A new type of solar thermal system for homes that can provide heat, hot water, and electricity is being tested in Boulder, Colo., over the next few months.

Cool Energy says its SlowFlow system could provide the average U.S. home with 80 percent of its heat, 100 of its hot water, and 60 percent of its electricity needs.

It's being developed with help from the National Science Foundation, the Department of Energy, and electricity and natural gas giant Xcel Energy.

The system consists of solar collectors, a Stirling engine, a hot water heater, a space heater, an insulated storage tank, and the SolarSmart Controller, a computer with networked communications.

The SolarSmart Controller uses weather, ambient temperature, building temperature, and sunlight data to determine the device's most effective usefulness for a given day. If, for example, it's cold and overcast outside and its building's internal temperature is below a given desired temperature, the device would generate its effort to heating the building. On warm and sunny days, it would direct itself to generate electricity instead.

But the centerpiece tech of the system, which won the 2009 Cleantech Open Sustainability Award for the Rocky Mountain region, is Cool Energy's SolarHeart engine. The proprietary Stirling engine was developed by Cool Energy to efficiently convert solar thermal energy or waste heat into electricity. When tested in the lab over a wide array of temperature and solar conditions, the device's SolarHeart engine was able to generate more than 2,000 watts of electricity, and achieve more than 16 percent efficiency for thermal-to-electrical conversion, according to Cool Energy statistics.

The complete Slow Flow system minus its solar collectors, which are located on the roof of the building.

A successful solar multi-use generator might allow customers to recoup their investment in the device more quickly compared to solar panels that provide electricity only. It might be especially effective in climates where homeowners need home heating oil or propane to heat their homes in winter, and electricity-guzzling air conditioners to cool their homes in summer.

Of course, the field test will offer more insight on this system's true real-world capabilities. And while this is certainly an innovative green tech product idea, Cool Energy is not the first to use a solar-driven Stirling engine.

Tessera Solar and Stirling Engine Systems have been testing a large-scale solar system that uses mirrored parabolic dishes that track the sun and heat hydrogen gas-filled pistons in a Stirling engine to generate electricity.