Different Kinds of Blades for Windmills

Carbon Fiber Blades

This material makes up most of the windmill blades sold today. Carbon fiber is lightweight but strong, and manufacturers hone the edges of the blades so that they slice through the air with minimum drag and maximum silence. The lower drag also means more efficiency in generating power. These blades are somewhat controversial, though, because the sharp edges make them especially harmful to migrating birds flying through them. Studies have shown that large numbers of songbirds die in wind turbine collisions during the spring and fall migrating seasons.

Wood has served as a material for windmill blades for centuries. Wood is durable and easy to mold. Wood still makes up some windmill blades today, thanks to its flexibility and long life, but contemporary wood blades are lighter and curved so they can offer more rotations per minute and create more power. Dutch researchers have taken the wood blade a step farther, making blades from ultra-light bamboo. In addition to weighing less than conventional wood, bamboo is a fast growing renewable resource that grows back and can be harvested quickly.

Some windmill owners experiment with making blades from plastic polyvinyl chloride (PVC) pipes. They cut the pipes lengthwise and sand or file down the edges to eliminate some of the pipe's curve and achieve a flatter blade surface. PVC blades are among the most affordable windmill blades, but plastic weakens and eventually fails when exposed for too long to the sun's ultraviolet light. Expect PVC blades to last less than two years, though they're inexpensive to replace.

The shape of a windmill blade also is an important factor in determining its effectiveness. Common shapes viewed from the side include flat blades with no rounded or pared edges, and a wing shape with a narrow leading edge and a bigger rounder trailing edge. Other blades have equally tapered leading and trailing edges with curved tops, much like airplane wings. Horizontal-axis windmills work most efficiently with the wing-shaped blades, while vertical-axis windmills produce the most energy with flat or equally rounded edges. A new kind of blade with curved tips is well suited to lower wind environments.