Geothermal heat pumps:
What are they and how do they work?
Q: What is a geothermal heat pump?
A: A geothermal heat pump is an electrically-powered device that uses
the natural heat storage ability of the earth and/or the earth's
groundwater to heat and cool your home or business.
Q: How does it work?
A: Like any type of heat pump, it simply moves heat energy from one
place to another. Your refrigerator works using the same scientific
principle. (See Mechanics of the Heat Pump Process on page 3.) By using
the refrigeration process, geothermal heat pumps remove heat energy
stored in the earth and/or the earth's groundwater and transfer it to
the home.
Q: How is heat transferred between the earth and
home?
A: The earth has the ability to absorb and store heat energy. To use
that stored energy, heat is extracted from the earth through a liquid
medium (groundwater or an anti-freeze solution) and is pumped to the
heat pump or heat exchanger. There, the heat is used to heat your home.
In summer the process is reversed and indoor heat is extracted from your
home and transferred to the earth through the liquid.
Q: You mentioned heating and cooling. Does it do
both?
A: One of the things that makes a heat pump so versatile is its
ability to be a heating and cooling system in one. You can change from
one mode to another with a simple flick of a switch on your indoor
thermostat. In the cooling mode, a geothermal heat pump takes heat from
indoors and transfers it to the cooler earth through either groundwater
or an underground loop system.
Q: Do I need separate ground loops for beating and
cooling?
A: No. The same loop works for both. All that happens when changing
from heating to cooling, or vice versa, is that the flow of heat is
reversed.
Q: What types of loops are available?
A: There are two main types: open and closed. The next two sections
will give you specifics about each.
Q: Does the underground pipe system really work?
A: The buried pipe, or "ground loop," is the most recent technical
advancement in heat pump technology. The idea to bury pipe in the ground
to gather heat energy began in the 1940s. But it's only been in the last
few years that new heat pump designs and improved pipe materials have
been combined to make geothermal heat pumps the most efficient heating
and cooling systems available.
| The Mechanics of the Heat Pump Process
Anyone who has a refrigerator or an air
conditioner has witnessed the operation of a heat pump, even
though the term heat pump may be unfamiliar. All of these
machines, rather than making heat, take existing heat and move
it from a lower temperature location to a higher temperature
location. Refrigerators and air conditioners are heat pumps
which remove heat from colder interior spaces to warmer
exterior spaces for cooling purposes. Heat pumps also move
heat from a low-temperature source to a high-temperature space
for heating.
An air-source heat pump, for example,
extracts heat from outdoor air and pumps it indoors. A
geothermal heat pump works the same way, except that its heat
source is the warmth of the earth.
The process of elevating low-temperature
heat to over 100 degrees F and transferring it indoors
involves a cycle of evaporation, compression, condensation and
expansion. A refrigerant, like Freon, is used as the
heat-transfer medium which circulates within the heat pump.
The cycle starts as the cold, liquid
refrigerant passes through a heat exchanger (evaporator) and
absorbs heat from the low-temperature source (liquid from the
ground loop). The refrigerant evaporates into a gas as heat is
absorbed. The gaseous refrigerant then passes through a
compressor where the refrigerant is pressurized, raising its
temperature to over 180 degrees F. The hot gas then circulates
through a refrigerant-to-air heat exchanger where heat is
removed and pumped into the home at about 100 degrees F. When
it loses the heat, the refrigerant changes back to a liquid.
The liquid is cooled as it passes through an expansion valve
and begins the process again. To become an air conditioner,
the flow is reversed. |
|
JC HEATING & COOLING
Geothermal Heating Systems
