Au Royaume Uni : November 17, 2009

With the UK government’s Department of Energy and Climate Change (DECC) announcing on the 22nd of October that £6 million is to be made available to fund exploration for geothermal energy sites, it would seem that the 10,000 year old Roman engineering breakthrough is finally back in fashion.

Unlike the intermittent nature of other renewable energy, geothermal sources produce a steady supply by exploiting the relatively constant level of latent underground heat available.  Across the UK temperatures at just a few metres deep range between 8 – 16˚C, locally these ground temperatures remain constant throughout the year. There is currently one geo-thermal energy station in the UK that has been operating for over 20 years pumping hot water from 1800m below the surface as part of a district heating network.  This system delivers more than 30,000MWh of heat and saves an estimated 11,000 tonnes of CO₂ per year.

With some local planning authorities enforcing a compulsory renewable energy component to new commercial builds, businesses are looking to geothermal energy as a viable alternative energy source at site level, both as a means to reduce energy costs and to cut carbon emissions.

Site level installations of heat pump technology can be installed horizontally or vertically dependent on the size of development, ground conditions and the local geothermal temperature gradient, and once installed the space can be re-utilised, e.g. car parking.  Vertical installations are more space efficient than trench fixtures and can take advantage of the increase in temperature with depth.  Boreholes are drilled to a depth of between 15-150m and a pipe system filled with water/antifreeze mix installed.  The fluid in the system absorbs the latent heat from the ground; this absorbed heat is then transferred to a refrigerant that is in turn compressed to increase temperatures to an output typically between 45-55˚C.  For every kW of energy required to run the heat pumps 3-4kW of thermal energy are delivered.  This cycle can be reversed for cooling purposes with the earth acting as a heat sink.

When considering alternative energy sources, geothermal heat pumps are seen to have many benefits – long life expectancy of around 25 years, pollution free, no ventilation requirement, low maintenance, unobtrusive and space economical.  These benefits will undoubtedly increase the popularity of this technology in the UK over those currently seen in other European countries.