Designing Buildings - User contributions [en]

Water source heat pumps

2014-09-23T16:48:40Z

Edward Thompson:

Heat pumps work by running a low-temperature, lower pressure refrigerant fluid in heat exchanger coils through a heat source, such as the outside air, the ground, or circulating water. The fluid ‘absorbs’ this heat and boils, even at temperatures below 0° C (although the coefficient of performance (COP) decreases with lower temperature). The resulting gas is then compressed, which further increases its temperature. The gas is passed into heat exchanger coils, where it condenses, releasing its latent heat. The process then repeats. This is the same process that is used to extract heat from a fridge. It can be used domestically or commercially and some systems can also be used to extract heat from a building to provide cooling.

Heat pumps can be used to provide hot water, space heating (either by providing hot water for under-floor heating or radiators, or supplying hot air) or other applications such as heating swimming pools.

In the UK, heat pumps are most commonly air-source or ground-source heat pumps. However, the temperature of ground water sources in the UK tends to be fairly constant for most of the year, at between 8 and 12°c. This makes water a more efficient heat source than the outside air, and the heat transfer rate with water is higher than that of air or the ground. In addition, unlike ground-source heat pumps, water-source heat pumps do not require trenches for coils to be laid in, although open loop systems often require filtration.

Water-source heat pumps require a suitable local water source, such as a lake, river, well, borehole and so on. They can be ‘open-loop’ or ‘closed-loop’ systems:
*Closed-loop systems pipe a mixture of water and anti-freeze to a water source such as a lake where it flows through coils or heat exchange panels in the water to exchange heat with it. The heated mixture is then piped to the heat pump and heat exchanged with the refrigerant.
*In open-loop systems water from the source is extracted and piped direct to the heat pump. Heat is then exchanged with the refrigerant and the water then returned to the source. As this involves extraction from and discharge to a water source, it is likely to require an extraction licence and a discharge license from the Environment Agency.

Closed-loop systems can be less efficient than open-loop systems, because of the losses caused by transferring heat between the water source and the fluid in the closed loop. However, they are less restrictive in terms of the danger of freezing, the water quality that can be used, the need for filtration or other forms of water treatment, the possibility of needing to use a corrosion resistant system and the need for licenses. Open-loop systems can also require more pumping.

Care must be taken with closed-loop systems to avoid the potential for the coils or heat exchange panels to be damaged by boats or other activities in or on the water.

Water source heat pumps are generally quiet, unobtrusive and have low maintenance requirements. However, care must be taken to ensure that the water supply is consistent and sufficient throughout the year.

Water-source heat pumps are eligible for payments under the government’s Renewable Heat Incentive (RHI) scheme. Domestic schemes may also be eligible for financing through the green deal, however, there has been very poor uptake of the Green Deal, and it is generally considered that better financial deals are available elsewhere. 

= Find out more =

=== Related articles on Designing Buildings Wiki: ===
*Air source heat pumps.
*Geothermal pile foundations.
*Green Deal.
*Ground energy options.
*Ground source heat pumps
*Renewable Heat Incentive.
*Solar thermal heating.
*Thermal labyrinths.

=== External references ===
*YouGen, [http://www.yougen.co.uk/renewable-energy/Heat+Pumps/ Heat pumps].
*[http://gdorb.decc.gov.uk/admin/documents/Green%20Deal%20Energy%20Saving%20Home%20Improvements%20Checklist%20Version%202.pdf DECC, Green Deal, Energy Saving Home Improvements].
*DECC,[https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/48406/5504-which-energy-efficiency-improvements-qualify-for-g.pdf Which energy efficiency improvements qualify for Green Deal Finance?] June 2012.

[[Category:Sustainability]]
[[Category:Products_/_components]]

Renewable heat incentive RHI

2014-09-23T12:10:33Z

Edward Thompson:

= Introduction =

Our society is heavily dependent on fossil fuels such as oil, gas and coal, and is likely to remain dependent on them for much of this century. Every year we emit more than 20 billion tonnes of carbon into the atmosphere by burning fossil fuels, half of which is absorbed in the seas and by vegetation, and half of which remains in the atmosphere.

The renewable heat incentive (RHI) was launched by the UK government in November 2011 to help reduce greenhouse gas emissions and meet targets to reduce the effects of climate change. Described by the government as ‘the world’s first long-term financial support programme for renewable heat’, it is similar to the feed in tariff scheme for elecricity generation, but is designed to incentivise heat generation.

The renewable heat incentive scheme makes payments to participants that generate renewable energy and use it to heat their buildings. The payments are intended to bridge the gap between the cost of fossil fuel heat installations and renewable heat alternatives.

It was initially a non-domestic scheme, only open to commercial, industrial, public sector, not for profit organisations and heat networks. A domestic RHI scheme was launched on 9 April 2014. (ref Gov.uk [https://www.gov.uk/government/policies/increasing-the-use-of-low-carbon-technologies/supporting-pages/renewable-heat-incentive-rhi Increasing the use of low-carbon technologies]).

= Non-domestic RHI =

Eligible technologies for the non-domestic RHI include:
*Solid biomass.
*Ground source heat pumps.
*Water source heat pumps.
*Deep geothermal energy.
*Solar thermal collectors.
*Biomethane injection and biogas combustion (other than landfill gas).

From 28 May 2014:
*Air-to-water air source heat pumps. 
*Biogas capacity limits extended beyond 200kWh and energy from waste extended to include industrial and commercial waste.

Equipment must use liquid or steam to deliver heat to spaces, water or processes. MCS is not required for the non-domestic RHI.

Payments are spread over 20 years, with the tariff depending on:
*The type of technology.
*The capacity of the technology.
*The amount of heat generated, as measured by class 2 heat meters.

Tariffs can be found on the [https://www.ofgem.gov.uk/environmental-programmes/renewable-heat-incentive-rhi/tariffs-and-payments Ofgem website].

= Domestic RHI =

The domestic RHI is targeted at, but not limited to, homes that are not connected to the gas network as these have the greatest potential for savings. Eligible technologies include: 
*Air source heat pumps.
*Ground source heat pumps. 
*Water source heat pumps.
*Biomass-only boilers and biomass pellet stoves with integrated boilers.
*Solar thermal panels (flat plate and evacuated tube for hot water only).

Tariffs depend on the technology adopted and have been set at a level that reflects the expected cost of renewable heat generation over 20 years. Payments are made on a quarterly basis over seven years. See Ofgem, [https://www.ofgem.gov.uk/environmental-programmes/domestic-renewable-heat-incentive Domestic RHI] for more information. 

