It's an idea he has been kicking around for 30 years, said Sanborn, who runs a recycling business, Material Management, from an old factory building where renovations are being interwoven with solar-powered designs.

Sanborn believes rising energy prices are ripening consumer interest in a low-cost alternative to heating with gas and oil. Solar panels that can be set in a window on winter days and put away in the evenings can conserve energy and save money, he said.

"This is not going to heat your home by itself," he said. But it will turn free solar energy into warm air to help lighten the load on the furnace.

Sanborn teamed up with a small manufacturer in Union City to build the solar panels out of materials he recycles from businesses in southeastern Michigan, Chicago and as far away as Texas.

Aluminum panels, tempered glass and insulation material are all left over from other businesses' manufacturing processes, he said.

The assembled solar panels are simple heat collectors with openings to allow cool air to be drawn in, warmed and circulated out in a continual convection current.

While the panel is exposed to the sun, he said, the temperature of the air entering it can be raised 30 degrees before it flows back out into the room, Sanborn said.

"Once you put it out, you don't need any more energy to make it work," he said.

Production started last week at Earth Energy Options in Union City, Sanborn said, to fill orders being taken through Sanborn's Material Management retail store and through the manufacturer.

Solar space heaters are just one of the creative ideas Sanborn is pursuing at the building on Mechanic Street where he revived a recycling business he and his wife, Cindy Sanborn, in Adrian and closed 10 years ago. They began renovating the building in Hudson in 2002 to pursue a goal of moving society toward an economy in balance with the environment.