Power for the World's Work

A. E. Dolbear

Congregationalist and Christian World

The primary sources of energy for doing the world's work are gravity and heat. All the forms of energy we are familiar with are resolvable into these. Even what we call water power is derived from the evaporation on the surfaces of the oceans due to heat, and only ocean tides are independent sources, and even these are dependent upon heat; for if the oceans were frozen there would be no tides. The working power of the tides as they now are is vast enough, taken as a whole, but on a limited area of a few acres such as can be controlled by man is much less than popularly supposed, and has always disappointed enthusiastic inventors who went so far as actually to test it without taking the trouble to compute it. One may be sure that the tides will never do much of the world's work.

The idea that electricity can be used as a substitute for heat or water power is seen to be illusory when it is remembered that steam or water power are antecedents of electric power, which in the absence of the antecedents does not exist. We therefore are compelled to consider heat as the source of energy for all the work of the world.

During the past hundred years the steam engine has been so perfected as to have increased enormously the amount of work done in the world. But the steam engine depends upon coal for its efficiency, and the supply is limited. To maintain her supremacy among nations England has drawn heavily upon her coal banks. At the present rate of consumption her supply may last a hundred years. Some of her enlightened men have been warning her of the danger, and she has been advised of the necessity for economy and especially of the advisability of appointing a committee of competent scientific men to devise methods of increasing the efficiency of steam engines; for it is a fact that the average steam engine utilized only about five per cent of the energy that is in coal.

Suppose this were done and the engine efficiency were increased in a high degree, this would only postpone the time of the exhaustion of coal.

But is there an adequate supply of energy which could be drawn upon for the purposes of life if coal were exhausted? We have immense storages of petroleum and gas in Pennsylvania, Ohio, Texas; likewise in southern Russia. Trinidad has immense quantities of pitch. All these are limited in amount; but the sunshine is inexhaustible. The aggregate amount of the energy which comes to us from the sun is certainly sufficient for all the work of the world and all the inhabitants it will hold.

The diameter of the sun is 860,000 miles, and its radiation of heat is as great as 10,000 horse power for every square foot of its surface. Of course the most of this is lost in space, but we receive about one fourth of one horse power on each square foot of the earth's surface, so that there is enough energy received on two square feet exposed to the sun to maintain all the needs of the body. Under ordinary conditions this energy is not available for life directly. There is needed an invention that will do for heat what mechanism will do for electricity, do for temperature what can be done for voltage. We can get no more power by making a galvanic cell twice as large, but by coupling two cells together in a certain way we can get twice as much work as we can get with one. In like manner, if a quart of water at one hundred degrees temperature be added to another similar quantity and temperature, we have two quarts of water with same temperature. The working power of heat lies in its temperature, and it is increase of temperature above surrounding things that gives the pressure used for power. If an invention could be made that would add temperature as we can add electro-motive forces, we then might get from sunlight all the energy we could possibly use.

Excerpts from an article in the Congregationalist and Christian World, by Prof. A. E. Dolbear.

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