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Ground loops
The three main compnents of a geothermal system are the ground loop, the heat pump and the distribution system (radiant floors or forced air). The ground loops are the heat exchanger that extracts and rejects heat from the ground to heat and cool the building depending on the season. If you think of the earth as a battery, then the ground loops would be the electrodes. The following pictures illustrate the ground loop installation process,which involves fusing high-density polyethelyne pipe together to circulate a water and environmentally friendly anit-freeze solution through the pipes. There are two primary types of ground loops, including closed and open and of those that are closed horizontal, vertical and slinky are the most common. The following pictures illustrate a slinky ground loop. Because the ground is cooler in the summer and warmer in the winter it is possible to use the ground as a heat source in the winter, and a heat sink in the summer. This is what makes geothermal heat pumps 3 to 5 times more efficient than a gas furnace. There is no combustion of fossil fuels because the system is working in balance with nature.
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In a slinky system trenches are 150' long, 3' wide, 10' apart and 5'
deep. This prevents the loops from drawing from each
other.
The pex tubing loops are fused together at temperatures of
approximately 500 deg F. This is the same tubing that the gas
companies use to distribute natural gas throughout the Northwest and
most of the country. The last picture illustrates why a
slinky is
so efficient. It compresses 600 linear feet of pipe in a 150
foot
trench. It maximizes the amount of pipe while minimizing the
amount of required trenching. Once the trenches are
back-filled
the loop field is ready for pretty much any type of
landscaping.
Vertical Ground Loops
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Vertical ground loops can fit in to tighter spaces because they require less area than a horizontal ground loop. The first two pictures show the drlling rig, which in this case is owned by a drilling contractor. Drilling contractors are usually hired to drill the boreholes. This back yard area was used to install a four-loop system at a house in North Portland. Loop depth's can range from anywhere between 130 to 200 vertical feet Loop's are typically closed just as in a horizontal loop with a water-antifreeze solution for the fluid. Vertical ground loops tend to be more expensive due to the type of equipment involved, but with fuel prices rising they will still pay back in the long run.
Delta-Montrose Electric Association, of Montrose CO, recently started a program that offers financing of the ground loop portion of a geothermal heat pump system. The ground loop can often account for as much as half of the instlallation costs of a geothermal system. It is likely one of the first programs of its' kind anywhere in the country. But with natural gas prices beginning a steady and upward climb for the indefinite future, more innovative programs like this are likely to occur in other parts of the country. For more information read the Delta-Montrose Electric Association press release located below.
Horizontal Boring
A recent technology that shows great promise to
significantly reduce the cost of installing ground loops is horizontal
boring, or directional drilling, as it is often known. With
horizontal boring the footprint of the ground loop is minimized because
the loop is 'bored', as opposed to trenched or drilled, in to the ground. It 
is also
much less expensive than vertical drilling because the equipment is
much smaller, so it can also fit in to much smaller spaces
than conventional
drilling equipment. Loop depths are typically 150 to 200' and
they do not require the substantial amount of excavation associated
with regular horizontal ground loops. The picture on the left
illustrates a typical horizontal boring unit.
Installation costs for a horizontal boring system are typically one-fourth that of conventional vertical drilling systems. It combines the best attributes of conventional horizontal and vertical types of systems: it minmizes the footprint and exacvation of the ground loop but it's much less expensive than installing a vertical system. For homeowners with small lots or extensive landscaping, horizaontal boring or directional drilling could be viable option for getting the high efficiency heating and cooling of a geothermal heat pump system.
Geothermal Heating Systems
There
are two primary types of heating systems used with geo-exchange heat
pumps including, forced-air and radiant floor systems.
Forced-air
systems are the most common because they use standard duct work to
transport conditioned air through out the home. Radiant floor
systems are much more efficient and comfortable
because
they actually heat the floor rather than the air, so it is possible to
maintain a lower temperature and still remain comfortable.
Since
warm air rises they maintain a more relatively constant temperature and
they don't produce huge blasts of hot and cold air. They do
require a ventiliation system because heating the floor does not
provide fresh air. They also typically require a separate
cooling
system. Geo-exchange forced air systems on the
other hand,
are capable of providing both heating and cooling. This is
because they use a duct work system to distribute conditioned air.
Geo-exchange Heat Pumps work in much the same way as a refrigerator. Rather than generating heat through the combustion of fossil fuels, a heat pump merely transfers heat back and forth between the ground and the building. The earth is constantly absorbing energy from the sun so it acts as a heat sink, or repository of heat for future use. In the winter the heat pump extracts heat from the ground, and in the summer the process is reversed by rejecting heat back to the ground.
Because there is no direct consumption of fossil fuels and because it uses the equivalent of approximatey ten 90-watt light bulbs in electricity, a geo-exchange heat pump is more efficient, cost-effective and more beneficial for the environment than natural gas or oil-fired furnaces. According to the US Dept. of Energy, 40% of all CO2emissions come from space heating and cooling. That's almost as much as auto emissions. The basic concept of geothermal heat pumps, the transfer of heat between the earth and buildings, is illustrated with the following graphic.
The earth is warmer in
the winter and cooler
in the summer than the outside air. Transferring heat back
and
forth between the earth and the building is a relatively simple
process, therefore you stay warm in the winter and cool in the summer
with a geothermal heat pump.
In addition to geothermal heat pumps we also sell tankless water heaters, heat recovery ventilators and electric radiant floor systems. Call us to find out how we can make your home or office more energy efficient.
Geo-exchange heat pumps provide comfortable space heating and cooling, and they can also be used to heat domestic hot water. Geo-exchange heat pumps are electrically powered systems that transfer heat back and forth between the earth and your building. The reduction in CO2 emissions is also significant because heat pumps do not burn fossil fuels. A geo-exchange heat pump must be installed by a licensed contractor in order to qualify for energy tax credits.
More
information on geothermal heat pumps, remewable energy and
energy efficiency: (requires Adobe or Flash Player)
Geothermal Heat Pump Information Survival Kit -
Oregon Institute of Technology Geo-Heat Center
The
Future of Geothermal Energy - Massachusetts
Institute of Technology
Modern Heating & Cooling for
Historic Structures - Geothermal Heat Pump ConsortiumGeothermal general information - Geothermal Heat Pump Consortium
Oregon Geothermal Map - Oregon Dept. of Energy
Oregon Renewable Portfolio Standard - Oregon Dept. of Energy
DIY Home Energy Efficiency - Energy Trust of Oregon
Geothermal Loop Tariff Press Release - Delta-Montrose Electric Association
Geothermal Energy Links
International Geothermal Association US Dept. of Energy - Geothermal Technologies Program International Ground Source Heat Pump Association
Oregon Dept. of Energy Geothermal Working Group Geo-Heat Center at OIT Geothermal Heat Pump Consortium - tax incentive Geothermal-biz - development information for the geothermal entrepreneur Geothermal Education Office Geothermal Education Association Geothermal Resources Council National Renewable Energy Laboratory - Geothermal Technologies Program Geothermal Heating and Cooling - one stop resource TriModal - a geothermal company
GeoDynamics Ltd - power from the earth Nicholls Boreholes - Nicholls Construction provides a comprehensive service of heating and cooling equipments, heat pump installation and water wells/boreholes, air to water, swimming pool, and ground source heat pumps in Sussex UK.
Refer to the heat pump schematic below or check out the Sustainability page for more information on geo-exchange heat pumps.
Green Energy Solutions - green
energy for a green planet.
