A Fresh Look at Ground- and Groundwater-Sourced Heat Pumps - An Alaska "Heat Rush"?

Authors: Munter, James A., J. A. Munter Consulting, Inc

Video Presentation

Abstract

Heat pumps are widely viewed as efficient methods for home heating, even in northern latitudes. Groundand groundwater-sourced heat pumps in Alaska come with higher upfront costs, but yield higher efficiencies compared to air-source heat pumps. Air-source heat pumps exhibit very low efficiencies when the weather is coldest and heat is most needed.

Despite generally low ground temperatures, the southern half of Alaska possesses prodigious amounts of extractable heat in the upper 1000 feet of the earth's crust. Efficient heat pumps have the potential for reducing overall energy usage in home heating, however prior studies have shown that they are not economically competitive in areas served by natural gas. In other areas such as Fairbanks, Juneau, and Seward, however, they appear viable based on a 15-year payback period.

Studies have shown that shallow loop earth systems in the Fairbanks area work best in south-facing soils with good seasonal solar exposure to offset long-term heat extraction from the soil. An alternative longterm heat source is deep boreholes where the geothermal gradient provides warmer conditions. Groundwater provides a potential heat transfer mechanism to enlarge the heat-extraction zone.

Traditional evaluation of heat pumps based on the number of years until "break-even" are increasingly being influenced by evaluation of carbon dioxide emissions of heating alternatives. At Fairbanks, wood stove air quality concerns and climate-warming soot are also potential factors. In Anchorage, potential long-term limitations on supplies of natural gas in Cook Inlet may also be a factor. Recent changes to tax law may also favor heat pump installations. These factors all may have the potential to cause a new "Heat Rush" in Alaska by increasing the overall long-term economic and environmental viability of air-, waterground- and groundwater-sourced heat pumps.

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