Applicants must first have a green deal assessment carried out, must install loft insulation if it is recommended, must have a domestic Energy Performance Certificate (EPC) and the renewable heating system, and the installer, must be certified under the Microgeneration Certification Scheme. The deemed heat use is taken from the EPC. 

NB A householder voucher scheme, the Renewable Heat Premium Payment scheme, which provided one-off payments to householders to help them purchase renewable heating technologies such as solar thermal panels, heat pumps and biomass boilers, closed on 31 March 2014 (ref gov.uk [https://www.gov.uk/renewable-heat-premium-payment-scheme Renewable Heat Premium Payment scheme]).

= Find out more =

=== Related articles on Designing Buildings Wiki ===
*Air source heat pumps.
*Biogas.
*Biomass.
*CHP.
*Earth-to-air heat exchangers.
*Energy performance certificates.
*Feed in tariff.
*Geothermal energy.
*Geothermal piles.
*Green deal.
*Green Deal Home Improvement Fund.
*Ground energy options.
*Ground pre-conditioning of supply air.
*Ground source heat pumps.
*Large scale solar thermal energy.
*Renewable energy.
*Solar photovoltaics.
*Solar thermal systems.
*Sustainable development: energy challenge.
*Thermal labyrinths.
*Tidal lagoon power.
*Wind Energy in the United Kingdom.
*Zero carbon homes.
*Zero carbon non-domestic buildings.

=== External references ===
*Gov.uk [https://www.gov.uk/government/policies/increasing-the-use-of-low-carbon-technologies/supporting-pages/renewable-heat-incentive-rhi Renewable heat incentive].
*[https://www.ofgem.gov.uk/environmental-programmes/renewable-heat-incentive-rhi/tariffs-and-payments Ofgem website].
*Ofgem, [https://www.ofgem.gov.uk/publications-and-updates/government-introduces-changes-non-domestic-renewable-heat-incentive Government introduces changes to Non-Domestic Renewable Heat Incentive]. 28 May 2014.
*Summary of [http://www.gshp.org.uk/RHI_Commercial.html Commercial RHI tariffs].
*Summary of [http://www.gshp.org.uk/RHI_Domestic.html Domestic RHI tariffs].

[[Category:Policy]]
[[Category:Sustainability]]

Ground energy options

2014-09-23T08:18:23Z

Edward Thompson:

= Introduction =

Below a depth of approximately 6m, the temperature of undisturbed ground remains fairly constant at the mean annual air temperature throughout the year. Depending on the location and depth this temperature is typically between 9 and 12ºC in the UK. This means that the ground can be used to as a heat source in the winter and as a source of coolth in the summer.

In general, the use of ground energy to provide heating and cooling in buildings requires equipment (heat pumps). The energy can be transferred to this equipment using a ground heat exchanger (closed loop system). This usually comprises a number of pipe loops, vertical or horizontal, with a primary process medium of water, or more normally a glycol solution which eliminates the possibility of freezing at the lower end of the application’s seasonal temperature range. An alternative system is to abstract and discharge ground water (open loop systems) from an aquifer beneath the building.

In the case of the closed loop system, the energy in the ground is (if the ground loop is sized appropriately) replenished by solar irradiation, rain and, sometimes, for deeper vertical collector systems, underground water flow. With open loop systems it is necessary to consider the sustainable yield available from the wells.

= Variations of ground energy =

== Horizontal – closed loop ==

[[File:Horizontal closed loop system.jpg|520x235px|alt=Horizontal closed loop system.jpg]]

With this variation, the energy or heat is transferred to the building using a series of ground collectors, laid horizontally at a depth of 1.5-2m. Each pipe run should be limited to 100m to avoid the need for more powerful circulation pumps. Pipe runs would normally be the same length to guarantee similar flow conditions, pressure drops and to ensure an even heat extraction from the ground.

The useable amount of heat or energy is dependent on the following:
*Solar irradiation for the specific area.
*Moisture content.
*Soil type.
*Size of pores.

Extraction rates are generally in the order of 10 W/m2 for dry sandy soil, to over 30 W/m2 for wetter loamy soils. Relatively inexpensive earth moving equipment is required for installation, although costs increase with greater depths. This type of collector is generally used for applications with lower power outputs where there is a large undeveloped area that is easy to excavate.

== Vertical (probe) – closed loop ==

A vertical closed-loop system utilises vertical ground heat exchangers or probes that are inserted into specially drilled boreholes up to depths of 150m.

[[File:Vertical closed loop system.jpg|523x404px|alt=Vertical closed loop system.jpg]]

Extraction rates generally vary between 20 W/m for loose dry substrate to ~80W/m for damper sandstones, granites and basalts.

The useable heat or energy is dependent on similar factors to the horizontal system although more specialist geological analysis is generally needed. Deeper test-bores can ascertain the type and depth of each soil/rock layer, the heat transfer potential for the different layers over the length of the borehole, the presence and height of water table and underground water flow.

Due to the requirement for a test bore, this type of system lends itself to larger applications where the initial testing costs can be justified. The data gathered helps to reduce risk during the design stage as non-optimum sizing has serious cost implications.

== Vertical – open loop ==

In this variation, ground water is extracted direct from the underground water aquifer, eliminating the need for a closed loop ground heat exchanger. The used cooled or heated water can then be returned to the ground via a return well.

[[File:Vertical open loop system.jpg|519x441px|alt=Vertical open loop system.jpg]]

Prior to the consideration of such a configuration, it is necessary to contact the Environmental Agency, initially to gain consent for a pumping test, then for a final abstraction licence for a pumping test, and finally for discharge consent. There is an additional requirement to consider the water quality of the water source, as this can have an adverse effect on the materials used within the heat exchanger.

= Feasibility and Evaluation =

== '''Generic guidelines for ground energy systems''' ==

=== Start considering the technology at an early stage in the project. ===
*Complete a ground energy desktop survey to establish the suitability of the geology and hydrogeology underneath the site to different types of ground energy systems. Suitable sources include the British Geological Survey and site specific Geotechnical Investigation reports.
*Establish the spatial limitations around the building.
*What is the indicative foundation design and is it suitable to act as part of the ground energy heat exchanger?

=== Optimise the heating and cooling building circuits. ===
*Use high temperature cooling where possible (eg chilled beams and air based systems with over sized heat exchangers).
*Use low temperature heat emitters (large radiators, underfloor heating and air based systems with oversized heat exchangers).
*Simultaneous heating and cooling can be provided from the same heat pump unit.

