How Home Geothermal Power Plant Systems Work

Here is how you can have a heating and air conditioning system in your home that can:
• Save energy and slash electric bills,
• Cut greenhouse gas emissions,
• Rid your yard of unsightly outdoor
equipment,
• Drastically reduce the cost of your
hot water, and
• Reduce maintenance costs
Costs will be lowered even as it improves the year-round comfort of your home.
This not science fiction, home geothermal heat pump systems are already installed and saving homeowners thousands of dollars a year. In fact, such units, called geoexchange systems, offer such a lengthy list of benefits that at first glance they do seem too good to be true. Their benefits, though, flow directly from the clever application of sound technology—what you can think of as good science. Once you understand how geoexchange systems work, you’ll understand how they can bring such an attractive list of benefits to your home.

What They Do
Geothermal heating and cooling systems provide heat in the winter and cooling in the summer, at efficiencies that are far better than those for most alternative systems. Like conventional heat pumps, they are essentially air conditioners that can also run in reverse to provide heat in the winter. The primary difference is that they rely on the nearly constant temperature of the earth for heat transfer instead of the widely fluctuating temperatures of the outside air. That is the key to the geoexchange unit’s surprising efficiency.

How They Work
Geothermal heat pump exchange systems, just like common heat pumps and air conditioners, make use of a refrigerant to help transfer (or pump) heat into and out of your home. The refrigerant helps the geothermal plant system take advantage of two primary principles of heat transfer:
1. Heat energy always flows from areas of higher temperature to areas of lower temperature.
2. The greater the difference in temperature between two adjacent areas, the higher the rate of heat transfer between them.
Refrigerators, air conditioners, and heat pumps all operate by pumping refrigerant through a closed loop in a way that creates two distinct temperature zones—a cold zone and a hot zone. The simplest example of such a system is the universally familiar home refrigerator. In a refrigerator, a fan blows the air inside the box over tubes containing refrigerant that is very cold (typically below 0°F). Heat flows from the interior air to the cooler refrigerant. The refrigerant is then pumped to the high-temperature section, which is exposed to room air outside the refrigerator box. Because the refrigerant is hot in this zone, it gives up heat to the relatively cooler air in the room, before flowing back to the cold zone to begin the loop again. An air conditioner works in exactly the same way, except that it extracts heat from the air inside a room or building and transfers it to the air outside the building. A conventional heat pump adds a reversing capability, so the hot zone and the cold zone can be switched. With the zones reversed, it can extract heat from the outside air in the winter and transfer it inside. Granted, being able to extract heat from frigid winter air seems like it shouldn’t work. But it will if we can expose the cold air to refrigerant that’s even colder than it is. And modern heat pumps can do that. If the outside air gets extremely cold, though, a heat pump just can’t make the temperature of the cold zone low enough. That’s when supplemental electric heating elements kick in. Working much like a toaster, they supply warmth to the house, but at very high relative cost.

Refrigerant cold zone Refrigerant hot zone
Typical home refrigerator Heat flows from areas of higher temperature to areas of lower temperature. Cooled air returns to inside of
refrigerator Air inside refrigerator flows over very cold refrigerant coils, giving up heat Warmed room air carries away heat from interior Room air is drawn over hot refrigerant coils Compressor pumps refrigerant through system circulating fan of an efficient Geothermal heat exchange pump, while relatively simple to operate, face one major challenge; their operating efficiency is lowest when demand is highest; that is, heat pumps have to work hardest when we want the most from them. As we’ve just seen, a regular heat pump extracts heat energy from outside air in winter, and rejects heat to outside air in summer. Unfortunately, the colder the outside air, the more difficult it is to extract heat from it, and the hotter the outside air, the harder it is to transfer heat to it. The temperature difference between the air and the refrigerant is small in both cases, lowering heat transfer rates within the system. Yet, the colder it gets outside, the higher the rate of heat loss through windows, around doors, and through walls and roofs, and the more heat we need to pump inside to keep indoor temperatures comfortable. In summer, we face a similar dilemma. The hotter it gets outside, the higher the rate of heat infiltration into the house, and the more heat removal we need to maintain comfort. A geothermal exchange system eliminates this dilemma by using the relatively constant temperature of the earth as a heat source in winter and a heat sink in summer, instead of outside air. Throughout most of the U.S., the temperature of the ground below the frost line (about 3 to 5 feet below the surface) remains at a nearly constant temperature, generally in the 45°–50°F range in northern lattitudes, and in
the 50°–70°F range in the south. So, in the winter, a geoexchange unit can extract heat from ground that’s relatively warm compared to the cold outside air, and in the summer, it can discharge heat to ground that is relatively cool, compared to the hot outside air. Since the difference between the refrigerant temperature and the ground temperature remains relatively high in both seasons, so do heat transfer rates. Consequently, the geothermal heat pump exchange system operates at much higher year round efficiencies than a standard heat pump.
The Cleanliness of Geothermal Heating and Cooling Pump Systems
Installing a geothermal system is environmentally responsible. Since a geoexchange system merely transfers heat from the ground into your home in winter, you don’t need to burn any fossil fuels to create a warm interior environment. This approach drastically reduces
carbon dioxide emissions (a greenhouse gas) compared with the operation of other heating systems, and completely eliminates the heating system as a potential source of carbon monoxide fumes within your home— making a geothermal heating & cooling pump system an
environmentally friendly as well as safe and healthy alternative to traditional oil and gas furnaces.

