Can science harness solar energy?

Title

Identifier

Wait and see

Language

English

Source

Volume XII (Issue No. 11) November 1960

Year

1960

Subject

Solar energy

Renewable energy sources

Alternative fuels

Rights

In Copyright - Educational Use Permitted

Fulltext

Wait and see Can Science Harness SOLAR ENERGY? J f all the oil, gas and coal in the earth’s crust could be extracted and set to burn ing in a giant furnace, and if all the world’s forests could be set on fire, the energy thus re leased would barely equal the energy that falls freely on this planet from the sun during any three clear days. The amount of solar energy streaming to earth each day is 32,000 times greater than the power presently utilized by the world’s population during the same 24 hours. If it could be converted to electricity, the solar energy falling on a rooftop would heat or cool a modern home and would operate all of its equip ment. Like the mirage of an oasis, these calculations tease the minds of scientists who are trying to harness the power of the sun. They know it is only a matter of time before the fossil fuels—oil, gas and coal —are exhausted. They know, too, that even atomic energy is not the answer to man’s longrange power needs, for its es sential element is also exhaus tible, and can use these sources of power—provided by nature during millions of years—but he cannot replace them. Whereever they are presently abun dant it is difficult to believe that one day they will be de pleted. But while that day is not imminent, it is inevitable. Eventually the world must depend on other sources of po wer. Because solar energy could serve mankind as long as life continues on this pla net, scientific investigators in some thirty nations are search ing for economical methods to trap the sun’s rays and put 78 Panorama them to work. They are driven not only by the needs of the future, but also by an increas ing awareness that many areas of the world must find a new source of energy—and must find it soon. Before the quest is ended, however, in many instances can inexpensive “banks” be built to store the energy of the sun so that it will be available when skies are overcast for long periods? The answer may be found in a simple blade of grass, which can absorb and store the sun’s energy—releas ing it as needed for growth. What plants do naturally through photosynthesis, man is trying to achieve through pho tochemistry. But for the pres ent at least, he has not found a practical way to duplicate the natural process. By taking a different ap proach to the problem one group of American researchers has met with more immediate success. One of the most sig nificant contributions in the field has been the development, in 1954 of a solar battery. It resembles a large tray and is filled with wafers of purified silicon, treated with arsenic and boron. Each disk-like cell acts as a tiny electric generator. Light striking the wafers sets up an electro-static charge which creates a flow of direct current, and also energizes dry cells for night operation. One of these batteries, mounted on a pole, has been used for six months to power an eight-fa mily rural telephone system in Georgia. Similar batteries have been used in solar-powered ra dios and in hearing aids. Un fortunately, refined silicon is still worth its weight in gold and solar batteries are too costly to be commercially practical. But this does not dis courage the experts, who point out that fifty years ago refined aluminum was even more ex pensive. Until a cheaper refining technology can be developed, the use of solar batteries will be confined mostly to highly specialized scientific projects. The Explorer VI, a U.S. satelite which was launched into orbit late last year is still re porting its scientific findings to the earth by means of record ing devices and radio equip ment powered by the energy of the sun. Its four “paddle wheel” arms contain 8,000 solar cells which provide a maximum of power with a minimum of weight. The space program is fur ther indebted to solar scient ists for the solar furnaces which are currently being used to de termine what happens to roc ket materials when they are ex posed to extreme temperatures November 1960 79 as they streak through the earth’s atmosphere. Sooner or later, any child having access to a magnifying glass learns how to focus the heat rays of the sun to bum holes in pa per. Solar furnaces are based on the same principle, but in stead of glass lenses they em ploy curved mirrors. One of the largest solar furnaces in the U.S. —in San Diego, Ca lifornia—uses a huge, curved aluminum mirror to gather and reflect the heat of the sun to a focal point. At midday, the furnace can reach tempera tures of 4,000 degrees Centi grade—enough to melt a steel bolt in seconds. Because solar furnaces generate extreme heat minus the associated contami nation of fuels used in conven tional industrial furnaces, it is a particularly valuable research tool. If and when the sunheated ovens can be mass-pro duced economically, they will be equally valuable to indus tries all over the world which depend on the attainment of extremely high temperatures. sing the same general principles on a much smal ler scale, scientists have been working to perfect solar cook ers which could be used in sun ny countries where firewood is scarce. One of the earliest of these was developed in North Africa around 1860. In India, which has a long record of achievement in this field, inex pensive solar cookers are now available in villages where the traditional fuel, dried cow dung, can be more efficiently used to fertilize the soil. The United States has de veloped two basic types of so lar cookers. One is a simple reflector which concentrates the sun’s rays on a cooknig pan, the other is a solar oven —an insulated metal box with a glass window surrounded by reflectors. It reaches tempera tures of 200 degrees Centi grade—enough to bake bread or roast meat in the same time required for conventional ovens. Although the solar house, the solar cooker, the solar furnace and the solar battery promise enormous benefits to men and. women everywhere, the solar still—which converts salt wa ter into fresh— may have the greatest potential of them all. Many different types of stills have been tried in the last hundred years—in Egypt, Chi le, Australia, France and the U.S. Experimental solar stills have produced about half a liter of fresh water daily per 900 square centimeters of area, and scientists claim that this rate of production should in crease in hot and arid climates. A family living in such a cli mate could depend on about 80 Panorama twenty liters of fresh water daily. The immediate objective of scientists experimenting with solar stills is fresh water pro duced cheaply enough for in dustrial and municipal use. The immediate objective of scientists experimenting with solar stills is fresh water pro duced cheaply enough for in dustrial and municipal use. The ultimate objective is cheap water for irrigation. If the world population con tinues to expand at its present explosive rate, man must have more water to supply his grow ing cities and to irrigate his wasted, arid lands. As onceabundant supplies of oil, gas, wood and coal are depleted, he must find new ways to power his factories, to move his ships, to bring warmth and light to his villages. Of neccessity, he must turn to the life-giving sun, the source of light and of nature’s abundance — the very center of his universe. * * * Why are they called "ten gallon" hats? ■ T isn’t a matter of Texas exaggeration or liquid ■ capacity but of folk etymology. The Spaniards in the old days of the Southweast used to ornament their large-brimmed hats with braid, often silver braid. Very fine hats might have had as many as five or seven or even ten of these braids. And the Spanish word for braid of this kind was “galon”. November 1960 81

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78-81

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