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Additional Topics/
GeoExchange Units Questions and Answers
Q: What is a GeoExchange unit?
A: A GeoExchange unit is a heating and cooling system that provides heat in winter and cooling in summer, at efficiencies that are far better than those for alternative systems. Like a conventional heat pump, it is essentially an air conditioner that can also run in reverse to provide heat in the winter. The primary difference is that it relies on the nearly constant temperature of the ground or ground water for heat transfer instead of the widely fluctuating temperature of the outside air. As a result, a GeoExchange unit saves energy, cuts electric bills, reduces greenhouse gas emissions, and offers lower maintenance and lower hot water costs than conventional heating and cooling systems.
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Q: How does a GeoExchange unit operate?
A: A GeoExchange unit simply transfers thermal energy (heat) from the ground or ground water into the space being conditioned during the winter months and transfers excess heat from the structure back into the ground or ground water in the summer months. Because the temperature of the ground or ground water remains fairly constant throughout the year—ranging from about 45-50 degrees F in northern latitudes to 70-80 degrees F in the deep south—operating efficiencies are high year-round.
The typical GeoExchange system consists of three main parts:
- The air handling system (fan and ductwork) that distributes air within the spaces being heated or cooled
- The ground or ground water heat exchanger that absorbs heat from the earth or discharges heat to the earth
- A reversible refrigerant loop that transfers heat between the air handling system and the ground or ground water heat exchanger.
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The air handling system is typical of any forced-air heating or cooling system. A fan moves heated or cooled air through ducts to the individual rooms in a building, and returns air to the GeoExchange system.
The ground-coupled heat exchanger can take a number of forms. In an open-loop system, two wells are typically used. These are similar to conventional water wells, with one acting as a source well, and the other acting as a sink. Water is pumped from the source well, through a water-to-refrigerant heat exchanger on the GeoExchange system, and returned to the second well. Alternately, the water from the source well can be returned to a lake, pond, or stream, if there is one in proximity to the site, and local regulations permit. The water remains unaffected by the system, except that its temperature is raised in summer and lowered in winter.
In a closed loop system, the ground-coupled heat exchanger takes the form of sealed high density polyethylene piping buried vertically or horizontally in the ground. In the case of vertical systems, a series of 4-in. to 6-in. diameter bore holes are made (typically using water well drilling equipment to attain depths of 150 to 300 feet), a loop of piping is inserted into each hole, the various loops are tied together by a manifold and then the holes are grouted and backfilled. For horizontal systems, similar piping loops are buried in horizontal trenches dug 4 to 6 feet deep, the piping is connected by headers, and the trenches backfilled. In both vertical and horizontal closed-loop systems, the water or water/nontoxic antifreeze mixture in these pipes remains within the pipes for the life of the system.
For purposes of describing system operation, let’s assume an open-loop system using two wells. The heating cycle begins when the ground water is pumped from the source well to a water-to-refrigerant heat exchanger (acting as an evaporator) on the GeoExchange unit. The tubes on the refrigerant side of the heat exchanger are filled with a liquid refrigerant at low temperature. As the liquid refrigerant flows through the heat exchanger, it absorbs heat from the ground water, and evaporates to form a cool gas (10° to 30°F cooler than the ground water). The water from the source well gives up heat as it flows through the heat exchanger, returning to the discharge well at a lower temperature.
The gaseous refrigerant from the evaporator passes through tubing to a compressor, which compresses it, raising its temperature and pressure (to an average of 180°F and 245 pounds per square inch (psi) pressure for most models). The hot, compressed gas then flows to a refrigerant-to-air heat exchanger, which acts as a condenser in the heating mode. Here, air flowing across the condenser tubing absorbs heat from the refrigerant and carries it throughout the house. As it releases heat, the refrigerant condenses to form a liquid, which then flows through an expansion device that reduces its pressure and consequently lowers its temperature again. Finally, the refrigerant re-enters the evaporator and the cycle is repeated.
