Ground Source Heat Pumps

Category: Ground Source Heat Pumps
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UK:  Heat pump manufacturers have welcomed the official extension to the Non-Domestic Renewable Heat Incentive (RHI), to now include air source heat pumps, following the announcement by the Department of Energy & Climate Change (DECC) on Wednesday 28 May 2014.

Under the incentive scheme companies receive regular payments for every kWh of renewable heat they use in their business, if generated by a ground, water or air source heat pump.

Tariffs are available for air source heat pumps at 2.5p/kWh and ground source heat pumps at a Tier 1 rate of 8.7p/kWh and Tier 2 rate of 2.6 p/kWh. Tier 1 is paid for the first 1,314 full-load equivalent hours and Tier 2 for all remaining output.

Businesses will receive a regular quarterly payment for the next 20 years, which provides long term and sustainable growth in the use of renewable technologies. The payments can amount to thousands of pounds

And help make the case for heat pumps much stronger, especially against traditional fossil fuel heating.

Eligibility of heat pumps

After the new regulations are introduced, applications submitted for ground-source and air-source heat pumps will be required to include the following:

  • A design seasonal performance factor (SPF) of at least 2.5
  • Measurement of electrical input to calculate SPF and provide quarterly meter readings
  • Ground-source heat pumps capable of simultaneous heating and cooling will have to measure heat drawn from the ground and provide quarterly meter readings
  • Ground-source heat pumps capable of cooling must provide a capacity value based on the heating function only
  • In addition to using naturally occurring energy in the form of heat. ground-source heat pumps will be able to, use heat from:
  • Heat gathered and stored in the ground using solar collectors providing no other subsidy for this heat is being received
  • Heat from space cooling or process cooling
  • Waste heat from industrial processes  

New Tariffs

Speaking at the ATMOsphere Europe 2013 Conference held in Brussels last week John Skelton F.Inst.R., Head of Refrigeration at Sainsbury’s, outlined the Company’s progress with regard to the installation of environmentally friendly RACHP technologies within their stores.
This includes:

167 CO2 refrigeration installations

17 LED lighting installations

78 Biomass boilers

12 Closed Loop Geothermal Heating and Cooling Systems

129,000 Solar panels

25% of Petrol Station energy from solar photovoltaic panels (PV)

These initiatives form part of Sainsbury’s 20x20 Sustainability Plan of which ‘Respect for our environment’ is a key objective.

John Skelton joined Sainsbury’s Supermarkets Limited as an apprentice in 1984. He has spent his career in retail refrigeration working for and on behalf of various UK food retailers. He has been instrumental in reducing Sainsbury’s carbon footprint and the step change to CO2 refrigeration. John has delivered CO2 to over 160 stores and continues to champion the switch to natural refrigerant solutions.

The presentation can be viewed here:

ATMOsphere presentation

In the first Fridgehub article on the subject of Geothermal/Ground Source Heat Pumps (18th September 2013) we outlined Sainsbury’s initiative to use this innovative technology to tap renewable energy from deep underground to provide energy efficient heating, hot water and cooling in a growing number of their supermarkets.

Fridgehub are privileged to have been granted permission by the Institute of Refrigeration to publish a case study written by John Skelton entitled “Closed Loop Geothermal Heating and Cooling for Supermarkets”.

In his introduction to the case study the author states that “The development of a closed loop geothermal heating and cooling system provided the ideal vehicle for Sainsbury’s to manage a store’s total carbon emissions whilst driving operational excellence”.

The case study describes the installation and energy performance of the integrated solution at Sainsbury’s store at Crayford, South East London (their first 100,000 sq. /ft. store)”.

Crayford was selected as a trial ‘carbon step change store’ as part of the Sainsbury’s business challenge to develop a lower carbon operational model. During 2010 the store’s sales area was being extended from 35,000 sq. /ft. to over 100,000 sq. /ft. and the challenge was set to achieve a zero absolute increase in the original store’s operational carbon footprint. An integrated geothermal system was selected to harness normally wasted store energy and to use it efficiently across the refrigeration and heating systems.

A key feature of this solution was that it required all of the delivery teams to change their normal ways of working from a design, installation and commissioning perspective. It was essential that the supply base drove the specification and worked collaboratively. In particular the collaboration between the disciplines of Refrigeration and Mechanical & Electrical engineering was critical to a successful outcome.

The system incorporates a primary circuit closed loop borehole system which provides access to the geothermal storage capacity of subsurface geology, adapting technology from the oil and gas drilling industry to utilise 15 x 200m deep boreholes.

The primary circuit which links the below ground boreholes to the refrigeration packs and the store heat pumps is filled with a glycol-water mix which exchanges geothermal energy due to the temperature differential with the surrounding geology. Due to the natural, relatively cool temperature of the ground a good condensing or cooling medium is delivered to the store’s refrigeration packs and heat pumps.

A secondary circuit delivers the store heating functions from the heat pumps, the performance of which is assisted by the rejected heat from the refrigeration packs.

The refrigeration packs are ‘standard’ Sainsbury’s CO2 with the addition of water to refrigerant heat exchangers in the refrigeration discharge circuit.

The heat pumps are fitted with water to refrigerant heat exchangers. The evaporator is supplied with the glycol-water mix from the borehole circuit, providing low grade heat. The condenser is connected to the store heating and hot water system and high quality heat produced by the compressors is rejected into a standard water-based circuit within the store which has enabled the requirement for natural gas to be discontinued.

Each of the working systems are sub-metered and monitored utilising the Sainsbury’s standard web-based system which enables both historical and cross-store comparisons. To ensure accuracy BSRIA were employed to check all of the monitoring points and calibrate and verify them, as well as to check the reporting/calculation methodology.