== '''Closed loop do’s''' ==
*For larger commercial systems, ie greater than ~100kW, a thermal conductivity test is advisable to confirm the insitu thermal properties.
*Carry out a desktop simulation using recognised software to ensure long-term performance can be guaranteed.
*Ensure boreholes are spaced adequately to reduce thermal interference.
*Try to balance heat abstraction and rejection to the ground.
*Consider using less expensive conventional plant for infrequent heating and cooling loads and/or higher relative seasonal heating and cooling loads.

== '''Open loop do’s''' ==
*For almost all open loop systems, Environment Agency (EA) approval is needed for both abstraction and discharge of ground or surface water.
*A pumping test will be needed to confirm the yield and to get permission from the EA to abstract and discharge a specified volume of water per hour/day/year.
*Start the process to obtain an abstraction licence and discharge consent as early as possible, as this process can take eight to nine months in the UK.

----

This article was created by --[[User%3ABuro%20Happold|Buro Happold]], 17 March 2013, based on a 2008 article in 'Patterns'.

= Find out more =

=== Related articles on Designing Buildings Wiki ===
*Dynamic thermal modelling of closed loop geothermal heat pump systems.
*Earth-to-air heat exchangers.
*Geothermal energy.
*Geothermal pile foundations.
*Ground preconditioning of supply air.
*Ground source heat pumps.
*Thermal labyrinths.
*Water source heat map.External references

[http://www.icax.co.uk/Heat_Pumps.html Heat Pumps]

[http://www.icax.co.uk/Mean_Annual_Air_Temperature.html Mean annual air temperature]

[[Category:Sustainability]]
[[Category:Products_/_components]]

Ground source heat pumps

2014-09-22T12:30:10Z

Edward Thompson:

= Introduction =

Heat is stored by the thermal mass of the ground of water thermal. There are two types of heat sources:
*Internal heat of the Earth
*Heat from the sun and stored in the ground

In the UK just a few metres below our feet the ground keeps a constant temperature of about 11-12C throughout the year.

== Internal heat of the earth ==

The Earth’s internal heat was originally produced during accretion. Since then heat has been produced by the radioactive decay of elements such as uranium, thorium and potassium. Due to its high enthalpy, this type of heat is often harvested in volcanic areas for electricity production and large district heating.

== Heat from the sun and stored in the ground ==

The majority of heat stored right in the Earth’s surface comes from the sun. This heat is widely available, and because of its low enthalpy, it is often harvested for local heat pump applications. There are two types of systems for utilising heat from the sun stored in the ground by a ground source heat pump:
*Open loop
*Closed loop

= Ground source heat pumps =

Ground source heat pumps can pump heat from the ground into a building to provide space heating and domestic hot water. For every unit of electricity used to pump the heat, 3-4 units of heat can be produced.

[[File:Example of a Ground Source Heat Pump System.jpg|423x308px|alt=Example of a Ground Source Heat Pump System.jpg]]

''Example of a ground source heat pump system.''

== Ground source heat pump system design ==

There are three important elements to a ground source heat pump system:
*Ground loop. This comprises of lengths of plastic pipe buried in the ground, either in a borehole or a horizontal trench. The pipe is a closed circuit and is filled with a mixture of water and antifreeze, which is pumped round the pipe absorbing heat from the ground.
*Heat pump. Heat pumps are very familiar to us in fridges and air conditioners. A heat pump works by using the evaporation and condensing of a refrigerant to move heat from one place to another. In this case, the evaporator (analogous to the squiggly loop in the cold part of the fridge) takes heat from the water in the ground loop; the condenser (analogous to the hot loop on the back of the fridge) gives up heat to a hot water tank which feeds the distribution system.
*A compressor. This uses electricity, (this is what makes the noise in a fridge) to move the refrigerant around the heat pump. It also compresses the gaseous refrigerant to increase the temperature at which it condenses to that needed for the distribution circuit.
*Heat distribution system. This consists of under floor heating or radiators for space heating and water storage for hot water supply. Some systems can also be used for cooling in the summer.

== Ground loop options ==

Three options are available for the ground loop:
*Borehole
*Straight horizontal
*Spiral horizontal (or 'slinky')

Each has different characteristics appropriate for different types of property. Horizontal trenches can cost less than boreholes, but require greater land area. For 'slinky' coils, a trench of about 10m length will provide approximately 1kW of heating load.

== Sizing ==

Sizing of the heat pump and the ground loops is crucial to the operation of the system and is is a job for specialists.

It is a good idea to explore ways of minimising space heating and hot water demand by energy efficiency measures.

NB A heat pump can be designed to meet 100% of space heating requirements and domestic hot water.

= Utilising ground energy =

[[File:How do you get useful heat from the ground.jpg|674x438px|alt=How do you get useful heat from the ground.jpg]] -[[File:How do you get useful coolth frmo the ground.jpg|688x457px|alt=How do you get useful coolth frmo the ground.jpg]]

== Running costs ==

The efficiency of a ground source heat pump system is measured by the Coefficient of Performance (CoP). This is the ratio of the number of units of heat output for each unit of electricity input used to drive the compressor and pump for the ground loop. Typical CoPs range between 2.5-4.The higher end of this range relates to under floor heating, because it works at a lower temperature (30-35°C) than radiators. Based on current fuel prices, assuming a CoP of 3-4, a ground source heat pump can be a cheaper form of space heating than oil, LPG and electric storage heaters. It is however more expensive than mains gas. If grid electricity is used for the compressor and pump, then an economy 7 tariff usually gives the lowest running costs.

== Environmental impacts ==

The main environmental impacts are:
*Pollution from using grid electricity generated through fossil fuel. Measures can be taken to reduce these impacts - for example, purchasing dual tariff 'green' electricity. However, even if ordinary grid electricity is used to run the compressor, the system will still produce less CO2 emissions than the most efficient condensing gas or oil boiler with the same output.
*Use of refrigerants in the system. Refrigerants are present in ground source heat pump systems and can pose a threat to the environment as they can be toxic, flammable or have a high global warming potential. However, new types and blends of refrigerants with minimal negative impacts are being developed. A correctly fitted system will also greatly reduce the potential for leakage, which is why using a professional installer is highly recommended.

----

This article was created by --[[User%3ABuro%20Happold|Buro Happold]], 17 March 2013.

= Find out more =

=== Related articles on Designing Buildings Wiki ===
*Air source heat pumps.
*Dynamic thermal modelling of closed loop geothermal heat pump systems.
*Earth-to-air heat exchangers.
*Geothermal energy
*Geothermal pile foundations.
*Ground energy options.
*Ground preconditioning of supply air.
*Sustainability.
*Water-source heat pumps.

