Absorption Heat Pumps
Absorption heat pumps are
essentially air-source heat pumps
driven not by electricity, but by a
heat source such as natural gas,
propane, solar-heated water, or
geothermal-heated water.
Because natural gas is the most
common heat source for absorption
heat pumps, they are also referred
to as gas-fired heat pumps.
There are also absorption coolers
available that work on the same
principal, but are not reversible and
cannot serve as a heat source.
essentially air-source heat pumps
driven not by electricity, but by a
heat source such as natural gas,
propane, solar-heated water, or
geothermal-heated water.
Because natural gas is the most
common heat source for absorption
heat pumps, they are also referred
to as gas-fired heat pumps.
There are also absorption coolers
available that work on the same
principal, but are not reversible and
cannot serve as a heat source.
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These are also called gas-fired coolers.
Residential absorption heat pumps use an ammonia-water absorption cycle to provide
heating and cooling. As in a standard heat pump, the refrigerant (in this case, ammonia)
is condensed in one coil to release its heat; its pressure is then reduced and the
refrigerant is evaporated to absorb heat. If the system absorbs heat from the interior of
your home, it provides cooling; if it releases heat to the interior of your home, it provides
heating.
The difference in absorption heat pumps is that the evaporated ammonia is not pumped
up in pressure in a compressor, but is instead absorbed into water. A relatively
low-power pump can then pump the solution up to a higher pressure. The problem then
is removing the ammonia from the water, and that's where the heat source comes in.
The heat essentially boils the ammonia out of the water, starting the cycle again.
A key component in the units now on the market is generator absorber heat exchanger
technology, or GAX, which boosts the efficiency of the unit by recovering the heat that is
released when the ammonia is absorbed into the water. Other innovations include
high-efficiency vapor separation, variable ammonia flow rates, and low-emissions,
variable-capacity combustion of the natural gas.
Although mainly used in industrial or commercial settings, absorption coolers are now
commercially available for large residential homes, and absorption heat pumps are under
development. The 5-ton residential cooler systems currently available are only
appropriate for homes on the scale of 4,000 square feet or more.
Absorption coolers and heat pumps usually only make sense in homes without an
electricity source, but they have an added advantage in that they can make use of any
heat source. Because of this, they can make use of solar energy, geothermal hot water,
or other heat sources. They are also amenable to zoned systems, in which different
parts of the house are kept at different temperatures.
The efficiency of air-source absorption coolers and heat pumps is indicated by their
coefficient of performance (COP). COP is the ratio of either heat removed (for cooling) or
heat provided (for heating) in Btu per Btu of energy input. Look for a heating efficiency of
1.2 COP or greater and a cooling efficiency of 0.7 COP or greater.
Residential absorption heat pumps use an ammonia-water absorption cycle to provide
heating and cooling. As in a standard heat pump, the refrigerant (in this case, ammonia)
is condensed in one coil to release its heat; its pressure is then reduced and the
refrigerant is evaporated to absorb heat. If the system absorbs heat from the interior of
your home, it provides cooling; if it releases heat to the interior of your home, it provides
heating.
The difference in absorption heat pumps is that the evaporated ammonia is not pumped
up in pressure in a compressor, but is instead absorbed into water. A relatively
low-power pump can then pump the solution up to a higher pressure. The problem then
is removing the ammonia from the water, and that's where the heat source comes in.
The heat essentially boils the ammonia out of the water, starting the cycle again.
A key component in the units now on the market is generator absorber heat exchanger
technology, or GAX, which boosts the efficiency of the unit by recovering the heat that is
released when the ammonia is absorbed into the water. Other innovations include
high-efficiency vapor separation, variable ammonia flow rates, and low-emissions,
variable-capacity combustion of the natural gas.
Although mainly used in industrial or commercial settings, absorption coolers are now
commercially available for large residential homes, and absorption heat pumps are under
development. The 5-ton residential cooler systems currently available are only
appropriate for homes on the scale of 4,000 square feet or more.
Absorption coolers and heat pumps usually only make sense in homes without an
electricity source, but they have an added advantage in that they can make use of any
heat source. Because of this, they can make use of solar energy, geothermal hot water,
or other heat sources. They are also amenable to zoned systems, in which different
parts of the house are kept at different temperatures.
The efficiency of air-source absorption coolers and heat pumps is indicated by their
coefficient of performance (COP). COP is the ratio of either heat removed (for cooling) or
heat provided (for heating) in Btu per Btu of energy input. Look for a heating efficiency of
1.2 COP or greater and a cooling efficiency of 0.7 COP or greater.
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