How Green is Geothermal Heating?
By Matt Power |
6/24/2010
New research from Switzerland finds wide differences in efficiency.
- The Life Cycle Assessment study looked at shallow geothermal loop installations, and found that the efficiency, when compared with conventional electric or fossil fuel-powered HVAC systems ranged from -31 percent (worse) to 88 percent (almost twice as efficient).
To arrive at those figures, the researchers developed sophisticated tools:
"The applied life cycle impact assessment methodology (ReCiPe 2008) shows the relative contributions of resources depletion (34%), human health (43%) and ecosystem quality (23%) of such GSHP systems to the overall environmental damage. Climate change, as one impact category among 18 others, contributes 55.4% to the total environmental impacts."
One of the biggest determinants of overall environmental impacts is the source of electricity used to power the heat pump, "followed by the heat pump refrigerant, production of the heat pump, transport, heat carrier liquid, borehole and borehole heat exchanger (BHE)."
Other contributing factors include: "degradation of coefficient of performance, as well as total leakage of the heat carrier fluid into the soil and aquifer," but these had compartatively minor impacts on the environment.
Source: Renewable & Sustainable Energy Reviews; Sep2010, Vol. 14 Issue 7, p1798-1813, 16p