=== External references ===

[http://www.gshp.org.uk Ground Source Heat Pump Association]

[[Category:Sustainability]]
[[Category:Products_/_components]]

Water source heat pumps

2014-09-19T18:45:24Z

Edward Thompson:

Heat pumps work by running a low-temperature, lower pressure refrigerant fluid in heat exchanger coils through a heat source, such as the outside air, the ground, or circulating water. The fluid ‘absorbs’ this heat and boils, even at temperatures below 0° C (although the coefficient of performance (COP) decreases with lower temperature). The resulting gas is then compressed, which further increases its temperature. The gas is passed into heat exchanger coils, where it condenses, releasing its latent heat. The process then repeats. This is the same process that is used to extract heat from a fridge. It can be used domestically or commercially and some systems can also be used to extract heat from a building to provide cooling.

Heat pumps can be used to provide hot water, space heating (either by providing hot water for under-floor heating or radiators, or supplying hot air) or other applications such as heating swimming pools.

In the UK, heat pumps are most commonly air-source or ground-source heat pumps. However, the temperature of water sources in the UK tends to be fairly constant for most of the year, at between 7 and 12°c. This makes water a more efficient heat source than the outside air, and the heat transfer rate with water is higher than that of air or the ground. In addition, unlike ground-source heat pumps, water-source heat pumps do not require trenches for coils to be laid in.

Water-source heat pumps require a suitable local water source, such as a lake, river, well, borehole and so on. They can be ‘open-loop’ or ‘closed-loop’ systems:
*Closed-loop systems pipe a mixture of water and anti-freeze to a water source such as a lake where it flows through coils or heat exchange panels in the water to exchange heat with it. The heated mixture is then piped to the heat pump and heat exchanged with the refrigerant.
*In open-loop systems water from the source is extracted and piped direct to the heat pump. Heat is then exchanged with the refrigerant and the water then returned to the source. As this involves extraction from and discharge to a water source, it may require an extraction licence and a discharge license from the Environment Agency.

Closed-loop systems can be less efficient than open-loop systems, because of the losses caused by transferring heat between the water source and the fluid in the closed loop. However, they are less restrictive in terms of; the danger of freezing, the water quality that can be used, the need for filtration or other forms of water treatment, the possibility of needing to use a corrosion resistant system and the need for licenses. Open-loop systems can also require more pumping.

Care must be taken with closed-loop systems to avoid the potential for the coils or heat exchange panels to be damaged by boats or other activities in or on the water.

Water source heat pumps are generally quiet, unobtrusive and have low maintenance requirements. However, care must be taken to ensure that the water supply is consistent and sufficient throughout the year.

Water-source heat pumps are be eligible for payments under the government’s Renewable Heat Incentive (RHI) scheme.

= Find out more =

=== Related articles on Designing Buildings Wiki: ===
*Air source heat pumps.
*Geothermal pile foundations.
*Green Deal.
*Ground energy options.
*Ground source heat pumps
*Renewable Heat Incentive.
*Solar thermal heating.
*Thermal labyrinths.

=== External references ===
*YouGen, [http://www.yougen.co.uk/renewable-energy/Heat+Pumps/ Heat pumps].

[[Category:Sustainability]]
[[Category:Products_/_components]]

Air source heat pumps

2014-09-19T18:38:53Z

Edward Thompson:

Air source heat pumps (ASHPs) use the external air as a heat source to provide heat for buildings.

They work by running a low-temperature, lower pressure refrigerant fluid in heat exchanger coils through the external air. The fluid ‘absorbs’ heat from the air and boils, even at temperatures below 0° C (although the coefficient of performance (COP) decreases with lower temperature). The gas is then compressed, which further increases its temperature. The gas is passed into heat exchanger coils, where it condenses, releasing its latent heat. The process then repeats.

This is the same process that is used to extract heat from a fridge. It can be used domestically or commercially and some systems can also be used to extract heat from a building to provide cooling.

Air source heat pumps can be air-to-water systems (providing hot water for direct use or to supply radiators or underfloor heating systems), or air-to-air systems (providing hot air, either directly into an internal space, or to be distributed by fans throughout a building).

Air source heat pumps can reduce energy consumption, fuel bills and carbon emissions, particularly where there is no mains gas supply, and so alternative heating systems would consume electricity, low pressure gas (LPG), oil, or coal.

They require the siting of one or more units, similar to an air conditioning units, outside the building. This may require planning permission, although in some areas, some installations may be considered to be ‘permitted developments’. Siting is important, as units can generate noise, and an electricity supply is required.

Air-to-water systems are most effective when providing lower-temperature hot water, over a longer period of time, than might be supplied by a conventional boiler. This lower-temperature hot water is appropriate for underfloor heating, or for large radiators. The coefficient of performance drops at higher sink temperatures (the temperature of the supplied water) required for smaller radiators, or for providing hot water. Higher temperature hot water might be better provided by other low-carbon systems such as solar thermal heating.

Because they provide lower-temperature hot water over long durations, they are generally most suitable for highly-insulated, air-tight buildings.

Air source heat pumps are generally low-maintenance and can be cheaper and easier to install and less disruptive than ground source heat pumps although their efficiency may be lower. Ground source heat pumps use a similar process but absorb heat from the ground, by circulating fluid through buried pipes. See ground source heat pump for more information.

Other benefits include; long life, low maintenance requirements, they are not polluting and unlike conventional heating systems they do not use combustible fuels or require flues. However, care must be taken over the selection of refrigerant, and leaks must be prevented.

Air to water heat pumps are be eligible for payments under the government’s Renewable Heat Incentive (RHI) scheme. They were eligible for funding under the Renewable Heat Premium Payment scheme, but this scheme closed on 31 March 2014 when the domestic Renewable Heat Incentive scheme was introduced.

= Find out more =

=== Related articles on Designing Buildings Wiki ===
*Combined heat and power CHP.
*Earth-to-air heat exchangers.
*Geothermal piles.
*Green Deal.
*Ground energy options.
*Ground pre-conditioning of supply air.
*Ground source heat pumps.
*Renewable energy.
*Renewable Heat Incentive.
*Solar thermal systems.
*Thermal labyrinths.
*Water-source heat pumps.
*Zero carbon homes.
*Zero carbon non-domestic buildings.

