Elemental power

Elemental power
Date:1 July 2011 Tags:, , , ,

1 Bottled sunlight

¨ Photovoltaic cells convert sunlight into electricity, while solar-thermal systems harness the Sun's heat. University of California, Berkeley, chemist Peter Vollhardt has designed a material that combines the two approaches, trapping light energy and storing it until it is released on demand as heat. The material, fulvalene diruthenium, has an atomic structure that changes shape when exposed to light, a reaction Vollhardt compares to loading a spring. A small amount of heat or a chemical catalyst prompts the molecules to snap back to their original state, emitting energy. Vollhardt's team is now developing a rechargeable heat battery. "My dream is to heat a cup of espresso with California sunlight," he says. Logan Ward

2 Fire down below

¨ A joint US-Icelandic drilling team went looking for hightemperature water near an Icelandic volcano in 2009, hoping to tap the ground for a geothermal well capable of generating 8 megawatts of power from steam at 300 degrees Celsius. But less than halfway to their projected 4 570 m depth, red-hot magma entered the well, forcing the team to stop drilling. It turned out to be a lucky break: the magma produced a flow of dry steam at 400 degrees, which, applied to a turbine, could generate 25 MW of electricity – enough to power 30 000 homes. The researchers are now seeking other shallow sources of magma as potential energy. Alex Hutchinson

3 Ocean-power boost

¨ By designing turbine blades to imitate the wings of aircraft, US Air Force Academy engineer Stefan Siegel has created an ultraefficient water turbine capable of converting 80 per cent of a wave's energy to usable power. Typical water turbines rely on the direct push of the water, or drag, but that method can waste half the potential energy of the wave's motion. The Cycloidal Wave Energy Converter has two hydrofoil blades that leverage Bernoulli's principle: they force water to flow faster over one side than the other, creating lift on the low-pressure side. "As they rotate, they absorb energy and create torque at the shaft," Siegel says. "We can hook up a generator directly to our main shaft, without a complicated power-takeoff system. That increases efficiency." Siegel estimates that a future ocean system could power 4 500 homes. US Department of Energy-funded testing begins in August. Sarah Fecht

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