For home cooling, the above process is reversed. The compressor sends the hot, dense gas directly to the water-to-refrigerant heat exchanger (now acting as a condenser). The water from the source well absorbs heat from the refrigerant and flows back to the discharge well at a higher temperature. As it gives up heat to the water, the refrigerant cools and condenses into a liquid. The cool liquid refrigerant flows through an expansion device (usually an orifice or valve), which further lowers its temperature and pressure. The cold liquid refrigerant then flows to the air-to-refrigerant heat exchanger, which now acts as an evaporator. Air from the home’s interior flows across the evaporator tubing, giving up heat to the refrigerant inside the tubes. The cooler air is moved through the house via the duct work. The warmed refrigerant evaporates as it absorbs heat from the air, and then returns to the compressor to repeat the cycle.
Most of the GeoExchange units installed today may also be equipped to provide hot water for domestic needs. In fact, hot water can be provided free during summer months, by using waste heat extracted from the home interior. Even in winter, the GeoExchange system can supplement the hot water provided by the gas or electric water heater, reducing overall hot water costs by about 30% annually. All of this is accomplished with a small supplemental heat exchanger called a desuperheater.
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Q: Why use ground water and open-loop design?
A: Ground water is attractive as a heat exchange medium in residential and commercial space conditioning. By using a GeoExchange unit, ground water can serve as a heat source (for heating) and a heat sink (for cooling).
The temperature of the ground water is nearly the same year-round, regardless of the temperature extremes on the surface. Thus, it is warmer than the outside air in winter and cooler in summer. Since GeoExchange unit capacity and efficiency vary significantly with the heat source/sink temperature (or temperature difference between the source/sink and conditioned space), a GeoExchange system offers considerable advantages over the more widely used air-to-air heat pump. Water will hold five times more heat than an equal weight of air and its heat content does not vary with its temperature. Air yields very little heat at temperatures below 25°F and will accept very little heat in the cooling cycle at temperatures above 85°F.
The only qualifications for the use of ground water with a GeoExchange system are that it must be abundant, of high quality, pumping costs must be reasonable, and conditions and regulatory requirements conducive to efficient discharge.
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Q: What is the temperature of the available ground water?
A: The temperature of shallow ground water in the U.S. ranges from 44°F in the north central areas to approximately 80°F in Florida and southern Texas. In North America, GeoExchange units can operate efficiently at ground water temperatures as low as 39°F, or even lower, with equipment currently being constructed. Higher temperature ground water will, of course, put less demand on the system and make it more efficient
In the extreme South, where the cooling cycle predominates, ground water temperatures average about 72°F. It leaves the GeoExchange unit at about 85°F. GeoExchange units have been used for many years in Florida.
In the North, where the heating cycle is crucial, ground water temperatures average about 52°F. There is less flexibility available in severe northern climates for lowering the ground water temperature before freezing occurs. Some GeoExchange units are designed to operate with a very small temperature drop in the water to avoid freezing damage.
While there is a small potential risk of changing the ambient temperature of the aquifer where recharge or aquifer volume is limited, a GeoExchange unit usually raises the temperature of the water by no more than 10°F, so the water is usually returned to the original aquifer with no change in water quality and only a modest temperature difference.
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Q: How much water does an open-loop GeoExchange unit require?
A: In order for a GeoExchange unit to operate at its specified heating and cooling capacity and efficiency, the proper ground water flow rate through the water-to-refrigerant heat exchanger must be maintained. The ground water aquifer, source well, and pumping system must be able to supply the required flow rate.
The water flow requirement of a GeoExchange unit is dependent on its sizing (which varies over a wide range for individual home, office, or other commercial applications), its design, water flow per Btu (British thermal unit)/hour of heating (which varies over a wide range for different manufacturers), and the temperature of available ground water (which varies from 44°F in the north central states to 80°F in the extreme southern states).