Making The Ground Connection
The unique aspect of the geoexchange system, and the key to its lengthy list of benefits, is the ground loop. The ground loop provides the means of transferring heat to the earth in summer, and extracting heat from the earth in winter. Physically, the “ground loop” consists of several lengths of plastic pipe typically installed either in horizontal trenches or vertical holes that are subsequently covered with earth and landscaping of your choice. Water inside the ground loop piping is pumped through a heat exchanger in the  geoexchange unit. In the summer, it absorbs heat from the refrigerant hot zone and carries it to the ground through the ground loop piping. In winter, it absorbs heat from the earth through the ground loop, and then transfers that heat to the refrigerant cold zone.
The length of the ground loop will be determined by the heating and cooling loads, which are determined in turn by the size of your home, its design and construction, its orientation, and the climate where you live. Whether the ground loop is most efficiently installed in horizontal trenches or in vertical bore holes depends on the type of soil near the surface (rocky, sandy, clay-laden, etc.), the geology of the deeper terrain in your area, and the amount of land available. Generally, horizontal loops are less
expensive to install, but require more land area. Vertical holes require much less land area, but require the expense of drilling.
Another ground connection scheme—called an open loop system— involves using wells instead of closed loop piping. Where water is plentiful, it can be pumped out of a well, through the heat exchanger at the geothermal heat pump unit, and then pumped back into another well to return to the groundwater. Since the water merely absorbs or gives up heat, but is not altered in any other way, it leaves the geoexchange unit as pure as it was when it entered it. Any one of these installation schemes results in the same high efficiency, when properly sized. Moreover, once the ground loop is installed, you can typically forget about it. The polyethylene piping (the same type used for cross-country natural gas lines) does not degrade, corrode, or break down in ground or water contact, so sound installations are expected to last 50 years or more.

Free Hot Water
As a side benefit, most geothermal systems can be designed to produce free hot water during the summer, by using waste heat extracted from the interior air during the air conditioning season. Even in the winter, the geoexchange unit can often help to reduce the use of electricity or gas by the hot water heater.

Premium Comfort Year Round
One of the complaints often heard from the owners of standard heat pumps is that the air coming from the vents in the winter is cool, creating a sense of draftiness. While the air is actually warmer than room temperature by several degrees, it is much cooler than the
average person’s skin temperature. Heat transfer principle #1 says that heat will flow from our skin (an area of warmer temperature) to the air coming from the vents (an area of cooler temperature). And that makes the air feel cold and “drafty.” Home geothermal power plant systems don’t have this problem. Because the ground temperature is much warmer than typical winter air temperatures, the geothermal heat pump exchange system can make the air much warmer than our skin—typically well over 100°F. Since the air from the vents is at a higher temperature than our skin, heat flows from the air to our skin, making us feel warm and cozy. Geothermal heat pump exchange systems also provide superior year-round humidity control, and modular designs often make zoned heating and air conditioning practical— for even more comfort  control through the entire house.

Standard Home Air Conditioner Geothermal Exchange System
(Cooling Mode)
Room air returns to air handler Room air returns to air handler Cooled air is distributed through the house via ductwork Cooled air is
distributed through the house via ductwork In cold zone, refrigerant absorbs heat from circulating interior air Pressure reducer
Compressor
Room air
returns to
air handler
Room air
returns to
air handler
Cooled air is
distributed
through the
house via
ductwork
Cooled air is
distributed
through the
house via
ductwork
In cold zone,
refrigerant
absorbs heat
from circulating
interior air
Pressure reducer
Compressor
Outside air carries away
heat from house interior
Fan in center of
unit pulls outside
air across hot
refrigerant coils
Ground loop releases
heat to cool earth
Ground loop
releases heat
to cool earth
Hot refrigerant flows
through coils, releasing
heat to cooler water in
ground loop
Note the absence of visible
outdoor equipment
Hot outside air
temperatures
Relatively cool
ground

