Hybrid Geothermal Heating System

Design Heat Loss: 9.2 kw (31,500 BTU/hr)
Heat Pump Capacity: 8.0 kw (27,300 BTU/hr)
Geothermal System Type: Horizontal Closed Loop Geothermal Ground Exchanger
Location: Prince George, BC

For this project, the geothermal heating system was designed as a Hybrid Geothermal System. The geothermal heat pump and ground exchanger were sized to provide 87% of the peak heating load for a 1,200 square foot workshop. An electric ceiling heater was also installed to provide supplementary heating when the outdoor temperature drops below -25°C.

A relatively common misconception about geothermal heating systems is that they are unable to maintain indoor building temperatures during the bitter cold days of winter without a supplementary heating source. In fact, a geothermal heating system can provide 100% of the building heating load and domestic hot water preheating requirements as long as it is designed properly.

The decision to design a geothermal heating system as a hybrid system can usually be traced back to economics, available land space, and practicality. In this case, it was a matter of economics and practicality since the land space was available for the increased size of the geothermal ground exchanger that would be required.

Economics of a Geothermal Heating System

Designing the geothermal heating system to provide 100% of the peak heating load would have required a larger ground source heat pump and additional land clearing for the horizontal ground exchanger.  This would have increased the overall cost of the geothermal heating system, without a large return on investment. 

Practicality of a Geothermal Heating System

On average, the temperature in Prince George, BC goes below -25°C for 85-90 hours per year. This data is obtained from American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) historical temperatures for the last ten years.  Therefore, this particular geothermal heating system will solely provide heat to the building for 99% of the year; and the supplementary electric ceiling heater would provide additional heat 1% of the time.

It was for these reasons that the Geothermal Heating System was designed as a Hybrid Geothermal System.  Below are some photos of the installation of the geothermal ground exchanger and ground source heat pump piping.