How Does Geothermal Heating Work?

by | Nov 20, 2015 | Answer Man, Blog, Cooling, Heating | 0 comments

How does geothermal heating workAs a kid years and years ago I read about geothermal power in a work of science fiction.  The idea that clean, free energy existed under the ground without massive refineries, smokestacks, or nuclear plants seemed very futuristic.  A short while later I learned that actual electrical power production using geothermal energy has been possible since the early 1900s, and continues to be used in geothermal hotspots around the world.  But when we talk about geothermal heating and cooling in your home, we aren’t talking about the production of power, just a method to regulate temperatures.  The principle is the same either way, and it’s just as amazing and clean as it was so many decades ago.

How it Works

The core of the Earth is hot, hot enough that it’s mostly molten metal and rock.  Tectonic friction and extreme pressures generate an amazing amount of heat, warming the Earth from inside.  In addition to this, the ground is an exceptional insulator, resisting changes in energy fairly well.  During the summer, the ground just below the surface is warmed and sees little variation in temperature throughout the seasons.  When you move down to about 30 feet, there is almost no change in temperature year round.

By pushing water beneath the surface into this relatively temperate zone, heat energy can be collected and piped back up into the home where a water radiator warms the entire home.  As an added benefit, this same heating system generates enough heat to act as the hot water system for your home.  All of this is made possible using an electric pump that replaces the refrigerants, compressors, and furnace fuels used in traditional heating and cooling.

Another version of the geothermal system uses an aquifer.  This underground source of water is usually deep enough for the water to already be temperature regulated.  Water from the aquifer is pumped up into the home where it is only used for heating (the water never leaves the radiator pipes) before it is returned to the aquifer.  This kind of heating doesn’t deplete the aquifer and no water needs to be filled into the system before it can begin working.

In short, a geothermal heating and cooling system uses water as a way to move heat into a home during the winter and a way to remove heat from a home during the summer.

Benefits Over Traditional Furnaces

When all is said and done, the goal is to regulate temperature in the home.  So is a geothermal system actually better than a more traditional forced air furnace?  While there’s never a catch-all system that’s right for everyone, a geothermal system is usually more energy efficient than a forced air or fueled system.  Geothermal heating systems also double as cooling systems during the summer, which makes them a total replacement for a typical HVAC system and putting them on par with reversible heat pumps as well (though again, they are more energy efficient BTU to BTU).

A few other ways where a geothermal system is more beneficial:

  • Some systems can be built completely vertical, using very little area
  • Water isn’t expended within the system
  • Zero carbon emissions at the home
  • Also heats your running water
  • No toxic refrigerants are used
  • No external fuel needed

In the interest of fairness, the drawbacks to this system are in installation costs and work.  If your home isn’t already equipped with a geothermal system, the excavation can take out a sizeable part of your yard (which will take time to restore to normal).  The lawn will regrow but the excavation and installation costs can be extreme.  If you’re building a new house or looking for ways to save on energy in the long run, it’s a worthwhile expenditure.


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