Heat Pump Project
MGE installed a closed-loop Ground Source Heat Pump (GSHP) system to meet the heating and air-conditioning needs of the Lussier Community Education Center. The center serves children and others on the west side of Madison.
The GSHP system is expected to reduce annual energy costs. A monitoring system has been installed and provides periodic data. Once it provides consistent data, it will help verify if actual performance demonstrates lower energy use. MGE will report the results on this page.
First report: Winter 2010-2011
The efficiency of the GSHP system during the heating system can be measured by Coefficient of Performance (COP), which is the ratio of the heat output in kilowatt-hours (kWh) to the energy input in kWh. Heat pump manufacturers predict the COP of just the heat pumps to be around 3.5, based on laboratory testing.
MGE monitoring includes all eight heat pumps, the loop pump and the energy recovery ventilator. The COP of the total system was measured to be just 2.2 for a three-week period during February and March 2011.
Using the initial data, we compared this result with a similar building with a standard efficiency air conditioner and natural gas heat. During the heating season, the Lussier building uses the same or more energy when the COP is less than 3.5. During the cooling season, the GSHP system is expected to perform better than standard AC systems. However, without more information we don't know if the savings will be large enough to justify the additional first cost of the system.
MGE will continue to monitor the system and do additional building system comparisons and report our results on this page.
How it works
Geothermal heat pumps use the earth's natural heat to assist with the heating and cooling of buildings.
- A series of U-shaped pipes will be buried in 20 holes about 300 feet deep to reach a constant ground temperature of about 50 degrees.
- Fluid (water with a small amount of environmentally friendly polypropylene glycol) circulates through the pipes and carries the heating or cooling to a series of heat pumps.
- The heat pumps amplify the heating and cooling effect and release it inside the building.
Winter heating mode
Summer cooling mode
For a geothermal heat pump to reach its maximum performance, a building must be energy efficient. The Lussier Center was built to exceed state energy codes—with high-performance windows, insulation and other features.
The geothermal system costs about 20% more to install than conventional commercial heating and cooling units.
Project engineering consultation
- Sustainable Engineering Group LLC (for the geothermal heat pumps)
- KJWW Engineering Consultants (for the HVAC engineering)