System information

ClimateMaster Geothermal Heat Pump Systems
3
Residential Products Technical Guide
System Components
Geothermal heat pumps have a number of names such as water-
source heat pump, Geoexchange, ground loop heat pump, earth-
coupled heat pump, ground source heat pump, etc. Technically,
“Geothermal” is defi ned as, “energy from the internal heat of the
earth.” This type of geothermal energy is called “high temperature
geothermal.” Temperatures can exceed 300°F [150°C] in
geothermal wells. Unfortunately, these hydrothermal reservoirs
are located only in limited areas of North America, primarily
in the Western part of the United States. Therefore, the term
“Geothermal heat pump” refers to “low temperature geothermal
energy,” which involves the use of a mechanical device that can
transfer heat to and from the ground to heat, cool and produce
domestic hot water (DHW) for residential and commercial
applications.
Geothermal technology is not new. The fi rst recorded geothermal
system was a 1912 Swiss patent. Ground water (open loop) heat
pumps have been used successfully since the 1930s. EEI (Edison
Electric Institute) sponsored closed loop research in the 1940s and
1950s, although the lack of suitable material for closed loop piping
slowed interest. U.S. researchers began investigating geothermal
closed loop systems again in the 1970s with the advent of plastic
pipe, which was suitable for the application. Oklahoma State
University was one of the pioneers of geothermal closed loop
technology during this time.
System Components
The basic concept of a geothermal heating and cooling system
involves the use of a very stable heat sink/heat source. Rather
than depending upon widely varying outdoor air temperature
as does a “conventional” air source heat pump, geothermal heat
pumps take advantage of the nearly constant ground temperature.
Figure 1 shows typical average annual ground temperatures and
air temperatures. Clearly, the ground temperature is a much more
stable source of energy than the air. This allows proven heat pump
technology to be applied in an inherently more effi cient manner.
For example, it is much easier to heat with 50°F [10°C] ground
than 15°F [-9.4°C] air.
Geothermal systems consist of three main components, the
geothermal (or water source) heat pump, the heat sink/heat
source, and the distribution system. Each component will be
addressed below.
The Geothermal Heat Pump
The Geothermal Heat Pump uses a compressor, a condenser,
an evaporator, a reversing valve, and a thermal expansion valve
(the basic heat pump refrigerant circuit) to transfer heat to and
from the ground to the home. Most geothermal heat pumps
installed in North America are packaged water-to-air heat pumps,
whereby the home is heated and cooled via a forced air or
ducted distribution system connected to a single indoor unit that
contains all of the refrigeration components. Water-to-water heat
pumps are also popular, which heat or chill water for radiant fl oor
applications, chilled water/fan coil applications or domestic hot
water (DHW) generation. Split systems are also available, which
allow the compressor section to be located remotely from the air
handling section.
Figure 1: Temperature Comparisons
Figure 2: Geothermal Heat Pump Concept