Renewables

Solar decathlon 2009

Issue 11 and Volume 113.

For three weeks in October, the U.S. Department of Energy hosted the Solar Decathlon—a competition in which 20 teams of college and university students competed to design, build and operate the most attractive, effective and energy-efficient solar-powered house.

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Winner of the rain-streaked 2009 event was Team Germany’s Cube House.

Rain usually spoils a solar power contest. But three days of showers—and thin-film photovoltaic technology — actually helped Team Germany win the 2009 event.

Team Germany’s Cube House was one of the most technologically advanced among the 20 clean energy prototype designs on the National Mall in Washington, D.C. Every exposed face of the building was covered with power-generating panels.

On the roof: an 11.1 kW PV system of 40 monocrystalline silicon panels. On the sides: 250 thin-film panels that looked like glossy clapboards. The thin films used copper-indium-gallium-diselenide layers, or CIGS.

The combination system was expected to produce 200 percent of the energy needed by the house. The thin film panels, while less efficient than conventional silicon, were projected to perform better in cloudy weather than silicon.

Team Germany got its proof on the competition’s fifth day when skies turned slate gray and a cold rain splattered the solar village. By late afternoon, the Team Germany house was producing 12.68 kW and consuming 12.33 kW, for a net export of 0.35 kW.

Team Illinois’ house finished a close second, emphasizing energy efficiency over power production.

“Team Germany built a gingerbread house packed with solar panels,” said Richard King, DOE Solar Decathlon director. “In the rain, the thin-film panels were making electricity. It made the difference.”

During the competition itself, teams received points for their performance in 10 contests: architecture, market viability, engineering, lighting design, communications, comfort zone, hot water, appliances, home entertainment and net metering.

A Taste for Mercury

Mercury pollution ranks as a significant environmental issue, posing potential dangers for organisms at or near the top of the food chain, such as fish, shellfish and humans. But some bacteria seem to know how to break down the worst forms of it, including its most toxic form, methylmercury.

A discovery by scientists at the University of Tennessee, KNOXville, and Oak Ridge National Laboratory has shed light on one of nature’s best mercury fighters: bacteria.

Scientists have known that a specific enzyme, known as MerB, gives the bacteria the ability to convert methylmercury into a less toxic form of mercury that poses substantially less environmental risk. This trait lets the bactieria survive in mercury-rich environments. Learning how this enzyme works potentially may be a viable way to combat methylmercury.

The researchers, working with colleagues from the University of Georgia and University of California, San Francisco, determined the mechanism of how the MerB enzyme breaks apart the methylmercury molecule.

The scientists used high-performance computers to determine how the enzyme’s three-dimensional structure breaks apart a key link in the methylmercury between mercury and carbon atoms. Once that bond is broken, the resulting substance is on the way to becoming less environmentally harmful.

Researchers found out how the enzyme creates an electric field that shifts electrons in the methylmercury, priming the toxin for deconstruction. A year ago the research would have been impossible. But using increasingly powerful tools enabled scientists to see how the chemical reactions interact.

The next challenge researchers face will be to take this new understanding of how methylmercury can be broken down and apply it in an ecosystem at large.

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