Thursday, December 18, 2008

Geothermal (Ground-Source) Heat Pumps

Geothermal Heat Pumps (GHPs)

Geothermal Heat Pumps (GHPs), also called Ground Source Heat Pumps, are one of the most efficient sources of heat. GHPs achieve efficiencies of 300 to 600% by taking advantage of the steady temperature of the ground beneath. During the winter, heat pumps take advantage of the warmer ground temperatures to produce heat. During the summer, GHPs take advantage of the cooler ground temperatures to cool your building. The greatest obstacle to the widespread use of geothermal/ground source heat is its cost of installation.

High Installation Costs

Commercial/Apartment buildings have to pay $22.75 a square foot for GHPs. The owner of a 17,000 square foot building would have to pay $386,750 for this system. He would also pay an additional 6-8% design cost to have the mechanical drawings done. In this case, that would be another $23,205 to $30,940.

Residential homes can expect to pay about $20,000 or about $10 square/foot for a 2,000 square/foot home.

Northern Climates – Additional Installation Costs

In northern climates, owners must have backup fossil fuel furnaces. Backups are needed, because once the ground freezes, there is no way to repair the system until spring. These fossil fuel furnaces mean flues, more ductwork, and dampers. Commercial/Apartment buildings might also require alarm systems and fire barriers. In new projects, it is also going to contribute to your architectural/design and contracting costs.

Payback Period

Even with these prices, the payback was five to eight years when fuel oil prices were $4.00 a gallon.

GHPs Act as Air Conditioners Too

Geothermal Heat Pumps (GHPs), like Air Source Heat Pumps (ASHPs), also make good air conditioning systems.

An Alternative that’s even better than Geothermal – Solar Hydronics

Solar Hydronics uses solar thermal panels to heat water before passing it to a storage/holding area. An electric boiler pulls this hot water into the under floor heating grid (Pex-Tubing) directly when it is the desired temperature. If the water temperature is too low, the electric boiler heats it to the desired temperature before passing it into the grid. The cooler water, then, passes back to the solar panel for heating.

The Ideal Situation

Ideally, you would store enough hot water to bypass the electric boiler controlling the under floor heating system. Air Source Heat Pumps (ASHPs) would utilize the latent heat to heat the rest of your home, and you would have generated heat for virtually free – except for a small electric bill you’d have for running the condensors for the ASHP.

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