U.S. Department of Energy - Energy Efficiency and Renewable Energy

Multimedia

Energy 101: Geothermal Heat Pumps (Text Version)

Below is the text version for the Energy 101: Geothermal heat pumps video.

The video opens with "Energy 101: Geothermal Heat Pumps." This is followed by an illustration of a house panning to a man standing beside it.

We all want to save money heating and cooling our house or office. Right? The answer may be under your feet. Literally.

The ground under the man's feet is shown in cross-section. A geothermal heat pump appears in this cross-sectional illustration of the ground.

Much of the heating and cooling can come from the ground — below the surface with something called… a geothermal heat pump.

The video shows the Earth rotating, then revealed in cross-section. The video then returns to the house with the cross-section of the ground with a geothermal heat pump.

You see, below the frost line—about 10 feet down—the Earth maintains a nearly constant temperature of 54 degrees.

The video shows a construction worker digging a tunnel deep into the ground. Next, the video follows the pipes that lay at the bottom of the tunnel.

We can tap into this energy to provide heating in the winter and cooling in the summer.

Okay, now here's how it works. Bury a loop of pipes—called a heat exchanger—just below the surface… and fill them with water… or a water and antifreeze solution.

The video returns to the house, where an animation of the geothermal heat pump shows the direction of heat transfer in a loop from the pipe to the home.

During the winter, the air is usually cooler than the temperature below ground. The solution circulates in a loop underground and absorbs the Earth's heat. This heat is brought to the surface and transferred to a heat pump. The heat pump warms the air and your regular heating system… warms the air some more to a comfortable temperature. Then ducts circulate the air to the various rooms.

The video shows the interior of a building with geothermal heat pump operating equipment.

A huge benefit is that the geothermal system doesn't have to work as hard to make people inside comfortably warm — and you save lots of money on your heating bill.

The video returns to the house, where an animation of the geothermal heat pump shows the direction of heat transfer in a loop from the home back to the ground.

In the summertime, the system works in reverse.  When it's hot outside… the temperature below the surface is cooler than the summer heat, so the fluid in the loop absorbs heat in the building and sends it underground. The ground's lower temperature cools it and it's circulated again and again.

Now, you're saving money on air conditioning.

The video shows images of a church building.

Now, this church uses a large geothermal heat pump to heat and cool the building. It has a very big parking lot, which lets it spread out its loop horizontally.

The video returns to the house, where an illustration of a vertically-oriented geothermal heat pump shows the direction of heat transfer from the ground to the home.

But if you don't have all that space, you can go straight down and use a vertical loop system instead.
A map of the United States appears on screen. Next, footage of geothermal heat pump digging and construction are shown.

Geothermal heat pumps can be used just about anywhere in the U.S. because all areas have nearly constant shallow ground temperatures—although systems in different locations will have varying degrees of efficiency and cost savings.

The constant temperature of the earth just below our feet is a sustainable resource— literally in our own back yard. It's a clean energy source ready for us to use, to heat and cool our homes and buildings while lowering our utility bills.