-About Geothermal-
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. 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. 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.
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.
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.
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 tre
nch, 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.
To ensure they receive the
highest-quality equipment, system design and installation, consumers should consider the
following guidelines when shopping for a GeoExchange system:
Ratings and Certification: Look for equipment that is
certified by the Air-Conditioning and Refrigeration Institute (ARI), a non-profit
organization that rates the performance of residential and small commercial GeoExchange
equipment. Certified equipment carries the ARI seal.
Warrantees:
Manufacturers’ terms of warranty vary. To assure a high-quality installation, seek a
performance guarantee on the installed system, as opposed to coverage limited to the heat
pump itself.
Sizing: GeoExchange
systems that are too large waste energy and do not provide proper humidity control. Check
to see that the contractor carefully determines your home’s heating and cooling
requirements using accepted procedures, such as those recommended by the Air Conditioning
Contractors Association. The actual size of the system should be within 15 percent of the
calculated load.
System Design: While
designing a residential GeoExchange system is not particularly complicated, always use
experienced contractors. The contractor should carefully select the size of the
GeoExchange system, the size and design of the loop, and the type of fluid that will
circulate through it. The contractor should also examine ways to use the GeoExchange
system to provide hot water. Finally, the contractor should examine your home to ensure
the ductwork is designed and installed properly to prevent leaks, as well as to ensure it
is properly insulated and has window glazing and other energy-efficiency features.
Minimizing heating and cooling needs reduces the required size, hence the cost, of the
GeoExchange system.
GeoExchange is becoming the system
of choice in many parts of the United States as consumers learn more about its aesthetic
advantages and long-term value, and as it becomes more widely available.
GeoExchange is no longer just for
the affluent, a reputation it once held because typical early buyers were owners of
upscale homes. They wanted the quiet comfort GeoExchange systems provide, and they were
more than willing--and could afford--to pay the cost premium associated with early
systems. This is because the extraordinarily low operating costs of GeoExchange systems
more than make up for any higher installation costs within a few years. According to the
U.S. Environmental Protection Agency, GeoExchange systems save homeowners 60 percent in
heating costs, and 50 percent in cooling costs, compared to conventional systems.
GeoExchange systems also save money in other ways. They are highly reliable, require
little maintenance, and are built to last for decades. They add considerably to the value
of homes.
Today, homeowners in all
income brackets can take advantage of the benefits of GeoExchange heating and cooling.
Initial costs have declined substantially as many more builders and heating and cooling
contractors nationwide make GeoExchange systems available, and as innovative techniques
enable the loops to be installed more quickly (often in one day) and for lower cost.
Corn Belt Energy offers a
4.45 cent
per kwh rate for these systems. Many financial institutions also now allow home buyers to
qualify for larger mortgages if they purchase a house that utilizes a GeoExchange system.
The reduction in monthly energy bills more than offsets the slightly higher mortgage
payment. With such mortgages, homeowners with GeoExchange systems can
begin saving money from day one, then go on saving year after year!
Today, the major barrier to wider
use of this marvelous technology is the fact that many consumers simply aren’t aware
it’s there.
GeoExchange is a smart investment
for consumers who want a system that provides a high level of comfort and low monthly
energy bills for as long as they own their homes
Gather more information
The most valuable information
sources are professionals with GeoExchange experiences in your area. The case studies
developed by GHPC as ell as those prepared by Geo Exchange manufacturers and utilities can
lead out to the architects, engineers, and installers responsible for actual GeoExchange
installations.
Contact Corn Belt Energy for
information on units installed in our service area and dealers who will install these
units.