Using the Earth to Heat and Cool Your Home

by Dave on June 5, 2009

As first appeared in Coastal Sussex Weekly, May 21, 2009:

by Matthew Peterson

Get this, the ground under your existing home or the lot on which you are about to build your new home has the potential to save you 30% to 70% on your monthly utility bills – AND – it is new technology that has only been in use since the Paleolithic Era.  Ground source heat pumps (what we all commonly call Geothermal) is considered by the EPA as the most energy-efficient, environmentally clean, and cost effective space conditioning system available.  This system sounds good to us from an environmental standpoint and even more so to those of us watching our bottom line.

For those amongst you that are driven by semantics, the word “geothermal” technically should only be used for systems that truly use geological sources – like where volcanic activity occurs close to the surface.  For the rest of us – we call these systems Geothermal…

These systems work in a very similar fashion to a typical air exchange unit – the difference is the sources that create the heat or cooling factor.  From the inside of the home or office, the distribution of the air is identical.  An air exchanger HVAC system uses outside air which needs to be heated on cold days and cooled on hot days to heat and cool the air.  This is not very efficient as the temperature extremes use a great deal of energy to force the air to become hot or cold.  Ground source heat pumps work in a different way.

As a high level overview, a ground source heat pump runs water or a fluid through a loop system into the earth to adjust the temperature by using the earth’s constant and temperate temperature and not the fluctuating seasonal air temperature.  In a heating cycle (when the air temperature outside is cold), the pumped water extracts heat from the ground.  That heat is transferred to the geothermal unit where it is compressed to a high temperature and distributed throughout the home.  In a cooling cycle (when the air temperature outside is hot), the process is reversed.  The earth is significantly cooler than the air so the pumped water removes heat from the home and puts it into the earth.  The water is cooled by the ground temperature and then distributed throughout the home.

The two systems we typically use in our region are open loop and closed loop.  The difference is very straightforward.  A closed loop system is the type that is described in the above explanation of sending the water into the earth, cooling it and heating it.  At times in a closed loop a fluid other than water (propylene glycol, denatured alcohol or methanol) is used.  An open loop system is more efficient and when able to be used, should be.  This system works in the same fashion described above except that the source of the water is an aquifer.  The water is extracted from the aquifer cycled through the system and then injected back into the aquifer – no net use of water and the loop is “completed”, if you will, through the ground water.  Because “new” water is used each cycle the efficiency increases because you are not cooling down or warming up the contained fluid, you are simply using different water that is already the temperature you need it to be.  The only caution is to make sure the supply and return wells are located far enough apart that you are not using the same water.

The cost of these systems are affordable from a cost benefit analysis when you factor in your energy savings over paying for the system through your mortgage and shows a clear money saving opportunity within three to seven years.  Additionally, through the Federal Tax Credits offered by way of the ENERGY STAR program, you can get 30% of the cost off of your taxes and most of the systems will qualify.  If you really want to increase the efficiency of these systems and make another positive impact to the environment, couple your geothermal/ground source heat pump with Solar Panels to power the system – you will greatly reduce your monthly bills and use very little fossil fuels to heat and cool your house.

Matthew Peterson is the Principal of Element Design Group in Lewes. He can be reached at Matthew@ElementDG.com.

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