A Hybrid Geo Heat Exchanger On Campus In Western Colorado

A hybrid geothermal borefield with supplemental boilers and cooling towers results in major energy reduction for a growing campus.

On the western edge of Colorado on the river of the same name rests the City of Grand Junction at 4,600 feet.  The rapidly expanding Colorado Mesa College made a choice to grow toward university status and become green at the same time, using a hybrid geothermal heat exchanger.  In 2006, the expanding campus installed its central core of vertical (heat exchange) boreholes and a loop connecting nearby existing buildings.  The local climate is somewhat balanced, in that peak heating loads and peak cooling loads are close to equal in BTUs needed per hour.

Deployment—

 The central loop has undergone several expansions in the 10 years since, and energy is supplied to and rejected from various buildings on a continuous basis by multiple heat pumps connected to the central loop.

Hybrid heat exchanger loop at Colorado Mesa U.

The loop is heated when any building performs cooling and the loop is cooled when any building desires heating.  Therefore, one building’s thermal waste can be another’s thermal gold mine.  Desired temperature range of this loop water is between 50° and 85° degrees.  It is referred to as a hybrid loop because cooling towers can chill the loop to stay under 85° in summer and boilers can heat the loop to stay above 50° in winter.  The main borefield and shared thermal energy between buildings has necessitated very little cooling tower use, and supplemental boilers have never fired in 4.5 years.

The system was designed and installed by Sound GeoThermal of Salt Lake City by one of IGSHPA’s (International Ground Source Heat Pump Association) best known engineers, Cary Smith.

—Bill Martin