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Let us take the steam engine, and see what we are now doing by luminous combustion. Good Pittsburg coal contains 87 per cent. of carbon, 5 per cent. of hydrogen, 2 per cent. of oxygen and 6 per cent. of ash; we therefore have in one pound of such coal:
|8,080 × 9|
|=||14,544 × 87|
|=||12,653||units in carbon.|
|34,662 × 9|
|=||62,391 × 5|
|units in hydrogen.|
units in coal.
15,772 × 7722 = 12,175,984 foot pounds of energy is occluded in the static caloric contained in one pound of such coal.
A horse-power is estimated as capable of raising 33,000 pounds one foot high per minute, and for this reason it is termed 33,000 foot pounds per minute. So we have 33,000 × 60 = 1,980,000 foot pounds per hour, as a horse-power.
The best class of compound condensing engines,3 with all the modern improvements, require 1.828 pounds of coal per 1 h.p. per hour. Thus we have -
|12,175,984 × 1.828||22,257,699|
|Foot pounds in one h.p.||1,980,000|
|Foot pounds lost per h.p.||20,277,699|
|Per cent utilized per h.p.||8.94|
|Per cent lost per h.p.||91.06|
In the ordinary practice of stationary non-condensing engines, from three to four pounds of coal are required per horse-power per hour. Now, taking the best of this class at 3 pounds, we have -
|12,175,984 × 3 =||36,527,952|
|Loss per h.p.||34,547,952|
|Per cent utilized per h.p.||5.42|
|Per cent lost per h.p||94.58|
From these facts it may be assumed that after making due allowance for variable qualities of the coal, the steam engine process, as at present practiced, will not utilize more than from 5 to 10 per cent. of the energy contained in the fuel used. It will thus be seen that the process of converting static to dynamic caloric by luminous combustion, by means of the steam engine, is an exceedingly wasteful and costly method, and leaves much room for economy.
Taking an ordinary grade of petroleum as consisting of 13 per cent. hydrogen, 78 carbon, 6 oxygen, 3 nitrogen and ash, we have as its energy in foot pounds per pound of oil -
|62,391 × 13|
|= 8,110 H.||}||19,454 units.|
|14,544 × 78|
|= 11,344 C.|
19,454 × 772 = 15,018,488 foot pounds. Thus, while our best coal contains twelve million, the petroleum contains fifteen million foot pounds of occluded energy in each pound, which is equal to 118,000,000 foot pounds, or 60 horse power for one hour, from one gallon of such oil.
At present electricity is generated by two methods, and both of these are second powers. Metals are smelted by luminous combustion as a first power, and then oxidized by non-luminous combustion as a second power, and coal is consumed by luminous combustion, by which steam is generated as a first power, to drive a dynamo-generator whereby electricity is obtained as a second power. Now, of the two methods, the latter is much the cheaper, and as I have shown that the best compound condensing engines only utilize 8.94, and a fair average single cylinder condensing engine only utilizes 5.42 per cent. of the energy of the fuel consumed, and as at the best not over 70 per cent. of the foot pounds obtained from the engine can be utilized as electricity, from which we must deduct loss by friction, etc., it will be readily seen that not more than 5 per cent. of the energy of the fuel can be developed by the dynamo-generator as electricity by the present method.
The great want of the present age is a process by which the static caloric of carbon or a hydrocarbon maybe set free by non-luminous combustion; or, in other words, a process by which coal or oil may be oxidized at a low degree, within an insulated vessel; if this can be accomplished (and I can see no reason why we should not look for such invention), we would be able to produce from twelve to fifteen million foot pounds of energy (electricity) from one pound of petroleum, or from ten to twelve million foot pounds from one pound of good coal, which would be a saving of from 90 to 95 per cent. of present cost, and leave the steam engine for historical remembrance.
Electricity may be generated by water or wind power to great advantage, and conveyed to a distance for motive power. The practicability of generating electricity at Niagara by which to propel trains to New York and return may be considered almost settled; and I conceive a second invention of importance which is now needed is an apparatus by which the rising and falling tides may be utilized for driving dynamo machines, by which electricity may be generated for lighting the coast cities, and it is not unreasonable to expect that such an apparatus will soon be provided; and in such an event gas companies would suffer.
It is a well known fact among electricians that the volume and tension of electricity vary both in the earth and in the atmosphere at different sections of the earth's surface, and I conceive that we may yet find means of utilizing this differential tension of electricity; indeed, it is reported that during a recent storm the wires of an ocean cable were grounded at both ends and a sufficient current for all practical purpose flowed from the European to the American continent, with all batteries removed, showing that the tension was so much greater in Europe as to cause the electricity to flow through the copper cable to this side in preference to passing through the earth or the sea. It is also said that during an east-going storm it was found impossible to work the telegraph lines between New York and Buffalo, but on taking off the batteries at both ends and looping the ends of the wire in the air, that a constant current of electricity passed from Buffalo to New York, and the line was kept in constant use in that direction without any battery connection until the storm abated. Now, how far or to what advantage we may be able to utilize this differential tension of electricity in the earth and the air, we cannot now say; but I think that we may justly look for valuable developments in this direction.
If, as I verily believe, a process will soon be discovered by which dynamic caloric can be produced by the oxidation of petroleum with non-luminous combustion in an insulated chamber, as we now oxidize zinc, electricity will then be obtained from so small a weight, and at such a low cost, as to insure aerial navigation beyond a doubt. Not with balloons and their cumbrous inflations, but with machines capable of carrying the load, and traveling by displacement of the air at high velocities. Therefore we may expect that aerial navigation will be developed in the near future to be one of the greatest enterprises of the world.
And lastly, will it pay to use luminous combustion as a first power for generating dynamic caloric for use as a second power, as is now practiced?
At the University of Pennsylvania, in Philadelphia, gas is consumed in an Otto gas engine, which drives a Gramme generator; and the lecture room is lighted with electricity, and I am informed that the light is both better and cheaper than when they used the gas in the ordinary gas burners. Hence we may expect to see gas consumed to advantage for producing electric lights.
Considering the difficulties of transmitting steam power to a considerable distance, and the comparative great cost of running small engines, it is more than likely that electricity as at present generated will be found to be economical for driving small motors.
Having thus endeavored to explain what electricity is, and the laws which govern the occlusion of static caloric, and the development of dynamic caloric (electricity), in conclusion I call the attention of the inventors of the age to the great need of a process for oxidizing coal or oil at a low degree, within an insulated vessel. With such an invention electricity would be obtained at such a low cost that it would be used exclusively to light and heat our houses, to smelt, refine, and manipulate our metals, to propel our cars, wagons, carriages, and ships, cook our food, and drive all machinery requiring motive power.
A paper read before the Engineers' Society of Western Pennsylvania, Nov. 15, 1881.
Dr. Joule - foot pounds in one unit.
"American Engineer," Vol. II., No. 10, page 182.