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:
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:
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.
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.
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.
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.
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.
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
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)