Geoexchange Projects at Peace Health Clinic
Geoexchange heating and cooling systems provide compelling economic and environmental benefits
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Geoexchange systems take advantage of relatively constant underground temperatures for heating and cooling.
  • Geologic

  • Energy

  • Friday Harbor and Spokane, Washington


GeoEngineers has been bringing environmental, geological and hydrogeological expertise to geoexchange projects since 2009. Our
geo-scientific knowledge and ground source heat pump (GSHP) systems experience yield lower initial costs, a quicker return on investment and better system performance for our clients.

How Geoexchange Works

When the earth is warmed by the sun, it maintains a relatively constant temperature of around 55 degrees Fahrenheit, not far below its surface. Geoexchange installations take advantage of this heat to transfer or exchange heat from the ground to warm a space or to collect heat from a space and reject it to the ground.

This is accomplished by extracting and then re-injecting groundwater directly from an aquifer (called an “open-loop” system), or more commonly, a system that consists of water- or refrigerant-filled coils (called a “closed-loop” system) located below ground. Both methods use an above-ground, electric-powered heat pump to compress or condense the fluid and make or extract heat to either heat or cool a building.

GeoEngineers advocates for hybrid design, or systems consisting of a downsized boiler or chiller used in concert with geoexchange wells. This design concept is readily applied throughout Europe and Canada and results in redundancy without compromising efficiency. We use this design approach to reduce risk and improve cost-effectiveness for faster payback.

According to the International Ground Source Heat Pump Association (IGSHPA) at Oklahoma State University, GSHP systems are 50 to70% more efficient than other heating systems, and 20 to 40% more efficient than other air conditioners. And the US Environmental Protection Agency named geothermal units “the most energy-efficient and environmentally sensitive of all space conditioning systems.”

Project Successes at Two Geological Extremes

Two completed project sites at geological extremes demonstrate how we successfully applied our geological know-how to assess, plan and design two operationally efficient and cost-effective geoexchange systems.

Peace Health Clinic in Friday Harbor (WA) is sited on bedrock, with no groundwater, while the SIERR Building at McKinstry Station in Spokane (WA) is sited on sand and gravel and a saturated aquifer. The geology below these two sites couldn’t be more different.


  • Using our geologic understanding of soil and groundwater, determined optimum borefield location and number, pattern and depth of geoexchange wells for each site.
  • Performed enhanced pilot studies which included geologic borehole logging, drilling capability and timeframe, feasibility tests of soil heat capacity, soil thermal conductivity and groundwater heat-transfer capacity.
  • Recommended heating and cooling system options best suited to the site’s geological conditions, based on GeoEngineers’ pilot study results.
  • Created simulations to predict energy savings and investment payback period.
  • Provided information to clients about advantageous government incentive programs.
  • Facilitated permitting with local agencies.
  • Worked with the mechanical engineering designer to design and monitor installation of the geoexchange systems.
  • Established long-term monitoring plan to check performance of installed systems.


Peace Health Clinic

Results of GeoEngineers analysis, design understanding and geologic expertise:

  • High-thermal-conductivity bedrock containing very conductive quartz mineralization maximized design performance. GeoEngineers’ geologic borehole description validated the unusually high thermal conductivity identified during the pilot test.

  • Recommended a hybrid design that resulted in faster payback than conventional design would have afforded.

  • GeoEngineers’ thermal analysis and geologic understanding provided confidence to the mechanical design team to proceed with this site-specific design.

  • Design modification based on geology and hybrid concept resulted in cutting first cost by 50%.

  • Reduced ground loop size by half, yet system will satisfy about 75% of the heating/cooling load.

  • Geologic and thermal understanding (post-analysis) resulted in (1) better performance of up to 35% and (2) performance cost savings of 22% over the base assumptions.

  • Thermal conductivity was found to be nearly double the base assumption, based on the enhanced analysis by GeoEngineers.

  • GeoEngineers’ geologic expertise and engineering approach helped guide this project from an estimated 300 ft./ton performing system to a 225 ft./ton performing system.

  • GeoEngineers’ earth science and engineering approach helped make this system more redundant, first-cost palatable and higher performing.

SIERR Building at McKinstry Station

Results of GeoEngineers analysis, design understanding and geologic expertise:

  • Maximized design performance based on presence of a world-class aquifer and the benefit of groundwater flow across closed-loop piping,

  • GeoEngineers’ groundwater understanding resulted in a calculated system performance five times higher than would have been assumed using a standard thermal conductivity test.

  • Using our geologic expertise, we were able to do a design modification after observing difficult drilling conditions during the pilot study. GeoEngineers’ analyses showed that drilling to 200 feet would be sufficient to meet heating and cooling load rather than the assumed 300 feet. Pre-determining the optimum drilling depth before construction reduced the potential for contractor change orders.

  • GeoEngineers’ geologic expertise and engineering approach helped guide this project from an estimated 60-ton, 175 ft./ton performing system to a 76-ton, hybrid, 53 ft./ton performing system.