What is a water-source heat pump?

Geothermal heat pumps (sometimes referred to as GeoExchange, earth-coupled, ground-source, or water-source heat pumps) have been in use since the late 1940s. Geothermal heat pumps (GHPs) use the constant temperature of the earth as the exchange medium instead of the outside air temperature. This allows the system to reach fairly high efficiencies.

While many parts of the country experience seasonal temperature extremes—from scorching heat in the summer to sub-zero cold in the winter—a few feet below the earth’s surface the ground remains at a relatively constant temperature.  Like a cave, this ground temperature is warmer than the air above it during the winter and cooler than the air in the summer. The GHP takes advantage of this by exchanging heat with the earth through a ground heat exchanger.    Also, these systems use groundwater but are ‘nonconsumptive’, i.e. they re-inject all of the groundwater used back into the ground with only a slight temperature change typically of  2 to 6 degrees. 

Even though the installation price of a geothermal system can be several times that of an air-source system of the same heating and cooling capacity, the additional costs are returned to you in energy savings in 5–10 years. System life is estimated at 25 years for the inside components and 50+ years for the ground loop. There are approximately 50,000 geothermal heat pumps installed in the United States each year.

Interesting facts regarding open loop systems and Oregon include: 

Portland has the oldest continuously operating open-loop system in the western hemisphere.  It is in the Commonweath Building downtown and was constructed in 1948.  It is now a national historic mechanical engineering landmark.

 The Oregon Institute of Technology (OIT) in Klamath Falls, is a leader in geothermal energy education and use.  They heat the campus with natural hot water and will soon be generating electricity as well. 

(Sources www.energysavers.gov and Roger Smith, Hydrogeologist)

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