=== External references ===
*BSRIA [https://www.bsria.co.uk/news/article/air-source-heat-pumps/ Air-source heat pumps - pros, cons and considerations for specifiers]. January 2009

[[Category:Sustainability]]
[[Category:Products_/_components]]

Ground source heat pumps

2014-09-19T18:24:02Z

Edward Thompson:

= Introduction =

Heat is stored by the thermal mass of the ground of water thermal. There are two types of heat sources:
*Internal heat of the Earth
*Heat from the sun and stored in the ground

In the UK just a few metres below our feet the ground keeps a constant temperature of about 11-12C throughout the year.

== Internal heat of the earth ==

The Earth’s internal heat was originally produced during accretion. Since then heat has been produced by the radioactive decay of elements such as uranium, thorium and potassium. Due to its high enthalpy, this type of heat is often harvested in volcanic areas for electricity production and large district heating.

== Heat from the sun and stored in the ground ==

The majority of heat stored right in the Earth’s surface comes from the sun. This heat is widely available, and because of its low enthalpy, it is often harvested for local heat pump applications. There are two types of systems for utilising heat from the sun stored in the ground by a ground source heat pump:
*Open loop
*Closed loop

= Ground source heat pumps =

Ground source heat pumps can pump heat from the ground into a building to provide space heating and domestic hot water. For every unit of electricity used to pump the heat, 3-4 units of heat can be produced.

[[File:Example of a Ground Source Heat Pump System.jpg|423x308px|alt=Example of a Ground Source Heat Pump System.jpg]]

''Example of a ground source heat pump system.''

== Ground source heat pump system design ==

There are three important elements to a ground source heat pump system:
*Ground loop. This comprises of lengths of plastic pipe buried in the ground, either in a borehole or a horizontal trench. The pipe is a closed circuit and is filled with a mixture of water and antifreeze, which is pumped round the pipe absorbing heat from the ground.
*Heat pump. Heat pumps are very familiar to us in fridges and air conditioners. A heat pump works by using the evaporation and condensing of a refrigerant to move heat from one place to another. In this case, the evaporator (analogous to the squiggly loop in the cold part of the fridge) takes heat from the water in the ground loop; the condenser (analogous to the hot loop on the back of the fridge) gives up heat to a hot water tank which feeds the distribution system.
*A compressor. This uses electricity, (this is what makes the noise in a fridge) to move the refrigerant around the heat pump. It also compresses the gaseous refrigerant to increase the temperature at which it condenses to that needed for the distribution circuit.
*Heat distribution system. This consists of under floor heating or radiators for space heating and water storage for hot water supply. Some systems can also be used for cooling in the summer.

== Ground loop options ==

Three options are available for the ground loop:
*Borehole
*Straight horizontal
*Spiral horizontal (or 'slinky')

Each has different characteristics appropriate for different types of property. Horizontal trenches can cost less than boreholes, but require greater land area. For 'slinky' coils, a trench of about 10m length will provide approximately 1kW of heating load.

== Sizing ==

Sizing of the heat pump and the ground loops is crucial to the operation of the system and is is a job for specialists.

It is a good idea to explore ways of minimising space heating and hot water demand by energy efficiency measures.

NB A heat pump can be designed to meet 100% of space heating requirements and domestic hot water.

= Utilising ground energy =

[[File:How do you get useful heat from the ground.jpg|674x438px|alt=How do you get useful heat from the ground.jpg]] -[[File:How do you get useful coolth frmo the ground.jpg|688x457px|alt=How do you get useful coolth frmo the ground.jpg]]

== Running costs ==

The efficiency of a ground source heat pump system is measured by the Coefficient of Performance (CoP). This is the ratio of the number of units of heat output for each unit of electricity input used to drive the compressor and pump for the ground loop. Typical CoPs range between 2.5-4.The higher end of this range relates to under floor heating, because it works at a lower temperature (30-35°C) than radiators. Based on current fuel prices, assuming a CoP of 3-4, a ground source heat pump can be a cheaper form of space heating than oil, LPG and electric storage heaters. It is however more expensive than mains gas. If grid electricity is used for the compressor and pump, then an economy 7 tariff usually gives the lowest running costs.

== Environmental impacts ==

The main environmental impacts are:
*Pollution from using grid electricity generated through fossil fuel. Measures can be taken to reduce these impacts - for example, purchasing dual tariff 'green' electricity. However, even if ordinary grid electricity is used to run the compressor, the system will still produce less CO2 emissions than the most efficient condensing gas or oil boiler with the same output.
*Use of refrigerants in the system. Refrigerants are present in ground source heat pump systems and can pose a threat to the environment as they can be toxic, flammable or have a high global warming potential. However, new types and blends of refrigerants with minimal negative impacts are being developed. A correctly fitted system will also greatly reduce the potential for leakage, which is why using a professional installer is highly recommended.

----

This article was created by --[[User%3ABuro%20Happold|Buro Happold]], 17 March 2013.

= Find out more =

=== Related articles on Designing Buildings Wiki ===
*Air source heat pumps.
*Dynamic thermal modelling of closed loop geothermal heat pump systems.
*Earth-to-air heat exchangers.
*Geothermal energy
*Geothermal pile foundations.
*Ground energy options.
*Ground preconditioning of supply air.
*Sustainability.
*Water-source heat pumps.

=== External references ===

=== [http://www.gshp.org.uk http://www.gshp.org.uk] ===

[[Category:Sustainability]]
[[Category:Products_/_components]]

Ground source heat pumps

2014-09-18T16:49:20Z

Edward Thompson:

= Introduction =

Heat is stored by the thermal mass of the ground of water thermal. There are two types of heat sources:
*Internal heat of the Earth
*Heat from the sun and stored in the ground

In the UK just a few metres below our feet the ground keeps a constant temperature of about 11-12C throughout the year.

== Internal heat of the earth ==

The Earth’s internal heat was originally produced during accretion. Since then heat has been produced by the radioactive decay of elements such as uranium, thorium and potassium. Due to its high enthalpy, this type of heat is often harvested in volcanic areas for electricity production and large district heating.

== Heat from the sun and stored in the ground ==

The majority of heat stored right in the Earth’s surface comes from the sun. This heat is widely available, and because of its low enthalpy, it is often harvested for local heat pump applications. There are two types of systems for utilising heat from the sun stored in the ground by a ground source heat pump:
*Open loop
*Closed loop

= Ground source heat pumps =

Ground source heat pumps can pump heat from the ground into a building to provide space heating and domestic hot water. For every unit of electricity used to pump the heat, 3-4 units of heat are produced.

[[File:Example of a Ground Source Heat Pump System.jpg|423x308px|alt=Example of a Ground Source Heat Pump System.jpg]]

''Example of a ground source heat pump system.''

