Most efficient wind turbine?

It looks a little like a big pinwheel. But the technology developed by Wind Sail Receptor, Inc. could change the commercial landscape of the small wind turbine market if it lives up to its claims for efficiency and silent operation.

The turbines use a four-blade architecture. The blades are of a special polyurethane material developed by inventor and WSRI chairman Richard Steinke. "An AK-47 round won't go through the blade. That's important in developing countries where we see a big market for small turbines."

He says the polyurethane material doesn't degrade from exposure to environmental ozone as do the composites used in traditional turbine blades, and it completely avoids use of polystyrene adhesives which give off vapors that can be problematic for blade assembly workers.

The shape of the blades is such that the turbines can capture more of the wind than traditional designs and, thus, can do useful work at much lower wind speeds. "I did 52 different iterations of blade shapes to optimize the rpm to the torque generated," says Steinke. "Existing wind turbines have a lot of inertia so they generally need a starter motor to get them going in low winds. Once the wind hits about 15 mph, they can run with winds as low as perhaps 7 or 8 mph. But our blade design lets us start generating power at 3 mph and we don't use a starting motor. We are fine tuning our generator and changing the bearing system and believe will be able to start generating electricity at 1.5 to 2 mph."

Another benefit of the blade shape: essentially no noise. "Noise has been a real environmental issue in many locations with the traditional wind turbines operating in the 50 to 125 dB range. Our wind turbines run at a sound level below 10 dB, about the sound level of normal breathing," says Steinke.

One reason the turbines can do useful work at such low RPMs is that they use generators able to generate power at even one RPM. The permanent magnet generators come from GinLong Technologies Inc. in China. GinLong has also developed inverters optimized for its generators.

Interestingly, the generators don't sit in the turbine nacelle. Steinke puts them at the base of the turbine and links them directly to the turbine rotor with a mechanical driveshaft -- there is no intervening gearbox. "I wanted something that won't break down so we went with a design having as few components as possible. Drivshafts don't break down," Steinke explains.

The mechanical connection is practical because the turbines can stand much shorter than traditional units generating the same amount of power. "Our highly efficient blades let our wind turbines mount on much shorter towers of 50 ft or less compared to the traditional 200 to 400-ft wind farm giants. This greatly expands our potential market," says Steinke. "We can duplicate the competition’s 150-ft blade diameter weighing 35,000 to 50,000 lb with one of our systems having a 30-ft blade diameter and weighing less than 12,000 lb."

WSRI is now producing 6-ft diameter turbines and expects to begin making 12-ft. units shortly. It has set up prototypes in Boulder City, Nev. and in Belgium. A 30-ft diameter model is awaiting completion of a custom-designed generator from GinLong. The turbines initially will be designed to work with 40 mph maximum winds until the generators get optimized for the wind loads, at which time Steinke expects to produce models able to operate at 50 mph wind speeds.

Wind Sail Receptor, Inc., http://www.windsailreceptor.com/

GinLong Technologies Inc., www.ginlong.com