From: randy@rls.UUCP (randall l. smith)
Newsgroups: misc.consumers.house
Subject: Re: Geothermal heatpump
Date: 30 Jul 92 19:34:39 GMT
Organization: The Internet

eliot@chutney.rtp.dg.com (Topher Eliot) writes:
> jheath@CERIS.Purdue.EDU (Jim Heath) writes:
>> Did you know anyone who tried one of those "geothermal" heatpumps
>> where the input (and output?) for the pump is buried below the
>> frostline?  I have heard that they are much better. 
>
> No, as far as I know these weren't geothermal.  For whatever reason,
> those don't seem to be used around here.

If the heat exchange occurs in the ground, it is considered geothermal.

In many parts of the country they haven't caught on.  They are a
superior form of heat transfer because of the consistant temperature
of the earth and the efficiency range for the heat pump.  You pay more
because the heat transfer line has to be buried in the ground and any
time there is earth to be dug for any reason, it is expensive.

The way heat pumps work is to simply transfer heat from one location
to another.  It is either moving heat into the dwelling for heating or
moving heat out of the dwelling for cooling.  It does this by way of a
heat exchanger.  The heat exchanger is simple and non mechanical flow
of fluid.  The fluid is moved by way of a pump, ergo heat pump.

For heating, the fluid (typically freon) flows from a small pipe into a
large chamber.  The expansion of the freon draws heat from the
surrounding air/earth/water and it is pumped (uncompressed) into the
dwelling where it is re-compressed and the freon subsequently releases
the heat.  For cooling, the flow of the freon is reversed.  The heat in
the building is thus drawn through the freon into the air/ground/water
and released there.

Heat *must* be within the efficiency range for heat exchange or the
release and capture cannot occur.  Heated freon simply flows through the
system with no beneficial effects.  Because the ambient air temperature
is often outside the efficiency range for an air based heat pump at
the times of greatest need, they must be backed up by conventional
heating and cooling equipment.

The efficient range for most heat pumps for heating is an ambient
temperature above 22F.  Much below that temp, heat cannot be drawn from
the air/ground/water to transfer into the dwelling.  For cooling the
ambient temperature is somewhere around 78F.  Much above that temp, heat
cannot be released to be drawn from the dwelling.

Because the ground temperature (below three feet) in most of the US is
around 55F year round, a geothermal heat pump is at it's most efficient.
Because some areas have a very rocky substrates, it is not cost effective
to bury the freon lines for geothermal heat exchange.

In effect the ground is used as a heat sink/supply to make the geothermal
heat pump an extremely efficient heating/cooling agent.  Much propaganda
has surfaced from the gas industry, assulting the heat pump because they
are totally electric and gas is cut from the equation.

Cheers!

- randy

uucp: randy@rls.uucp
bang: <backbone>!osu-cis!rls!randy
inet: rls!randy@tut.cis.ohio-state.edu
Unquestionably, there is progress.  The average American now pays out
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