Introduction
Heat pumps have been very popular for several years and are unique in their ability to:
- Extract heat from a colder medium and transfer it to a hotter medium through a refrigeration-type cycle.
- Operate as either a heating unit or cooling unit with the positioning of a valve.
The most common type of heat pump extracts heat from the outdoor air and transfers it to the house at a higher temperature. The performance of a heat pump depends on the temperature difference between the outside and inside and, consequently the performance of the common air-to-air unit is lowest when the outside temperature is the lowest and this is when heating of the home is most needed. Therefore auxiliary heat which is much lower in efficiency must be utilized on the colder days. Having a large number of these heat pumps accents the peak power that a utility must provide on the coldest days which results in their operation of lower efficiency generating equipment which increases overall consumer power costs and increases pollution of the air.
The ground source or geothermal heat pump has been recognized as having superior efficiency to the standard air units because the ground is almost always at a more favorable temperature than the ambient air. For example, when outside air temperature is 10 F, the ground temperature six feet under the surface may be about 40 degrees F. Again, since the heat pump efficiency is a function of the temperature difference, the geothermal system will be superior. In this case, for example, the temperature difference for the air unit will be 65 F (assuming 75 F inside temperature) but for the ground unit the temperature difference will be 75 - 40 = 35 F.
Geothermal heat pump installations involve placing pipes in the ground and circulating a fluid within the pipes to extract the heat. Arrangements can be pipes laid horizontally in a pit or trench or placed vertically in holes drilled into the earth.
The direct exchange geothermal (DXG) heat pump utilizes buried copper pipe filled with circulating refrigerant to remove heat from the earth. It does not require an additional pump to move the refrigerant through the ground or any intermediate heat exchanger. The direct exchange technology is new and has exciting possibilities. In tests performed to date, the DXG system has reduced residential heating and cooling bills by as much as half. Since the technology is new, system improvements are expected which will produce even greater savings.
Back to TopWhat is a Desuperheater?
A desuperheater makes it possible for DX systems to provide almost free water heating throughout the summer. Instead of sending all the waste heat outdoors some can be captured and channeled to a water heater. Once the desuperheater has been installed (for about $400) the only cost of using it is the energy needed to circulate the water.
Back to TopOther Advantages DX Heat Pumps
DX systems offer a number of advantages beyond simply reducing energy consumption. These advantages fall into the following categories:
- Longer life and less maintenance
- Greater comfort
Longer Life and Less Maintenance
Properly installed ground-source heat pumps cause less wear on the compressor than air-to-air heat pumps. This is because the temperature underground is more uniform than above ground so there is less stress on the system.
A DX system may be located entirely indoors and underground. This protects the equipment from the elements and temperature extremes while eliminating the need for costly defrost cycles, or outdoor fans. The result is fewer maintenance problems and longer equipment life than air-to-air systems. Heat Pump systems require less maintenance than oil or gas systems. DX systems do not emit combustion gases so therefore do not need to be vented. As a result DX heated homes are easier to build and can be built more energy efficiently.
Greater Comfort
Conventional forced air heating systems provide heat in short blasts which can dry out a house, making it uncomfortable and possibly even damaging it. DX systems, on the other hand provide a cooler, more prolonged flow of air.
DX systems can dehumidify a home better than standard central air conditioners, providing a higher level of comfort.
Back to TopAir-to-Air Heat Pumps
DX heat pump systems are not the only type of heat pumps in use today. The most common are the air-to-air and water heat pumps which draw or release heat into the air or water. DX systems draw or release heat into the ground instead.
The economics of using an air-to-air or water based heat pump are radically different than a ground source heat pump. Determining which is best for you basically depends on the following:
- Do you live in an area with a moderate climate or one temperature extremes?
- Is your area humid or dry?
Do you live in an area with a moderate climate or one temperature extremes?
DX systems work best when it is very warm or very cold. Air-to-air and water heat pumps work best in moderate temperatures and lose efficiency at extreme temperatures. Air-to-air and water heat pumps have their greatest problems in severe cold because they require defrosting to keep the refrigerate in them from freezing, greatly reducing their efficiency.
As a result, areas such as South Carolina are good candidates for air-to-air and water heat pumps while Nebraska and Florida are good candidates for DX systems.
Is your area humid or dry?
Air-to-air heat pumps work poorly in humid environments because it difficult eliminate excess heat when there is high humidity.
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