G.— ENGINEERING. 161 



the pumping and ventilating loads are almost continuous, and the load 

 factor of which is therefore very high, and chemical or metallurgical works 

 where processes are almost continuous. Other industries record a much 

 smaller load factor, corresponding to the length of their working day. 

 Combination of these various classes of industrial load again raises the 

 general load factor. At the present time certain undertakings in this 

 country which are supplying a wide range of industrial loads from a 

 common source are enjoying load factors ranging from 40 to 50 per cent. 

 Were domestic requirements to be expanded greatly and added to these 

 industrial loads, the resultant load factor would be further raised in value. 

 Finally, there is the railway traction load, which must inevitably grow 

 to large dimensions. The load factors of generating stations supplying 

 railway demands are found to have values of 40 and 50 per cent. 



If all these classes of demand can be met from a common source of 

 supply, the general load factor can be raised to a maximum value. The 

 result is to reduce the capital expended on generation to a minimum 

 value. This has been done on a wide scale in this country on the north- 

 east coast, where a supply over a wide area of approximately 1,400 square 

 miles has been afforded for many years past by three or four principal 

 generating stations supplemented by seven smaller waste-heat stations 

 interconnected by trunk transmission lines. The annual load factor is 

 not far short of 50 per cent., and the average costs of electricity supplied 

 are very low ; a large proportion of the output being delivered, of course, 

 in the form of high-pressure 3-phase energy. 



At the present time the amount of electricity generated in Great 

 Britain, omitting privately-owned generating stations, amounts to about 

 7,000,000,000 units annually, of which 5,069,000,000 are sold by authorised 

 undertakers, the balance being required for railway and tramway traction 

 purposes. 



It is found that in the four years 1921-2 to 1924-5 the average rate 

 of growth has been exactly 20 per cent, per annum, the growth of output 

 for power having been 25.3 per cent., domestic supplies 27 per cent., and 

 traction 12 per cent, per annum respectively. 



In recent Government publications it has been estimated that the 

 output in Great Britain within the next fifteen years may reach a total of 

 21,000,000,000 units, or an even higher figure if electricity systems fulfil 

 the requirements of a more extensive railway electrification. Let us see 

 what are the possibilities of future development. While it may be unwise 

 to predict an estimate of future demands, it is at least wise to endeavour 

 to make some survey of possible extensions, however extravagant the 

 results may seem at the moment. This survey enables us to have some 

 vision of the extent of development and to plan the engineering system 

 and methods of distribution in an economic and co-ordinated manner, 

 while paying due regard to the more immediate needs. In other words, 

 to be able to plan boldly but without prejudicing practical judgment by 

 the adoption of a too extravagant immediate outlook. 



An exhaustive survey has recently been completed by an influential 



committee of the National Electric Light Association relating to nine of 



the United States of America, and the Report of this survey ought to be 



read carefully by all who are interested in assisting a wide and wise 



1926 M 



