When the sun is not shining, or the wind dies down, the power from any device depending on them will be shut off. If this is an incremental part of another power system, say a hydroelectric or a coal-fired plant, this variability is no problem. The operators will simply adjust the output from the main generators to compensate for the varying solar or wind power in the same way as they do to meet changing demands during the day.

For some purposes, solar energy could be used by itself on a basis of “making hay while the sun shines.” If it is used to pump water into a reservoir, or in the electrochemical manufacture of aluminum, or the production of hydrogen, operations could proceed when the sun shines and be shut down when it does not.

With improvements in solar cells as well as in batteries, it may become practical to mount solar panes on the car top, to charge the batteries while the car is traveling as well as while parked. Such an automobile is now being tested in Florida. An enterprising inventor in California has even attached a battery to solar cells mounted in the wings of a light airplane, and demonstrated that it will fly on sun power.

Bottled Sunshine

Photochemical production of fuels by sunlight is another way to use solar energy. A natural process of this kind is photosynthesis. Green plants use the sun’s light to make energy-rich compounds such as carbohydrates. Man’s earliest use of solar energy was burning firewood to cook his food and warm his domicile.

By fermentation, another natural process, alcohol can be made from many plant materials and extracted for use as fuel. From 10 to 20 percent alcohol can be mixed with gasoline in automobiles without altering the engine. Engines can also be converted to burn pure alcohol. Up till now, alcohol has been more expensive than gasoline, but the picture is changing, and motorists have begun using the mixture called “gasohol.” Brazil has undertaken an intensive project to produce alcohol and become independent of petroleum imports. For commercial production, various kinds of quick-growing plants are being studied in a search for more economical processes. Such methods for using solar energy are classified under the term “bio-mass.”

Some forward-looking scientists would like to use sunlight to decompose water directly into hydrogen and oxygen. Of course, this can be done by electrolytic decomposition, but they are looking for a photochemical method. What is needed is a suitable catalyst for the reaction, something that will work the way chlorophyll serves to produce sugar from water and carbon dioxide. If this can be found, compressed hydrogen may come to be used as a fuel for automobiles in the future.

Such fuels as alcohol or hydrogen, produced with sunlight, have a great advantage over hydrocarbons. They do not pollute the environment. Furthermore, they do not disturb the balance of carbon dioxide in nature as do fossil fuels, because each year’s supply is cycled from and back to the atmosphere.