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Ground source heat pump test wells drilled at Altus, Sheppard

  • Published
  • By Glynn Batla
  • REM
RANDOLPH AIR FORCE BASE, Texas --  The Earth maintains a nearly constant temperature throughout the year, just a few feet below the surface. That temperature is a consistent 62 -67 degrees Fahrenheit and can be used in the winter as a heat source and during the summer as a cooling source. A ground source heat pump (GSHP) takes advantage of this phenomena.

A GSHP feasibility study is currently underway at Altus, Sheppard, and Vance Air Force Bases and will include 3 test bore holes per base, drilled 400' deep. The 4 3/4 " diameter bore holes are fitted with a 1 1/4" plastic piping loop and U-bend at the bottom of the well. The test wells are then grout filled to provide good thermal connection to the surrounding soil or rock. The grout also protects the ground water from contamination and prevents artesian wells from flooding the property. The heat load testing is then conducted to evaluate the thermal characteristics and heat sink capability that will determine if this technology is sound and reliable for the specific geographical areas and bases. Close geographical GSHP sites have provided positive information regarding this type of technology.  AETC is sinking test wells to confirm specifics as geology can change from one side of the base to the other and test bore holes need to be completed before signing off on a large project commitment.

Once validated as feasible, additional wells could be drilled approximately 20 feet apart
yielding about 1 ton of heating/cooling capacity per 400' well. GSHPs are characterized by high investment costs and low operational costs compared to other HVAC systems. Their overall economic benefit depends primarily on the relative costs of electricity and fuels. Based on recent prices, GSHPs currently have lower operational costs than any other conventional heating source almost anywhere in the world.

The lifespan of a GSHP system is anticipated to be longer than conventional systems, which are normally still operational for 25 to 30 years with routine maintenance. Most loop fields are warranted for 25 to 50 years and are expected to last 50 to 200 years.