Going underground: exploring the potential for heat ‘batteries’ to support power grids

The massive switch in the energy world can be simply boiled down to us using less (or no) fossil fuels – in our cars, our home heating, industrial processes or global freight – and instead relying mainly on renewable electricity to replace them.

At home that means swapping gas boilers for heat pumps, in travel it means ditching petrol and diesel for electric vehicles, and so on.

All that means power systems nationwide need to double in size to cope with the growing electricity demand, and we need to do that in a way that makes best use of renewable energy sources such as wind and solar.

The challenge is harnessing that renewable electricity which is so varied in output – for instance when the wind doesn’t blow or the sun doesn’t shine – which poses significant challenges to the electricity system, bringing extra costs.

This is being explored in a new Government-funded project involving E.ON at the University of Leeds which aims to address these challenges by integrating geothermal storage into the energy system, looking at flexibility solutions can reduce network connection costs, lower bills for customers and increase home energy efficiency.

The geothermal long duration energy storage (LDES) project will take excess renewable electricity and store it as heat in the ground, ready for when it is needed. Doing that offers a more cost-effective and scalable solution than expanding power networks or paying renewable generators to switch off when demand is low or too much power is being produced (these payments are called ‘curtailment costs’ and are factored into customers’ bills).

On the flip side, we often have to call on fossil fuelled generation sources to cover the demand for power when renewable sources are not performing at their optimum. This also adds costs to customer bills.

The benefits to consumers from effective flexibility deployment are huge. In the UK alone government analysis estimates savings of between £40 and £70 billion by 2050. Across the EU, analysis by Smart Energy Europe and DNV estimate that E71billion could be saved each year from 2030.

From an E.ON perspective, our role will be to give our insights on the commercial side of this solution – analysing the data to make sure the system is optimised to provide the low-cost, low-carbon heat for which it is designed.

The innovative LDES geothermal storage project aims to lay the foundations for a more resilient, efficient, and decarbonised energy system – meeting the need for rising electricity demand alongside the growth of low-carbon heating networks which are projected to meet up to 20% of the UK’s heat demand in the coming decades.

The project will demonstrate how electrifying heat can go from being a burden and challenge on the grid to a major flexibility opportunity that lowers the costs which come from the wider grid being less flexible. By using geothermal storage, excess renewable energy can be stored and deployed more effectively at lower cost, making best use of green electricity resources and speeding up the UK’s transition to net zero.

The LDES project will see E.ON working alongside LCP Delta, Northern Powergrid, the University of Leeds, Leeds City Council, and Star Refrigeration.

The group has been awarded funding through Ofgem’s Strategic Innovation Fund (SIF) which is looking to accelerate the transition to net zero by supporting innovation in the electricity and gas sectors. It focuses on developing scalable, practical solutions that address key challenges such as decarbonisation, system resilience, and affordability.