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What is geo-exchange technology?
Geo-exchange systems exploit the differential between the earth’s mean temperature (typically down to about 225’ from the surface) and the outside air temperature. The earth stores the heat that it absorbs from the sun. Depending upon the region, ambient soil structure, presence of water, etc., the temperature of the earth at these depths hovers around 45 to 60 degrees Fahrenheit. During the heating season, heat is extracted from the earth and through a heat pump. That heat is distributed to the building using either radiant floors or forced-air. During the cooling season, the process is reversed; heat is extracted from the building and distributed back into the earth. In our area this is accomplished by drilling a series of 4 7/8” holes to a depth of between 175’ and 225’. The number of holes required depends primarily on the size of the building. Piping containing water (and an antifreeze component) is looped down and up each hole, and then everything is filled with grout similar to that used in drilling for oil or natural gas. The system is closed, meaning that the liquid stays within the system; nothing is taken from or added to the earth except heat. The liquid within the system is pumped into the building, where the extraction or exchange process takes place. The tops of the holes are generally located about 6 feet below the surface, and all manifolds and piping to and from the building are underground. No maintenance is required for the loop fields, as the holes and piping are called, and have a useable life of at least 50 to 100 years.
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Is it expensive?
Geo-exchange systems cost more than gas forced-air or boiler-based/conventional A/C heating and cooling systems. The price of the heat-pumps themselves are similar to the other appliances, but the cost of creating the loop field is unique to geo-exchange systems. However, because geo-exchange systems use no fossil fuels and eliminate the need for air-conditioning compressors, the annual energy savings are typically between 50 and 65 percent lower. Those savings recoup the cost of the system over a reasonable period of time, and after that provide a positive cash flow.
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Is geo-exchange technology new?
Geo-exchange technology is not new. Albert Einstein used the technology to heat and cool his home in New Jersey in the 1920’s. Between then and about 1980 it was not widely used, but has since been successfully used in both commercial and residential applications. In fact, the number of systems in the United States currently in place reaches into the hundreds of thousands.
Considering rising energy prices, uncertainty about supply, and the need to preserve the integrity and beauty of our environment, geo-exchange technology is a compelling solution to all of our heating and cooling needs.
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Some Interesting Facts about geo-exchange:
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According to the Environmental Protection Agency, geo-exchange is the most energy-efficient, environmentally clean, and cost-effective space conditioning system available.
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Energy costs with geo-exchange typically are 25 to 50 percent less than other HVAC systems.
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The use of geo-exchange lowers electricity demand by nearly 1 kW per ton of capacity.
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Today, more than 650,000 geothermal heat pump units are installed in the U.S., resulting in an annual savings of 5.2 billion kWh, 26 trillion Btus of fossil fuels, reduced electricity demand by 1.7 million kW and the elimination of nearly 4 million tons of CO2.
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Those 650,000 installations are equivalent to:
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Taking 840,000 cars off the road,
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Planting 250 million trees, or
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Reducing US reliance on imported fuels by 14 million barrels of crude oil per year.
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Because they burn no fossil fuels on site, geo-exchange systems generate virtually no carbon dioxide emissions.
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For businesses, geo-exchange systems provide the architect with optimal design flexibility because the roof and landscape are free of chillers, air handlers and other outdoor equipment. In addition, with geo-exchange systems, boiler rooms can be eliminated and the size of mechanical rooms can be reduced.
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Because geo-exchange systems are so flexible, they are ideal for renovating buildings with historical merit. One successful strategy is to use smaller heat pumps dispersed in closets, basements, and attics to provide space conditioning and ventilation with minimal ducting. Additionally, there are no unsightly condensers on the roof or grounds to distract from the building's historic charm.
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The elimination of outdoor or rooftop equipment means the geo-exchange system is not exposed to temperature extremes, dirt, pollution or vandalism.
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Geo-exchange systems have a lower life-cycle cost than conventional systems, even in hot, humid regions where the demand for air conditioning is high. Geoexchange systems also have long equipment life (20 + years).
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If every school district that needed to replace heating and cooling systems over the next 10 years decided to install geo-exchange systems, the total energy savings over that time would exceed $11 billion.
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The electricity required to power one million homes for one year would be saved, if every school that could use geo-exchange did so.
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EPA found that geo-exchange systems can reduce energy consumption--and corresponding emissions--by over 40% compared to air source heat pumps and by over 70% compared to electric resistance heating with standard air-conditioning equipment. Combining geo-exchange with other energy-efficient measures, such as window or insulation upgrades, can increase these savings even further.
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Geo-exchange systems use the Earth's energy storage capability to heat and cool buildings, and to provide hot water. The earth is a huge energy storage device that absorbs 47% of the sun's energy -- more than 500 times more energy than mankind needs every year -- in the form of clean, renewable energy. Geo-exchange systems take this heat during the heating season at an efficiency approaching or exceeding 400%, and return it during the cooling season.
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