Published Sunday March 3, 2013:  Updated January 13, 2014


Our Geothermal Ground Loop Installation

-Environmental Burdens:

As with any home improvement, there is an environmental burden that goes along with it. 
I found it ironic that in order to install something as green and environmentally friendly as a geothermal ground loop, lots of dirty fossil fuel was consumed during in the drilling/construction process.  
To install a geothermal ground loop at my house, the energy burden breakdown was as follows:


Energy Requirements

 TaskTo drill a 
single 300' hole
 kWh/gal Energy 
per 300' hole
 
 Total Energy 
 Drill rig 20 gallons diesel 34.8 696 kWh 2080 kWh
 Water pumps 3 gallons gas 33.4 100 kWh 300 kWh
 Transportation 20 gallons diesel 34.8  696 kWh


Even with such a dirty job like drilling wells 300' deep, the energy savings from no longer heating with fossil fuels quickly offset the environmental damage initially incurred.  

This energy pollution caused by burning 80 gallons of diesel and 9 gallons of gasoline (3076 kWh total) is recovered in the form of energy savings of operating more efficient (and solar powered) equipment, in less than 26 winter heating days.


Water requirements:

 Water Requirements Water per 300' hole Total Water
 Water lost to the ground 1000 gallons 3000 gallons
 Water to drill a hole (50 gpm) 9000 gallons 
 Total Water 10000 12000 gallons

Besides the water lost into the ground during the drilling process, all of the water is re-circulated and re-used.  


Equipment 

The geothermal heat pump in my basement weights about 350 lbs.  It has a lot of metal in it.  I imagine a lot of natural resources and energy went into building it.  
Fortunately geothermal heat pumps last twice as long as conventional air conditioning equipment.  


R-22

The HCFC refrigerant that is used in most home A/C units is R-22.  If allowed to enter the atmosphere, molecule for molecule, it would have a global warming potential 1700 times greater than CO2.  It also depletes the ozone layer (but not nearly as bad as the old R-12 refrigerant did). Most A/C systems have an outdoor compressor and an indoor evaporator coil. Because of the distance separating between these two systems, it requires a lot more R-22 refrigerant.  


R-410A
All newer air conditioning systems (including our heat-pump) now use R-410A instead of R-22.  It has no ozone depleting potential but has a very high global warming potential (1890 times greater than CO2) if allowed to leak out into the atmosphere.  




Our home's ground-loop heat pump has both the compressor and evaporator contained inside the same chassis.  In this configuration, it uses a lot less of this environmentally harmful chemical.  

64 ounces of R-410A in the heat pump vs. 214 ounces of R-22 for the old air conditioner.