The requirements of GeoExchange units sized to provide 50,000 Btu/hr space heating output (typical sizing for an average modern home) can range from 5 to 15 gpm (gallons per minute), approximately 7,200 to 21,600 gallons per day, depending on the design of the specific equipment. Such GeoExchange units can require even higher water flows during the summer if equipped with ground water heat exchangers for space cooling, and an additional water flow of 1 to 3 gpm (1,440 to 4,320 gallons per day) can be required if a separate GeoExchange unit is used for water heating in the home. The required water flows for GeoExchange units are therefore much larger than the 300 to 400 gallons per day required for most domestic water supply systems.
The consumption of GeoExchange units supplying 75, 20, and 15 million Btu/year of space heating, hot water heating and space cooling, respectively, can range from 500,000 to 2,000,000 gallons per year. This depends on the characteristics of the specific equipment and installation.
The water flow requirement per ton varies with the water temperature and the manufacturer's choice of design. As a general rule of thumb, a minimum flow of about 2.5 to 3 gpm for every 12,000 Btu per hour (ton) of heating and cooling will be needed (though some units specify flows as low as 1.5 gpm/ton for open-loop systems and 3 gpm/ton for closed-loop systems). For instance, one manufacturer says that if the ground water temperature is 55°F, the company's 3-ton (36,000 Btu) unit requires a flow rate of 2.5 to 3 gpm/ton. If the water temperature is 50°F, the required flow rate for this equipment in the heating mode grows to 5 gpm, while at forty-five degrees water must flow at the rate of 10 gpm. Water temperature has the opposite effect in cooling mode. The system should be designed to handle peak water consumption (including any ground water used for other domestic needs), whether peak consumption occurs during cooling or heating.
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Q: Are open-loop ground water GeoExchange systems viable everywhere?
A: Water use restrictions are more stringent in western states. These states adhere to the prior-appropriation system of water law. When disputes over water use arise, priority is given to parties having senior water rights. Many western states have also specified preferred uses that are given priority over other senior water rights.
Eastern states generally follow riparian water law, which specifies that the water flowing on or under one's land may be used as long as it is put to reasonable use. Generally, a riparian landowner is not subject to quantity limitations.
Thus, GeoExchange unit users are more likely to be subject to water quantity limitations in the western states. However, these limitations may only apply to commercial applications since domestic use of GeoExchange units may be considered a preferred use, exempt from most water use restrictions. As yet, few states have actually defined the status of GeoExchange unit systems in their statutes. Their status is therefore subject to interpretation of state regulatory agencies. Most state statutes describe domestic use in similar language.
Note: If water rights issues become too limiting, closed-loop systems may be required.
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Q: What do I do with the ground water in an open-loop system after the GeoExchange unit has used it?
A: A GeoExchange unit does not consume any water in the heat exchange process. If eight gallons of water go in the GeoExchange unit, eight gallons of water will come out. Thus, you will need a method to discharge this water.
Typical methods of discharge include returning the water to the aquifer from which it was extracted; secondary use of the water, such as industrial process applications or agricultural uses; evaporation and/or seepage ponds; and discharging to ponds, streams, rivers, lakes or the land surface. Naturally, it would be desirable to have plumbing installed to allow for secondary use of the discharge water, if this is permitted, for lawn and garden watering when the ground conditions warrant it.
Most sewer systems cannot handle the large volumes of water which GeoExchange units can produce (up to 10,000 or more gallons per day). Sewer lines may back up and tile fields will become overloaded, so disposal in sanitary sewers or septic systems is not recommended.
While ponds could be attractive and have multiple uses, they consume large amounts of land area, which would restrict their potential use in more densely populated areas. Discharge to the land surface may create bogs, accelerate pollutants leaching into ground water, and form icy areas in the winter. In addition, surface discharge in some areas may accelerate sinkhole activity.
