Thursday, July 23, 2009

A SOLAR-POWERED BOILER

HEATING YOUR HOME’S WATER SUPPLY WITHOUT USING GAS OR OIL

Why use natural gas or oil to heat your home’s water supply when the sun can do it for free? The big boiler in the sky lays down 100 watts of power across a single square foot. The simple solar-powered hotwater system that I’ve built from scratch will put these free watts to work on the rooftop of my new eco-conscious home. Once I get it installed, it will generate about 450 gallons of hot water a day, plenty for my family of four, while consuming half the amount of energy of a conventional hot-water system. Plus, it will fuel my home’s radiant heating system, a series of polyethylene pipes built into the floor that use hot water to warm the house. The first step is to build two 150- square-foot solar collectors—tidy sandwiches of glass, copper tubes, aluminum sheets and foam insulation held together by a pair of aluminum frames. I’ll position the panels at 65 degrees to the plane of the roof, facing south, like my house, to catch as much sun as possible to heat up the fluid (the antifreeze glycol) flowing through the copper tubes. Next I’ll install a pair of insulated 158-gallon storage tanks in the basement to hold my supply of municipal water. To heat it up, a pump will circulate hot glycol from the collectors through a heat exchanger inside each tank. When sensors in the roof-mounted panels hit about 60°F, a controller automatically turns a valve to start circulating the glycol. One tank distributes water for showers and dishes while the other services the radiant floors. What happens during the winter when the sun’s intensity wanes? That’s where heat from my newly drilled geothermal well comes in. More on that project next month.—JOHN B. CARNETT

Source of Information : Popular Science July 2009

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