PRESIDENTS ADDRESS. 17 



Fifteen years ago electricity was generated chiefly by large recipro- 

 cating steam engines, direct coupled to dynamos or alternators, but 

 of late years steam turbines have in most instances replaced them, and 

 are now exclusively used in large generating stations, because of their 

 smaller cost and greater economy in fuel. The size of the turbines 

 may vary from a few thousand horse-power up to about 50,000 horse- 

 power. At the end of last year the central electric stations in the 

 United Kingdom contained plant aggregating 2f million kilowatts, 

 79 per cent, of which was driven by steam turbines. 



Much discussion has taken place as to the most economical size 

 of generating stations, their number, the size of the generating units, 

 and the size of the area to be supphed. On the one hand, a compara- 

 tively small number oi very large or super-stations, instead of 

 a large number of moderate-sized stations dotted over the area, results 

 in a small decrease in the cost of production of the electricity, because 

 in the super-stations larger and slightly more economical engines are 

 employed, while the larger stations permit of higher organisation and 

 more elaborate labour-saving appliances. Further, if in the future the 

 recovery of the by-products of coal should become a practical realisation 

 as part of the process in the manufacture of the electric current, the 

 larger super-stations present greater facilities than' the smaller 

 stations. On the other hand, super-stations involve the transmission 

 of the electricity over greater distances, and consequently greater capital 

 expenditure and cost of maintenance of mains and transmission appa- 

 ratus, and greater electrical transmission losses, while the larger 

 generating unit takes longer to overhaul or repair, and consequently a 

 larger percentage of spare plant is necessary. 



The greatest element in reducing the cost of electricity is the pro- 

 vision of a good load factor; in other words, the utilisation of the 

 generating plant and mains to the greatest extent during the twenty- 

 four hours of each day throughout the year. This is a far more 

 important consideration than the size of the station, and it is secured 

 to the best advantage in most cases by a widespread network of mains, 

 supplying a diversity of consimiers and uses, each requiring current 

 at different times of the day. The total load of each station being thus 

 an average of the individual loads of a number of consumers is, in 

 general, far less fluctuating than in the case of small generating and 

 distributing systems, which supply principally one class of consumer, 

 a state of affairs that exists in London, for instance, at the present 

 time. It is true that there may be exceptional cases, such as at 

 Kilmarnock, where a good load factor may be found in a small area, 

 but in this case the consumers are chiefly mills, which require current 

 for many hours daily. 



There is no golden rule to secure cheap electricity. The most 



