How Geothermal Energy Works
A Few of the Geothermal Advantages
Owners of geothermal systems can relax and enjoy high-quality heating and cooling year after year without all the extra expense. These geothermal (or geo-exchange) renewable energy systems work on a different principle than an ordinary furnace/air conditioning system, and they require very little maintenance or attention from homeowners.
How do we get geothermal energy?
Furnaces must create heat by burning fuel, typically natural gas, propane, or fuel oil. With geothermal or geo-exchange, there’s no need to create heat, hence no need for chemical combustion. Instead, the Earth’s natural heat is collected in winter through a series of pipes, called a loop, installed below the surface of the ground or submersed in a pond or lake. Fluid circulating in the loop carries this heat to the home.
An indoor geothermal or geo-exchange system then uses electrically-driven compressors and heat exchangers in a vapor compression cycle–the same principle employed in a refrigerator–to concentrate the Earth’s energy and release it inside the home at a higher temperature. In typical systems, duct fans distribute the heat to various rooms.
In summer, the geothermal or geo-exchange process is reversed in order to cool the home. Excess heat is drawn from the home, expelled to the loop, and absorbed by the Earth. Geo-exchange or geothermal power systems provide cooling in the same way that a refrigerator keeps its contents cool–by draw. They do the work that ordinarily requires two appliances, a furnace and an air conditioner.
More Geothermal Advantages
The geothermal equipment can be located indoors because there’s no need to exchange heat with the outdoor air. They’re so quiet homeowners don’t even realize they’re on. They are also compact. Typically, they are installed in a basement. The indoor location also means the geothermal or geo-exchange equipment is protected from mechanical breakdowns that could result from exposure to harsh weather.
Geo-exchange or geothermal energy systems work differently than conventional heat pumps that use the outdoor air as their heat source or heat sink. These systems don’t have to work as hard (which means they use less energy) because they draw heat from a source whose temperature is constant.
How Does Geothermal Work?
The temperature of the ground or groundwater a few feet beneath the Earth’s surface remains relatively constant throughout the year, even though the outdoor air temperature may fluctuate greatly with the change of seasons. At a depth of approximately six feet, for example, the temperature of soil in most of the world’s regions remains stable between 45º and 70°. This is why well water drawn from below ground tastes so cool even on the hottest summer days.
In winter, it’s much easier to capture heat from the soil at a moderate 50° F. than from the atmosphere when the air temperature is below zero. This is also why geo-exchange systems encounter no difficulty blowing comfortably warm air through a home’s ventilation system, even when the outdoor air temperature is extremely cold.
Conversely, in summer, the relatively cool ground absorbs a home’s waste heat more readily than the warm outdoor air. Studies show that approximately 70 percent of the energy used in a geothermal heating and cooling system is renewable energy from the ground. The remainder is clean, electrical energy which is employed to concentrate heat and transport it from one location to another. In winter, the ground soaks up solar energy and provides a barrier to cold air. In summer, the ground heats up more slowly than the outside air, transferring heat from the interior out of the house.
Free Hot Water is another benefit of a Geothermal Energy System
Geothermal systems can also provide all or part of a household’s hot water. This can be highly economical, especially if the home already has a geo-exchange system, hence a ground loop, in place.
Because geothermal or geo-exchange systems heat water so efficiently, many manufacturers today are also offering triple function systems. Triple function geothermal power systems provide heating, cooling and hot water. They use a separate heat exchanger to meet all of a household’s hot water needs.
Once installed, the loop in a geo-exchange or geothermal renewable energy system remains out of sight beneath the Earth’s surface while it works unobtrusively to tap the heating and cooling nature provides.
Today, homeowners in all income brackets can take advantage of the benefits of geothermal power. What’s more, some electric utilities around the nation now have incentive programs and low-interest financing programs which makes geothermal or geo-exchange even more affordable.
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