Geothermal systems provide consistent indoor temperature and humidity levels, while operating quietly. If you are an environmentalist, geothermal systems reduce the carbon footprint of your home or business by producing heating and cooling on site with the renewable resource of your land.

Extracting Heat From The Earth

Len Calderone for | AltEnergyMag


It might be a balmy 40 degrees outside, but down deep in the Earth it's a different story with energy being produced by nuclear reactions firing off deep inside our planet, where even solid rocks turn to a hot bubbling soup.

It's hard to think of Earth as a hot place, especially if you live in the northern hemisphere, exposed to changing seasons. Underground, it's a very different story. Geologists have estimated that there's about 42 million megawatts of geothermal energy trapped inside Earth, which is comparable to the energy made by 25,000 major power plants.

Even with all this potential energy, there are only a few locations where geothermal energy can be easily sourced, such as Yellowstone National Park. Yet, we can extract heat stored in the ground from pretty much anywhere, because heat pumps make use of the fact that the ground is usually warmer than the environment above it in the winter because of the energy it systematically receives, year-round, from the Sun.

Utilizing the sun's energy, within the top10 feet or so of the Earth's surface, the temperature stays a steady 50–60 °F. So, you don't have to live on top of a volcano or have a geyser in your backyard.  

The popular heating systems that we use work by generating heat where it's needed. Electric heating systems convert energy into heat by passing an electric current through wires. Gas and oil central heating systems burn fuels with oxygen from the air in a process called combustion, heating hot water that circulates through the radiators in our homes.

Heat pumps simply pick heat up and move it from one place to another, usually from the ground into the building itself. An air conditioner moves heat from the inside to the outside. A heat pump does the reverse. It moves heat from the ground to the inside even in the winter.



Geothermal heat pumps are typically more efficient than heat pumps that use outside air because the temperature of the ground is closer to the desired indoor temperature all year than outdoor air temperatures. Like heat pumps that use outside air, geothermal systems are good at keeping temperatures and humidity levels constant inside the building, making homes more comfortable than conventional heating systems.

How do engineers turn geothermal heat and steam into something you can use for heating? Water or a glycol solution is circulated through ground loops warming the liquid to the consistent temperature of the Earth. Depending on your site and installation needs, loops can be configured in a shallow field, or inserted into deep wells drilled exclusively for the geothermal system. 


To understand how geothermal heat pumps work, we need to look at an air conditioner, which removes heat from the home. This is accomplished by moving the hot air across the evaporator coil, which absorbs the heat and transfers it to the unit outside of the home. An air conditioner does not blow cold air into the house; it actually removes the hot air, reducing the inside temperature, making it feel cooler in the house.

A conventional heat pump operates in the summer similar to an air conditioner. In the winter time it simply reverses the flow of refrigerant and absorbs heat from the outside then dispersing that heat into the home. How exactly is that done? Even when it is very cold outside there is still heat in the air. Most heat pumps have the ability to extract heat from the air down to -5 °F. The colder it is, the less heat the heat pump can obtain. The lower the temperature the less efficient an air-to-air heat pump becomes, and at -5 °F, the air-to-air heat pump will not extract heat from the air. Therefore, there needs to be a form of backup heat in the northern states.  

With a geothermal heat pump, the main equipment resides inside the home and is connected to a set of “loops” that are buried under the ground because the ground temperature is on average a consistent 55 °F. The ground now becomes the source of energy and is transferred from the earth to the fluid that is being circulated inside of the underground loops and then transferred into the home.



The geothermal heat pump is using basic air conditioner and heat pump technology to remove the energy or heat from the fluid in an earth loop. The answer to the success of a geothermal system is that it's using negligible energy to extract the heat from the earth during the winter and it transfers that heat into the home. During the summer, the reverse happens and the system extracts the heat from the home and disperses that heat into the consistent temperature of the earth.

Unlike an ordinary heat pump, whose efficiency depends on the inconsistent outside air temperature, which varies greatly, the geothermal system relies on the consistent temperature deep underground, delivering high efficiency no matter what the weather is.

The advantages of using a geothermal heat pump are the costs of heating and cooling, which could be half of the cost of an oil or electric system. A reasonably insulated 2,000 sq. ft. house can be heated or cooled for about a dollar a day. Geothermal systems are often more expensive to install than conventional heating or cooling systems; but by pairing geothermal installations with a well sealed house, and insulation, the size of the system that is required could be reduced, along with the installation costs. On the plus side, the payback can be in as little as two to three years while heating and cooling costs would be at a predictable rate of electric consumption.

The only disadvantage of geothermal heat pumps is that you will need a big enough lot for a series of vertical wells to be drilled or for coiled pipe to be placed in a trench. If your home is next to a pond, the coils can be placed in the water. Not all properties are suited for ground source heat pumps, but many are.

Geothermal systems provide consistent indoor temperature and humidity levels, while operating quietly. If you are an environmentalist, geothermal systems reduce the carbon footprint of your home or business by producing heating and cooling on site with the renewable resource of your land. These systems are also very robust and could last twenty years or more.


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Len Calderone - Contributing Editor

Len contributes to this publication on a regular basis. Past articles can be found in the Article Library and his profile on our Associates Page

He also writes short stores that always have a surprise ending. These can be found at

Len Calderone

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