The District of Columbia is soliciting design proposals for a community heat pump system, the latest pilot project to attempt to scale a decades-old geothermal heating and cooling technology to the neighborhood level.
The district's Public Service Commission asked developers May 17 to apply to construct a large community heat pump system, capable of serving multiple buildings.
In doing so, Washington, D.C., joined a spate of other regional efforts to try to expand the use of a technology that the U.S. Environmental Protection Agency sees as the most energy-efficient, cost-effective and environmentally friendly way to heat and cool a building.
Despite the benefits of geothermal energy, electricity and natural gas remain the largest household energy sources in the U.S., according to the U.S. Energy Information Administration. Roughly 14% of all U.S. homes in 2020 used heat pumps as their primary means of heating their homes, according to the agency.
Geothermal heat pumps, also known as ground-source heat pumps, have been in use since the 1940s. They draw thermal energy from the ground by pumping a refrigerant through a circuit of underground tubing leading into and out of a building. In the summer, the system reverses by drawing warm air out of the building and sinking it back into the earth. The process takes advantage of the relatively constant temperature a few feet below ground, which lies between 45 degrees F and 75 degrees F depending on latitude.
The downside of geothermal heat pumps is that installation, which involves boring holes into the ground, can be burdensome. Air source heat pumps, by contrast, transfer thermal energy from the outside using similar technology as an air conditioner but in reverse. The above-ground equipment is easier to install but less energy efficient in cold temperatures.
"When geothermal systems can be connected to a municipally based infrastructure, like city water ... city sewer [or] electricity, then it will become mainstream," Egg Geo President Jay Egg said in an interview. Egg Geo is a mechanical services company focused on geothermal HVAC consulting and contracting technologies.
"While it's very effective to build a geothermal well or put in a geothermal exchange field, we're not going to be expected to do that any more than we're expected to drill our own water well," said Egg, who consults with developers and governments on building geothermal energy networks.
A recent slew of pilot projects is putting community geothermal heat pumps to the test.
In Washington, D.C., the Public Service Commission said its community heat pump program would be funded by a $21.55 million subaccount committed for pilot projects in the 2016 merger of Exelon Corp. and Pepco Holdings.
In 2021, the New York State Energy Research and Development Authority launched a community heat pump pilot program for large construction projects, such as those at universities, medical campuses, residential complexes and downtown corridors. Thirty projects, including those at the Rockefeller Center, Syracuse University and in the city of Troy, have already been awarded funding.
In Massachusetts, the nonprofit HEET is working with utility companies Eversource Energy and National Grid USA on two more pilot projects that deploy geothermal heat pumps at the community level.
The Eversource project will install a geothermal heating system in a neighborhood in Framingham, Mass., with construction scheduled to start in mid-2022. Depending on the outcome of the demonstration, Eversource said geothermal heat pumps may serve as a "potential option to complement or replace delivered fuels and natural gas service for heating and cooling."
The National Grid project will explore community heat pump networks as an alternative to replacing leak-prone natural gas piping. In April, the company released a plan for eliminating standard natural gas in Massachusetts and New York by 2050 and possibly using geothermal heating as an alternative.
As of 2015, the most recent data available, heating and air conditioning accounted for 51% of U.S. household energy consumption, according to the EIA, making it a key target for emissions reduction. One way to decarbonize, Egg said, is by decarbonizing electricity in general and switching to electric-only heating. The other way is to install geothermal networks to lessen some of that electric load.
"On the one hand, we have to invest billions of dollars in [geothermal] infrastructure. On the other hand, we have to invest billions of dollars in electric and the electric grid," Egg said.
The U.S. Energy Department's fiscal year 2023 budget request includes $202 million in geothermal technologies funding, nearly double that of the 2021 enacted level. Most of that funding would support enhanced geothermal and hydrothermal power production, harnessing the thermal energy found in hot rock or geysers, hot springs and fumaroles.
However, $34 million is earmarked for "low-temperature" geothermal resources, or the weaker thermal energy beneath every home or commercial building that can be used for space or hot water heating. Citing a 2019 study, the DOE said that "through the adoption of advanced technology scenarios, geothermal district-heating installations could increase to 17,500 nationwide, and 28 million U.S. households could realize cost-effective heating and cooling solutions through geothermal heat pumps."
The DOE's Office of Building Technologies requested up to $46 million for HVAC, water heating and refrigeration research and development, including heat pumps, and $217 million for the integration of energy-efficient technologies in residential and commercial buildings.
However, the request is not nearly enough for large-scale geothermal energy network deployment, according to Egg.
"It's just research," Egg said. "The cities and communities are going to need billions of dollars to do this, if not trillions."
A May 13 Information Technology & Innovation Foundation report, analyzing the DOE's budget request, also referred to the geothermal and building technologies programs as "underappreciated offices."
The report noted that geothermal power, unlike solar, wind and hydropower, is neither intermittent nor weather-dependent. Yet, the Geothermal Technologies Office has "consistently received less funding than the other three renewable energy offices do."
Alternative heating and cooling may be spurred by other policy forces. In April, Washington state became the first to mandate electric heating in its commercial and multifamily building codes, requiring builders to install air- or ground-source heat pumps or electric resistance heating. And May 4, Senate Democrats introduced a bill that would subsidize $10 billion in American-made electric heating equipment.
"The only solution to going all-electric and not having to increase the electrical grid capacity is the geothermal heat pump solution," Egg said.
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