== Ground source heat pump system design ==

There are three important elements to a ground source heat pump system:
*Ground loop. This comprises of lengths of plastic pipe buried in the ground, either in a borehole or a horizontal trench. The pipe is a closed circuit and is filled with a mixture of water and antifreeze, which is pumped round the pipe absorbing heat from the ground.
*Heat pump. Heat pumps are very familiar to us in fridges and air conditioners. A heat pump works by using the evaporation and condensing of a refrigerant to move heat from one place to another. In this case, the evaporator (analogous to the squiggly loop in the cold part of the fridge) takes heat from the water in the ground loop; the condenser (analogous to the hot loop on the back of the fridge) gives up heat to a hot water tank which feeds the distribution system.
*A compressor. This uses electricity, (this is what makes the noise in a fridge) to move the refrigerant around the heat pump. It also compresses the gaseous refrigerant to increase the temperature at which it condenses to that needed for the distribution circuit.
*Heat distribution system. This consists of under floor heating or radiators for space heating and water storage for hot water supply. Some systems can also be used for cooling in the summer.

== Ground loop options ==

Three options are available for the ground loop:
*Borehole
*Straight horizontal
*Spiral horizontal (or 'slinky')

Each has different characteristics appropriate for different types of property. Horizontal trenches can cost less than boreholes, but require greater land area. For 'slinky' coils, a trench of about 10m length will provide approximately 1kW of heating load.

== Sizing ==

Sizing of the heat pump and the ground loops is crucial to the operation of the system and is is a job for specialists.

It is a good idea to explore ways of minimising space heating and hot water demand by energy efficiency measures.

NB A heat pump can be designed to meet 100% of space heating requirements, but it will usually only pre-heat domestic hot water, so top up heating (e.g. an immersion heater) will be required.

= Utilising ground energy =

[[File:How do you get useful heat from the ground.jpg|674x438px|alt=How do you get useful heat from the ground.jpg]] -[[File:How do you get useful coolth frmo the ground.jpg|688x457px|alt=How do you get useful coolth frmo the ground.jpg]]

== Running costs ==

The efficiency of a ground source heat pump system is measured by the Coefficient of Performance (CoP).This is the ratio of the number of units of heat output for each unit of electricity input used to drive the compressor and pump for the ground loop. Typical CoPs range between 2.5-4.The higher end of this range relates to under floor heating, because it works at a lower temperature (30-35 degC) than radiators. Based on current fuel prices, assuming a CoP of 3-4, a ground source heat pump can be a cheaper form of space heating than oil, LPG and electric storage heaters. It is however more expensive than mains gas. If grid electricity is used for the compressor and pump, then an economy 7 tariff usually gives the lowest running costs.

== Environmental impacts ==

The main environmental impacts are:
*Pollution from using grid electricity generated through fossil fuel. Measures can be taken to reduce these impacts - for example, purchasing dual tariff 'green' electricity. However, even if ordinary grid electricity is used to run the compressor, the system will still produce less CO2 emissions than the most efficient condensing gas or oil boiler with the same output.
*Use of refrigerants in the system. Refrigerants are present in ground source heat pump systems and can pose a threat to the environment as they can be toxic, flammable or have a high global warming potential. However, new types and blends of refrigerants with minimal negative impacts are being developed. A correctly fitted system will also greatly reduce the potential for leakage, which is why using a professional installer is highly recommended.

----

This article was created by --[[User%3ABuro%20Happold|Buro Happold]], 17 March 2013.

= Find out more =

=== Related articles on Designing Buildings Wiki ===
*Air source heat pumps.
*Dynamic thermal modelling of closed loop geothermal heat pump systems.
*Earth-to-air heat exchangers.
*Geothermal energy
*Geothermal pile foundations.
*Ground energy options.
*Ground preconditioning of supply air.
*Sustainability.
*Water-source heat pumps.

=== External references ===

=== [http://www.gshp.org.uk http://www.gshp.org.uk] ===

[[Category:Sustainability]]
[[Category:Products_/_components]]

Ground source heat pumps

2014-09-18T16:47:36Z

Edward Thompson:

= Introduction =

Heat is stored by the thermal mass of the ground of water thermal. There are two types of heat sources:
*Internal heat of the Earth
*Heat from the sun and stored in the ground

In the UK just a few metres below our feet the ground keeps a constant temperature of about 11-12C throughout the year.

== Internal heat of the earth ==

The Earth’s internal heat was originally produced during accretion. Since then heat has been produced by the radioactive decay of elements such as uranium, thorium and potassium. Due to its high enthalpy, this type of heat is often harvested in volcanic areas for electricity production and large district heating.

== Heat from the sun and stored in the ground ==

The majority of heat stored right in the Earth’s surface comes from the sun. This heat is widely available, and because of its low enthalpy, it is often harvested for local heat pump applications. There are two types of systems for utilising heat from the sun stored in the ground by a ground source heat pump:
*Open loop
*Closed loop

An example of an open loop system is a ground source heat pump.

= Ground source heat pumps =

Ground source heat pumps can pump heat from the ground into a building to provide space heating and, in some cases, pre-heating domestic hot water. For every unit of electricity used to pump the heat, 3-4 units of heat are produced.

[[File:Example of a Ground Source Heat Pump System.jpg|423x308px|alt=Example of a Ground Source Heat Pump System.jpg]]

''Example of a ground source heat pump system.''

== Ground source heat pump system design ==

There are three important elements to a ground source heat pump:
*Ground loop. This comprises of lengths of plastic pipe buried in the ground, either in a borehole or a horizontal trench. The pipe is a closed circuit and is filled with a mixture of water and antifreeze, which is pumped round the pipe absorbing heat from the ground.
*Heat pump. Heat pumps are very familiar to us in fridges and air conditioners. A heat pump works by using the evaporation and condensing of a refrigerant to move heat from one place to another. In this case, the evaporator (analogous to the squiggly loop in the cold part of the fridge) takes heat from the water in the ground loop; the condenser (analogous to the hot loop on the back of the fridge) gives up heat to a hot water tank which feeds the distribution system.
*A compressor. This uses electricity, (this is what makes the noise in a fridge) to move the refrigerant around the heat pump. It also compresses the gaseous refrigerant to increase the temperature at which it condenses to that needed for the distribution circuit.
*Heat distribution system. This consists of under floor heating or radiators for space heating and water storage for hot water supply. Some systems can also be used for cooling in the summer.

