Ground source heat pumps (also called geothermal systems) are a fairly new and innovative method of heating and cooling a building, but the idea is relatively simple: The earth below ground maintains a consistent temperature of around 57°F. Instead of heating the building from the freezing air outside, or cooling the building from the blistering air outside, you heat it or cool it from this 57°F. Because this geothermal temperature is much closer to people’s normal comfort zone, it requires much less energy to use. In figure below you can see how this system works.
The U.S. Environmental Protection Agency (EPA) credits geothermal as “the most energy-efficient, environmentally friendly heating and cooling technology available.”
The only by-product of using a ground source heat pump is warm water. With this ground source water, you can heat both the air and the water needs for your building.
Generally speaking, geothermal systems come in two standard configurations: vertical closed loop or horizontal closed loop.
- Vertical Closed Loop: The most common system is the vertical one. In this system, loops of piping are fed several hundred feet into the earth, which requires a great deal of boring. Given the depth, the ground source temperature remains consistent throughout the year. On a site with expansive soils or bedrock, the vertical systems are too expensive.
- Horizontal Cosed Loop: Horizontal closed loop systems are installed in trenches only 5 feet below the surface of the earth. Due to this shallow installation, the ground temperature changes seasonally. Although horizontal loops are much easier to install and work for bedrock sites, they do require significantly more surface area (approximately 2,500 square feet of surface area per ton of cooling) in order to work effectively.
The Advantages of Geothermal
- Cost savings: Homeowners with geothermal units typically realize energy savings of 25% to 50% over conventional gas, oil, or heat pump systems. As a general rule, a typical 2,000-square-foot house can be heated or cooled for as little as $1 a day. Because a geothermal system also produces hot water as a by-product, it’s up to 30% less expensive to operate than a traditional gas or electric water heater.
- Pollen and dust free: A geothermal system does not draw spores and pollen into the building as a forced-air heating system does. If you have allergies or asthma, this is a welcome change and you’ll notice a marked improvement in your indoor air quality.
- Fume free: Because the geothermal system does not involve combustion, a pilot light, or a chimney, no odor or fumes will be added to the house.
For smaller buildings, installation cost is the main drawback. Drilling the holes for the vertical system can be prohibitive for single-family homes. Another possible roadblock is the lack of qualified contractors who know how to properly design, install, and service these systems.
Tip: Look for equipment certified by the Air-Conditioning and Refrigeration Institute (http://www.ari.org), a nonprofit organization that rates residential and small commercial systems.
Given their affordable installation cost, low operating costs, low maintenance costs, and overall energy efficiency, geothermal systems are an excellent choice to consider for your home. ....read more
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