sequently covered with earth and
landscaping of your choice.
Water inside the ground loop piping
is pumped through a heat
exchanger in the geoexchange unit. In
the summer, it absorbs heat from the
refrigerant hot zone and carries it to
the ground through the ground loop
piping. In winter, it absorbs heat from
the earth through the ground loop,
and then transfers that heat to the
refrigerant cold zone.
The length of the ground loop will
be determined by the heating and
cooling loads, which are determined
in turn by the size of your home, its
design and construction, its orientation,
and the climate where you live.
Whether the ground loop is most efficiently
installed in horizontal trenches
or in vertical bore holes depends on
the type of soil near the surface
(rocky, sandy, clay-laden, etc.), the
geology of the deeper terrain in your
area, and the amount of land available.
Generally, horizontal loops are less
expensive to install, but require more
land area. Vertical holes require much
less land area, but require the expense
of drilling.
Another ground connection
scheme—called an open loop system—
involves using wells instead of
closed loop piping. Where water is
plentiful, it can be pumped out of a
well, through the heat exchanger at
the geoexchange unit, and then
pumped back into another well to
return to the groundwater. Since the
water merely absorbs or gives up
heat, but is not altered in any other
way, it leaves the geoexchange unit as
pure as it was when it entered it.
Any one of these installation
schemes results in the same high efficiency,
when properly sized.
Moreover, once the ground loop is
installed, you can typically forget
about it. The polyethylene piping (the
same type used for cross-country natural
gas lines) does not degrade, corrode,
or break down in ground or
water contact, so sound installations
are expected to last 50 years or more.
Free Hot Water
As a side benefit, most geoexchange
systems can be designed to produce
free hot water during the summer, by
using waste heat extracted from the
interior air during the air conditioning
season.
Even in the winter, the
geoexchange unit can often help to
reduce the use of electricity or gas by
the hot water heater.
Premium Comfort Year Round
One of the complaints often heard
from the owners of standard heat
pumps is that the air coming from the
vents in the winter is cool, creating a
sense of draftiness.
While the air is actually warmer
than room temperature by several
degrees, it is much cooler than the
average person’s skin temperature.
Heat transfer principle #1 says that
heat will flow from our skin (an area
of warmer temperature) to the air coming
from the vents (an area of cooler
temperature). And that makes the air
feel cold and “drafty.”
Geoexchange systems don’t have
this problem. Because the ground temperature
is much warmer than typical
winter air temperatures, the
geoexchange system can make the air
much warmer than our skin—typically
well over 100°F.
Since the air from the vents is at a
higher temperature than our skin, heat
flows from the air to our skin, making
us feel warm and cozy.
Geoexchange systems also provide
superior year-round humidity control,
and modular designs often make zoned
heating and air conditioning practical—
for even more comfort control
through the entire house.
Room air
returns to
air handler
Room air
returns to
air handler
Warmed air
is distributed
through the
house via
ductwork
Warmed air
is distributed
through the
house via
ductwork
In hot zone,
refrigerant
gives up heat
to circulating
interior air
Pressure reducer
Compressor
Ground loop absorbs
heat from warm earth
Ground loop
absorbs heat
from warm
earth
Cold refrigerant flows
through coils, absorbing
heat from warmer
water in ground loop
Geoexchange System
(Heating Mode)
Cold outside air
temperatures
Relatively warm
ground
Page 3

