December i8, 1902] 



NA JURE 



161 



power is not where it is wanted industrially. In the nature of 

 things, water powers are generally in hilly countries, and are 

 seldom near the sea. The result is that a water power as a rule 

 cannot command the same price as steam or gas, because it is 

 not where it is wanted. The idea in starting many of the 

 water-power stations also was that works which needed power 

 would come and settle near. As a matter of fact, the cost of 

 power is a much smaller item in most industries than is generally 

 supposed, and it does not pay to start a works in an otherwise 

 not perfectly suitable locality simply for the sake of the cheap 

 water power. In such industries as engine building, flour mill- 

 ing, spinning and weaving, and so on, the chance of reducing 

 the expense for power is not enough to overcome other con- 

 siderations. It may be said that in electro-metallurgical pro- 

 cesses the whole cost is practically the electrical energy, and so 

 carbides, aluminium, electrolytic soda and chlorate of potash 

 will be made at water powers. Even this, however, is mis- 

 leading. Carbides and aluminium are generally made at water- 

 falls, and chlorate nearly always is. Electrolytic soda and 

 bleach are made at water powers, but are also made extensively 

 by steam-driven plant. Against the cheaper power, we have to 

 put extra carriage for materials and for coal, which is often 

 needed in addition, and extra carriage for finished products, and 

 very often extra cost of labour, as labour is often dear and bad 

 in water-power districts. It may thus easily pay to use much 

 more expensive power if the other conditions are more favour- 

 able. Steam power, for instance, will cost three or three-and-a- 

 half times as much, and yet it pays to make electrolytic caustic 

 and bleach in England where the other conditions are all favour- 

 able. It is not, therefore, the want of water power that has 

 kept the electrolytic industry back in this country. For a water 

 power to be really valuable, it should be near a source of 

 material, on the sea, and should have a great head of water, so 

 that the capital cost of development is small. Such a water 

 power is very valuable — to the landlord. 



A blast furnace is more valuable than a water power. There 

 are plenty in England. But the owners, who have been wasting 

 the gas up to now, will not give it away ; they will want rent, 

 so that it will only just pay to use this gas rather than make 

 it. The electrical industry thus does not gain, but the iron- 

 masters do. 



Carbon Cells. 

 ■ For many years, " electrical energy direct from coal " has 

 been the dream of the electro-chemist. That is to say, he has 

 dreamed of an electrolytic cell in which the consumed electrode 

 is carbon. The best way to realise the difficulties of this 

 problem is to consider it solved and see what it means. The 

 carbon must be in contact with an electroljte, and that electro- 

 lyte must either be in contact with a second electrolyte which 

 wets the other electrode or must itself be in contact with that 

 electrode. This second electrode must almost certainly be metal, 

 as there are no other non-metallic conductors available. Such 

 compounds as the hydrides, nitride, oxides, chloride, bromide, or 

 the sulphide, or silicide, of carbon are not salts in the electrolytic 

 sense. Carbon forms part of the electro- positive radicle in the 

 organic radicles and part of the electro-negative radicle in the 

 cyanogen compounds, but it is never a radicle by itself. To sum 

 up the matter shortly in the light of modern theory, carbon 

 never forms ions, and has therefore no solution pressure, and 

 can therefore give no electromotive force. At ordinary or 

 moderate temperatures, carbon is practically inert. Oxidising 

 agents will attack some forms slightly, and sulphuric acid will 

 attack it. In this latter case, the formation of water and its 

 combination with the acid is the determining factor. At high 

 temperatures, oxygen, sulphur, silicon, and to some extent 

 nitrogen, and many of the metals combine with carbon, but 

 there is no dissociable salt of carbon formed. The carbon cell 

 thus seems impossible. Such schemes as Mr. Reed's, ingenious 

 as it is, is not a solution of the problem. It would be simpler 

 to reduce zinc oxide with the carbon and then put it in a zinc 

 cell. 



It is hardly necessary to discuss thermopiles or thermo- 

 magnetic engines as possible economical producers of electric 

 power. 



Steam Engines. 



