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Ground Source Heat Pumps (GSHP) Jargon Buster

Ground Source Heat Pumps (GSHP) Jargon Buster
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Definitions:

GROUND SOURCE HEAT PUMP
Electrically driven device that extracts heat from the ground in order to provide, via a simple heat exchange mechanism, space and water heating for a building.
(EESC ’11)

GROUND SOURCE HEATING PUMPS PUMPS (GSHP)

At about 1.0m below the ground level the ambient temperature is stable at about 5 degrees C and this can be harnessed using GSHP.
GSHP systems have four essential components:
A pump
A condenser
An evaporator, and condenser
Plastic pipes known as ground loops or ‘slinkies’ laid at a depth of 1.0m
Operating on the same principle as a fridge, ground loops or ‘slinkies’ contain a water based refrigerant or ‘brine,’ which absorbs the latent heat of the ground.
The refrigerant is then pumped through the evaporator and condenser under pressure to raise the temperature to approximately 50 degrees C to heat water for distribution around a building, normally in an underfloor heating system.
Although providing sufficient hot water for heating an average 3 bedroom house, they would not be able to meet all the DHW needs of a domestic hot water cylinder, consequently most GSHP package today are sold with roof mounted solar thermal hot water heating systems
Powered by electricity (ideally green tariff or renewable supply)
GSHP is not providing renewable energy, however due to their high ‘coefficient of performance’ ratios of power in to heat out they have low energy consumption and associated CO2 emissions when compared with conventional gas fired domestic heating systems and can show savings in the order of 40%.
Larger commercial system using deep well bores harness the natural geo-thermal properties of ground water at approximately 100 m. deep, operating on the same principle as domestic scale GSHP, but on a larger scale.

(based on Building Magazine Steve Piltz, Turner & Townsend ’08
corrected by NGS BRM ’09 but not entrirely convinced by this one)

GROUND SOURCE HEAT PUMP (GSHP)
A system that extracts heat from the ground, upgrades it to a higher temperature and releases it where required for space and water heating.
(GreenSpec AEP ’09)

Application Options:

Carbon Reduction:

Always use green tarrif electricity or site generated renewable energy to drive pumps

Value Engineering

Site investigation drilling is an opportunity to get GSHP pipes into the ground to save drilling twice
But it needs a bit of coordination between two parties

Deep drilled GSHP make use of the steady temperature deep below ground

GSHP in piles below basements is common
GSHP below basement floor is possible but unnecessary unless there is no site area
GSHP below ground floor is possible but unnecessary unless there is no site area`
GSHP drilled below site is common and site subsoil and ground water dictates if practical and if in/expensive
Drilling through rock is price predictable
Drilling through rock generates arisings that could be put to use on site as landscape mulch not landfilled
Check for Radon Offgassing
Drilling through subsoil and ground water can result in price unpredictability

Coils or slinky GSHP make use of steady temperature below ground

Can also be shallow to exploit solar gains but limited use in winter
GSHP coils below existing basement is impractical to impossible
GSHP coils below existing ground floor is impractical to impossible
GSHP coils shallow below site soil is common and practical but expensive: excavation of trenches

GSHP grids below pavement exploit pavement used as solar panels

is practical and potentially multifunctional
Recycled brick/concrete sub-base
permeable pavement,
water retaining,
solar heated GSHP.

Consider:

Use with low temperature Under Floor Heating (UFH)
Use with low temperature radiators not conventional radiators
Always use green tarrif electricity or site generated renewable energy to drive pumps
RHI funding for use of GSHP
FIT funding for PV panels to drive motors

Avoid:

Raising the temperature to serve conventional radiators
Grid electricity uless paying for Green Tarrif Electricity
Laying GSHP grids below ‘car par spaces’, put them in the ‘drive’