Disposing of the water to a stream, river, or lake may be effective, but your local government may have specific regulations dealing with this issue. If the ground water used in the GeoExchange unit was of poor quality, discharging it to higher quality water will contaminate the discharge aquifer or body of water. Also, heating ground water may raise the temperature enough to be harmful to surface water dwelling creatures. Check with your local authorities before making your decision.
In close quarters, care must be taken so that the discharge doesn't infringe on a neighbor's property. Often, local ordinances prohibit any kind of discharge, and although variances can sometimes be obtained, they can be costly and time-consuming.
The disposal methods preferred by the National Ground Water Association, from a water conservation standpoint, are secondary use of the water and returning the water to the production aquifer.
When returning the water to the original aquifer, the water should remain in a closed system. There are several methods for returning the water to its aquifer. They are: using a single well for supply and disposal; using two wells and alternating withdrawal and disposal between the wells in winter and summer; and using two wells, but not alternating their function.
Single well -- For return of water in a supply well, approximately 100 feet of vertical separation is required for every 12,000 Btu of heating or cooling produced per hour. A typical domestic GeoExchange unit, with a 60,000 Btu capacity, would require 500 feet of separation in the well from the point of disposal to the point of supply. If 1000 feet of vertical separation were needed, it probably would be inadvisable to use this system. Higher drilling and pumping costs could make this system impractical in many areas. Also, local regulations may restrict the use of a single well for both potable water and return.
Two-well system (alternating) -- This method could take advantage of any temperature variations that may exist in the ground water from this process. In winter, a return well injects cooler water back into the aquifer. summer, the return well (now acting as a supply well) could withdraw this cooler water from the aquifer for more efficient cooling. The second well could be used in a similar way for warmer water. Alternating supply and return may also be beneficial as a preventive maintenance measure. The alteration in each well helps prevent clogging of the well screen, a common problem. This method of design is rarely practiced, probably due to its larger initial investment. The system would require an additional pump (one per well) and more piping compared to other systems.
Two-well system (nonalternating) -- A general rule to follow is to drill the return well to the same aquifer at the same depth as the producing well. Return wells in sand and gravel aquifers must have a screen to help prevent incrustation and facilitate water movement. Water is always returned below the water level to reduce precipitation of dissolved solids on the well casing.
If a return well is drilled, it must be placed far enough from the supply well to prevent an overlapping thermal effect between the two wells. Raphael G. Kazman in his report, Use of Twin Wells and Water-Source Geothermal Units for Energy Conservation in Louisiana, created a table for use by the project engineer or designer to approximate the needed spacing between the production and return wells. These wells alternate their roles: the well used for production in the summer is used for return in the winter and vice versa.
Kazman reported that if each house in an entire housing development were equipped with twin wells and GeoExchange units, the return water of one property owner might be pumped by his neighbor. The studies he conducted indicate that to maintain the same well discharges without danger of interference with neighbors, the spacing between the twin wells must be increased, possibly as much as 20 percent or more. To minimize interference and short-circuiting between neighboring sets of twin wells, the summer well should always be located on the street side of any lot, and the winter well should be drilled in the backyard, he says.
Two wells, even in the same aquifer, keep the temperature difference separate, if properly spaced, because underground water flows so slowly. The spacing of the supply and return wells is dependent upon several variables, among which are:
- selection of the optimum GeoExchange unit based on available well capacity and operating cost
- the length of the critical season of operation (overall duration of the heating season in the North, air-conditioning season in the south)
- the actual number of days that the GeoExchange unit will be called upon to operate and the percentage of time during those days that it will actually be in operation
- the aquifer characteristics: permeability, thickness, and specific capacity.
Spacing the supply and return wells at least 100 feet apart are best for most locations. For good aquifer conditions, this spacing might be less, while greater spacing may be necessary for poor aquifer conditions. The return well has to be constructed as well as, or better than, the supply well--it is not just a dumping hole.
