If
you like the idea of doing your bit for the environment,
whilst enjoying the benefits, then pick up the
phone or fill out the form on the contact page.
All our details
along with a web form can be found
on the contact page click
here
Tel:
0114 287 0723
How
Ground Source Heat Pumps Work
Just
below the ground’s surface, 1 - 2m
deep, the ground has a year round temperature
of between 8°C – 12°C, varying
only slightly between seasons
The Ground Source Heat Pump is a system that
extracts heat from the ground. A water or water
antifreeze mix is pumped around a circuit of
buried pipe work taking the low grade heat from
within the ground. This low grade heat is then
upgraded to a higher temperature through the
utilisation of a refrigeration gas within the
heat pump circuit.
This gas is compressed and
forced through the heat pump circuit before the
pressure is released in the condenser along with
the heat where it is required in the internal
house pipe work circuit. The heat is now used
for space heating and water heating.
The heat pump function can be reversed for cooling
purposes; this is particularly useful for commercial
applications like in offices where cooling is
needed on hot summer days.
Ground source heat pumps are a highly efficient
method of providing hot water and heating for
your home.
Due to the constant ground temperature a high coefficient of performance (COP)
can be achieved even at low outdoor temperatures. This results in a year round
high seasonal performance factor (SPF.)
Manufacturers continually boast high figures in COP & SPF in order to sell
their heat pumps, however the market is much more tightly regulated than it used
to be and we have no reason to doubt that a well designed, well tuned heat pump
installation could not achieve these figures.
Ground source heat pumps are considered more efficient than air source heat pumps
and typically have a higher SPF
There
are two different types of ground source heat
pump installation:
Closed
Loop System
Open
Loop System
The
more usual ‘closed loop’ Ground
source heat pump
Two examples of a ground source heat pump can
be seen below. The ‘closed loop’ installation
comprises of plastic piping buried in the ground
and connected to a heat pump.
A water-antifreeze
mixture is passed around the looped pipe where
it absorbs heat from the ground. The fluid
flows into an electrically powered heat pump,
comprising a compressor and a pair of heat
exchangers before discharging back to the underground
loop.
‘Horizontal
loops’
Piping
is installed horizontally in trenches. The depth
of the trenches will vary according to the design
and soil characteristics, but is generally 1.5 – 2m
deep. Horizontal loops require much more surface
area than vertical loops.
Around 200m of pipework
is generally required for a single dwelling.
Video shows a horizontal loop system
‘Slinky
coils’
The ‘Slinky’ is
a variation of the ‘Horizontal loop’.
Slinky coils are flattened coils of overlapping
piping, which are spread out and laid either
horizontally or vertically.
Their ability to
focus the area of heat transfer into small volume
reduces the length of the trenches and hence
the quantity of land needed. A 10m long trench
laid with a ‘Slinky’ coil will typically
supply 1kW of heating load.
‘Vertical
loops’
Most
commercial and institutional projects using GSHPs
use ‘Vertical loop’ systems. The
advantage of a vertical loop system, which consists
of pipe inserted into vertical bore holes, is
less space is required.
Holes are spaced at around
5m intervals and usually vary between 15m and
60m according to the design and soil characteristics.
However, some vertical loop heat pump systems
can be drilled as much as 200m down. Each system
is designed to the specific building the heat
pump is intended to provide heat for. Generally
a series of shallower bore holes are preferred
to one or two really deep ones.
Video shows a vertical loop system
The
less common open loop ground source heat pump
system
In
an open loop (or water to water) ground
source heat pump, ground water is abstracted,
usually from an aquifer or possibly from
an adjacent river and passed through the
heat pump before being returned to the
ground or river.
A constant supply of water
is needed. This type of ground source heat
pump system is highly efficient because
of the relatively high temperature of ground
water, but the installation can be more
complex and require regulatory approval
from the environmental agency.
Open loop
ground source heat pump systems are usually
confined to larger commercial buildings
rather than domestic properties.
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