SMALL SCALE WIND POWER PRICES

The National Renewable Energy Laboratory (NREL) conducts research to bring the price of wind power down. It has different goals for utility scale and small scale wind power. NREL's ambitious goal for small scale wind power is to have the price be at 7 cents a kilowatt hour by 2008--three years from now. This would be below the residential retail power price that is currently being charged for electricity in many areas of the US. At that price, individuals who purchase retail power could afford to convert to wind power if they had a backup for when the wind does not blow.

NREL's Jim Johnson, who conducts tours for the public at the NREL wind energy test site on highway 128 between Golden and Boulder Colorado says, "Some of the past technology improvements that have reduced the cost of wind power have come in the areas of variable speed frequency generators and increasing the rotor span through up-sizing of windmill blades."

Thirty years ago, when I had a franchise to sell windmills, machines were faced with the problem of trying to feed so-called "clean" power into the grid at a constant AC cycle of 60 hertz. To do that engineers would apply a brake to the hub of the rotor so the blades would not start unless the wind speed was high enough to turn the blades fast enough to produce 60 hertz power. Or they would apply a brake when the wind blew too hard to keep the blades from turning too fast. An improvement in that was to put a hinge on the tail of small windmills so they could move the blades out of the wind, keeping blade speed constant during higher winds. Now with variable speed generators and gear boxes, clean power can be produced using a wider spectrum of wind speeds.

Manufacturers also increase windmill efficiency by increasing the "wingspan" of windmill blades. Mr. Johnson, an expert in materials technology explains, "Blades are now made from light, end-cut balsa wood to give strength. That is covered with fiberglass molded in top and bottom sections and glued together with an epoxy." He showed me several blades that NREL had tested for various manufacturers. The fiberglass is about 3/8 to 1/2 inch thick. With this stronger material, safe, effective blades can be made longer. Thus, for example, a machine that was rated as a 500 kilowatt windmill may with longer blades be re rated at 750 kilowatts. The longer blades would allow the windmills to take advantage of a larger span of wind within the circumference of the blades.

Probably the most common method of increasing windmill efficiency is to increase tower height. Johnson says towers are strong now and tower failures in the early days of wind generation have been overcome. Past tower failures generally occurred in high winds when blades would rotate too fast and subsequent vibrations would create system failure. Now spring applied brakes prevent rapid rotation as a backup to hydraulic braking systems.

Whether or not NREL's 7-cent per kilowatt hour goal is reached depends not only on technology, but on increased experience of windmill installers, the ability to cut the cost of cranes needed to install higher towers to mount the windmills on and the reduction of manufacturing costs that will occur as more machines are made.