== Ground loop options ==

Three options are available for the ground loop:
*Borehole
*Straight horizontal
*Spiral horizontal (or 'slinky')

Each has different characteristics appropriate for different types of property. Horizontal trenches can cost less than boreholes, but require greater land area. For 'slinky' coils, a trench of about 10m length will provide approximately 1kW of heating load.

== Sizing ==

Sizing of the heat pump and the ground loops is crucial to the operation of the system and is is a job for specialists.

It is a good idea to explore ways of minimising space heating and hot water demand by energy efficiency measures.

NB A heat pump can be designed to meet 100% of space heating requirements, but it will usually only pre-heat domestic hot water, so top up heating (e.g. an immersion heater) will be required.

= Utilising ground energy =

[[File:How do you get useful heat from the ground.jpg|674x438px|alt=How do you get useful heat from the ground.jpg]] -[[File:How do you get useful coolth frmo the ground.jpg|688x457px|alt=How do you get useful coolth frmo the ground.jpg]]

== Running costs ==

The efficiency of a ground source heat pump system is measured by the Coefficient of Performance (CoP).This is the ratio of the number of units of heat output for each unit of electricity input used to drive the compressor and pump for the ground loop. Typical CoPs range between 2.5-4.The higher end of this range relates to under floor heating, because it works at a lower temperature (30-35 degC) than radiators. Based on current fuel prices, assuming a CoP of 3-4, a ground source heat pump can be a cheaper form of space heating than oil, LPG and electric storage heaters. It is however more expensive than mains gas. If grid electricity is used for the compressor and pump, then an economy 7 tariff usually gives the lowest running costs.

== Environmental impacts ==

The main environmental impacts are:
*Pollution from using grid electricity generated through fossil fuel. Measures can be taken to reduce these impacts - for example, purchasing dual tariff 'green' electricity. However, even if ordinary grid electricity is used to run the compressor, the system will still produce less CO2 emissions than the most efficient condensing gas or oil boiler with the same output.
*Use of refrigerants in the system. Refrigerants are present in ground source heat pump systems and can pose a threat to the environment as they can be toxic, flammable or have a high global warming potential. However, new types and blends of refrigerants with minimal negative impacts are being developed. A correctly fitted system will also greatly reduce the potential for leakage, which is why using a professional installer is highly recommended.

----

This article was created by --[[User%3ABuro%20Happold|Buro Happold]], 17 March 2013.

= Find out more =

=== Related articles on Designing Buildings Wiki ===
*Air source heat pumps.
*Dynamic thermal modelling of closed loop geothermal heat pump systems.
*Earth-to-air heat exchangers.
*Geothermal energy
*Geothermal pile foundations.
*Ground energy options.
*Ground preconditioning of supply air.
*Sustainability.
*Water-source heat pumps.

=== External references ===

=== [http://www.gshp.org.uk http://www.gshp.org.uk] ===

[[Category:Sustainability]]
[[Category:Products_/_components]]

Ground source heat pumps

2014-09-18T15:46:27Z

Edward Thompson:

= Introduction = Heat is stored by the thermal mass of the ground of water thermal. There are two types of heat sources: *Internal heat of the Earth *Heat from the sun and stored in the ground In the UK just a few metres below our feet the ground keeps a constant temperature of about 11-12C throughout the year. == Internal heat of the earth == The Earth’s internal heat was originally produced during accretion. Since then heat has been produced by the radioactive decay of elements such as uranium, thorium and potassium. Due to its high enthalpy, this type of heat is often harvested in volcanic areas for electricity production and large district heating. == Heat from the sun and stored in the ground == The majority of heat stored right in the Earth’s surface comes from the sun. This heat is widely available, and because of its low enthalpy, it is often harvested for local heat pump applications. There are two types of systems for utilising heat from the sun stored in the ground by a ground source heat pump: *Open loop *Closed loop An example of an open loop system is a ground source heat pump. = Ground source heat pumps = Ground source heat pumps can pump heat from the ground into a building to provide space heating and, in some cases, pre-heating domestic hot water. For every unit of electricity used to pump the heat, 3-4 units of heat are produced. [[File:Example of a Ground Source Heat Pump System.jpg|423x308px|alt=Example of a Ground Source Heat Pump System.jpg]] ''Example of a ground source heat pump system.'' == Ground source heat pump system design == There are three important elements to a ground source heat pump: *Ground loop. This comprises of lengths of plastic pipe buried in the ground, either in a borehole or a horizontal trench. The pipe is a closed circuit and is filled with a mixture of water and antifreeze, which is pumped round the pipe absorbing heat from the ground. *Heat pump. Heat pumps are very familiar to us in fridges and air conditioners. A heat pump works by using the evaporation and condensing of a refrigerant to move heat from one place to another. In this case, the evaporator (analogous to the squiggly loop in the cold part of the fridge) takes heat from the water in the ground loop; the condenser (analogous to the hot loop on the back of the fridge) gives up heat to a hot water tank which feeds the distribution system. *A compressor. This uses electricity, (this is what makes the noise in a fridge) to move the refrigerant around the heat pump. It also compresses the gaseous refrigerant to increase the temperature at which it condenses to that needed for the distribution circuit. *Heat distribution system. This consists of under floor heating or radiators for space heating and water storage for hot water supply. Some systems can also be used for cooling in the summer. == Ground loop options == Three options are available for the ground loop: *Borehole *Straight horizontal *Spiral horizontal (or 'slinky') Each has different characteristics appropriate for different types of property. Horizontal trenches can cost less than boreholes, but require greater land area. For 'slinky' coils, a trench of about 10m length will provide approximately 1kW of heating load. == Sizing == Sizing of the heat pump and the ground loops is crucial to the operation of the system and is is a job for specialists. It is a good idea to explore ways of minimising space heating and hot water demand by energy efficiency measures. NB A heat pump can be designed to meet 100% of space heating requirements, but it will usually only pre-heat domestic hot water, so top up heating (e.g. an immersion heater) will be required. = Utilising ground energy = [[File:How do you get useful heat from the ground.jpg|674x438px|alt=How do you get useful heat from the ground.jpg]] -[[File:How do you get useful coolth frmo the ground.jpg|688x457px|alt=How do you get useful coolth frmo the ground.jpg]] == Running costs == The efficiency of a ground source heat pump system is measured by the Coefficient of Performance (CoP).This is the ratio of the number of units of heat output for each unit of electricity input used to drive the compressor and pump for the ground loop. Typical CoPs range between 2.5-4.The higher end of this range relates to under floor heating, because it works at a lower temperature (30-35 degC) than radiators. Based on current fuel prices, assuming a CoP of 3-4, a ground source heat pump can be a cheaper form of space heating than oil, LPG and electric storage heaters. It is however more expensive than mains gas. If grid electricity is used for the compressor and pump, then an economy 7 tariff usually gives the lowest running costs. == Environmental impacts == The main environmental impacts are: *Pollution from using grid electricity generated through fossil fuel. Measures can be taken to reduce these impacts - for example, purchasing dual tariff 'green' electricity. However, even if ordinary grid electricity is used to run the compressor, the system will still produce less CO2 emissions than the most efficient condensing gas or oil boiler with the same output. *Use of refrigerants in the system. Refrigerants are present in ground source heat pump systems and can pose a threat to the environment as they can be toxic, flammable or have a high global warming potential. However, new types and blends of refrigerants with minimal negative impacts are being developed. A correctly fitted system will also greatly reduce the potential for leakage, which is why using a professional installer is highly recommended. ---- This article was created by --[[User%3ABuro%20Happold|Buro Happold]], 17 March 2013. = Find out more = === Related articles on Designing Buildings Wiki === *Air source heat pumps. *Dynamic thermal modelling of closed loop geothermal heat pump systems. *Earth-to-air heat exchangers. *Geothermal energy *Geothermal pile foundations. *Ground energy options. *Ground preconditioning of supply air. *Sustainability. *Water-source heat pumps.

