Fascinating Ideas, Tried and True
Geothermal Heat Pump
Back in February 2006, the Bangor Daily News published an op-ed I wrote
asking: Why doesn't every new home utilize a geothermal heat pump for
heating and cooling? The op-ed described my experience with installing
a heat pump at my home and my motivation for doing so. Here is that
op-ed. The next section has pictures that tell the story about the installation.
After 14 years of heating and cooling my home and with basically no
maintenance costs, my ground source heat pump is still working well. Today
there are government incentives for installing heat pumps in homes.
Geothermal pump gives free heat
Free heat from a
geothermal heat pump warms my kitchen as I write this commentary. For
every dollar of electrical energy that goes into the heat pump, I get
3.6 dollars of electrical heat. That’s 2.6 dollars of free heat. And by
purchasing clean green power from hydroelectric dams and wind power,
it’s possible to heat one’s home without burning oil and without
generating global warming gases.
The idea of installing a geothermal heat pump began in
2004 when I read about how the polar ice caps are melting at a record
pace and how atmospheric carbon dioxide was at record levels and
increasing dramatically. The possibility of peak oil production
occurring in this decade accompanied by increasing demand for oil in
China has made oil prices skyrocket.
I watched as President Bush set up a string of
permanent military bases in the oil producing regions of Iraq. I
watched as our own Maine National Reserve troops were sent to oil-rich
Iraq with the false goals of fighting terrorism and weapons of mass
destruction. I watched as oil companies made obscene profits while
people suffered. Something had to be done. The freedom we should be
fighting for today is freedom from Middle East oil.
So, how does one economically heat one’s home without
oil and without pollution? Natural gas is a clean-burning fuel but it
still increases carbon dioxide in the atmosphere and contributes to
global warming. Solar is good, but there just isn’t much sunlight
available in January in Maine when we need the most heat. Geothermal
heating coupled with green power produced from hydroelectric, wind and
solar power met the requirements.
Green power does cost a little more than the standard
offer. But even though electricity is expensive in the Bangor area, my
heating costs will be less than heating from oil. Some drawbacks are
the high installation cost and that geothermal heating is not
well-established in Maine. To extract heat from the ground, one must
bury a large amount of pipe in the ground. Still geothermal heating is
a well-established technology. Ninety-five percent of new homes in
Sweden have installed geothermal heating. Five hundred thousand units
have been installed in Canada and the United States.
To minimize the installation cost, I decided on a
smaller hybrid system that I installed myself for about $3,000. I
estimated that this system could produce about 75 percent of my yearly
heating needs since maximum heat loads are only required on the coldest
days. My current oil furnace would provide the extra heat needed to
warm the house on those days. As an added benefit the system would
provide low-cost air conditioning in the summer while providing
domestic hot water and heat for my swimming pool.
So, eight weekends later, twice as long as planned and
with a series of intense learning situations otherwise known as
correcting my own mistakes, I had a working geothermal heat pump. On
Jan. 1, warm air came from the register.
Of course I am still on a learning curve but the
success I’ve had with this system so far makes me wonder why most new
houses aren’t built with a geothermal heat pump for heating and cooling.
David LaBrecque is a research associate in the Chemistry Department at the University of Maine.
Installing a Ground Source Geothermal Heat Pump
Heat pumps for heating and cooling a home can be divided into three categories: Air to Air, Well Type and Ground Loop.
Air to air is the easiest and least expensive to install. It's like an
oversized air conditioner. The downside is it is not as efficient as
the other two types and may not work well on the coldest days in the
Winter when it is needed most. The well type is the most expensive, but
it doesn't matter how cold it is outside because it is extracting heat
from deep underground where the temperature is pretty constant. It also
does not require much of a backyard area. The major expense comes from
digging a series of wells, the number of wells needed will depend on
your homes heating needs. The last type is a ground loop heat pump.
Pipes for circulating an antifreeze liquid are buried as deeply
underground as an excavator can dig. Excavators cost less, but ground
temperature 6' to 8' below ground level varies with the seasons. Given
my budget, I opted for the ground loop approach. The first step is to
hire and excavator to dig the pipe trench.
huge piles of dirt. My trench was about 300 feet long and ranging from
6 to 8 feet deep. This was about as deep as this excavator could dig.
excavator operator was an older guy, close to retirement, and he gave
me a good price. He warned me not to go in the trench because it could
suddenly collapse on you. After he had dug the trench, it was my job to
throw the 6 3/4" black plastic pipe in the trench. I wanted to space
them apart with a long pole and a rake, but the task proved difficult.
So I settled for just leaving the pipe where it landed in the trench.
the pipes have to come into the basement where the heat pump is
installed. There are twelve holes drilled through the basement wall
here. Three are on the left and are just out of sight. Leaking into the
basement is a concern, so silicon sealant was used to seal these holes
around the pipes. Note the drainage pipe that was cut during the
excavation. Proper ground drainage should be installed to minimize
basement leaks. The excavator operator advised me that the pipes should
be continuous through the entire trench with no couplings. He told me
he had never seen pipes leak that were continous stretches of pipe, but
he has seen couplings leak.
neighbors could hear the excavator and see large hills of dirt growing
in an area close to their backyards. One neighbor thought we were
building some huge building near their property. It's a good idea to
let your neighbors know what you are doing and that in a day or two,
the area will be back to normal and all signs of the excavation will be
Here is the trench in February 2006, about 4 months after the trench was backfilled. We've added fill and mulch since then.
pipes have to come into the basement and go into input and output
headers. The headers can be made out of low-cost PVC pipe. I added
extra T's and valves onto this header in case I wanted to expand the
loop. For example a rooftop solar hot water collector and tank could be
used if I had extracted too much heat from the ground. That is I had
cooled the ground around the pipes to temperatures below freezing where
the heat pump could not operate well. These T's were also used for
filling the pipes. It's important to get all the air out of the pipes.
Professionals bring in special pumps to do this quickly. If you have
time like I did, you can keep adding the antifreeze solution to the
pipes over a few weeks as needed, until all of the air, the bubbles in
the high point in the clear pipe on the right are gone.
is the installed hot air heat pump. I paid about $1700 from a Florida
company for this 20,000 BTU heat pump back in 2005. The specs on this
particular model indicate it can extract heat from 30 degree F ground
loop water. Note the green circulator pump that circulates ground loop
antifreeze liquid through the pipes to the header. The gauges on the
pipes measure the difference in pressure across the heat exchanger in
the heat pump. These will indicate if the liquid is freezing. I also
attached the probe from an indoor/outdoor thermometer to measure
temperature of the water coming back from the ground loop. Initially I
would have to turn off the heat pump when the return antifreeze water
was getting too cold. I added an Omega controller (not shown) to
automatically shut down the heat pump when the return water was too
cold and to keep circulating the water until the ground temperature and
the water had come back up to temperature. This was back in 2006 and I
haven't made any significant changes since.