The primary question in all heat motors is, What temperature 

 range is available ? In the case of a steam engine, there is 

 enormous waste of mutivity — to use a variation of Lord Kelvin's 

 convenient term — in boiler flues. We burn carbon and hydrngen, 

 capable even with air of giving a temperature of some 1500" C. , 



MO. I729, VOL. 67] 



and the heat is degraded down to some 200 C. That is to say, 

 instead of getting the heat with a mutivity of about 0825, we 

 degrade it down to, say, 0^35, a clear loss of 045 out of O'S, or 

 56 per cent. This degradation is apart from the efficiency ; 

 the efficiency is concerned with the loss of heat up the chimney. 

 The higher limit in large modern reciprocating engines may be 

 taken, roughly, at 600° A. (327' C. or 620 F). Above this, there 

 is difficulty in lubrication and to some extent weakening of the 

 material. The pressure corresponding to this temperature for 

 saturated steam is out of the question, and the pressure may 

 be taken at, say, 125 megadynes per square centimetre or 12^ 

 atmospheres, or 200 lb. per square inch, and steam leaving the 

 boiler superheated to 600° A. does not get at the cylinder 

 lubrication at that temperature. Our limits in the steam engine 

 are thus pretty clearly defined. The pressure is the essential 

 factor. Superheating is not much good in the way of getting 

 higher mutivity in the boiler, nor is it very important in getting 

 much more energy into the steam. 



The turbine is under the same limit as regards pressure ; in 

 fact, high pressures are perhaps even more difficult to use, and 

 superheating does not, as already explained, seriously increase 

 the mutivity of the heat taken in by the boiler. 



One of the chief disadvantages of steam engines for stations 

 with small load-factors is the difficulty of storing energy so as to 

 get uniform boiler load. Batteries are no longer used for this, 

 and the difficulty reduces the value of steam in comparison with 

 the gas engine. Mr. Druitt Halpin has proposed, and used, 

 "thermal storage." Lagged vessels are filled with water 

 raised to the temperature of the working steam. This arrange- 

 ment, however, is not isothermic ; that is to say, to get out the 

 energy the temperature must fall. What is wanted is a reser- 

 voir containing something which undergoes a physical or 

 chemical isothermal change. For instance, a substance that 

 fuses at the right temperature and has a high latent heat of 

 fusion, or a substance which, like sulphur, changes allotropically 

 with considerable change of internal energy, at a suitable tem- 

 perature. Unfortunately, there is no substance within the range 

 of practical engineering. Moreover, the storage is on the wrong, 

 side of the engine. To store heat with a mutivity of only some 

 o - 35 is not so promising as to store some higher form of energy. 

 The secondary battery thus begins with an apparent advantage. 

 The difficulty of storage is another drawback to the steam 

 engine, and gives the gas engine a further advantage. 



The Gas Engine. 



There is no other comprehensive name that covers the type of 

 engine worked by gas and oil. The combustion need not be 

 internal, and perhaps will not be internal in the future, but in a 

 sense all are worked by gases. 



We have in the gas engine a machine which, from a thermo- 

 dynamical point of view, ought to be exceedingly good ; but the 

 difficulties in building, especially very large engines to utilise the 

 high possible mutivity and saving by having the heat produced 

 where used, reduce the efficiency of the gas engine enormously. 

 In spite of that, the large gas engine seems likely to oust the 

 steam engine for large powers during the next few years. The 

 best way to get a high efficiency out of a gas engine would 

 probably be to make it compound, exhausting at a temperature 

 suitable for raising steam. The steam engine would then ex- 

 haust at a temperature suitable for raising SO., vapour. But 

 the chances are that Dowson, Mond or other producer gas 

 will be available at such low prices that the extra steam and 

 dioxide engines would not pay for attendance, interest and de- 

 preciation. With very cheap gas, the first thing is to make big 

 engines, the next to make them so that they never breakdown, 

 and the last thing to make them efficient. The gas engine 

 may be, comparatively speaking, in the state Watt left the steam 

 engine, but it will doubtless make very rapid advances, as it 

 is in the hands of very competent and highly educated en- 

 gineers. 



Dynamos. 



As regards efficiency, we have reached the practical limit 

 already, for further reduction in dynamo losses would make no 

 appreciable difference in the total efficiency of a station. In 

 fact, we are rather following continental practice in having 

 slow-running machines with many poles, even for direct cur- 

 rents, and efficiencies are perhaps lower (or large machines than 

 in the best English practice of a few years ago. This is also true 

 as regards output from a given size. We are not likely to 

 make much advance in dynamos now, as we are limited on 



