G : Why Go For Geothermal?

Why go for Geothermal?

Of all the green/renewable heat sources geothermal is by far the most constant and reliable.

Its disadvantages are

  1. Its initial installation cost (this is now subsidised by government), and
  2. The level of expertise and experience needed to dimension and install the correct kit. (thus allowing less experienced or honorable operators to cut corners)

There are ten key reasons why use of Ground Source Heating is beneficial to the country as a whole:

  1. Ground Source Heating provides one of the most economic routes to providing on-site renewable heating, reducing emissions of greenhouse gases and meeting the government's binding targets on renewable energy.
  2. Ground source heat pump installations have very low running costs because they exploit the fundamental characteristic of the ground to act as an efficient store of thermal energy. In very cold weather, when heating is most needed, a ground source heat pump has access to warmer temperatures from the ground than an air source heat pump has from ambient air.
  3. The Thermal Energy Storage capacity of the ground allows GSHPs to be used efficiently at all hours of day and night – this provides the opportunity to use GSHPs at night when electricity is cheaper.
  4. GSHPs do not suffer the problems of "intermittency" that effect renewable energy from wind turbines, photovoltaic cells or solar thermal panels. Indeed the Thermal Energy Storage capacity of the ground can be used to compensate for the intermittent supply of energy from other renewable sources.
  5. Although ground source energy requires upfront investment, the reductions in emissions of greenhouse gases are very great and an investment in ground source energy lasts much longer than other investments in renewable energy. The ground works installed for ground source systems, a major part of the cost, can be expected to last for over 50 years. The ground source heat pumps themselves are very reliable pieces of equipment with a long life – longer than air source heat pumps which have to be located outside, have more moving parts, including air circulation fans, and need to incorporate energy-consuming defrosting elements to contend with the formation of ice in winter. GSHP installations compare favourably with all other forms of Renewable Heating and all other mechanisms for generating Renewable Electricity in terms of life span.
  6. Many forms of investment in renewable energy require imports as equipment like photovoltaic panels, wind turbines and solar panels come from abroad and provide employment abroad. Investment in sound ground source energy installations, which requires a detailed understanding of the local geology and local conditions, provides skilled employment in Britain for the local expertise in designing an appropriately sized system and local employment in installing the ground works.
  7. GSHP systems are good citizens: they are silent, free from polluting chemicals, reliable and invisible. They are welcomed by planning authorities and architects. They produce no carbon emissions on site, and none at all if powered by renewable electricity. There have never been any political objections to GSHP systems in the way that wind turbines have caused unrest and resentment and expensive government schemes on other technologies have raised eyebrows at the wisdom of excessive government spending.
  8. GSHP systems, uniquely amongst renewable energy technologies, offer the opportunity to recycle heat energy. Heat energy can be captured when it is freely available in the summer, stored in the ground over the autumn, and released to heat buildings in winter. This singular merit is attributable to use of the ground for Thermal Energy Storage, which is an integral part of ground source energy.
  9. Unlike any other form of Renewable Technology the power of a heat pump can be reversed in summer to provide cooling. In the case of an air source heat pump (or an air conditioning chiller) heat taken out of a building in summer is merely "wasted" to the atmosphere. It is a very expensive option to provide cooling by heat exchange with hot air. The radical, renewable cooling, alternative is to use a ground source heat pump to heat exchange with cold ground: the primary advantage is that it is much more efficient than heat exchanging with hot air.
    The secondary advantage is that a by-product of renewable cooling is to deposit heat into the ground – in advance of the time in winter when the heat pump will be looking to extract heat from the ground.
  10. GSHP systems contribute to the Energy Security of the UK by providing heating and cooling from energy which occurs naturally in the UK, instead of relying on imported fossil fuels. 

 If you can answer most of the following 10 questions with a yes, then it probably is an efficient way to achieve Carbon Footprint Reduction for your house.

  1. Is your house a new build where you can incorporate design features e.g. underfloor heating, well suited to the use of a Ground Source Heat Pump?
  2. Are you able to claim back, or have your project zero rated, for VAT? (New Build)
  3. Does your house have a garden or outside area where where the ground is suitable for you to put either boreholes or slinkies i.e an area large enough to accommodate several cars (boreholes) or to accommodate one or more tennis courts (slinkies*)?
  4. Is your house well insulated, i.e. walls and roof insulation done in the last ten years?
  5. Does your house already have underfloor heating?
  6. If your house has only radiators, is there quite a bit of reserve, i.e. one third or more are usually not used?
  7. Do you wish, or require, to cool your house during the summer months?
  8. Do you have the space in an outhouse, garage, or utilities room to accommodate something the size of a fridge?
  9. Are you prepared to invest for the long term, i.e. to accept a payback period of several years? (depending on energy prices)
  10. Do you want to reduce your heating bills by a half or two thirds? (particularly if you currently use fossil fuels i.e. oil.)

The build quality and age of your house will determine two important questions

  1. Is the house suitable for a GSHP heating system? Sometimes, e.g. for older buildings, it is simply not a solution which will give the best results in terms of heating performance or economic use of energy.
  2. The size of heat pump required,


The average pre 1980's 4-5 bedroom home that has good loft insulation and double glazing is likely to have an average heat loss of around 75W/m2 (average heat loss per square metre of floor space). Such a property would require a 17kW heat pump system. However, the same home constructed using the latest techniques and materials, could have an average heat loss as low as 40W/m2, and therefore only need an 8kW heat pump system.  

* GSHP installers are increasingly moving away from the installation of slinkies because of problems with overcooling of the ground, i.e. permafrost above the collectors and manifold.

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