How Geothermal Systems Work


Geothermal – Energy From the Ground

Geothermal HVAC systems get their name from the way they work. Geo means from the earth and thermal means heat. So geothermal systems use the energy stored in the ground to heat your home during the winter and they move energy back into the ground during the summer to create cooling. Average ground temperatures in the Carolinas are between 60 and 65 degrees all year round. That’s cooler than even nighttime temperatures in the Charlotte area during the summer and much warmer than winter nights. The warm ground is from stored energy in the earth that geothermal systems use instead of generated electricity or natural gas to change the temperature of the air in your home.

How Geothermal Systems Work in the Winter

In Winter, average high temperatures in the Charlotte area only in the low 50’s and temperatures are often around the freezing mark at night. Traditional heat pumps capture the energy in the outside air and transfer that heat indoors. Unfortunately, the colder it is outside, the less heat is available to transfer indoors. When temperatures get too cold, traditional heat pumps require supplemental heating to warm the air in your home. A geothermal heat pump has a big advantage over a traditional heat pump. Instead of trying to capture energy from air that may be 40 degrees or more below the desired indoor temperature, it gets energy from an underground loop, where the temperature is still around 60 to 65 degrees (a difference of only about 10 degrees from where most people would set their thermostat). It is pretty easy to see that a geothermal system doesn’t have to work nearly as hard to warm the air it is pumping through your home. Since this process is very efficient, it uses a lot less purchased energy than running a traditional heat pump or using a natural gas or propane furnace for heating. The most efficient natural gas furnaces turn 97% of the energy put into them into heat, while geothermal units routinely produce 3-5 times as much energy (in the form of heat) as is used to run the system. That is a huge difference in energy use.

How Geothermal Systems Work in the Summer

In the summer, average high temperatures in the Charlotte area are in the high 80’s from June through August. Traditional Heat Pumps and Central Air Conditioners can be considered air-to-air units because they cool the air in your house and release the hot air outside your house. The hotter it is outside, the harder it becomes for these systems to cool your home and the more energy they use. Because geothermal systems take advantage of ground temperatures, they don’t need to work nearly as hard as traditional HVAC systems to cool your home. Geothermal systems still cool the air in your house, but they use an underground or underwater loop system to move the heat into the ground instead of the air. The liquid in this loop system acts as a coolant, but instead of pushing the heat from your home out into the 90 degree air, it is transferred into the 65 degree ground, making cooling a lot more efficient.

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Geothermal Loops – The Key to Unlocking Free Energy

A  loop is the basis for every geothermal system. There are several options for installing loops depending on your property location and size, but they all work the same way. The loop is an underground pipe that is filled with an environmentally safe mixture of alcohol and water.

There are three main types of geothermal loops. The right one for your system depends upon the property that your home sits upon. They all provide the same access to stored energy in the earth or water, but installation costs can vary significantly between loop types.

Loop Types

How Geothermal Systems WorkThe easiest type of loop to install is a water loop, because the pipes sit at the bottom of a pond or lake, there is little digging involved. Geothermal systems that use a water-based loop are sometimes referred to as Water Source Heat Pumps.
Horizontal loops can be used when there is enoughHorizontal Loop for Geothermal System property available to stretch out loops several hundred feet across the lot.  This is the second easiest geothermal installation method because it does not require specialized drilling, but can be completed with ordinary trenching equipment.
Save on your energy bills with geothermal heating and coolingA third type of loop system is the vertical loop.  Vertical loop systems are used when there is not enough land available for a horizontal loop or to minimize the impact on landscaping.  Because they require specialized drilling similar to that used for wells, vertical systems are generally more expensive to install, but will still return more than their investment over the life of the system.

The Rest of the Geothermal Heat Pump

While the loop is the heart of what makes the geothermal unit different than a traditional heat pump, there is more to a geothermal system. Geothermal heat pumps require only one unit (rather than an indoor and outdoor unit for traditional heat pumps). This unit is usually housed indoors, which helps protect it from the weather, helping it to outlast traditional systems. In addition, the system requires traditional ductwork for cooling and heating the air throughout the house.

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