Dallas, Texas, United States – School districts across the nation are starting to replace conventional electric Heating, ventilating, and air-conditioning systems (HVACs) with ground source heat pumps (GSHP). Since the 1990s, when a handful of campuses installed the first GSHP systems, the technology has proven reliable and efficient with energy costs 30 to 50% less than the chiller systems of old. Many new schools now forgo the old roof-top units to install GSHPs connected to 250-foot-deep wells that transfer heat via water-filled polyethylene tubing.
“The earth temperature in our market is 70 degrees, so we have a resource that lets you keep a building at 70 degrees year-round,” said Don Penn, owner of Image Engineering Group Ltd., which has installed multiple GSHP systems since the 1990s.
Across the country, HVAC contractors are showing interest in learning about geothermal heat pump systems since schools and local governments have embraced the technology. Globally, installations of geothermal heat pumps are expected to grow from 2.94 million units in 2010 to 5.66 million in 2015 – a 14% increase, according to Dallas-based research and consulting firm Markets and Markets.
“The popularity has a lot to do with enthusiasm by contractors who see their friends making money doing it,” said Jim Bose, executive director of the Oklahoma-based International Ground Source Heat Pump Association.
The technology, a sort of hybrid of solar energy and energy efficiency, has staying power because the costs are now only about 5% to 10% more than traditional heating and cooling systems, said Penn. In Dallas, conventional HVACs and GSHP systems cost $17 to $20 per square foot. Drilling a well adds another $5 to $6 per foot. Because the schools save 30% to 50% on electricity costs, they can expect to make up the extra up-front installation costs in as little as two years. Over the life of the system, these organizations could save considerably more on electricity compared to using a conventional electric HVAC system, Penn said.
In the winter, geothermal heat pumps transfer heat from the earth into a home, school or office building. In the summer, they transfer heat underground. Some critics have said the systems are not perfect because they have potential to lose efficiency if the ground becomes heat-saturated in warm climates.
While GSPH systems have become increasing popular for homes in colder climates, they are especially suited for large to mid-size buildings with plenty of land that can dissipate heat, Penn said. A GSPH for a 100,000-square-foot building requires a well system with 100,000 square feet of land. Schools have become ideal for the systems because they have extra land to place related wells.
Penn said the heat pumps he first installed 18 years ago are still operating (they have a 24-year life span) and the wells are rated to last 100 to 200 years.