From Adobe-

Geothermal Heating & Cooling System Facts
· The U.S. Environmental Protection Agency has identified geothermal heat pumps as a
technology that significantly reduces greenhouse gas and other air emissions associated
with heating, cooling and water heating residential buildings, while saving consumers money,
compared to conventional technologies.1 For every 100,000 units of typically sized
residential geothermal heat pumps installed, more than 37.5 trillion Btu’s of energy used for
space conditioning and water heating can be saved, corresponding to an emissions
reduction of about 2.18 million metric tons of carbon equivalents, and cost savings to
consumers of about $750 million over the 20-year-life of the equipment.
· Geothermal heat pump systems, also known as “geoexchange,” are the most energyefficient,
environmentally clean, and cost-effective space conditioning systems available,
according to the Environmental Protection Agency.1
· Geothermal heat pumps strengthen U.S. energy security. Every 100,000 homes with
geothermal heat pump systems reduce foreign oil consumption by 2.15 million barrels
annually and reduce electricity consumption by 799 million kilowatt hours annually.
· Geothermal heat pumps are efficient. The use of geoexchange lowers electricity demand by
approximately 1 kW per ton of capacity.
· Geothermal heat pumps are environmental. They generate no on site emissions and have
the lowest emissions among all heating and cooling technologies. 1
· Geothermal heat pumps save money. Schools now using geothermal heat pump systems
save more than $25 million in energy costs – meaning more money for books, equipment
and teachers. Homeowners can save 25 to 50 percent on home electric bills compared to
conventional heating and cooling systems. Electric bills for a 2,000 sq. ft. home can be
reduced to as low as $1 a day, using a geoexchange system.
· Geoexchange systems represent a savings to homeowners of 30 to 70% in the heating
mode and 20 to 50% in the cooling mode, compared to conventional systems.
· EPA found that geoexchange heating and cooling systems can reduce energy
consumption—and corresponding emissions—by more than 40% compared to air source
heat pumps and by over 70% compared to electric resistance heating with standard
air-conditioning equipment.
· Geoexchange systems use the Earth’s energy storage capability to heat and cool buildings,
and to provide hot water. The earth is a huge energy storage device that absorbs 47% of the
sun’s energy – more than 500 times more energy than mankind needs every year – in the
form of clean, renewable energy. Geoexchange systems take this heat during the heating
season at an efficiency approaching or exceeding 400%, and return it during the cooling
season.
GeoExchange Heating and Cooling
Systems: Fascinating Facts
· EPA found that, even on a source fuel basis – accounting for ALL losses in the fuel cycle
including electricity generation at power plants – geoexchange systems are much more
efficient than competing fuel technologies. They are an average of 48% more efficient than
the best gas furnaces on a source fuel basis, and over 75% more efficient than oil furnaces.
In fact, today’s best geoexchange systems outperform the best gas technology, gas heat
pumps, by an average of 36% in heating mode and 43% in cooling mode!
· The U.S. General Accounting Office estimates that if geoexchange systems were installed
nationwide, they could save several billion dollars annually in energy costs and substantially
reduce pollution.2
· Surveys by utilities indicate a higher level of consumer satisfaction for geoexchange systems
than for conventional systems. Polls consistently show that more than 95% of all
geoexchange customers would recommend geoexchange to a family member or friend.
· Today there are now more than 1,000,000 geoexchange installations in the United States.
The current use of geothermal heat pump technology has resulted in the following emissions
reductions:
? Elimination of more than 5.8 million metric tons of CO2 annually
? Elimination of more than 1.6 million metric tons of carbon equivalent annually
· These 1,000,000 installations have also resulted in the following energy consumption
reductions:
? Annual savings of nearly 8 billion kWh
? Annual savings of nearly 40 trillion Btus of fossil fuels
? Reduced electricity demand by more than 2.6 million kW
· The monumental impact of the current use of geoexchange is equivalent to:
? Taking close to 1,295,000 cars off the road
? Planting more than 385 million trees
? Reducing U.S. reliance on imported fuels by 21.5 million barrels of crude oil
per year.

What is Geoexchange?

How it Works

How it Works Movie
Slide Show: Modern Heating & Cooling for Historic Structures
Commonly Asked Questions
Comparing Systems
Homeowners in virtually every region of the United States are enjoying a high level of comfort and significantly reducing their energy use today with geoexchange (geothermal) heating and cooling.

This marvelous technology relies primarily on the Earth’s natural thermal energy, a renewable resource, to heat or cool a house or multi-family dwelling. The only additional energy geoexchange systems require is the small amount of electricity they employ to concentrate what Mother Nature provides and then to circulate high-quality heating and cooling throughout the home.

Homeowners who use geoexchange systems give them superior ratings because of their ability to deliver comfortably warm air, even on the coldest winter days, and because of their extraordinarily low operating costs. As an additional benefit, geoexchange systems can provide inexpensive hot water, either to supplement or replace entirely the output of a conventional, domestic water heater.

Geoexchange heating and cooling is cost effective because it uses energy so efficiently.1 This makes it very environmentally friendly, too. For these reasons, federal agencies like the Environmental Protection Agency and the Department of Energy, as well as state agencies like the California Energy Commission, endorse it.

Owners of geoexchange systems can relax and enjoy high-quality heating and cooling year after year. Geoexchange systems work on a different principle than an ordinary furnace/air conditioning system, and they require little maintenance or attention from homeowners. Furnaces must create heat by burning a fuel–typically natural gas, propane, or fuel oil. With geoexchange systems, there’s no need to create heat, hence no need for chemical combustion. Instead, the Earth’s natural heat is collected in winter through a series of pipes, called a loop, installed below the surface of the ground or submersed in a pond or lake. Fluid circulating in the loop carries this heat to the home. An indoor geoexchange system then uses electrically-driven compressors and heat exchangers in a vapor compression cycle–the same principle employed in a refrigerator–to concentrate the Earth’s energy and release it inside the home at a higher temperature. In typical systems, duct fans distribute the heat to various rooms.

In summer, the process is reversed in order to cool the home. Excess heat is drawn from the home, expelled to the loop, and absorbed by the Earth. Geoexchange systems provide cooling in the same way that a refrigerator keeps its contents cool–by drawing heat from the interior, not by injecting cold air.

Geoexchange systems do the work that ordinarily requires two appliances, a furnace and an air conditioner. They can be located indoors because there’s no need to exchange heat with the outdoor air. They’re so quiet homeowners don’t even realize they’re on. They are also compact. Typically, they are installed in a basement or attic, and some are small enough to fit atop a closet shelf. The indoor location also means the equipment is protected from mechanical breakdowns that could result from exposure to harsh weather.