The first full year’s operation at Crayford delivered approximately a 55% energy saving in heating and refrigeration against an agreed benchmark for a like-sized store utilising standard systems (i.e. air-cooled CO2 refrigeration packs and gas boilers for heating).

The installation demonstrates that there are tangible benefits from considering a building’s carbon emissions as a ‘whole’ and ensuring the different engineering disciplines work together to reduce direct and indirect emissions, highlighting Sainsbury’s collaborative supplier philosophy.  The Closed Loop Geothermal Heating and Cooling system at Crayford has delivered significant savings in refrigeration energy consumption, as well as a highly efficient ground source heating system to the store.

From the outset, this design concept was intended to be both sustainable and replicable, and as a result of the experience at Crayford the systems has now been implemented in an additional 11 Sainsbury’s stores during the past 3 years making a significant contribution to their 20 by 20 target of a 30% reduction in absolute operational carbon emissions by 2020 versus a baseline of 2005.

The IoR article can be viewed here:

Closed loop refrigeration


  • ATMOsphere European Conference 2013
  • John Skelton F.Inst.R
  • The Institute of Refrigeration

Many case study sessions that focus on cutting-edge natural refrigerant technologies and projects in the areas of industrial, commercial and transport refrigeration as well as heat pumps and air-conditioning were included at the ATMOsphere Europe 2013 Conference.

The full range of presentations from ATMOsphere Europe can be found on

A geothermal heat pump or ground source heat pump (GSHP) is a central heating and/or cooling system that pumps heat to or from the ground.  Ground source heat pumps harvest heat absorbed at the Earth's surface from solar energy.  It uses the earth as a heat source (in the winter) or a heat sink (in the summer). 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. Ground source heat pumps are also known as "geothermal heat pumps" although, strictly, the heat does not come from the centre of the Earth, but from the Sun.

Ground source heat pumps use pipes which are buried in the ground to extract heat from the ground. This heat can then be used to heat radiators, underfloor or warm air heating systems and hot water in a building.

A ground source heat pump circulates a mixture of water and antifreeze around a loop of pipe – called a ground loop – which is buried in the ground outside the building. Heat from the ground is absorbed into the fluid and then passes through a heat exchanger into the heat pump. The ground stays at a fairly constant temperature under the surface, so the heat pump can be used throughout the year – even in the middle of winter.

The length of the ground loop depends on the size of the building and the amount of heat needed. Longer loops can draw more heat from the ground, but need more space to be buried in. If space is limited, a vertical borehole can be drilled instead.

The benefits of installing a ground source heat pump (GSHP) include:

  • Lower fuel bills, especially when replacing conventional electric heating systems
  • Could be eligible for income through the government’s Renewable Heat Incentive (RHI*) for non-domestic buildings
  • Lower the building’s carbon emissions, depending on which fuel you are replacing
  • Can be used to heat and provide hot water
  • Needs little maintenance – GSHP’s are known as ‘fit and forget’ technology.
  • Renewable Heat Incentive – Commercial RHI - Owners of ground source heat pumps systems (and other eligible renewable heat technologies) installed since 15 July 2009, can apply to Ofgem to be paid around 10 pence/kWhour of renewable heat generated for the next 20 years.

Unlike gas and oil boilers, heat pumps deliver heat at lower temperatures over much longer periods. During the winter they may need to be on constantly to heat the building efficiently. Occupants will also notice that radiators won't feel as hot to the touch as they might do when using a gas or oil boiler.

Heat from the ground is absorbed at low temperatures into a fluid inside a loop of pipe (a ground loop) buried underground. The fluid then passes through a compressor that raises it to a higher temperature, which can then heat water for the heating and hot water circuits of the house. The cooled ground-loop fluid passes back into the ground where it absorbs further energy from the ground in a continuous process as long as heating is required.

Normally the loop is laid flat or coiled in trenches about two metres deep, but if there is not enough space a vertical loop down into the ground can be installed to a depth of up to 100 metres.  Heat pumps have some impact on the environment as they need electricity to run, but the heat they extract from the ground, the air, or water is constantly being renewed naturally.

In July, retail giant Sainsbury’s launched the installation of their 12th Ground Source Heat Pump at their store at London Colney in St. Albans.  They have showcased their use of this innovative technology that taps renewable energy from deep underground to provide energy efficient heating, hot water and cooling for the stores.  The roll out of Ground Source Heat Pumps at 12 stores follows Sainsbury’s successful world-first use of the geo-thermal technology at its Crayford store, enabling it to supply 30 per cent of its energy from on-site renewable sources.  It has also installed 74 biomass boilers since 2008, which use wood pellets - a renewable resource - to heat stores rather than using fossil fuel-based gas.

GSHP Resources

The Ground Source Heat Pump Association - The Association provides information on GSHPs via a this website and telephone helplines and makes presentations to promote the ground source industry to key audiences.

Energy Savings Trust – Advice to homeowners on Ground Source Heat Pumps, installation, financial benefits, Planning permissions.

B&ES - Ground Source Heat Pump Guidance - Great resources that will provide more detail on Ground Source Heat Pumps

B&ES – TR 30 - The first part of the forthcoming suite of TR30 publications, this looks at different applications of Heat Pumps technology.  It provides generic installation requirements for a range of renewable energy systems including biomass fuels, solar hot water and combined heat and power (CHP).

Ground source heat pump

Image Credit: Advance NRG

This article is brought to you by Fridgehub – a major new industry website for manufacturers, distributers, service providers, operators and consumers of refrigeration, air conditioning and heat-pump (RACHP) products and services.

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