Ground temperatures are a constant 55° all year no matter what the weathers like
Geothermal works because the ground beneath our feet is warmer than the outside air in the winter and cooler in the summer. Inserting a series of small pipes into the ground allows heat to be transferred to and from your home. In this process heat is not created, it is transported therefore no fuel is burned.
Two Pieces to the Geothermal System:
1. Heat Pump – the inside unit known as the heat pump
2. Ground Loop – underground pipes which connect to the heat pump
Winter Operation: The underground pipes, called a ground loop, circulate water which absorbs the heat from the earth and returns it to the indoor heat pump. The heat pump extracts the heat from the liquid then distributes it throughout your home as warm air. With the heat removed, the water is re-circulated to collect more heat from the ground. In this case the loop water is warmer when it comes into the home than when it goes back into the earth since the heat is being removed.
Summer Operation: The indoor heat pump takes the hot air from your home and removes the heat. This leaves behind cool air to be distributed through your vents as air-conditioning. The removed heat from the air is rejected into the earth through the ground loop. In this case the water is warmer leaving the home then when it returns since heat is rejected into it.
This is not a new technology, this is not a science experiment, this not rocket science. In fact in many European nations geothermal heating and cooling is the standard. In Sweden and Switzerland more than 75% of new homes have geothermal.
The EPA has acknowledged geothermal systems as the most energy efficient, environmentally clean, & cost-effective space conditioning systems available.
This is a high level explanation of geothermal, for more specifics read about loop fields andsystem sizing. You should also watch the video below.