Theoretically, an aquifer will accept the same amount of water that it will yield. In reality, however, it will only accept 75 to 80 percent of its yield in return. Therefore, an aquifer that will yield 18 gpm will only accept approximately 14 gpm and the remaining 4 gpm will run out on the ground. The contractor and homeowner should be concerned about the possible plugging of the return well by deposits of sand or high amounts of iron being present in the ground water. Air dissolved in the water can also induce corrosion.
It should be noted that in aquifers with low permeability, gravity feeding of return water might not provide sufficient pressure to allow infiltration into the aquifer. If the discharge water is returned to an aquifer other than the supply aquifer, and the two aquifers are separated by a thickness of low-permeability material, interference should be minimal or nonexistent.
Supply and return aquifers must be chemically compatible to assure that mixing of the two water types does not result in precipitation of salts or hydroxides from solution, which might lead to eventual plugging of the aquifer surrounding the return well.
Local policies vary widely concerning the use of return wells. Several states, including Wisconsin and Minnesota, do not allow any type of underground injection return at this time. Several others have adopted a general policy to discourage this type of disposal method. On the other hand, Oregon encourages return of this water. Many of the other states have some form of permit or notification procedure.
Enforcement is often lax, however, particularly for small domestic systems. Regulatory agencies commonly have statutory authority to regulate these systems but no formal program. More than one-third of the states have no permit or notification requirements.
Regulations for return of water to surface water generally correspond to the federal National Pollutant Discharge Elimination System standards. Disposal to a leach field and septic tanks is generally not a problem, but is usually not recommended. However, many states require that septic tanks be spaced a certain distance (generally around 50 feet) from a well.
Disposal to sewers is regulated on the state level in only four states. The state of Minnesota, for example, had forbidden for many years the use of any type of return well. The law was amended in late 1981 to allow the construction of a minimum number of return wells.
Provisions of the law said that the wells must withdraw from and return to the same aquifer, the wells must be constructed so as to allow for inspection of water quality and temperature, the system must be constructed as a completely closed system which is sealed against the introduction of foreign substances, and the owner must agree to allow inspections by the health department. The law does not allow for a domestic supply well to be used in conjunction with a GeoExchange unit. Again, remember to check with your local officials.
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Q: Won't I be in danger of depleting my property's ground water supply, not to mention my neighbor's, if I have a GeoExchange unit installed?
A: Most
problems regarding GeoExchange unit dewatering have stemmed from improper
determination of well yield. Domestic wells are normally designed
to produce enough water for household use only, which is usually 300
to 400 gallons per day. Ground water heating may require 10,000 gallons
of water or more per day in extremely cold weather. An adequate water
well design for household usage may not be sufficient to also sustain
a GeoExchange unit.
Uncontrolled overpumping
and overdevelopment of the ground water may cause problems such as
aquifer drawdown and well interference. Aquifer drawdown indicates
that more water is being withdrawn from the aquifer than is being
replaced and usually manifests itself by smaller yields, lower water
levels in wells, and higher pumping costs.
Pumping a well
usually creates a cone-shaped depression of the water table (the two-dimensional
surface representing the top of the ground water), with the lowest
point on the cone being the well location where the water is being
pumped. With overpumping, two or more closely spaced wells may have
an overlapping of their individual cones of depression. This is called
well interference and also is reflected by lower well yields, as some
of the available ground water must now supply two or more wells instead
of one.
The way to prevent
water-level declines is not to pump water to waste when the well is
used to supply water to the GeoExchange unit, but to use it and then
return it to the aquifer through a return well.
The spent water,
which may have been used in the summertime to remove heat from the
interior of a building, will be warmer than the native ground water.
In the winter, on the other hand, it is cooler than the sources of
ground water. The spent water, if returned too close to the production
well, will break through or shortly appear in the production stream.
Thus, if the volumes pumped during each season are nearly equal, the
temperature of the ground water will not change significantly even
after a decade or more of operation.
Whether the water
is returned into the same producing aquifer by way of the supply well
or a second well, no aquifer drawdown or well interference will occur.