[[Category:Sustainability]]
[[Category:Products_/_components]]

Ground source heat pumps

2014-09-18T15:39:11Z

Edward Thompson:

= Introduction = Heat is stored by the thermal mass of the ground of water thermal. There are two types of heat sources: *Internal heat of the Earth *Heat from the sun and stored in the ground In the UK just a few metres below our feet the ground keeps a constant temperature of about 11-12C throughout the year. == Internal heat of the earth == The Earth’s internal heat was originally produced during accretion. Since then heat has been produced by the radioactive decay of elements such as uranium, thorium and potassium. Due to its high enthalpy, this type of heat is often harvested in volcanic areas for electricity production and large district heating. == Heat from the sun and stored in the ground == The majority of heat stored right in the Earth’s surface comes from the sun. This heat is widely available, and because of its low enthalpy, it is often harvested for local heat pump applications. 
 
There are two types of systems for utilising heat from the sun stored in the ground: *Open loop ground source heat pumps*Closed loop ground source heat pumps An example of an open loop system is a ground source heat pump. = Ground source heat pumps = Ground source heat pumps can pump heat from the ground into a building to provide space heating and, in some cases, pre-heating domestic hot water. For every unit of electricity used to pump the heat, 3-4 units of heat are produced. [[File:Example of a Ground Source Heat Pump System.jpg|423x308px|alt=Example of a Ground Source Heat Pump System.jpg]] ''Example of a ground source heat pump system.'' == Ground source heat pump system design == There are three important elements to a ground source heat pump: *Ground loop. This comprises of lengths of plastic pipe buried in the ground, either in a borehole or a horizontal trench. The pipe is a closed circuit and is filled with a mixture of water and antifreeze, which is pumped round the pipe absorbing heat from the ground. *Heat pump. Heat pumps are very familiar to us in fridges and air conditioners. A heat pump works by using the evaporation and condensing of a refrigerant to move heat from one place to another. In this case, the evaporator (analogous to the squiggly loop in the cold part of the fridge) takes heat from the water in the ground loop; the condenser (analogous to the hot loop on the back of the fridge) gives up heat to a hot water tank which feeds the distribution system. *A compressor. This uses electricity, (this is what makes the noise in a fridge) to move the refrigerant around the heat pump. It also compresses the gaseous refrigerant to increase the temperature at which it condenses to that needed for the distribution circuit. *Heat distribution system. This consists of under floor heating or radiators for space heating and water storage for hot water supply. Some systems can also be used for cooling in the summer. == Ground loop options == Three options are available for the ground loop: *Borehole *Straight horizontal *Spiral horizontal (or 'slinky') Each has different characteristics appropriate for different types of property. Horizontal trenches can cost less than boreholes, but require greater land area. For 'slinky' coils, a trench of about 10m length will provide approximately 1kW of heating load. == Sizing == Sizing of the heat pump and the ground loops is crucial to the operation of the system and is is a job for specialists. It is a good idea to explore ways of minimising space heating and hot water demand by energy efficiency measures. NB A heat pump can be designed to meet 100% of space heating requirements, but it will usually only pre-heat domestic hot water, so top up heating (e.g. an immersion heater) will be required. = Utilising ground energy = [[File:How do you get useful heat from the ground.jpg|674x438px|alt=How do you get useful heat from the ground.jpg]] -[[File:How do you get useful coolth frmo the ground.jpg|688x457px|alt=How do you get useful coolth frmo the ground.jpg]] == Running costs == The efficiency of a ground source heat pump system is measured by the Coefficient of Performance (CoP).This is the ratio of the number of units of heat output for each unit of electricity input used to drive the compressor and pump for the ground loop. Typical CoPs range between 2.5-4.The higher end of this range relates to under floor heating, because it works at a lower temperature (30-35 degC) than radiators. Based on current fuel prices, assuming a CoP of 3-4, a ground source heat pump can be a cheaper form of space heating than oil, LPG and electric storage heaters. It is however more expensive than mains gas. If grid electricity is used for the compressor and pump, then an economy 7 tariff usually gives the lowest running costs. == Environmental impacts == The main environmental impacts are: *Pollution from using grid electricity generated through fossil fuel. Measures can be taken to reduce these impacts - for example, purchasing dual tariff 'green' electricity. However, even if ordinary grid electricity is used to run the compressor, the system will still produce less CO2 emissions than the most efficient condensing gas or oil boiler with the same output. *Use of refrigerants in the system. Refrigerants are present in ground source heat pump systems and can pose a threat to the environment as they can be toxic, flammable or have a high global warming potential. However, new types and blends of refrigerants with minimal negative impacts are being developed. A correctly fitted system will also greatly reduce the potential for leakage, which is why using a professional installer is highly recommended. ---- This article was created by --[[User%3ABuro%20Happold|Buro Happold]], 17 March 2013. = Find out more = === Related articles on Designing Buildings Wiki === *Air source heat pumps. *Dynamic thermal modelling of closed loop geothermal heat pump systems. *Earth-to-air heat exchangers. *Geothermal energy *Geothermal pile foundations. *Ground energy options. *Ground preconditioning of supply air. *Sustainability. *Water-source heat pumps. 

[[Category:Sustainability]]
[[Category:Products_/_components]]