Geothermal Basics

When most people hear the words “Geothermal Energy”, they automatically get visions of volcanoes and hot springs.  And, while these areas definitely supply the necessary “ground heat”, geothermal energy is not limited to just those areas.   As our energy costs continue to climb, perhaps this might be a good time to revisit geothermal basics.

Geothermal heating and cooling has been around for quite a while, but because it is relatively expensive, has never become widespread.  It is estimated that only about 3.5% of new homes built include a geothermal heating/cooling system.  The most common is the geothermal heat pump,  which works similarly to the way your current electric heat pump works.

During the winter months, the system draws heat from the ground, which stays at a relatively constant 55F temperature once you get 6-10′ underground.  During the summer months, hot air is cooled by passing through the same pipes that are buried below the frostline and cooled before returning to the house/office building.

So, it is much simpler and much, much shallower than trying to build a geothermal generator using super-heated water from hundreds or even thousands of feet underground.  In these applications, the steam produced is used to turn turbines, which in turn produce electricity.   These are obviously limited to commercial electricity production.

There are four basic types of geothermal heat pumps that can be applied to residential use.  They are a closed-loop system (horizontal), a vertical (closed-loop) system, a pond/lake (closed-loop) system, and an open-loop system.

You can visit the U.S. Dept of Energy website for a more detailed look at each of the four systems.  The Department of Energy estimates that geothermal energy could provide as much as 10% of our energy needs, if fully implemented.  Most geothermal energy projects are located in the western U.S., Alaska, and Hawaii.