Dan Goldfish, age 16, of Tulsa, Okla., for his question:
HOW DOES A WINDMILL PRODUCE ENERGY?
Nowadays, sensible people dream of a day when solar energy will make our dirty old fossil fuels obsolete. Much of the planning for this fabulous future is being done in Arizona. The possibilities include solar panels and solar pools and even windmills for, after all, the winds are caused by the sun.
Windmills have been used since ancient times to pump water for turning great stones to grind grains. The basic trick is to capture the force of the wind in a circle of revolving propellers. The wind, of course, is moving air. Usually it starts when pockets of denser air blow into pockets of lighter air. Since light air is caused by the beaming sun, wind power qualifies as a form of solar energy.
However, this did not interest the makers of windmills in times past. They were interested in setting their sails to catch the strongest drafts and in converting this revolving motion into other directions to do useful work. This was done by systems of shafts and clockwork type gears attached to the spinning sails.
Old style windmills had huge sails with slats or canvas covers. A modern windmill is a circle of steel propellers up to eight feet wide. To capture the strongest breeze, the spinning circle is hoisted about 20 feet on top of a steel tower. There is a fantail vane that adjusts the propeller circle to face into the wind.
The center of the propeller is a short horizontal shaft. When the wind blows, the propeller and the shaft spin around converting wind power into the energy of rotary motion. A windmill of this sort may be used to pump water up from the ground. However, this operation needs up and down motion.
The rotary motion from the spinning propeller needs a system of gears to change its direction. This may be two small and two large wheels. The two small gears are fixed to the horizontal shaft that rotates with the propeller. As they turn, they lock into two larger gears attached to a system of bars and elbows which moves a strong vertical rod up and down. This motion hoists up the water from the well.
A windmill also may be hitched to an electric power plant. In this case, rotary energy is used to turn a generator.
At present, many farms have wind electric mills that can produce up to 2,000 watts. But solar energy scientists are working on improvements. Naturally, this type of free energy is available only in windy areas. But in the future, we can expect far more efficient windmills equipped with storage batteries to supply energy between breezes.