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SUNSHINE, our greatest source of potential power, is now largely wasted. It is highly probable, however, that a few years hence science will find a way to harness the mighty energy of the sun's radiation. Solar engines and solar heating apparatus will then make it economically practicable for us to use at least a small portion of our now-wasted sunshine to run our factories, light our streets, cook our food, and warm our houses. In the United States we use, each year, something like a half billion tons of coal, a half billion barrels of oil, and fifty billion horsepower hours of water power for heat, light, and power.If it were possible to convert all this energy into power—which of course it isn't—it would produce seven trillion horsepower hours. If it were possible to convert completely into power all the solar energy that each year falls on the United States in the form of sunshine, it would amount to seven thousand trillion horsepower hours. Of course, some of the sunshine that comes to us through 93,000,000 miles of space is needed for the general heating of the earth and for the growing of plant life: but above those fundamental needs, solar radiation provides a potential supply of power many thousand times as great as the amount now supplied by other sources".
That the use of solar radiation for power is no vague dream of the far-distant future is shown by the fact that at present a solar power plant with a thermal efficiency of 4.32 per cent —over one third of the efficiency of the best steam engine—has been built and is being operated.
Dr. Charles Greeley Abbot, the secretary of the Smithsonian Institution and the world's leading authority on solar radiation, says that before long we shall find a commercially practicable method of harnessing sunshine. "Financial success probably awaits the solver of the problems of collecting solar heat for power purposes," he says. "With our present outlook it seems to me likely that within another generation or two power demands will lead to the sun as the most available source of supply."