World-Gen Volume 27 No 1 - page 26

5-55052-01 published at the Oregon Institute
of Technology concluded that geothermal
heat pumps (GHP’s) have considerably
lower operating and maintenance costs than
existing alternatives. In that study, three
HVAC systems were considered: (1) rooftop
units with gas heat and expansion (DX)
cooling (air cooled condensers) (2) air-
source heat pumps (3) geothermal heat
pumps. NREL reports,
“The GHP system is
the most expensive to install, but the least
expensive to operate and maintain. Rooftop
units with gas heat and DX cooling are the
least expensive to install, but the most
expensive to operate and maintain. Air-
source heat pumps have higher installation
costs than gas roof top units, but do not save
considerably in annual operating costs,
mostly due to the significant amount of
supplemental electric required in winter
Although the propane cost savings are
clearly evident, the efficiency of the geo-
thermal heating and cooling system in even
a well-insulated home is hard to measure.
More field data is needed to truly assess
the role of the geothermal system com-
pared to the role of a well-insulated home in
maintaining a comfortable indoor tempera-
ture. Some data on the internet is skewed in
favor of the manufacturer’s opinion of sys-
tem efficiency in order to increase sales.
One must do some homework and select
the right contractor to decide whether his
or her house is too big, too “leaky”, or is
located in too mild of a climate to assess the
“efficiency” of a potential geothermal sys-
tem in the home.
Bottom line is; you have to heat your
home some way. If you are interested in tak-
ing care of the earth, the environmental ben-
efits might tip you in the direction of a geo-
thermal system. According to “Geothermal
Professionals”, the use of a ground source
heating pump system can save on average
about 4 tons of CO2 per year. Installing a
three-ton geothermal system is equivalent to
planting over 1 acre of trees or taking two
cars off the road. The overall environmental
benefits of geothermal are clear, geothermal
does not directly emit carbon dioxide, car-
bon monoxide, or other greenhouse gases
that contribute to climate change. While
such a system (depending on the source of
electricity needed to run it) can indirectly
contribute to GHG emissions, the overall net
emissions of GHGs are significantly less
than traditional methods of heating and cool-
ing a home. In addition, when looking at the
environmental impact, one must also consid-
er the potential consequences of installing
an open loop geothermal system versus a
closed loop geothermal system.
Most of Nutmeg’s installs are vertical
closed loop geothermal systems that can fit
in almost anyone’s backyard. Wierzbicki
explains, “With a closed loop system, home-
owners can set it and forget it.” A closed
loop system requires little maintenance after
it is installed, uses less electricity to operate
and does not release water or minerals into
the ecosystem surrounding a home. Open
loop systems need to discharge into a dump-
ing ground and might change the water tem-
perature of a nearby lake, well, or pond. The
systems require a larger pump, which
causes a homeowner to use more electricity.
If a homeowner identifies minerals in the
loop, he or she needs to add filtration to
keep the pump clean. If the water level of
the water source connected to the loop ever
drops, a homeowner can run out of water.
When deciding on whether to install a
geothermal system or ground source heat-
ing pump, it is helpful to look at geothermal
from an industry perspective. Where is the
market for geothermal heating and cooling
going and would geothermal be a sustain-
able heating and cooling alternative if subsi-
dies no longer existed? According to
“In the new construction market,
geothermal is going to grow and prosper.
When the utility cost savings are weighed
against an increased cost in mortgage, it is
clear that geothermal is a good investment.
In the retrofit market to existing homes with
the 30% tax credit, I believe we will see a
slight increase in demand to what we are see-
ing now.”
However, Wierzbicki admits that with-
out the tax credit, there will most likely be a
large decrease in demand in both the new
construction and retrofit markets for geo-
thermal heating and cooling systems. He
surmises, “If oil prices were fixed at 4 dol-
lars/gallon or more and field data showed
geothermal reduced operating costs by 60%,
geothermal would stand as a strong heating
and cooling alternative without subsidy.”
When looking at geothermal heating
and cooling in respect to other alternative
renewable energy resources such as solar,
Wierzbicki confirms, “If air conditioning is
important, solar and geothermal do not
compare.” Only, geothermal effectively
cools the home. Plus, the sun doesn’t shine
every day for effectively heating the home.
According to Nutmeg, solar and geothermal
complement each other rather than act as
competitive alternatives. Wierzbicki sug-
gests coupling a geothermal system with a
solar electric field to save on your electricity
bill while using the geothermal system.
This will give the homeowner the lowest
possible operating and utility costs.
If you are thinking of installing a geo-
thermal system, it is best to do some
research on your house first. Then assess
your financing options, find a contractor
that will be transparent about pricing and
offers quality assurance, and weigh the
environmental benefits of installing a closed
or open loop system together with your
expected utility cost savings. Even if you
don’t end up installing a geothermal system
in your home, through this process, you
will learn why your home gets so cold in
the dead of winter and why you wake up
sweating with AC blasting during the hot-
test summer nights.
Stephen Wierzbicki started Nutmeg
Mechanical Services Inc. in 1982. Nutmeg
aligned with the Comfort Institute Group
and is BPI accredited to perform audits.
Nutmeg is aligned with Carrier and its
Energy Experts 360 program.
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