Geoexchange works differently than conventional heat pumps that use the outdoor air as their heat source or heat sink. Geoexchange systems don’t have to work as hard (which means they use less energy) because they draw heat from a source whose temperature is moderate. The temperature of the ground or groundwater a few feet beneath the Earth’s surface remains relatively constant throughout the year, even though the outdoor air temperature may fluctuate greatly with the change of seasons. At a depth of approximately six feet, for example, the temperature of soil in most of the world’s regions remains stable between 45 F and 70 F. This is why well water drawn from below ground tastes so cool even on the hottest summer days.

In winter, it’s much easier to capture heat from the soil at a moderate 50o F. than from the atmosphere when the air temperature is below zero. This is also why geoexchange systems encounter no difficulty blowing comfortably warm air through a home’s ventilation system, even when the outdoor air temperature is extremely cold.2 Conversely, in summer, the relatively cool ground absorbs a home’s waste heat more readily than the warm outdoor air.

Studies show that approximately 70 percent of the energy used in a geoexchange heating and cooling system is renewable energy from the ground. The remainder is clean, electrical energy which is employed to concentrate heat and transport it from one location to another. In winter, the ground soaks up solar energy and provides a barrier to cold air. In summer, the ground heats up more slowly than the outside air.

Making Hot Water

Geoexchange systems can also provide all or part of a household’s hot water. This can be highly economical, especially if the home already has a geoexchange system, hence a ground loop, in place.

One economical way to obtain a portion of domestic hot water is through the addition of a desuperheater to the geoexchange unit. A desuperheater is a small, auxiliary heat exchanger that uses superheated gases from the heat pump’s compressor to heat water. This hot water then circulates through a pipe to the home’s water heater tank. In summer, when the geoexchange system is in the cooling mode, the desuperheater merely uses excess heat that would otherwise be expelled to the loop. When the geoexchange unit is running frequently, homeowners can obtain all of their hot water in this manner virtually for free. A conventional water heater meets household hot water needs in winter if the desuperheater isn’t producing enough, and in spring and fall when the geoexchange system may not be operating at all.

Because geoexchange systems heat water so efficiently, many manufacturers today are also offering triple function geoexchange systems. Triple function systems provide heating, cooling and hot water. They use a separate heat exchanger to meet all of a household’s hot water needs.

The Earth Connection

Once installed, the loop in a geoexchange system remains out of sight beneath the Earth’s surface while it works unobtrusively to tap the heating and cooling nature provides. The loop is made of a material that is extraordinarily durable but which allows heat to pass through efficiently. This is important so it doesn’t retard the exchange of heat between the Earth and the fluid in the loop. Loop manufacturers typically use high-density polyethylene, a tough plastic. When installers connect sections of pipe, they heat fuse the joints. This makes the connections stronger than the pipe itself. Some loop manufacturers offer up to 50-year warranties. The fluid in the loop is water or an environmentally safe antifreeze solution that circulates through the pipes in a closed system.

Another type of geothermal heating and cooling is Direct geoexchange (DX) systems, which utilize copper piping placed underground. As refrigerant is pumped through the loop, heat is transferred directly through the copper to the earth.

To ensure good results, the piping should be installed by professionals who follow procedures established by the International Ground Source Heat Pump Association (IGSHPA). Installers should be certified by IGSHPA or be able to show equivalent training by manufacturers or other recognized authorities at a recognized institution, such as one of the many regional geoexchange training centers located throughout the United States.

The length of the loop depends upon a number of factors, including the type of loop configuration used; a home’s heating and air conditioning load; soil conditions; local climate; and landscaping. Larger homes with larger space conditioning requirements generally need larger loops than smaller homes. Homes in climates where temperatures are extreme also generally require larger loops. A heat loss/heat gain analysis should be conducted before the loop is installed.

Types of Loops

Most loops for residential geoexchange systems are installed either horizontally or vertically in the ground, or submersed in water in a pond or lake. In most cases, the fluid runs through the loop in a closed system, but open-loop systems may be used where local codes permit. Each type of loop configuration has its own, unique advantages and disadvantages, as explained below:

Horizontal Ground Closed Loops. This configuration is usually the most cost effective when adequate yard space is available and trenches are easy to dig. Workers use trenchers or backhoes to dig the trenches three to six feet below the ground, then lay a series of parallel plastic pipes. They backfill the trench, taking care not to allow sharp rocks or debris to damage the pipes. Fluid runs through the pipe in a closed system. A typical horizontal loop will be 400 to 600 feet long per ton of heating and cooling capacity. The pipe may be curled into a slinky shape in order to fit more of it into shorter trenches, but while this reduces the amount of land space needed it may require more pipe. Horizontal ground loops are easiest to install while a home is under construction. However, new types of digging equipment that allow horizontal boring are making it possible to retrofit geoexchange systems into existing homes with minimal disturbance to lawns. Horizontal boring machines can even allow loops to be installed under existing buildings or driveways.

