THE CUTTING EDGE: COMPUTING / TECHNOLOGY / INNOVATION : Now Generation : New Turbogenerators Promise Cheaper, Cleaner Energy


Jim Wensley and Robin Mackay have a little idea for low-cost, environmentally safe and hassle-free energy production--so little, in fact, that it weighs only 165 pounds.

It's a turbogenerator small enough to fit in a footlocker but powerful enough to do the work of a traditional generator weighing nearly 10 times as much. After three years of intensive research and development, Wensley and Mackay--president and vice president of Tarzana-based Capstone Turbine Corp.--are preparing to use their 32-horsepower turbogenerators to power oil well pumps, electric vehicles and to provide electricity to remote places all around the world.

"This is the future of power generation," Wensley said.

He's not the only one who thinks so. Capstone's low-emission turbogenerator--and similar designs being developed at AlliedSignal Aerospace in Torrance and a few other companies--are drawing interest from potential customers ranging from power utilities to automotive firms.

"This is a fascinating technology," said Edan Prabhu, manager of technology transfer for Southern California Edison Co. "If all the magic pans out, the number of uses would be limited only by our imagination."


Turbogenerators are electric power generators fueled by gas turbines. Both turbines and generators have been around for decades, but engineers only began to build compact combinations of the two about four years ago, said Thomas Sebestyen, director of the Department of Energy's advanced propulsion division. Recent advances in electronics have allowed designers for the first time to harvest a 60-hertz alternating current from the ultra-fast-spinning turbogenerators without using bulky, breakable mechanical gears.

A turbine is like a glorified windmill, with blades that spin around a central axis. The turbine sucks in air and heats it to temperatures in excess of 1,500 degrees Fahrenheit. The heated air rapidly expands, pushing the turbine's blades around in circles. Some of that mechanical energy is used to power the turbine itself; the rest can be used to run a generator. (A jet engine, which is a turbine, uses the excess energy to create the thrust that propels an airplane.)

Traditional generators use diesel engines and are refrigerator size and larger. A hollow metal tube that makes up the core of the generator spins 1,800 times per minute, and then mechanical gears convert the electrical output into a standard alternating current of 60 hertz--and less than 40 horsepower, or 30 kilowatts, of energy.

Turbogenerators combine a fast-spinning gas turbine and a generator on the same shaft, which spins at a rate of 80,000 to 96,000 rotations per minute. Since it spins roughly 50 times faster than a traditional generator, it can be built 50 times smaller and still produce the same amount of electrical current. But the fast-spinning turbogenerator produces an alternating current of 1,600 hertz--much higher than what is produced by a conventional generator--which must then be converted to the standard 60 hertz using small electrical components such as capacitors and a diode.

These new designs also allow small turbogenerators to rely on air bearings to facilitate the turning of the shaft without using lubricants such as oil or water, thereby eliminating most maintenance problems. When properly silenced, the Capstone turbogenerator is no louder than a vacuum cleaner.

Turbogenerators are inherently low in emissions because the combustion process--in which the air is superheated to turn the turbine--is continuous. Early tests show that they are capable of meeting the ultra-low vehicle emission standards set by the California Air Resources Board.


"There are a lot of power generating devices around that are noisy and have big maintenance problems and high emissions," Mackay said. "We tried to eliminate all three."

Engineers at AlliedSignal Aerospace are converting a turbogenerator used to power M-1 tanks into a 300-pound, 67-horsepower power source for a hybrid electric bus, said Charles Weinstein, director of advanced technology.

Weinstein said AlliedSignal is also creating a version of its turbogenerator for full- and mid-size cars such as the Ford Taurus. The company also has contracts to work with Renault and Peugeot, he said. The first of those turbogenerators is expected to be ready for delivery a year from now.

Engineers at Ford Motor Co. plan to test ways to incorporate both the Capstone and AlliedSignal turbogenerators into cleaner, more efficient cars as part of the Department of Energy's Hybrid Vehicle Propulsion System program.

"What we're looking for with turbogenerators is an efficient way to create electricity to drive car motors," said Richard Belaire, technology group leader for engines in Ford's alternative power source technology department. Ford has been working with Capstone since 1992 to use its turbogenerator as a range extender for an electric vehicle.

The more powerful AlliedSignal turbogenerator is being considered for a hybrid electric vehicle that would use a smaller battery to start the car and replace a traditional engine with a turbogenerator to provide better performance, he said.

By the end of 1998, Belaire said, he expects to present the Department of Energy with at least one design for a car equipped with a turbogenerator.

Although clean-burning hybrid electric vehicles offer the possibility of mass production, venture capitalists backing Capstone--including Sevin Rosen Funds, the Dallas-based firm headed by Compaq Computer Chairman Ben Rosen--expect the machines to make their first commercial success in the utilities market.

"The core technology is applicable to many different market segments--stationary power, backup power, cogeneration and lighting," said Eric Young, a general partner with the Canaan Partners venture capital firm in Menlo Park, which has invested $1.5 million in Capstone.

Prabhu envisions installing the "mini generators" at the ends of overloaded power lines to provide an inexpensive alternative to building whole new lines.

Over the next few months, Southern California Edison will be testing some of the turbogenerators to see how they hold up under continued use for a variety of applications. Prabhu predicted they could be widely installed within a year or two at the earliest.

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