Understanding the Basics of Geothermal

Submitted by Toby Grabs, director of operations

A geothermal HVAC (heating, ventilation and air conditioning) system uses ground source heat pumps to heat the air inside a building in the winter and cool the air inside a building in the summer, using the ground to either extract heat in the winter or take heat in the summer. Many people are familiar with high temperature geothermal heating being used to generate electricity in geologically active states like California where the geological forces, or a thin layer in the crust, cause the high heat present under the crust of the earth to be close to the surface. Indeed, in many places in the western US, rain seeping down into the ground is able to get heated just below the surface of the earth to the boiling point resulting in geysers!

That kind of thermal energy is many miles below the surface in Wisconsin. However, even in ‘geologically inactive’ locations, like Wisconsin, there is still some thermal energy present underground (thanks in part to the breakdown of naturally occurring radioactive elements and leftover heat from the formation of the earth). That thermal energy keeps the temperature below ground a constant 50-60 degrees Fahrenheit even when it is well below zero above ground. This is what causes an underground cave in Wisconsin to maintain a year-round temperature of about 55 degrees regardless of the air temperature above ground.

Our existing geothermal HVAC system in the monastery building and the geothermal system that will be installed in the retreat and guest house (RGH) will take advantage of this thermal energy using a closed loop of circulating liquid. In the winter, that thermal energy will be extracted from below ground in the circulating liquid and brought into the building through the heating coil in each room. In the summer, thermal energy is taken out of the building using the same circulating liquid and put in the ground. That is why geothermal HVAC systems are sometimes referred to as geo-exchange systems.

Currently, the retreat and guest house is using an old, inefficient natural gas burning boiler to generate heat in the winter. Burning natural gas is not sustainable and generates greenhouse gas emissions. The new geothermal HVAC system will also replace the old, inefficient, and noisy chiller unit outside the back door of the RGH that currently loudly provides cooling in the RGH.

We still need to raise $625,000 to finish the net zero energy initiative, of which the new geothermal HVAC system will be a big part. Please consider donating.