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There are four basic types of ground loop systems. Three of
these—horizontal, vertical, and pond/lake—are closed-loop systems. The
fourth type of system is the open-loop option. Which one of these is
best depends on the climate, soil conditions, available land, and local
installation costs at the site. All of these approaches can be used for
residential and commercial building applications.
Closed-Loop Systems
Most closed-loop geothermal heat pumps circulate an antifreeze
solution through a closed loop—usually made of plastic tubing—that is
buried in the ground or submerged in water. A heat exchanger transfers
heat between the refrigerant in the heat pump and the antifreeze
solution in the closed loop. The loop can be in a horizontal, vertical,
or pond/lake configuration.
One variant of this approach, called direct exchange, does not use a
heat exchanger and instead pumps the refrigerant through copper tubing
that is buried in the ground in a horizontal or vertical configuration.
Direct exchange systems require a larger compressor and work best in
moist soils (sometimes requiring additional irrigation to keep the soil
moist), but you should avoid installing in soils corrosive to the copper
tubing. Because these systems circulate refrigerant through the ground,
local environmental regulations may prohibit their use in some
locations.
Horizontal
This type of installation is generally most cost-effective for
residential installations, particularly for new construction where
sufficient land is available. It requires trenches at least four feet
deep. The most common layouts either use two pipes, one buried at six
feet, and the other at four feet, or two pipes placed side-by-side at
five feet in the ground in a two-foot wide trench. The Slinky™ method of
looping pipe allows more pipe in a shorter trench, which cuts down on
installation costs and makes horizontal installation possible in areas
it would not be with conventional horizontal applications.
Vertical
Large commercial buildings and schools often use vertical systems
because the land area required for horizontal loops would be
prohibitive. Vertical loops are also used where the soil is too shallow
for trenching, and they minimize the disturbance to existing
landscaping. For a vertical system, holes (approximately four inches in
diameter) are drilled about 20 feet apart and 100–400 feet deep. Into
these holes go two pipes that are connected at the bottom with a U-bend
to form a loop. The vertical loops are connected with horizontal pipe
(i.e., manifold), placed in trenches, and connected to the heat pump in
the building.
Pond/Lake
If the site has an adequate water body, this may be the lowest cost
option. A supply line pipe is run underground from the building to the
water and coiled into circles at least eight feet under the surface to
prevent freezing. The coils should only be placed in a water source that
meets minimum volume, depth, and quality criteria.
Open-Loop System
This type of system uses well or surface body water as the heat
exchange fluid that circulates directly through the GHP system. Once it
has circulated through the system, the water returns to the ground
through the well, a recharge well, or surface discharge. This option is
obviously practical only where there is an adequate supply of relatively
clean water, and all local codes and regulations regarding groundwater
discharge are met.
Hybrid Systems
Hybrid systems using several different geothermal resources, or a
combination of a geothermal resource with outdoor air (i.e., a cooling
tower), are another technology option. Hybrid approaches are
particularly effective where cooling needs are significantly larger than
heating needs. Where local geology permits, the "standing column well"
is another option. In this variation of an open-loop system, one or more
deep vertical wells is drilled. Water is drawn from the bottom of a
standing column and returned to the top. During periods of peak heating
and cooling, the system can bleed a portion of the return water rather
than reinjecting it all, causing water inflow to the column from the
surrounding aquifer. The bleed cycle cools the column during heat
rejection, heats it during heat extraction, and reduces the required
bore depth.
6 comments:
Interesting information on the various types of Geothermal Pump Systems. I think Hybrid system should be more suitable for Malaysian users since it focused more on cooling needs such as air-conditioners rather than heating needs.
Any alternative energy production methods should be considered so that we can have more options in hand.
It will be better if the alternative energy production is affordable.
This design takes advantage of the moderate temperatures in the ground to boost efficiency and reduce the operational costs of heating and cooling systems, and may be combined with solar heating to form a geosolar system with even greater efficiency.
Geothermal heat pumps are durable and require little maintenance. They have fewer mechanical components than other systems, and most of those components are underground, sheltered from the weather.
Geothermal, or ground source heat pumps, take advantage of the constant ground or groundwater temperatures to heat and cool your home at a cost of 25-50% less than traditional electric, gas or oil fired heating and cooling systems.
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