Ground Source Heat – How does it work?
I’ve been asked a lot to explain how our Ground Source Heating and Cooling System will work. My feeling is that the lack of understanding of this technology, coupled with the inability of the manufacturers to clearly explain it without making your eyes water, keeps the success of this efficient heating solution limited.
First, using the ground to heat and cool your house is called Ground Source. The device which cycles the liquid through tubes down into the ground to capture heat and up into the house to exhaust this heat is called a heat pump. Geothermal is a wrongly used term to describe the above when in fact it more accurately describes the process of capturing heat from thermal heat sources in the earth like volcanic heated water and steam.
The simple explanation of Ground Source is to look at the refrigerator in your home. The GSHP works the same way. Imagine that the interior of the fridge is the ground – cool at approx. 4ºC to 15ºC depending on the time of year. Then imagine that the rear of your fridge is the interior of your home. Please, anyone, correct me if I’m wrong, or provide a less clunky explanation.
The coil on the rear of the fridge (your heat pump coil) runs loops around and through a compressor (your heat pump) and then travels into the interior of your fridge (into an insulated space in the GSHP that is coupled around the ground loop) and back out to the rear to complete the loop.
The interior of the fridge is warmed when you open the door and exchange the mass of cool air with warm air, as well as when you place warm masses or items of food in there (essentially the equivalent of your ground loop that travels through the ground storing warm energy in tons of liquid – any temperature above 0 Kelvin has energy so the 10 to 15ºC in the ground is balmy).
What happens is the compressor outside the fridge condenses the liquid in the coil to a gas which exhausts any heat before it is pumped into the fridge space. The now cooled gas volume absorbs the warm air trapped in the fridge (ground) as it travels through its long loop. Energy in the form of heat always travels toward the cold, and in this case the energy drains into the coil (warmth in the ground stores in the ground loop).
As the gas in the coil warms, it does what it can to convert back to a liquid and begins to expand, increasing pressure. The warmed compressed gas is pumped to the outside rear of the fridge (into your home) and hits a warmer zone (your home’s GSHP) where it absorbs more warmth, converting back to a liquid. At this point, as it turns to a liquid and passes through the compressor, it can no longer hold the energy it has stored and intensely evacuates the excess heat at near boiling.
On your fridge, a fan blows through this coil (Forced Air Handler) to expel the heat from the liquid before it is condensed once again and the cycle repeated. In the case of a Radiant in floor heating water to water system such as ours, the floor loops of liquid travel into the warm area of the heat pump and wrap around the condensing coil to exchange heat before being pumped through the floor of the house again. And voila.
Eyes watering yet? See our Geo supplier’s website for meaningless colourful illustrations, or better yet, give them a call as they are much better at explaining how it works and best of all, how it will work for you – 4 Seasons Geothermal.