Why geothermal energy?
The climate emergency means that our energy system must be entirely revised. By 2050, in the working life of anyone in their mid-thirties, greenhouse gas emissions in the UK will be net zero, and to achieve this, all electricity and heat will have to be as close to zero emissions as possible.
From a slow start, low carbon energy development in the UK has picked up in recent years, with 16 straight coal- free electricity days in May and June 2019. But it is a huge task to get to and stay at zero emissions, and concerns about the intermittency, visual intrusion and land take and of renewables on one hand, and the cost and security issues around nuclear on the other, mean that new technologies are needed.
Geothermal energy is a renewable source of power and heat…
- that runs 24 hours a day, whatever the weather,
- on the smallest surface footprint of any energy source,
- with no buildings higher than 10m,
- that could supply the UK with 20% of its electricity needs,
- and can help support the electricity grid with despatchable power
Advantages of geothermal
- Unlike other renewable electricity generators, geothermal plants are ‘on’ 24 hours a day, and have very little visual or surface impact. Geothermal power is permanently available and independent of the weather.
- The technology relies on the heat from the earth, a virtually infinite resource, unlike fossil fuels. It does not rely upon the use or import of raw materials as for example biomass does. With no variable fuel costs or fuel supply issues, geothermal plants can be run at full tilt and have a typical capacity factor of more than 90%- i.e. they are in active use for almost all the time.
- With many people’s disquiet at the visual intrusion, expense and intermittency of other renewable resources on one hand, and dismay at the expense and security issues around nuclear development on the other, geothermal electricity offers an acceptable face of low-carbon energy development.
- When Eden Project and EGS Energy took a geothermal exhibition to the Royal Cornwall Show in 2013, in response to the question ‘Do you support geothermal development in Cornwall’, over 99% of those who responded said ‘yes’.
- As a distributed base load electricity generator, and with the potential to be used as a dispatchable load that can be ramped up and down at will, geothermal generators can help support the national grid and local distribution grids, a feature becoming ever more important with increasing numbers of solar and wind developments.
- Geothermal generates both heat and power. The by-product heat can provide affordable heat to local heat networks, agriculture and industry, creating jobs and replacing imports with home-grown produce from geothermally heated green houses and fish farms. Geothermal heated spas and swimming pools for year round use can support tourism.
- The development of the geothermal industry will produce a number of high value jobs, through direct employment and spin-off industries. Based on a study by the Geothermal Energy Association, 100MW of installed capacity should produce between 1400 and 1700 full-time high-quality jobs, and build academic and engineering excellence in the Universities of the region.
Worldwide potential of geothermal energy
Geothermal energy is the heat in the rock beneath our feet. In general the deeper you go, the hotter it gets, but in some places with tectonic plate movements or active volcanoes, like California or Iceland, the heat is closer to the surface. There, geothermal heat and power stations are routine and are cost competitive with gas or wind power. Wells drilled into the rock intersect with hydrothermal reservoirs, and the superheated water brought to the surface runs turbines to create electricity, and used for heating or industry.
Now, improvements and falling costs in drilling technology, and lower temperature electricity generation, mean that the potential for geothermal heat and power is spreading to areas where the temperatures are not so extreme and the geological activity lies far in the past, but has left a legacy of hot rocks. One of these places is Cornwall. Here, two projects are piloting these lower temperature ‘Enhanced Geothermal Systems’ or EGS. One of them is at the Eden Project.
These lower-temperature EGS systems have enormous potential. In the US, the geological survey undertook a geothermal resource assessment in 2008. Conventional hydrothermal resources in the US were estimated at 40GW, but including potential EGS systems brought the total to over ten times that, at 516GW. (For scale total UK installed capacity is 85GW across all technologies.) In Australia, the figures are equally impressive, with the Government’s Geoscience Australia body estimating that 1% of the geothermal energy shallower than five kilometres and hotter than 150°C could supply the country’s total energy requirements for 26 000 years.
Based on their analysis of the key megatrends the world in the next 50 years, Bill Gates’ Breakthrough Energy Coalition has identified geothermal as one of five areas of focus.
As of January 2019, 14.6 GW of geothermal electrical capacity has been installed across 24 countries, with another 12.5 GW in planning across 82 countries.
Geothermal potential in the UK and Cornwall
The reason that Cornwall is a good place for an EGS plant is the same reason it was an important mining area – namely the spine of 300 million- year-old granite that runs down the peninsula. The granite brings heat closer to the surface, cutting the cost of drilling. With the highest heat flows in the country at around 120-140W/m2, Cornwall is recognised as the best place to exploit the UK’s deep geothermal resources.
Heat flow map of Cornwall
Much of the early experimental work in rock fracturing was carried out at Rosemanowes near Camborne in Cornwall.
A 2012 report by the engineers Sinclair Knight Merz concluded that Cornwall’s generating capacity could be as much as 4GW of electricity, more than Hinkley C, with 13GW of by-product heat for heating local businesses and housing.
Potential geothermal energy in the UK
Other Geothermal Projects in Cornwall
Geothermal Engineering Limited (GEL) has secured funding of £10.6 million from the European Regional Development Fund to explore the geothermal resources deep beneath Cornwall. With £2.4 million from Cornwall Council and £5 million raised privately, the funding has allowed GEL to drill two deep geothermal wells from its site at United Downs, near Redruth. If circulation testing over the next few months proves successful, a 1-3MW power plant will be built at the site to demonstrate the technical and commercial viability of supplying both electricity and heat.