Future Forward: The Future of Heat Transfer May Lie Underground
This particular webcam interview was recorded by Todd Danielson, the editorial director of Informed Infrastructure. You can view a video of the full interview in the window at the top of this page.
According to the U.S. Department of Energy website (www.energy.gov), approximately 50,000 geothermal heat pumps are installed in the United States each year. Charlie Copeland is hoping to increase that number as much as possible to avoid what he calls not “climate change,” but an existing “climate crisis.”
“Whatever we can do to diminish the use of fossil fuels is something we go to work on … hard,” he explains about his business. Copeland and his engineering firm are proponents of many forms of renewable energy systems, and one he’s particularly keen on is the geothermal heat pump. Heat pumps operated with electricity generated from wind and solar, in lieu of fossil fuels, is the goal of many states such as New York.
Typical air-to-air heat pumps operate based on outdoor air temperature, which depending on locality can range from 0 degrees Fahrenheit to more than 100 degrees Fahrenheit outdoors. Geothermal heat pumps, however, rely on the relatively constant temperature of the ground (below the topsoil layer), which typically is in the 50-degree Fahrenheit range (10-15 degrees Celsius). Geothermal pipes containing water or a mixture of water and antifreeze are buried in the ground horizontally or vertically. This improves the efficiency from roughly 300 percent for air to air to as much as 600 percent for ground sources. Geothermal pipes are connected to a standard heat-pump system that moves heat in and out of buildings, residences and individual rooms.
During the summer, for example, the system absorbs warm air in a building and pumps it into the colder ground, which cools the fluid and returns it to the building to cool the interior. During the winter, the opposite takes place, where warmer ground temperatures can be concentrated to warm the pumped fluid and therefore the building.
“As long as you don’t overload it with too much heat, you can use that underground surface to either reject heat or absorb heat,” explains Copeland. “And you’re doing it at a constant temperature in the 50-degree range and not at 95 or 100 degrees, or 10 degrees.”
Location, Location, Location
Geothermal heat pumps can be used in a surprisingly large number of circumstances, but obviously not everywhere (at least to be economically viable). “It certainly doesn’t work for a 50-story building sitting on a little tiny piece of land,” admits Copeland. He also notes that not all local soils can absorb that much heat from cooling.
To help developers and owners—including individual homeowners—research if a geothermal heat pump is suitable for their location and/or lot, Copeland’s firm helped develop the New York City Geothermal Screening Tool as well as a simpler tool geared toward residents in Westchester County, N.Y., called Westchester GeoPossibilities (geopossibilities.ny.gov).
“The New York City tool is a very detailed tool that looks at different types of structures,” explains Copeland. “There could be 15 different types of structures, from a simple warehouse to a sophisticated office building to a residential tower to a single residence to a museum.”
The New York City tool uses sophisticated USGS underground geological survey maps that show how much rock and soil are underground, or if there’s an aquifer that can’t be touched. The Westchester tool, according to Copeland, is more oriented toward residential buildings. Developers hope it demonstrates that the original New York City screening tool can be adapted for a suburban county, creating a new model that’s more broadly applicable across the nation.
Applicable for Your Designs?
Although economic feasibility depends on each situation—and there are many variables that must be considered—Copeland believes all infrastructure engineers should at least consider geothermal heat pumps for their designs.
“Even if you’re limited on area, I wouldn’t give up on it,” he says. “[Perhaps] putting in an electric-operated cooling tower that rejects heat to the atmosphere can be a way of complementing geothermal.”
As international news and research reports continue to point to the need to limit climate change to avoid catastrophe, perhaps geothermal heat pumps running on electricity from renewable energy sources can contribute toward a more-sustainable future.