 20,160,000 British thermal 

 units. We may assume that on an average a modern 

 gas-engine requires 9500 B.Th.U. per B.H.P. hour, 

 and hence a ton of coal utilised in this way will produce 

 2122 B.H.P. hours. There is not much difference, 

 NO. 2740, VOL. 109] 



therefore, in the amount of the mechanical energy 

 obtained from the coal by the two methods. 



It is pointed out that in certain cases an economy 

 in fuel consumption can be obtained by using both 

 steam and gas plant in the same station. The gas 

 plant is almost immediately available, and so can be 

 used to cope with any sudden temporary increases in 

 the load, with consequent economies. 



It has often been urged that it would be more 

 economical to extract the potential by-products from 

 the coal first of all and then utilise the resulting fuel 

 products for power purposes. The author makes a 

 careful examination of this procedure. He points 

 out that serious thermal losses are involved in treating 

 coal . for by-product recovery and converting into 

 coke or power gas or both. These losses range from 

 25 to 50 per cent. In the case of a power-house 

 equipped with ammonia recovery producers for gasi- 

 fying the whole of the coal, the total coal consumption 

 would be from 70 to 80 per cent, greater than that of a 

 corresponding coal-fired station. Considering it from 

 the commercial point of view, he concludes that the 

 prospects of obtaining through the medium of by- 

 product recovery processes bulk supplies of electrical 

 energy at a lower cost than coal firing are practically 

 negligible. 



Owing to the increasing attention devoted to the 

 question of fuel conservation during the past twenty 

 years, important developments in the utilisation of 

 thermal products, which were formerly wasted on 

 an enormous scale, have taken place. In particular, 

 the surplus fuel gases produced at iron and steel works 

 have been successfully utilised ; for instance, at the 

 important coke-oven works of Messrs. Pease and 

 Partners, Durham, the waste heat is transformed 

 into electrical energy by the supply company, and is 

 " pumped " into the high-tension transmission mains 

 for utilisation throughout the district. 



The concluding chapter discusses hydro - electric 

 power-houses, and important stations in America, 

 Mexico, and Sweden are described. The attraction 

 of cheap electric power has caused flourishing towns 

 to spring up in the neighbourhood of some of the 

 American waterfalls, but there are few cases where 

 the hydro-electric power generated is transmitted to 

 a considerable distance. 



The author assumes that the reader is an engineer. 

 The general reader, therefore, will occasionally have 

 difficulty in understanding his nomenclature. The 

 importance, for instance, of the load-factor of a station 

 is emphasised, but even the engineer would appreciate 

 being reminded that the load-factor is the ratio of 

 the average load to the maximum possible load. 

 The higher this factor, the more promising the com- 