Vertical Ground Closed Loops. This type of loop configuration is ideal for homes where yard space is insufficient to permit horizontal buildings with large heating and cooling loads, when the Earth is rocky close to the surface, or for retrofit applications where minimum disruption of the landscaping is desired. Contractors bore vertical holes in the ground 150 to 450 feet deep. Each hole contains a single loop of pipe with a U-bend at the bottom. After the pipe is inserted, the hole is backfilled or grouted. Each vertical pipe is then connected to a horizontal pipe, which is also concealed underground. The horizontal pipe then carries fluid in a closed system to and from the geoexchange system. Vertical loops are generally more expensive to install, but require less piping than horizontal loops because the Earth deeper down is alternatingly cooler in summer and warmer in winter.

Pond Closed Loops. If a home is near a body of surface water, such as a pond or lake, this type of loop design may be the most economical. The fluid circulates through polyethylene piping in a closed system, just as it does in the ground loops. Typically, workers run the pipe to the water, then submerge long sections under water. The pipe may be coiled in a slinky shape to fit more of it into a given amount of space. Geoexchange experts recommend using a pond loop only if the water level never drops below six to eight feet at its lowest level to assure sufficient heat-transfer capability. Pond loops used in a closed system result in no adverse impacts on the aquatic system.

Open Loop System. This type of loop configuration is used less frequently, but may be employed cost-effectively if ground water is plentiful. Open loop systems, in fact, are the simplest to install and have been used successfully for decades in areas where local codes permit. In this type of system, ground water from an aquifer is piped directly from the well to the building, where it transfers its heat to a heat pump. After it leaves the building, the water is pumped back into the same aquifer via a second well–called a discharge well–located at a suitable distance from the first. Local environmental officials should be consulted whenever an open loop system is being considered.

Standing Column Well System. Standing column wells, also called turbulent wells or Energy WellsTM, have become an established technology in some regions, especially the northeastern United States. Standing wells are typically six inches in diameter and may be as deep as 1500 feet. Temperate water from the bottom of the well is withdrawn, circulated through the heat pump’s heat exchanger, and returned to the top of the water column in the same well. Usually, the well also serves to provide potable water. However, ground water must be plentiful for a standing well system to operate effectively. If the standing well is installed where the water table is too deep, pumping would be prohibitively costly. Under normal circumstances, the water diverted for building (potable) use is replaced by constant-temperature ground water, which makes the system act like a true open-loop system. If the well-water temperature climbs too high or drops too low, water can be "bled" from the system to allow ground water to restore the well-water temperature to the normal operating range. Permitting conditions for discharging the bleed water vary from locality to locality, but are eased by the fact that the quantities are small and the water is never treated with chemicals.

Other loop designs are also being used. In a few places, for example, home builders have installed large community loops, which are shared by all of the homes in a housing development.

From Adobe File-
Comparing Heating Systems
Central heating systems have been considered a necessity in our homes and businesses for many years. When comparing available systems, consumers should carefully consider safety, installation cost, operating costs, maintenance costs, and comfort.

Types of Systems
There are two basic types of systems — those that require a flame to operate (i.e., combustion based), and those that do not. Most central systems presently installed create heat by combustion, just as they did in the early part of the century. These systems use a furnace to burn a fossil fuel (such as oil, natural gas or propane) or, in some instances, wood. More advanced, non-combustion systems operate by transferring or moving heat from one location to another.

Combustion-Based Systems
Until the last few years, combustion-based systems have been the preferred heating systems for home and business owners because of their moderate installation and operating costs, and wide availability in the market place. Unfortunately, there are a number of serious safety and related maintenance concerns with these systems.
Some combustion-based systems present an explosion hazard if the storage or delivery of their fuel is not carefully controlled. Explosions due to improperly installed or maintained gas pipes and delivery systems are often in the news. Since these systems require a flame to operate, failures or improper installation of system components (for example, heat exchanger, damper, chimney, or flue) can result in property loss to fire. Fortunately, smoke detectors have saved many lives that might have been lost to fires caused by combustion-based heating systems.
In addition to heat, combustion-based heating systems also create by-products such as carbon monoxide. Carbon monoxide is a result of the incomplete burning of fuel in combustion-based systems. Incorrectly installed systems, chimneys that are blocked by birds nests, or downdrafting can cause carbon monoxide to remain inside of buildings. This is especially dangerous in modern, well-sealed buildings, where it is difficult for outside combustion air to reach the furnace, and where carbon monoxide can be trapped and build up over time. Furnaces, water heaters, and other appliances must be properly vented outside.
Combustion-based systems that deliver heat through ducts present occasional “blasts” of hot air. This not only reduces comfort directly, but tends to dehumidify the air. The addition of a central humidifier (with its associated installation, operating, and maintenance costs) can correct this humidity problem. Combustion based central heating systems are often coupled with low-efficiency central air conditioners. This raises installation and operating costs significantly, while adding an entirely separate unit to be maintained.

