Ground Source Heating & Cooling

Contact H2Ogeo to discuss environmental risk assessments and technical requirements for installing ground source heat pumps.

The Environment Agency recognises that Achieving UK climate change targets requires a massive shift from fossil fuels to renewable energy and other technologies with low greenhouse gas emissions. Ground source heat is one technology that could help achieve this.

Ground source heating and cooling (GSHC) systems utilise a renewable energy source, i.e. the warming of the ground by solar radiation. There are two types of GSHC systems: ‘closed loop’ and ‘open loop’. In general, open loop systems require more detailed assessment, planning and regulation. In open loop systems, water is abstracted from the ground and pumped through a heat exchanger before it is pumped back into the ground, a sewer or river. Open loop systems require more detailed assessment, planning and regulation.

In closed loop systems, fluid is re-circulated through a heat exchanger connected to a sealed system of pipes in boreholes, trenches or piles. The fluid moves heat energy between the ground and/or groundwater and the heat exchanger.

It is important that operators understand the potential environmental risks of a proposed scheme and take steps to reduce environmental risks, H2Ogeo provides technical support and advice on the potential environmental sensitivities and risks.

The Government’s Planning Portal has some useful information relating to ground source heat pumps and the planning permission requirements. On the whole there is little planning permission required to install a heat pump. In England, Scotland and Wales, domestic ground source heat pumps are generally allowed as permitted developments, but check with your local authority to find out whether you need planning permission or not. In Northern Ireland you must consult with your local authority regarding planning permission for ground source heat pumps.

Building regulations do apply to the installation of heat pumps and installation should be carried out by a qualified installer.

How do they work?

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 or can be installed in a vertical loop down into the ground to a depth of up to 100 metres for a typical domestic home.

Environmental Considerations

The Environment Agency’s GP3 Document identifies the following potential impacts arising from both closed and open loop systems installed at depth:

• changes in groundwater flow and quality by interconnecting aquifers, posing contamination risks or changes to flow during both drilling and installation;
• mobilise contaminants if installed inappropriately on contaminated sites;
• result in undesirable temperature changes in the water environment and for example, impacting on ecology.

In addition, open loop systems can cause:

• restrictions on the availability of groundwater for abstraction impacting on existing water users or the environment – if water is available these risks should be low providing the water is returned to the same aquifer (and not to rivers or sewers) making the abstraction non-consumptive;
• adverse impacts of returning water into an aquifer such as localised mounding of groundwater levels, causing flooding or impacting on adjacent structures including scheduled ancient monuments.

Closed loop systems have few additional environmental issues associated with them other than the need to avoid groundwater pollution from leaking circulation fluid.

Regulation

Open loop schemes that abstract and discharge water to the environment are regulated. These schemes require a groundwater investigation consent (GIC) followed by an abstraction licence if the abstraction is greater than 20 m3 per day; they also require an environmental permit to discharge to groundwater or surface water. Where necessary to prevent pollution, the Environment Agency will set temperature limits on these environmental permits. These permits and consents ensure that schemes comply with environmental legislation such as the Habitats Directive and the WFD.

Operation of a closed loop GSHC scheme does not require an environmental permit. However, it is strongly recommend that non-hazardous pollutants are used in closed loop systems to avoid pollution. If a developer proposes to use hazardous substances in a sensitive location such as a Source Protection Zone 1 the Environment Agency may issue a notice to prevent pollution. H2Ogeo can assist in determining the environmental sensitivity of the site and recommending the best solution for the client.

Before you start drilling a borehole (for both closed and open loop schemes) you can seek the advice of H2Ogeo to understand the geology and hydrogeology you will be drilling into to anticipate and mitigate any problems. H2Ogeo provides desk based hydrogeological assessments in line with the Environment Agency’s guidance to identify the environmental sensitivity and potential risks relating to your ground source heat/cooling system.

For more information you can download the Environment Agency’s Environmental good practice guide for ground source heating and cooling here or contact H2Ogeo for further specialist advice.

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This article has been prepared using text/data and information from the following sources:
Source References:
EA’s concerns – Groundwater protection: Principles and practice (GP3), August 2013 Version 1.1
Environmental good practice guide for ground source heating and cooling GEHO0311BTPA-E-E, Environment Agency
http://www.energysavingtrust.org.uk/Generating-energy/Choosing-a-renewable-technology/Ground-source-heat-pumps#4