The Zero Energy Home is here and copper is helping.
The U.S. Department of Energy’s “Building America” program partners with home building companies and community groups to develop Zero Energy Homes-ZEH-that generate as much or even more energy than they use.
Most homes depend on power from utilities such as electric and gas companies to heat water, operate appliances, light the darkness, warm occupants in winter and cool them in summer. But in a ZEH power is provided by solar photovoltaic and solar water-heating panels installed on the roof, as well as by an innovative heat pump system that taps into the earth itself.
Although the solar panels and geothermal heat pump draw their energy from very different sources, both systems use the same basic, elemental material-copper-for optimum heat-transfer performance. More than 225 feet of copper tubing was buried in each home’s back yard for the heat pump, and additional copper tubing and wiring went into the rooftop solar systems.
The tubing is used to circulate refrigerant liquids that act as a heat-transfer medium. In the solar panels, sunlight heats the liquid in enclosed copper coils that loop through-but do not mix with-the water in the home’s domestic hot-water system.
In the direct exchange heat pump the liquid is pumped down several lengths of copper tubing buried below frost depth, where the surrounding earth remains at a constant temperature of about 56 degrees F. The liquid in the tubing stabilizes at this temperature and is pumped back to the surface, where the heat pump puts it to work preheating the home in winter and cooling it in summer.
The Copper Development Association in America is a sponsor and its members provided the tubing and other copper materials for a demonstration ZEH.