About Carbon Monoxide
When inhaled, carbon monoxide interferes with the delivery of oxygen throughout the body, and can cause unconsciousness and death. Even small amounts of this colorless, odorless gas cause symptoms ranging from headaches, dizziness, weakness, nausea, confusion, and disorientation, to fatigue. Prolonged exposure may cause permanent brain damage. Children, pregnant women, the elderly, and people with anemia or with heart or respiratory problems are especially sensitive to carbon monoxide exposure.
Over 1,500 people die and over 10,000 reportedly take ill from carbon monoxide exposure each year. Many carbon monoxide poisonings are not detected, as doctors confuse its symptoms with influenza or food poisoning.
The U.S. Consumer Product Safety Commission and others recommended the installation of carbon monoxide detectors, although it is not clear that detectors will protect consumers from low levels of carbon monoxide over long periods of time. Detectors have also been the subject of recalls by their manufacturer due to failure to alarm at dangerous levels of carbon monoxide.
Carbon monoxide is an insidious killer. To help assure safe operation, combustion-based heating systems should be checked frequently for indoor air pollution hazards. Other sources of carbon monoxide, such as barbeque grills and automobiles, should never be operated in enclosed spaces.

Heat Transfer Systems
Non-combustion or heat transfer systems include heat pumps and GeoExchangeSM systems. Heat pumps operate by capturing heat from outdoor air and transferring it inside of a home or business. GeoExchangeSM systems capture and transfer heat from the earth.
Nearly all heat transfer systems can be reversed, providing central cooling as well as heating. Some heat pumps and most GeoExchangeSM systems also provide domestic hot water at low operating costs.

Heat Pumps
Beginning in the 1970s, air-source heat pumps came into common use. They have the advantage of no combustion, and thus no possibility of indoor pollutants like carbon monoxide. Heat pumps provide central air conditioning as well as heating as a matter of course. And they are installation-cost competitive with a central combustion furnace/central air conditioner combination.
Heat pumps operate by moving or transferring heat, rather than creating it. During the summer, a heat pump captures heat from inside a home or business and transfers it to the outdoor air through a condensing unit. During the winter, the process is reversed. Heat is captured from outdoor air, compressed, and released inside.
Much less electricity is used to move heat rather than create it, making heat pumps more economical than resistance heating. However, in all but the most moderate climates, the heating ability of the heat pump is limited by freezing outdoor temperatures. So electric resistance heat is used to supplement outdoor-air-source heat pump during the coldest weather, preventing “cold blow.”
Depending on climate, air-source heat pumps (including their supplementary resistance heat) are about 1.5 to 3 times more efficient than resistance heating alone. Operating efficiency has improved since the 70s, making their operating cost generally competitive with combustion-based systems, depending on local fuel prices. With their outdoor unit subject to weathering, some maintenance should be expected.

GeoExchangeSM Systems
More recently, even more advanced and efficient heating and cooling systems have emerged using the GeoExchangeSM process. Sometimes called geothermal or ground-source heat pumps, these systems move or transfer heat like the air-source heat pumps. However, they exchange heat with the earth rather than the outdoor air.
Since earth temperature remains relatively constant throughout the year, GeoExchangeSM systems operate more efficiently than air-source heat pumps and generally without the use of resistance heat. And because they are working from those constant earth temperatures, there are no blasts of hot air or “cold blow” as with other systems.
Nearly all GeoExchangeSM systems on the market have the ability to provide low-cost domestic hot water, further increasing their operating efficiency. Thus, GeoExchangeSM systems are generally 2.5 to 4 or more times more efficient than resistance heating and water heating alone, and have no combustion or indoor air pollutants.
Since there is no outdoor unit (as with air-source heat pumps or the central air conditioners used with combustion-based systems), no weather-related maintenance is required.
Although their installation cost is somewhat higher due to the required underground connections for heat transfer to and from the earth, GeoExchangeSM systems provide low operating and maintenance cost and greater comfort.

Conclusions
When comparing heating systems, safety, installation cost, operating costs, and maintenance costs must be considered. To simplify the selection process, installation, operating, and maintenance costs can be combined into a life-cycle cost — the cost of ownership over a period of years. The table below compares the various types of central heating systems:

Consumers who take the necessary steps to insure the safety of combustion-based systems (frequent inspection and maintenance, smoke detectors, carbon-monoxide detectors, and other safety precautions) may wish to consider these moderate life-cycle cost systems. Others should consider more advanced heat transfer systems — heat pumps (with their moderate installation, operating, and maintenance costs), or GeoExchangeSM systems (with their low operating and maintenance costs and high levels of comfort).
A recent study by the U.S. Environmental Protection Agency showed that GeoExchangeSM systems generally have the lowest life-cycle cost of all systems available today. The study also shows that GeoExchangeSM systems have the lowest impact on our environment. And consumers rank their comfort and satisfaction with GeoExchangeSM systems higher than all others. While a higher initial investment is required, the investment is paid back through low energy bills (enhancing resale value), excellent family safety, and real comfort.

