From windmills to wind turbines: modern wind energy
Modern wind turbines depend on technology developed for airplanes and rockets, but they trace their ancestry at least as far back as the windmills of medieval Europe. For some six hundred years, windmills grew in mechanical sophistication, but their rotors all had four blades. Most of them, especially later in the period, were large structures that protected the mechanism and provided storage. That’s not what windmills looked like on the American prairie.
Daniel Halladay of Connecticut invented a new way to use wind power to pump water in 1854. His design still had four blades, but otherwise it looked very different. Instead of being mounted on a large building, it worked at the top of a simple scaffolding that was much less expensive to build. A tail on the rotor made it entirely self-governing. That is, no human intervention was ever required to orient it to the wind. His design also enabled the windmill to regulate its own speed. A windmill rotating too fast in a very strong wind can easily break apart. That Halladay’s windmills could adjust their speeds automatically made them even more low-maintenance.There turned out to be a huge marked for these sturdy and inexpensive machines. Farms and cattle ranches not located by a river required water pumped from underground. So did railroads. Other manufacturers eventually eclipsed Halladay’s company. Eventual improvements to his original design included using more than four blades and building the entire structure from galvanized steel instead of wood. By 1970, the various manufacturers had installed more than six million windmills in the United States alone. Most of them were one horsepower or less to meet the needs of one small farm or one part of one.
Wind power for electricityBy the late nineteenth century, this American design had found an entirely new use. In Charles F. Brush of Cleveland, Ohio, built a very large windmill with a multiple-blade rotor almost 56 feet in diameter (as opposed to as little as four feet for some of the smaller machines) to generate electricity. It produced 12 kilowatts of power.Eventually, the Halladay design had to be abandoned for electricity production. The aerodynamic principles of the best European tower mills proved superior for that application. Danish engineer Poul la Cour built a wind-driven electric generator that our than doubled Brush’s output. Unfortunately, steam plants that required burning fossil fuels could make larger and cheaper plants and put la Cour out of business.The idea of using the wind to generate electricity had been born, however, and would not die in infancy. The new field of aeronautics demonstrated that airplane propellors could make better wind turbines than any traditional windmill blade design. The extension of the power grid to American rural areas in the 1930s and 40s put a temporary crimp on wind power as it offered farmers more power at a cheaper cost.[MORE]