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Page:Popular Science Monthly Volume 44.djvu/57

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49
ELECTRICITY AT THE WORLD'S FAIR.

of a hundred per cent. The consumer, therefore, can have in an available form not more than ten per cent and probably not over seven per cent of the heat in the fuel with which the cycle of operations started. This is an efficiency much below that obtainable from the direct combustion of the fuel by even the most wasteful methods, and at no price at which electrical energy can be furnished could the two forms of heating be brought on the plane of economic equality. A direct comparison of the actual number of heat units (pound-degree Fahr.) present in each instance will show with perhaps greater clearness the economic relations of the two methods of heating. A horse power of electrical energy is equivalent to 2,565 heat units per hour. A pound of coal contains 13,000 heat units, and costs, with coal at five dollars per ton of 2,000 pounds, a quarter of a cent. If we give to the coal an efficiency of but ten per cent, it will require two pounds to equal the available heating power of the electrical horse power, allowing that all the heat in the latter case is utilized. This will cost the user half a cent, and making due allowance for the collateral expenses of coal as a fuel, such as kindling, removal of ashes, and cost of handling, it is very evident that electricity can not hope to offer any economical competition. The commercial promoters of electrical heating count upon a charge to the consumer of five cents per horse power per hour for cooking purposes, and a cent and a half for heating purposes. This is very much under the figures at which electric power is now being furnished for lighting purposes—the charge for this being at the rate of from twelve to fifteen cents per horse power-hour—but it is proposed to make the same discrimination between light and heat that the gas companies have instituted. At the lower figure electric heating is nearly three times, and at the higher nearly ten times, as expensive as that by coal, allotting to coal the above very low duty. But coal has no such low efficiency. The radiant heat from hard coal is fully twenty-five per cent of the total heat generated, and of this fully one half is utilized in a grate fire, which is the most wasteful of the heating devices in use. In the best forms of grates which have been devised, in which the surplus heat is used to warm the air supply of the room, as much as thirty-five per cent of the heat may be made available, while in close stoves of the best patterns the efficiency will not fall below seventy per cent.

With gas the comparison is of course much more favorable, as here the cost of a unit of heat is much greater than in the case of coal. Illuminating gas has a heating value of six hundred and fifty to eight hundred heat units per foot, according to the quality of the gas. At the lower figures it requires a trifle under four feet to equal the heat value of an electrical horse power.