How Geothermal Works
No matter what climate you live in, the temperature throughout the year varies. For some climates that means blazing summers that cool to frigid winters. What many people don't realize is that the temperature below ground (regardless of climate or season) stays fairly consistent all year.
The ground is able to maintain a higher rate of temperature consistency because it absorbs 47% of the suns energy (heat) as it hits the Earth's surface. WaterFurnace geothermal systems are able to tap into this free energy with an earth loop. This technology is then used to provide your home or office with central heating and cooling.
Heating
During the heating cycle, a WaterFurnace geothermal heat pump uses the earth loop to extract heat from the ground. As the system pulls heat from the loop it distributes it through a conventional duct system as warm air. The same heat energy can also be used for a radiant floor system or domestic hot water heating.
Cooling
In the cooling mode, the heating process is reversed - creating cool, conditioned air throughout the home. Instead of extracting heat from the ground, heat is extracted from the air in your home and either moved back into the earth loop, or used to preheat the water in your hot water tank.
Geothermal vs. Geoexchange: what's in a name?
Geothermal energy has been used to heat and air condition buildings for several decades, and, during that time, these geothermal systems have been called many different things. Some of the more popular variations include geo-thermal, geoexchange, ground-water, ground-water assisted, ground-water-source, water-to-water, and even our company name, water furnace heating and cooling.
Geothermal heat pumps (sometimes referred to as GeoExchange, earth-coupled, ground-source, or water-source heat pumps) have been in use since the late 1940s. Geothermal heat pumps (GHPs) use the constant temperature of the earth as the exchange medium instead of the outside air temperature. This allows the system to reach fairly high efficiencies (300%-600%) on the coldest of winter nights, compared to 175%-250% for air-source heat pumps on cool days.
While many parts of the country experience seasonal temperature extremes—from scorching heat in the summer to sub-zero cold in the winter—a few feet below the earth's surface the ground remains at a relatively constant temperature. Depending on latitude, ground temperatures range from 45°F (7°C) to 75°F (21°C). Like a cave, this ground temperature is warmer than the air above it during the winter and cooler than the air in the summer. The GHP takes advantage of this by exchanging heat with the earth through a ground heat exchanger.
As with any heat pump, geothermal and water-source heat pumps are able to heat, cool, and, if so equipped, supply the house with hot water. Some models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings. Relative to air-source heat pumps, they are quieter, last longer, need little maintenance, and do not depend on the temperature of the outside air.
A dual-source heat pump combines an air-source heat pump with a geothermal heat pump. These appliances combine the best of both systems. Dual-source heat pumps have higher efficiency ratings than air-source units, but are not as efficient as geothermal units. The main advantage of dual-source systems is that they cost much less to install than a single geothermal unit, and work almost as well.
Even though the installation price of a geothermal system can be several times that of an air-source system of the same heating and cooling capacity, the additional costs are returned to you in energy savings in 5–10 years. System life is estimated at 25 years for the inside components and 50+ years for the ground loop. There are approximately 50,000 geothermal heat pumps installed in the United States each year.