Geothermal

GEOTHERMAL HEAT PUMP ENERGY
HOW IT WORKS!

DEFINITIONS

WHAT IS HEAT EXTRACTION?

While it may be difficult to explain the technology of extracting heat from air, water or
ground, the concept is easier to comprehend once one understands the principles of
heat extraction and heat exchange. Consider the following:

All matter contains heat. Zero degrees Kelvin/Rankine (minus 273 degrees
Celsius/minus 460 degrees Farenheit) is absolute zero. This is a hypothetical, but
fairly well substantiated, theory. There is nowhere in the universe where absolute zero
exists. Temperatures in outer space have been found to be approximately three
degrees Kelvin, which supports the theories developed by scientists.

Cold is the absence of heat. Cold exists only in relative terms, and plays no part in
scientific theory. While we all verbalize such expressions as "It is cold out", to be
technically correct we should say "the heat level outside is ten degrees farenheit"
(which, admittedly, is pretty cold).

Heat always flows from higher temperature matter to lower temperature matter by
conduction (from molecule to molecule), by convection (air currents) and by radiation
(electro-magnetic waves).

Heat can be moved or "extracted" from one source and delivered to another by
various means such as "heat exchangers".

WHAT IS A HEAT PUMP?
A heat pump, as the name suggests, is a device that "pumps" heat from one location
to another. The most popular heat pump is the air-source type (air-to-air), which
operates in two basic modes:

As an air-conditioner, a heat pump's indoor coil (heat exchanger) extracts heat from
the interior of a structure and pumps it to the coil in the unit outside where it is
discharged to the air outside (hence the term air-to-air heat pump) and

As a heating device the heat pump's out door coil (heat exchanger) extracts heat from
the air outside and pumps it indoors where it is discharged to the air inside.
The problem in comprehending such technology is that it is difficult to understand how
heat extracted from,say, ten degree air (or water) can heat anything. This is where the
unit's compressor and the "phase-change" physical properties of the refrigerant come
into play: the compressor boosts the extracted heat to a much higher temperature gas
which gives up its heat as it condenses to a liquid in the condensing coil and is
distributed to the structure by the fan or blower in the air-handler.

WHAT IS GEOTHERMAL HEAT PUMP HEATING AND COOLING?
Differences between air-source and geothermal heat pumps

As with air-to-air heat extraction technology, geothermal (ground water/ground
source) technology utilizes a type of heat pump known as a geothermal heat pump.
This type of geothermal heat pump device extracts its heat from water rather than
from air. While the principles are fundamentally similar, the methodology varies in that
water is pumped through a special type of heat exchanger and is either "chilled" by
the evaporating refrigerant (in the heating mode) or heated by the condensing
refrigerant (in the cooling mode).

WHY IS A GEOTHERMAL HEAT PUMP BETTER?
Water stores tremendous quantities of heat. In nature, few substances have a higher
specific heat (one BTU per pound) than does water, making it an ideal heat storage
medium for both natural and man-made phenomena.

Air, on the other hand has a very low specific heat (.018 BTU per cubic foot). There is
3472 times more heat stored in a cubic foot of water (62.5 BTU per degree F) as in a
cubic foot of air . In other words it would be necessary to move 3472 cubic feet of air
through a heat exchanger in an air-to-air heat pump in order to expose that heat
exchanger to the same quantity of heat stored in a cubic foot of water (7 1/2 gallons)
that is moved thru a geothermal heat pump.

While these differences are significant, there is more: the heat transfer characteristics
of water make it superior to air. Conduction is more rapid, more complete, and more
efficient a heat transfer phenomenon than convection. A ground-water heat pump
extracting heat from water at freezing is approximately equal in performance to that of
an air-source heat pump extracting heat from 60 degree air.

What are Closed Loops?

Closed Loops:
A closed loop is one in which both ends of the loop's piping are closed. The water or
other fluid is recirculated over and over and no new water is introduced to the loop.
The heat is transferred thru the walls of the piping to or from the source, which could
be ground, ground water, or surface water. As heat is extracted from the water in the
loop the temperature of the loop falls and the heat from the source flows toward the
loop.

In closed loop operation water quality is not an issue because corrosives become
rapidly "spent" or used up and corrosion caused by poor water quality is quickly
curtailed The wire-to-water efficiencies of circulators used in closed loop operation are
very high and the costs of pumping the water are lower as compared to open loops.
System efficiencies are somewhat lower in closed loop operation, but given the lower
pumping costs associated with this method, economics sometimes, but not always
favor this approach. Installed costs, however, are higher and need to be considered if
the consumer already has a well or other water source.