By Kyle Field
To decarbonize their homes, people around the world are looking for alternatives to furnaces that burn natural gas, propane, or heating oil. Electric-powered heat pumps pull heat energy from the air or the ground to warm or cool the indoors.
Eliminating fuels saves money and it also cleans up the air in your home. No combustion at home also means no exhaust gases are circulated through the air you live in every day. Clean air at home is one of the big benefits of switching to a heat pump system.
What’s the difference between air-source and ground-source heat pumps?
Within the world of heat pumps, there are two major technologies that operate in similar ways but pull from very different sources. These two options are air-source heat pumps (ASHP) and ground-source heat pumps (GSHP).
ASHPs use ambient air outside a home. They extract heat from the air, compress it, and push it through indoor ductwork. In cold climates, the variable temperatures of the outside air makes this more challenging.
GSHPs, on the other hand, drill down below earth’s the frost layer to use the more consistent heat energy underground.
Both systems use the same core heat pump technology, but air-source heat pumps do have to work harder to extract the small amount of heat in ambient air when temperatures drop below freezing.
Ground-source heat pumps pull from a much more stable source for their heat. As such, they are much more efficient at heating a home in the coldest winters, no matter what the air temperature drops to outside.
Air-source heat pumps
Let’s look more closely at air-source heat pumps. These units are being used more as homeowners look for alternatives to heating their homes by burning natural gas or other hydrocarbon-based fuels. They work best in more moderate climates.
ASHPs come in a few different varieties and can be installed using existing ductwork in a home or in a ductless mini-split configuration. A mini-split system means you would have a central condenser installed as well as wall-mounted units in any of the rooms you want to cool or heat.
Whatever the configuration is inside the home, air-source heat pumps start with a heat exchanger placed outside the house. The exchanger extracts heat or cold from outside air and moves it into the home through an internal system.
Ground-source heat pumps
Ground-source heat pumps like those used in modern residential geothermal systems, have been in use since the 1940s. These systems use the earth itself as a heat sink by drilling down below the surface temperatures, which reaches up to about at least 8 feet deep in the United States.
Below the frost layer, the earth maintains a nearly constant temperature around 55 degrees Fahrenheit. This provides the foundation for a predictable geothermal heating and cooling system.
With a geothermal energy system, a closed-loop pipe is laid either horizontally or vertically in the ground surrounding a house. Then water or another liquid circulates inside the pipes through the stable temperature of the earth, collecting this heat energy.
The liquid carries the heat from underground back into the heat pump inside the home. The heat pump then transfers the heat into the air of the home, warming it up without burning any fuel.
In the summer, the heat pump removes the warm air from your home and releases it into the earth through the same closed-loop pipes. Then the cooler water from the surrounding earth is pumped back into your home and releases natural dehumidified air conditioning.
The surrounding earth is an ideal place to pull heat from in the winter or to dispose of excess heat in the summer.
The fact that the temperature does not swing much in extremely hot weather or extremely cool weather results in a system that will continue to perform well in extreme temperatures, bringing homeowners some serious utility bill savings as it offsets the high cost of winter fuels and AC in the summer.
Pros and cons of air-source vs. ground-source heat pumps
Both air-sourced and ground-sourced pumps run purely on electricity. They have different pros and cons, allowing homeowners to find a solution that best fits their needs.
Ground-source pumps generally save more energy. This is simply because of their use of consistent temperatures below the surface of the earth as opposed to air-source heat pumps use of variable air temperatures outside the home.
Pulling energy from below the earth’s surface also means that the system is not affected by bad weather or storms because everything that is not indoors is buried underground. There is no equipment outside the home that can be damaged or impacted by weather changes.
Converting air temperatures can take more energy than converting ground temperatures. This is how ASHPs consume more electricity than GSHPs.
On the positive side, ASHP systems may cost less up front and typically give you a better return on your investment in more moderate climates. But they lose their advantage as outdoor temperatures fall.
Dandelion Energy’s ground-source heat pumps
Heat pump-based systems are increasing in popularity as homeowners look for ways to save money on their rising utility bills.
Ground-source heat pumps have been around for decades now. However, Dandelion Energy is breaking new ground, advancing the core heat pump and drilling technology used during installation. These advancements make geothermal ground-source heat pumps more affordable and easier to put in place.
Curious about what Dandelion is doing to improve geothermal ground-source heat pumps? Get more of your geothermal and Dandelion questions answered by visiting their FAQ page, reading more on their blog, or reach out to them directly.
This article was supported by Dandelion; images from the company