Management of
the heat balance within an aquifer is essential in urban areas where
heat transfers between several users may have to be coordinated. Spacing
of private domestic wells is likely to depend on property boundaries
rather than the hydrologic characteristics of the aquifer under development.
Random installation of GeoExchange units could lead to thermal interference
through improper well spacing. Efficiency of the GeoExchange system
would be considerably reduced where a sufficient amount of interference
exists.
Through careful
planning and analysis of the aquifer prior to housing construction,
it is possible to avoid the problem of well interference. Production
and injection wells can be spaced for optimum dissipation of thermal
energy within the aquifer. Well spacing should be based on the heating
and cooling load for the proposed number of residential units to be
built at a given location, as well as the hydrologic properties of
the aquifer to ensure the efficient utilization of ground water for
the operation of GeoExchange units. Thus, it is crucial that the well
yield be correctly and accurately determined by a qualified contractor.
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Q: What if I can't use a well?
A: Water-to-air
GeoExchange units, as the term suggests, can be adapted to water supplies
other than wells, such as a freshwater lake or a stream. Another alternative
to a well system would be a closed-loop, earth-coupled system.
The closed-loop
GeoExchange system requires only that the heat exchanger be buried
in solid contact with the earth. In using closed-loop exchangers,
there is no depletion of the aquifer, since no water is withdrawn
from the ground. The earth-coupled exchanger is filled one time with
potable water or other heat exchanger fluids; therefore, it does not
contaminate the GeoExchange unit by precipitating out minerals from
the soil.
Two general types
of earth-coupled systems have been used with GeoExchange units. The
first type is a vertical heat exchanger. The second type is the earth-coil
or horizontal heat exchanger. A serpentine length of plastic pipe
buried four to six feet below the earth's surface is called an earth-coil
or ground loop.
Both horizontal
and vertical earth-coupled exchangers utilize low-wattage circulator
pumps to send water from the GeoExchange unit out through the continuous
closed-loop to exchange heat with the earth, and then back to the
GeoExchange unit.
The vertical heat
exchanger is typically constructed using water well drilling equipment.
The water from the GeoExchange unit is circulated through the vertical
loops of piping, exchanging heat with the earth before returning to
the GeoExchange unit. This flow is achieved by means of a low-wattage,
inexpensively operated circulation pump. Vertical heat exchanger piping
is filled with water or a water/nontoxic antifreeze mixture (depending
on location), pressure-tested, and sealed. A vertical closed-loop
system does not draw water from the earth.
The horizontal
serpentine earth-coil has two plastic exchanger pipes in a single
trench typically dug 2 to 3 feet wide and 6-feet deep. In the case
of a double layer design, the trench is partially backfilled after
laying the first pipe, then completely backfilled after the second.
In urban areas, earth coils can be laid out in a curved pattern around
the boundary of a lot.
Heat exchange
will drop to only 10 to 20 percent of normal performance if the soil
around the pipe becomes dry. When multiple pipes are to be buried
in the same trench, the horizontal or vertical separation required
between pipes is two feet. The length of the earth-coil required will
vary with the climate and soil conditions.
For example, in
Oklahoma where many of these systems have been installed, approximately
300 linear feet of wetted pipe or 450 linear feet of dry pipe per
nominal ton of GeoExchange unit cooling capacity is required.
In the northern
U.S. where heating is clearly dominant and cooling is of minor importance,
10 to 25 percent of propylene glycol USP should be used in the closed
loop vertical heat exchanger to prevent freezing of the water in the
GeoExchange unit exchanger.
Using current
technology, a properly sized GeoExchange unit, duct system, water
piping and water pump can provide a midwinter COP (coefficient of
performance), according to advocates of the earth-coupled GeoExchange
unit, of up to 4.2 with proper loop field design and good soil conditions.
Averages are somewhat lower in northern climates, but rise in the
middle U.S. Their performance is reported to be higher in autumn and
spring.
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Q: If I live in the city, can I use a GeoExchange unit?