Federal Incentives

US Energy Policy Act
USDA Farm Bill

State Incentives
Alabama

Colorado
Connecticut
Delaware
Florida

Hawaii
Idaho
Illinois
Indiana

Iowa
Maryland
Massachusetts
Minnesota
Montana
Nebraska
Nevada
New Hampshire
New Jersey
New York
North Dakota
Ohio
Oregon
South Carolina
South Dakota
Tennessee
Wisconsin

Summary

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There are numerous incentives offered for geothermal heating and cooling systems across the United States. For more information, please choose from either the Federal menu items or choose a state from the list located on the right. For additional information on state energy alternatives, click here.

If your state is not listed, please contact your state energy office or local electric utility for more information.

The Energy Independence and Security Act of 2007 offers Incentives for GeoExchange

On December 19, 2007, President Bush signed the Energy Independence and Security Act of 2007 as Public Law 110-140. Among the sweeping changes enacted were numerous provisions that will benefit GeoExchange heating and cooling technology.

Section 439 Cost-Effective Technology Acceleration Program directs the General Services Administration (GSA) to accelerate the use of cost-effective technologies in its facilities (Federal government owned or operated buildings), with a stated goal of achieving the maximum feasible replacement of existing HVAC technologies with GHPs.

Section 412 Study of Renewable Energy Rebate Programs directs the Department of Energy to develop a plan for carrying out the renewable energy rebate program established by the Energy Policy Act of 2005, a program authorizing a 25% rebate (up to $3000) for expenditures to install a renewable energy system.

Section 422 Zero Net Energy Commercial Buildings Initiative directs the Department of Energy to develop and disseminate technologies, practices, and policies for the development and establishment of zero net energy commercial buildings.

Section 433 Federal Building Energy Efficiency Performance Standard directs the Department of Energy to establish revised Federal building energy efficiency performance standards that will reduce fossil fuel-generated energy consumption by 55% by 2010.

Section 434 Management of Federal Building Efficiency directs all Federal agencies to ensure that any large capital energy investment in existing buildings employs the most energy efficient technologies that are life-cycle cost effective.

The Geothermal Heat Pump Consortium works hard to represent our industry, making sure our voices are heard and that we are included in policies that direct the future of our country’s energy market. We applaud both Congress and the Bush administration for passing a comprehensive energy plan that encourages conservation and energy efficiency.

The full text of the Energy Independence and Security Act of 2007 (Public Law 110-140) is at http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=110_cong_bills&docid=f:h6enr.txt.pdf

The IRS issued tax credit rules for homeowners info can be found at: http://www.irs.gov/newsroom/article/0,,id=154657,00.html

The information for builders is located at: http://www.irs.gov/newsroom/article/0,,id=154658,00.html

For information on any other tax credits, please visit the ENERGY STAR website at: http://www.energystar.gov/index.cfm?c=products.pr_tax_credits

United States Department of Agriculture Assistance Programs

The Farm Security and Rural Investment Act (Farm Bill)
The Farm Security and Rural Investment Act of 2002 (the Farm Bill) established the Renewable Energy Systems and Energy Efficiency Improvements Program under Title IX, Section 9006. This program currently funds grants and loan guarantees to agricultural producers and rural small business for assistance with purchasing renewable energy systems and making energy efficiency improvements, including the installation of geothermal heat pumps.

New for 2006, the program offers both grants and guaranteed loans for eligible projects. In addition, projects with total eligible costs under $200,000 can apply under a Simplified Application Process designed to streamline the application process for small projects.
Some key provisions of the program are:

* Applicants may qualify for a grant, a guaranteed loan, or a combination of both.
* Grant request must not exceed 25% of the eligible project costs. Renewable energy grants can range from $2,500 to $500,000. Energy efficiency grants can range from $1,500 to $250,000.
* Projects under $200,000 total project costs qualify for a simplified application process.
* Loan guarantees can be for up to 50% of total eligible project costs. Guarantees can range from $5,000 to $10,000,000 per project.
* Projects can qualify for combined grant and loan guarantee, but the grant portion is still subject to the above limits and combined funding assistance cannot exceed 50% of total eligible project costs.

To learn more about the Farm Bill, please visit the USDA’s site at: http://www.rurdev.usda.gov/rbs/farmbill/index.html

Tagged with: heat pump exchange systems • heating and air conditioning system in your home • Home Geothermal Power Plant Systems

Filed under: Geothermal Power • heat pump exchange systems

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