SOLAR power is about to bring some focus to your roof.
Concentrated solar power has traditionally been confined to the desert, where huge arrays of mirrors focus the sun's rays to heat water, oil or salt. Now, thanks to cheap microprocessors and sun-tracking technology, a start-up called Avalanche Energy is bringing it to the rooftops of ordinary houses. The firm plans to make solar water heating more affordable than ever before.
Alex Pina, CEO of Avalanche, has built a prototype solar water heater the size of a satellite dish. The device, called ThermalSquare, concentrates sunlight into a beam that heats water directly, then pumps it into the existing hot water tank. There are no expensive heat transfer fluids, vacuum tubes or silicon panels.
When ThermalSquare goes on sale early next year, it will cost about $1000 to install, and the firm claims it will pay for itself in hot water within three years, although the exact time will vary with location. After this period, Pina says the system will continue to provide hot water for 20 years.
"It is a very interesting technology. If they can get below $1000 I think it will fly," says Ram Narayanamurthy of the Electric Power Research Institute, a non-profit organisation funded by the utility industry and based in Washington DC. Narayanamurthy says solar water heating has been forsaken in recent years because cheap natural gas and photovoltaic panels prove better buys. Existing solar water heaters cost several thousand dollars, making them an expensive option for homeowners, he says.
To keep the cost of ThermalSquare down, its two collector dishes, which catch and focus light, are stamped out of sheet metal. The first, which is about 1.2 metres in diameter, or the size of a big beach ball, focuses sunlight onto the second, smaller mirror. This redirects a concentrated beam of light onto a water intake pipe that leads to the hot water tank. The beam heats the water directly, up to a temperature of 60 °C. Pina says the device can heat 180 litres of water from 15 to 60 °C every day. A control circuit ensures that if the water gets any hotter than this, it is pushed through the heating region faster, filling the tank faster and not wasting energy heating the water more than required.
Add-on modules will allow the unit to provide cooling or electricity generation using heat exchange. The firm's first pilot trial will be in Massachusetts this summer.
This article appeared in print under the headline "Focused sunlight heats water on your roof"
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