Geothermal Energy in the UK

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1 Geothermal Energy in the UK Jon Busby British Geological Survey

2 Outline Geothermal energy in the UK Background to geothermal in the UK context UK geothermal resources Engineered geothermal systems Direct use geothermal Ground source heat pumps

temperature resources Is it possible to exploit geothermal energy?

3 Where is the UK? The United Kingdom is located in an intra-plate region We do not have high temperature resources Is it possible to exploit geothermal energy? By Alataristarion - G, CC BY-SA 4.0 Evidence of warm water at depth has been known for over 2,000 years The Roman Baths, Bath

temperatures of >150 C at drillable depths (4-5 km).

a heat pump. Rocks for direct use at depth are usually sandstones and limestones.

4 What are the UK s geothermal options? Engineered Geothermal Systems (EGS) Generation of electricity with a binary cycle, but we need temperatures of >150 C at drillable depths (4-5 km). Direct Use Waters (or brines) from sufficient depth that the heat can be used directly without a heat pump. Rocks for direct use at depth are usually sandstones and limestones. Ground source heat pumps (GSHP) GSHPs provide space heating and cooling. There is potential for both open loop and closed loop and using the water in disused mine systems. Credit GeoWarmth Heat Pumps Ltd

The EGS resource = Heat production (μwm -3 ) Buried granite (unproven) The subsurface distribution of granite has been derived from interpretations of gravity data.

5 The EGS resource = Heat production (μwm -3 ) Buried granite (unproven) The subsurface distribution of granite has been derived from interpretations of gravity data. Most outcropping granites have been geochemically sampled from surface and borehole samples High heat producing granites occur in The eastern Highlands batholith Lake district and northern England Cornubian batholith (SW England) Outcropping and subsurface distribution of granite

6 Deep temperatures for EGS Modelled temperatures at depths of a) 5km and b) 7 km.

7 EGS resource base For depths of 4.5 km and temperatures > 175 C, technical potential power = 2280 MWe, but is restricted to regions of high heat producing granites. If we can drill to 6.5 km then technical potential power increases to 222,393 MWe. EGS resource base

8 EGS development South-west England offers the best prospects for EGS Carnmenellis Bodmin 123 Dartmoor 117 Hot Dry Rock research project carried out in the 1980s Land s End NOW. 133 St Austell United Downs Deep Geothermal Power project 18M project to develop a 2 well commercial 1MW demonstrator Heat flow in mw m -2 Temperatures at 5 km depth Land s End 208 C Carnmenellis 203 C St Austell 223 C Bodmin 201 C Dartmoor 188 C

Shallow sub-surface temperatures Temperatures have been measured in boreholes or mines. Depths are relative to ground level. The black dots indicate the measurement locations.

9 Shallow sub-surface temperatures Temperatures have been measured in boreholes or mines. Depths are relative to ground level. The black dots indicate the measurement locations. Temperatures at 200 m depth Temperatures at 500 m depth So, there are some high temperatures that indicate a geothermal gradient well above the UK average. Depths of mine workings Temperatures at 1km depth

Permian breccias and sandstones The Triassic Sherwood

10 Deep saline aquifers The aquifers with the greatest potential for low enthalpy, direct heat use are; The Permian breccias and sandstones The Triassic Sherwood Sandstone These are found in several basins at depths > 1500 m

The Direct use resource The Inferred Geothermal Resource for the Permo-Triassic sandstones for the whole of the UK has been calculated as 201 x 10 18 to 328 x 10

11 The Direct use resource The Inferred Geothermal Resource for the Permo-Triassic sandstones for the whole of the UK has been calculated as 201 x to 328 x J A reasonable estimate for the Probable Geothermal Reserve is 20% of this heat in place Heat in place for the Sherwood Sandstone Group Northern Ireland not shown.

Southampton scheme Brine from a depth of 1.

The geothermal provides 18% of a 30,000 MWt

scheme contributes major savings in carbon

12 Southampton scheme Brine from a depth of 1.8 km at 76ºC is pumped to a heat exchanger where the heat is transferred to clean water. The brine, at 28ºC, is discharged to the sea. The geothermal provides 18% of a 30,000 MWt district heating scheme (the rest is gas CHP) The scheme contributes major savings in carbon emissions (10Kt yr -1 ) It demonstrated that deep geothermal is possible in the UK

13 Direct use projects under development Manchester, district heating Carboniferous limestone, 3300 m depth Stoke, district heating Carboniferous, 2km Crewe, district heating Permo-Triassic, 3-4 km depth Worcester, green houses Permo-Triassic, 2 km depth

. all values in W m -1 K -1 Thermal properties Data derived from measurements, numerical

14 Ground source heat pumps (GSHP) Open loop GSHP require a shallow aquifer, but closed loop are suitable for most locations We provide.. all values in W m -1 K -1 Thermal properties Data derived from measurements, numerical techniques and modelling Temperatures Estimated temperatures at 100 m below ground level Mean measured temperatures in the UK at 100m depth vary between about 7-16 C.

15 Very shallow temperatures for horizontal loop collectors UK Met Office soil temperature data TEMPERATURES AT 1 M DEPTH ( C) Seasonal Maximums (August) Mean annual temp Seasonal min temp Seasonal max temp England Scotland Wales Seasonal Minimums (February) N. Ireland Temperature records from UK Met Office station at Eastbourne; blue 30 cm depth, red 100 cm depth The temperature cycle can be extrapolated to other depths to obtain accurate temperatures This is required for designing passive heating and cooling systems

16 Mine waters thermal resource Zones of extraction-related subsidence above a recently worked longwall panel (Younger and Adams, 1999). Stoop and Room coal working Advantages The workings create water pathways in otherwise impermeable rocks as a result of subsidence The roadways and shafts may connect to depth where temperatures are higher (e.g. 30 C at 800 m) Groundwater may already be available from gravity flows or mine water pumping schemes Partial collapse into ancient coal workings Disadvantages The mine water may be contaminated leading to corrosion and scaling

17 UKGEOS Glasgow Geothermal Energy Research Field Site (GGERFS)

18 Conclusions Despite being a region without hot geothermal resources, the UK has geothermal potential for power generation and direct use applications There are incentive schemes in place for geothermal power generation and heat Optimism for geothermal is higher than it has been for several decades and a number of schemes are under development The risk to reward ratio is considered to be high. With no geothermal drilling insurance scheme in place, some geothermal successes are needed to build confidence

19 Thank-you for your attention Jon Busby British Geological Survey Keyworth Nottingham UK Tel: +44 (0) ; Website:

UK data for geothermal resource assessments

UK data for geothermal resource assessments Jon Busby UK data for geothermal resource assessments Outline 1. Data availability 2. Sub-surface temperatures 3. The EGS resource 4. Deep saline aquifers Publicly