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A GEOTHERMAL SYSTEM is a type of HEAT PUMP. In winter, a heat pump extracts heat from the outside air. The colder it is outside, the harder the system.

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Presentation on theme: "A GEOTHERMAL SYSTEM is a type of HEAT PUMP. In winter, a heat pump extracts heat from the outside air. The colder it is outside, the harder the system."— Presentation transcript:

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2 A GEOTHERMAL SYSTEM is a type of HEAT PUMP. In winter, a heat pump extracts heat from the outside air. The colder it is outside, the harder the system has to work. In summer, a heat pump dumps heat from the home. The hotter it is outside, the harder the system has to work Typical Heat Pump Operation Image courtesy:

3 Just a few feet down, the Earth maintains a constant temperature of ~50°F (10°C) year round. Geothermal heat pumps use the ground (geo) as a heat exchanger (thermal) INSTEAD of air like the more typical heat pump. – In the winter… They extract heat from the Earth to heat your home. It’s FAR more efficient to extract heat from a 50°F ground source than much colder outside air. – In the summer… They dump heat from your home to cool it. It’s FAR more efficient to dump heat to a 50°F ground sink than to much hotter outside air.

4 Typical Setup -Wells are dug. -Plastic piping goes from unit into and out of the wells. -Piping is filled with antifreeze; often water mixed with alcohol. -Piping can also be horizontal, or placed in a pond, etc.

5 Image courtesy: In summer, heat from home is dumped into the Earth; Another way to think about it: cold water from the Earth is used to cool the home. In winter, heat from the Earth is used to heat the home; Another way to think about it: heat is extracted from the water coming from the Earth, and colder water is returned.

6 Advantages Heat pump is inside and very quiet. Most units also provide domestic hot water. Not subject to wild swings in oil/gas prices. Few moving parts and low maintenance. System life 25+ years; 50+ years for the loop. Very high energy efficiency (300%-600%, EPA). Payback in 5-10 yrs over a conventional system. One-time tax break of 30% of unit cost.

7 Personal experience System added in June 2008 Replaced an older oil-burning forced-air furnace and exterior air-conditioner (HVAC). Cost of the unit was similar to a new high- efficiency gas or oil furnace. Extra cost of $7,500 was incurred to dig 3 wells (each 150 ft deep) and lay tubing in my suburban front-yard.

8 Costs to date…. Summer Cooling Sum of June-Sept 2007 Electric Bill: $595 Sum of June-Sept 2008 Electric Bill: $585 Difference: - $10 Winter Heating Sum of Nov 2007-Feb 2008 Electric Bill: $528 Sum of Nov 2008-Feb 2009 Electric Bill: $740 Difference: $212

9 Comparison of Costs Cooling costs during the summer – negligible Heating costs/month with oil: $275 Heating costs/month with geothermal: $53 Estimated payback time: 3-10 yrs (depends on price of heating oil)


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