Perpetual Power?

A glass tankful of bluish chemicals, half darkened and half sunlit, is now busy generating electric current. What is more, it can keep on keeping on--at least in theory--for as many ages as the sun shines and the earth survives.

Unlike many scientific developments, this invention by an M.I.T. chemist is more than an advance into the hinterlands of already explored territory--it is a landing on a strange and alien coast. The light-transforming action of this cell can be roughly compared to the synthesis of food within green plants, a process which scientists have not been able to duplicate, even crudely.

More important still is the effect which this discovery may have on future civilization. The development of modern industrial civilization was dependent on the exploitation of new sources of power. Wood (solar energy stored by plants) long ago ceased to be sufficient for civilization's needs. Waterpower (solar energy stored by rainfall) still fills only part of the bill. For the rest, mankind is dependent on coal, oil and gas--which represent not the day-to-day income of solar radiation but the earth's accumulated capital of solar energy. Exhaustion of British coal supplies (in about 500 years), of U.S. supplies (in about 2,000), presents no immediate problem. But industrial civilization will eventually be doomed if new means are not found of tapping the sun's current energy on a large scale. This research may be the beginning of such a development.

Its investigator is Physicist Eugene Rabinowitch, working for the $615,000 Solar Energy Research Fund established by Godfrey Lowell Cabot to find methods of harnessing the 200 trillion horsepower which the sun pours on the earth. Rabinowitch's researches led him to explore the most imaginative and difficult solution of the mundane power problem: the artificial imitation of the chemical process which goes on inside green plants. Rabinowitch began by looking for organic dyes which, like chlorophyll in plants, might build up compounds with the help of light's energy, which can be released and utilized when the compounds break down.

Methylene blue and purple thionine looked promising. Whereas chlorophyll combines water and carbon dioxide into glucose in the presence of light, these pigments transform ferrous sulfate [Fe (SO4)] into ferric sulfate [Fe2 (SO4)3]. The ferrous compound consists of two "ions"--a positively charged iron atom linked with a negative sulfate unit. Under the influence of these pigments and light, the ions regroup themselves into the ferric form-two positive units linked with three negative units. And in the dark this reaction reverses itself. Regrouping of the ions upsets the electrical balance of the solution, creating electrical potentials.

To tap this current Rabinowitch arranged a simple device. "If now two metal electrodes are immersed in such a solution," he explained last week, "and if the liquid around one electrode is illuminated and the other is kept dark, the system becomes a galvanic cell in which chemical energy, formed by the conversion of light, is itself immediately converted into electrical energy." Galvanic cells and batteries--usually making current from the slow dissolving of zinc in sulfuric acid--are not uncommon, but Rabinowitch's is unique in that it will never wear out.

The output of Rabinowitch's cell is measured in thousandths of amperes, but he is working to improve its efficiency. Not over .1% of the absorbed light is converted into electrical energy, as compared to chlorophyll, which utilizes about 1% of the light it absorbs.

"Quantitatively, the result at present is not significant," concedes Rabinowitch. (Neither, he might have added, was Galvani's first circuit, in 1790.) "But qualitatively it is important."

This file is automatically generated by a robot program, so reader's discretion is required.