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NREL Research Teams Win Three R&D 100 Awards

Golden, Colo., Oct. 4, 2001 - Since 1982, the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) has won 28 R&D 100 awards in the annual competition for innovative technology sponsored by R&D Magazine. This year, three NREL research teams have brought that total number of awards to 31.

The 2001 awards are for a solar cell that has shattered world efficiency records, an antenna that reconfigures itself to direct its power at selected subscribers and a battery charger capable of extending the cycle life of lead-acid batteries.

The solar cell, called a "TJ" solar cell for "triple junction," is capable of record-breaking efficiency in converting sunlight to electricity and maintaining a high efficiency under great concentrations of solar energy. Recently, the TJ solar cell reached 34 percent conversion efficiency under a concentration of 400 suns, the power of our sun concentrated by solar arrays.

"The TJ solar cell is a very sophisticated yet manufacturable solar cell," Principal Scientist Jerry Olson said.

Developed jointly with Spectrolab Inc., the TJ solar cell has the potential to produce enormous amounts of electric power for homes, businesses, industry, institutions and communities, competing well against conventional systems for generating electricity.

The Dynamically Reconfigurable Wireless Networks (DRWiN) electronically scanning antenna is the world's first low-cost scanning antenna that enables higher quality and more reliable wireless service to a larger customer base within a given geographic area.

"This technology, based on tunable dielectric materials, could revolutionize the way wireless electronic communications is accomplished, serving more customers at lower cost," NREL Project Team Leader David Ginley said. DRWiN is used to accurately, rapidly and inexpensively transmit and receive signals to and from stationary and moving targets.

DRWiN can reconfigure itself from broad beam to narrow beam in order to direct information to selected subscribers, and then reconfigure back to broad beam to acquire new subscribers requesting service. This leads to the ability to serve more customers with higher quality data transfers. The antenna's performance directly translates to increased revenue for service providers.

The award for the DRWiN electronically scanning antenna went to NREL and its R&D partners, Paratek Microwave Inc. and Russia's St. Petersburg State Electrotechnical University. Paratek has commercialized the technology.

The current interrupt charging algorithm is a simple approach for recharging lead-acid batteries that extends the cycle life of the batteries by 300 to 400 percent. Lead-acid batteries used in electric vehicles have, until now, lasted only about 150 to 200 deep discharge cycles, primarily because the batteries have been charged using a constant current and voltage.

In contrast, NREL and its partners, Recombination Technologies and Optima Batteries, devised a new and more efficient way to charge batteries. Their method involves applying a current to the battery for five seconds to overcharge the battery slightly, then interrupting the current for five seconds. This allows the battery to cool and avoid going into the oxygen recombination cycle, which leads to early failure of the negative battery plate due to oxidation of sulfuric acid into sulfate.

"Our idea was to increase the cycle life of lead acid batteries to have less waste in our landfills," said Mechanical Design Engineer Matt Keyser. "By increasing the cycle life, consumers will use fewer batteries over time."

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