What is a Ground-Source Heat Pump?

Heat pumps can come in a number of different forms, varying from air to air, water to air and ground to water. This article will concentrate on the ground to water form. Ground-Source heat pumps are a form of low carbon technology which galvanises “naturally occurring underground low-level heat and converts it to high-grade heat using an electrically driven or gas-powered heat pump” [1].

The main advantage to Ground Source Heat Pumps is that they can be highly cost-efficient energy applications due to the fact that they run on an endless supply of clean, pollution-free heat from the ground [3].

25% of the UK’s total carbon dioxide emissions are generated from households [4]. Therefore, to reduce the carbon footprint of our living, it seems logical to increased energy efficiency in the home. One way of doing this is through heat pumps and in particular Ground-Source Heat Pumps.

When is it suitable?

This form of technology often requires a large amount of civil engineering work; therefore it is best suited to new-builds or renovation work [1]. To implement a Ground Source Heat Pump, you need the right geological conditions; therefore careful background work needs to take place before any installation occurs.

How does it work?

For domestic use, trenches that are dug and buried within a garden, house pipes which extract heat from the ground, as shown in figure 1. The ground loop pipe is used to circulate a combination of water and antifreeze, which acts to absorb heat which is then pumped through a heat exchanger in the heat pump [2.] Low-grade heat is firstly extracted and passes through a heat compressor, which converts it into a higher temperature, which can then be used for heating water for the hot water system of the house [2]. The ground loop fluid that has carried this heat is now cooler and it enters back into the ground to absorb more heat energy and to start the process again, therefore producing a continual loop of heated energy [2].

The longer the ground loop, the more heat that can be drawn from the ground, however if you have limited space you can install vertical loops up to a depth of 100 meters [2].

For the most detailed and up-to-date information on ground source heat pumps and heat pumps in general, visit the Heat Pump Association website at www.heatpumps.org.uk .

Advantages of using Ground Source Heat Pumps

• Useful heat output is greater than the energy required to operate the pump [4].
• Reduction of carbon dioxide emissions: when a ground-source heat pump is used to replace an oil boiler, an average of 540 kg of CO₂ can be saved every year.
• Can be used for space heating and the heating of hot water.
• Can lower fuel bills.
• It is generally thought of as a low maintenance technology.

Figure 2, below, is a savings chart provided by the Energy Saving Trust, which shows the general savings that can be made from using a Ground-Source Heat Pump.

Suppliers of Ground-Source Heat Pumps

• Danfoss Heat Pumps [5] is a company, which has a wide range of heat pumps for domestic and commercial application. They design, supply and install the heat pump, providing a full installation service, apart from the digging of the ground works.
• Nu-Heat [6] claims to be the largest specialist supplier of warm water under-floor heating systems to the UK domestic market. They design and supply the complete package, providing one point of contact. They also offer a 3-day training course on the use of heat pumps, which entitles you to apply for grants.
• Ice Energy [7] has installed over 5000 Ground-Source Heat Pumps. They will also provide a free training course for your own plumber if you wish him to install the pump for you.

References

[1] Carbon Trust (2010) [Online]. Available from www.carbontrust.co.uk/cut-carbon-reduce-costs/products-services/technology-advice/

[2] Energy Saving Trust (2010) [Online]. Available from http://www.energysavingtrust.org.uk/Generate-your-own-energy/Ground-source-heat-pumps

[3] Heat Pump Association (2010 [Online]. Available from www.heatpumps.org.uk

[4] The Green Consumer Guide (2010) [Online]. Available from www.greenconsumerguide.com/domestic.php

[5] www.ecoheatpumps.co.uk

[6] http://www.nu-heat.co.uk

[7] http://www.iceenergy.co.uk/heat-pumps

Figure 1: Energy Saving Trust (2010) [Online]. Available from http://www.energysavingtrust.org.uk/Generate-your-own-energy/Ground-source-heat-pumps