Introduction

        A geothermal heating and cooling system can increase the comfort in your home while saving energy by using the constant temperature of the earth as an energy source.  While the system requires a more expensive ground loop system, it also saves money on utility bills and may require less maintenance than other options.  Learning about all of the facets of a geothermal system is very confusing at first due to its high technology, but a little study is well worth the effort.

Why is a geothermal system better than others?

        A geothermal system is more energy efficient than other systems, because it produces 3 to 4 times more units of energy than it uses!  An electric heating system produces one unit of heat for one unit of energy.  Electricity is produced with over 99 percent of the energy of the fuel burned being converted to electricity at the plant, but because of transmission, the cost of electricity is higher than gas per unit of energy.  A gas furnace produces 80 to 97 percent of a unit of energy per unit of energy in natural gas.  This means that a geothermal system uses less of our natural resources to heat the same home making a favorite way to help the environment.

        Geothermal systems cost more than many other types due to the cost of its technology.  It is this technology that produce the special multi-speed blowers (creating less drafts) and special compressors inside the units (lowering maintenance and lasting longer).   Because the compressor in inside the house (in the furnace), there is no noisy and large outside unit to hide in the bushes.

Just how does a geothermal system create more energy than it uses?

        A geothermal heating and cooling system uses the familiar “heat-pump” system to transfer heat into the house (in winter) and out of the house (in summer).  The heat is transferred by compressing and throttling (expanding) a refrigerant (like Freon) from a coil in the air handling system to the ground loop.  Other systems convert gas or electricity directly to heat.  If  these systems were perfect (i.e. 100%) they would create one unit of heat for one unit of energy.  The geothermal unit actually gets its heat from the ground and not gas or electricity!

        The compressor is housed in the indoor system (as opposed to outside) because it transfers heat from a coil (that the air blows across) to a pipe filled with liquid.  This long pipe is buried in the ground several feet deep, put down several short wells, or put in a pond.  The liquid in the loop transfers its heat to the ground it is buried in.  This system is often designed to run in a low mode most of the time making a house very comfortable and even.  The system then goes into high mode when low is no longer maintaining a constant temperature at the thermostat.  This is also a feature of other “high-end” equipment.

Why is a geothermal system different from other systems?

        Most air conditioners and other heat-pumps use the outside air to exchange heat for cooling.  They do this by putting a compressor outside and running a fan to blow air across the coils to exchange heat (or cool) with the inside coil.  It is fan/compressor units that make the outdoor patio a noisy place and often need replaced due to wear from weather.  The geothermal units keep the compressor inside and exchange heat with liquid (which exchanges the heat with the ground) using only a near silent pump.  These compressors are often better than those in most typical air conditioning systems.   Many geothermal systems have low speed ECM (better electronic construction) fans that keep the house more comfortable by causing less draft.  Geothermal systems also must have long trenches, wells or ponds to replace the outside fan/compressor unit.  These ground loops add cost to the systems.

What is required to be able to install a geothermal system?

        Inside the house, the air handler unit looks quite similar to most other furnace/air conditioners.  It is the ground loop that makes geothermal systems unique.  The horizontal loop system requires a trench 4-6 feet deep and about 100 feet long per ton of heating.  This will typically be up to 400 feet of trench.  If  there is not enough yard area to use for a horizontal loop, wells can be drilled.  A well is more expensive that a horizontal loop, but takes a fairly small area.  The wells would be about 150 feet deep and require one for each ton of heating.  Often a larger electric service is required since most systems have a back-up system of electric resistance heat in case some part of the compressor or ground loop system fail.

Check out these web sites for more info and examples to see if a Geothermal System is right for you:

Geothermal Energy Program

Geothermal Resources Council

Water Furnace International