A: GeoExchange
units can be installed in some urban and suburban areas if they utilize
dedicated water systems not interconnected with the domestic water
or sanitary systems.
Several houses,
all the apartments in a building or an entire community could be looped
into a network of ground water distribution and return, if conditions
were right. In addition, vertical closed-loop systems can be installed
in urban and suburban areas where the bore holes can be drilled in
parking lots, open plazas, or even under the footprint of new buildings,
if the bores are drilled and the loops installed before building construction
begins. Open-loop, two-well systems can even be installed if land
area is sufficient to permit proper well spacing, aquifer capacity
is sufficient, and local regulations permit.
In short, it is
technically feasible to use a GeoExchange unit in a city or a suburb.
However, local government restrictions or local ground water or geologic
conditions may limit its use, so be sure to check with your appropriate
authorities.
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Q: If GeoExchange units are so terrific, why didn't people use them long ago?
A: Nicholas
Carnot first proposed the basic principle of the GeoExchange unit
in 1824. This theory was advanced 30 years later when Lord Kelvin
proposed that refrigerating equipment could be used for heating. But,
because of cheap, readily available fossil fuels, the GeoExchange
unit remained a researcher's curiosity until the mid-1930s when several
manufacturers designed custom systems using the GeoExchange unit for
comfort heating. Following the delays caused by World War II, commercial
production of GeoExchange units began in 1952 and production and use
has continued to grow since.
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Q: Why am I just now learning about GeoExchange units?
A: Most
homes have natural gas, fuel oil, or propane space and hot water heating
systems. Much of this equipment is relatively inefficient, but these
fossil fuels were abundant and cheap when it was installed. Subsequent
fuel price increases, though, have significantly increased the cost
of heating with these systems.
In addition, according
to the National Ground Water Association, there has been a general
ignorance about ground water. Many mistakenly believed ground water
resources were limited. Also, many believed GeoExchange units were
only able to utilize ground water of 60°F or warmer, ground water
contained chemicals which would promote corrosion or scaling of the
heat exchanger, or ground water flowed in underground rivers
or veins that required a water witch to locate them. Of course, as
we have already shown, these beliefs were false.
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Q: How can I get more information on GeoExchange units for my specific applications?
A: We suggest
that you contact your local heating and air-conditioning contractor.
If they can't help you, contact local HVAC suppliers, electric cooperatives,
HVAC trade organizations or the National Ground Water Association
for a list of contractors in your area who are familiar with GeoExchange
units.
The following
materials are suggested for more information on ground water, wells,
and GeoExchange units:
| Publication | Category | Cost |
| American's Priceless Ground Water Resource | consumer literature | $1.00 |
| Ground Water Heat Pumps | consumer literature | $1.00 |
| When You Need a Water Well | consumer literature | $1.00 |
| Guidelines for the Construction of Vertical Boreholes for Closed Loop Heat Pump Systems | technical manual | $30.00 |
You may purchase listed publications from:
National Ground Water Association
601 Dempsey Road
Westerville, Ohio 43081
(800) 551-7379
614-898-7786 fax
ngwa@ngwa.org or visit www.ngwa.org
Additional
information sources:
Geothermal
Heat Pump Consortium
701 Pennsylvania Avenue, NW
Washington, DC 20004-2696
202-508-5500
www.ghpc.org
Geo-Heat Center
3201 Campus Drive
Klamath Falls, Oregon 97601
541-885-1750
geoheat.oit.edu
International
Ground-Source Heat Pump Association
490 Cordell South
Oklahoma State University
Stillwater, Oklahoma 74078-8018
800-626-4747
www.igshpa.okstate.edu
American Society
of Heating, Refrigeration, and Air Conditioning Engineers
1791 Tullie Circle NE
Atlanta, Georgia 30329
404-636-8400
www.ashrae.org
Air Conditioning
and Refrigeration Institute
4301 N. Fairfax Drive
Arlington, VA 22203
703-524-8800
www.ari.org
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