Geothermal heat pumps stand out as a unique and energy-efficient way of keeping your home comfortable year-round. If you've been thinking about having one installed in your home, here are a few things you'll need to know about your new geothermal system.
What the Word "Geothermal" Means
When someone says the word "geothermal," visions of volcanos, geysers and hot springs tend to come to mind. But a geothermal pump doesn't get its energy from those places. Instead, it simply uses the stored heat energy deep underground to its advantage.
As sunlight reaches the surface, much of the heat energy it contains is absorbed into the earth. In most regions, this allows the underground temperature to remain constant throughout the year – according to the U.S. Department of Energy, ground temperatures in most latitudes range from 45 to 75 degrees Fahrenheit.
Geothermal heat pumps, also known as "ground source heat pumps," take advantage of this by drawing the heat energy from underground and transferring it into your home during the winter. During the summer months, the heat pump extracts the latent heat energy from your home's indoor air and transfers it below ground. Even during the winter, there's usually enough heat energy below ground for the heat pump to effectively harvest.
Geothermal Benefits and Drawbacks
There are several benefits to owning and operating a geothermal heat pump:
- Geothermal heat pumps are more energy-efficient than other heating and cooling systems. In fact, it takes just a single kilowatt-hour of electricity for a geothermal heat pump to produce 12,000 BTU of climate control. Standard heat pumps require an average of 2.2 kilowatt-hours to achieve the same result. These systems also tend to be the most efficient of all HVAC systems.
- Most geothermal heat pumps are also quieter than other HVAC systems, since the need for an outdoor condenser fan is eliminated by the geothermal heat pump setup.
- Geothermal heat pumps are not only an eco-friendly way of heating and cooling your home, but it's also one that can enhance your home's resale value.
Installing a geothermal heat pump can be an expensive undertaking, however. According to geothermal HVAC systems expert Jay Egg, these systems can cost anywhere from $5,000 per ton to $9,000 per ton to purchase and install. However, as much as 60 percent of that cost can be offset by a combination of local and federal incentives.
Geothermal heat pumps are also limited by a number of building site considerations, including land availability, soil and rock composition and ground/source water availability.
Closed-Loop or Open-Loop
As the name implies, closed-loop systems utilize a self-contained network of buried pipe filled with a heat-transferring antifreeze solution. There are four types of closed-loop systems available, each with their own benefits and drawbacks:
- Horizontal – This setup is ideal for homes located in areas where deep trench digging isn't possible, but the shorter trenches can be offset by the greater expanse of land available.
- Vertical – This setup requires drilling up to 400 feet deep, but the vertical orientation does not disturb existing landscaping and is ideal for homes with relatively small lot sizes.
- Closed pond – Instead of using a horizontal or vertical setup, this one uses a preexisting lake or similar body of water as a medium of heat energy exchange.
- Direct exchange – This setup does away with the traditional heat exchanger. Instead, the refrigerant is pumped directly underground via copper tubing, where it then collects or expels the latent heat within. While this option offers more flexibility, it requires special attention be paid to soil condition. If the soil is too acidic, there's a good chance that the copper tubing will corrode. Some municipalities also frown upon heat pumps that use the direct exchange method.
Then there's the open-loop method, which uses actual surface water from a lake or pond or water from a nearby well to transfer heat to and from your home. Open-loop systems are not self-contained and require a steady supply of clean water to properly function.
Deciding between an open-loop or closed-loop geothermal heat pump requires looking at a number of variables in and around your home, including its ecology and hydrology, current land availability and the energy savings it'll offer in comparison to purchase and installation costs.
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