technologies

Ground Source Heat Pumps

The Basic Principles & Benefits of a Ground Source Heat Pump

It might not feel like it at times, but the earth is a giant battery of heat. Ground source heat pumps extract this heat from the earth and use it to provide heating and hot water. The energy (heat) extracted from the ground is much greater than the energy (electricity) used to power the process which means that ground source heat pumps are the most efficient method of providing year round heating and hot water.

The image below shows how temperature variance reduces with depth. You can see that the temperature range falls rapidly as depth increases and this is the reason that ground source heat pumps are able to provide heating hot water efficiently during the colder months.

Involving a specialist heat pump contractor like us will ensure that the best and most appropriate solution is recommended. Every project is considered on an individual basis and we develop a bespoke heat pump design to produce the most efficient system,and maximise your return on investment.

Below are the key principles and benefits of a ground source heat pump, but we’d love to hear from you and develop a proposal that meets your particular requirements.

What are the benefits of a ground source heat pump?

Reduction of C02 emissions – unlike biomass, oil or LPG, GSHPs produce no carbon emissions on site.
Reduction of energy bills – GSHPs are one of the most efficient forms of energy supply. Running the systems requires a small level of electricity; however, a quality system will deliver an energy output of three to four times the input. This ratio is called Coefficient of Performance (COP).
Income generation – heat pump funding and grants such as the Renewable Heat Incentive (RHI) allow a significant return of investment for ground source heat pump installations.
Safety and convenience – the system requires little to no maintenance and has a life in excess of 25 years. It also removes any requirement for purchasing and storing any natural or combustible fuel components.

What is a ground source heat pump?

Any heat pump system which extracts heat directly from the earth is called a ground source heat pump. A typical ground source heat pump is able to extract four times more energy from the ground than the energy used by the heat pump and this makes ground source heat pumps one of the most efficient solutions for providing heating and hot water.

What are the different heat source options for ground source heat pumps?

There are two different methods of extracting heat from the ground:

Vertical boreholes are the most common heat source for ground source heat pump systems. The holes are drilled using a rotary drilling rig. The exact number and dimensions of the borehole array will depend on the thermal conductivity and volumetric capacity of the ground that you are drilling, but they are typically 100-150m deep.
Horizontal heat collectors use a number of trenches of approximately 1000mm depth and 900mm width. The length of the trenches will depend on the land available but they will usually be between 50m and 200m long.

How does a ground source heat pump installation work?

A ground source heat pump system circulates a solution of water and glycol around a network of pipework which travels underground. The temperature underground is more constant throughout the year than the air temperature at the surface and this means that, during the colder months of the year, the ground temperature is warmer than the surface air temperature.

Heat pump efficiency is a product of the difference between its heat source (the ground) and the heat use (the heating or hot water system). By using the warmth of the earth as the heat source, a ground source heat pump provides heating and hot water very efficiently, and a more efficient heating system is a less expensive one to run.

What can a ground source heat pump be used for?

Ground source heat pumps can provide all your space heating and hot water. They can also provide cheap cooling if you have a suitable distribution system installed.

Historically, heat pumps were not able to achieve high enough temperatures to meet all hot water demands and this meant that they often had to be topped up with a conventional system such as, direct electric or oil. However, modern heat pumps can achieve heating and hot water temperatures of 60℃+ and can provide 100% of your heating and hot water.

It has also been common for heat pump systems to only be recommended with underfloor heating. However, modern heat pumps can run efficiently with conventional radiators at efficiencies that make them much less expensive to run that oil or gas heating. In addition, there are also highly efficient radiators, such as Jaga Strada, which can be used with heat pumps and actually offer better efficiency than underfloor heating.

What are the stages of a ground source heat pump installation?

A commercial or large-scale ground source heat pump system will typically follow this process:

Site set up and planning – the first stage of installing a ground source heat pump system is the one that is most often forgotten. Site set up and planning includes:
- Setting out all trenches and boreholes accurately
- Double checking that you have sufficient capacity in your electrical supply for the heat pump system
- Having a waste management plan to deal with the waste water, earth, and drilling arisings.
- Attain planning permission for the system. Not all heat pump systems require planning but Ofgem make it a requirement of the Renewable Heat Incentive scheme that you send evidence of planning approval, or that planning isn’t required.
- Ensure that all health and safety measures are taken care of. This includes: risk assessment and method statements, fencing off dangerous areas, providing welfare facilities is required, and making sure all operatives are suitably qualified and wearing the correct Personal Protective Equipment (PPE)
Dig or drill – the next step is usually to install the heat source for the heat pump system. Sizing the heat source correctly is the most important part of designing a heat pump system. If you undersize the heat collector then you will freeze the ground and the system will not work properly. If you oversize the heat collector then you will waste money, time and land. For ground source heat pumps there are two options available for your heat source:
- Vertical boreholes are the most common heat source for ground source heat pump systems. The holes are drilled using a rotary drilling rig. The exact number and dimensions of the borehole array will depend on the thermal conductivity and volumetric capacity of the ground that you are drilling.
- Horizontal heat collectors use a number of trenches of approximately 1000mm depth and 900mm width. The length of the trenches will depend on the land available but they will usually be between 50m and 200m long.
Manifolding – Once the boreholes or horizontal collectors are finished they need to be connected together to form a common flow and return. A manifold is used to bring all flow pipes together and all return pipes together. It is usually a good idea to also include flow regulators and isolation valves on the manifold too. Once the manifolding is complete, the main flow and return pipes are taken to the plant room ready for connection to the ground source heat pumps.
Mechanical heat pump installation – The next step is to install the heat pump system. The mechanical installation happens first and includes all pipework, buffer vessel, valves, pumps, and the heat pumps themselves. This work is carried out by highly skilled and experienced engineers who will ensure that the installation is completed according to the design.
Electrical and controls installation – Once the mechanical installation is complete we can start the electrical and controls installation. One of the most common reasons for faults and under performing systems is not setting the control strategy correctly and not making sure that the heat pump system interfaces correctly with the rest of the heating/cooling/hot water system.
Commissioning and testing – The commissioning and testing process should include:
- Making sure the controls are set up correctly
- Checking that the whole system is successfully tested under pressure
- Flushing and filling the system thoroughly and properly
- Making sure that all air is removed from the system
- Making sure that the system controls are setting up as required by the owner and that the system is operating as it is meant to
- Gathering all the information required for the Renewable Heat Incentive application
Handover – this stage includes demonstrating the system to the client and showing them the various parts of the heat pump installation. It also includes handing over the operation and maintenance manual for the system.
Monitoring, servicing, and maintenance – The final stage is ongoing and involves:
- Remote monitoring: we use remote monitoring to log all the parameters of the system performance. This enables us to pick up any faults in the system quickly and to make sure our engineers have everything they need to fix the problem when they get to site. Our monitoring service also includes the periodic remote reading and submission of heat meter data to Ofgem for the Renewable Heat Incentive scheme.
- Servicing: All heat pump manufacturers require the heat pump system to be regularly and correctly serviced for the manufacturers warranty to remain valid. Regular servicing is also important to maximise the heat pump longevity. Correct and preemptive servicing can add years to the life of your heat pump system.
- Maintenance: There are two types of maintenance that people require: emergency, and non-emergency. It is important that you have a servicing and maintenance contract with a company which understands your system and has the resources to react quickly to any problems that arise.

Considering Installing a Ground Source Heat Pump?

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