Ground Source Heat Pumps

Ground source heat pumps provide hot water and heating for a range of properties including homes and businesses in what is one of the cleanest and most efficient ways to produce thermal energy.

A ground source heat pump uses the constant latent geothermal heat in ground water to produce thermal energy ideal for heating and hot water. Ground source heat pumps use electricity and so for every 1kW of electricity used to operate the heat pumps, 3kW to 5kW of heat energy is produced and available for heating purposes.

How does it work?

A ground source heat pump works by extracting a combination of solar energy and energy contained in rainfall which is stored in the upper strata of the ground. Pipes filled with a water/antifreeze mix need to be buried around 1.2-1.5 meters deep underground. The heat pump then circulates this cold fluid around the array of pipes, extracting energy from the surrounding ground. It is critical that sufficient pipe is buried and spread over a large enough area so that this energy extraction is sustainable meaning ground temperatures will return to normal before the start of each heating season.

The warmed fluid coming back from the ground array transfers energy across a heat exchanger to a very cold refrigerant gas. The then warmed gas passes through an electrically driven compressor where it is compressed, generating the high grade heat needed to provide heating and hot water for your home.

As a by-product of the heat pump providing heating, the ground side is cooled.  This cooling can be harnessed and used to provide for a gym or other communal space. The ground array can also be used as a heat dump for a larger air conditioning system, making better use of the available heat than releasing it to the excess air.

What do I need to install it?

A small plant room approximately 2.5m x 1.5m in size will be needed for the internal heat pump unit and cylinder. The back of a garage is ideal for this kind of installation. Externally an area of open ground will be required for a horizontal array, with the area required dependant on the heat load of the target property. If sufficient open space is not available options are available to insert the collector pipe vertically into a number of boreholes down into the water table, larger installations boreholes can be more cost effective than horizontal collectors.

The key to installing heat pumps of any kind is that the heating emitter circuit is optimised to work with heat pumps and run at lower flow temperatures (around 40^o-50^oC) than used with a conventional fossil fuel boiler. This means the compressor will have less work to do to convert the low grade heat extracted from the ground into high grade heat needed for heating. The installation as a whole will therefore use less electricity, increasing efficiency and decreasing running costs.

With a modern property and underfloor heating, lower flow temperatures are easy to ensure. Underfloor heating on either solid or joisted floors can be designed to run at temperatures even below 40^oC in certain properties (we offer a full in-house design and installation package for Underfloor Heating – Please click here for more details) and low flow temperature radiators can be built in if required.

In a domestic retrofit environment we will undertake a careful assessment of the existing radiators. Often radiators were designed using the Mears formula, which significantly oversized the emitters to ensure that rooms could be brought up to temperature quickly when the boiler fired. This oversizing often exactly matches the heat pumps requirements, so generally only the radiators in rooms that are already cold with the existing heating system need upsizing whilst the rest will work with a heat pump system.

How much will it save me?

A well installed heat pump should run at a Seasonal Coefficient of Performance (SCOP) of around 3:1 to 5:1 on average throughout the year, depending on the flow temperature of the system between 35degC and 55degC. This means that for every 1kWh of electricity needed to run the compressor 3-5kWh of heat will be generated by the heat pump.  At an electricity cost of 28p/kWh (as per the April 2022 Ofgem Price Cap) therefore a heat pump will cost around 6-9p/kWh to run.

Features

• Fuelled by the inexhaustible supply of solar energy in the ground
• High reliability and quiet running
• Intrinsically safe and can be located and sited either internally or externally
• Compliant with Building Regulations Part L requirements as well as carbon reduction requirements
• One of the cornerstones of the Microgeneration Certification Scheme backed by the Government

Benefits

• Unrivalled life costs and low operating costs
• Solely run on electricity with no concerns regarding safety issues surrounding oil or gas
• Fuel storage not required
• VAT is only 0% VAT and grants are provided under renewable energy schemes by the Government
• Maximum living comfort when coupled with underfloor heating as part of a renewable energy system

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