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In just four years, gas heating will be banned in new UK housing developments. Where will the construction industry turn for low carbon heating, asks Lucy Cotton of GeoScience Limited.

Seequent has been closely involved with the geothermal industry for a number of years, supporting it with a range of solutions to drive the advances in renewable energy the world needs. (For example, we developed the specialist 3D subsurface modelling of Leapfrog Geothermal to allow teams to ‘see inside’ reservoirs, and make more confident decisions on well-targeting and operations.)

We believe this important energy resource has the potential to alleviate some of the largest drivers of non-renewable consumption. Therefore, part of our environmental ambition as a company is to provide the tools and enhance the workflows that will enable geothermal experts to evaluate, develop and operate more effectively within one of our most promising renewable energy sectors.

This month we would like to thank Lucy Cotton, Geologist of independent earth science consultancy GeoScience Limited, for looking at how geothermal science is answering the need for low carbon district heating across Europe, and the UK in particular.

“Geothermal energy is one of the very few readily available technologies that can replace fossil fuel heating at any scale from individual houses to large multi-purpose residential and commercial developments.”

The single, largest, energy consuming sector in the UK is heat (confirmed by BEIS, the Department for Business, Energy and Industrial Strategy). It contributes over one third of the UK’s annual carbon emissions and domestic space heating alone accounts for 43% of that consumption.
While low carbon heat solutions such as heat pumps (air, water and ground source), biomass systems and water solar heating are available, the vast majority of domestic heating in the UK comes from the gas network.

Not for much longer.

In 2019, the UK Chancellor announced that from 2025, gas heating for new housing developments would be banned. Although a step in the right direction for sustainable growth, the blanket statement did not necessarily provide an immediate solution for construction companies, and the challenge ahead is enormous. With a large amount of development happening across the country, and with many schemes extending beyond 2025, developers are having to adapt and turn to alternative methods for low carbon heating.

One such method is geothermal district heating systems.

Europe’s place in the geothermal race

District heating from geothermal energy is not a new concept. There are currently around 250 district heating systems in Europe supplied by geothermal energy, with a total installed capacity of more than 4.5GWth (European Geothermal Energy Council, EGEC, 2018). They vary in size from less than 1MWth to more than 50MWth, often with heat pumps assisting the shallower or lower enthalpy geothermal resources.

Installed geothermal district heating capacity per European country. EGEC Geothermal Market Report 2018

France is one of the leaders of the geothermal district heating market in Europe. In fact it was ADEME, the French Agency for Energy and the Environment, that declared the cost of district heating and cooling to now be cheaper with geothermal than natural gas. This shift in economics could be the incentive that makes geothermal energy not only technically viable but also a competitive option for the future of heating. And it’s an incentive that’s been needed for a while.

“There has been a lot of focus on decarbonising electricity,” says Kathy Hicks, owner of environmental and geological assessment consultancy Carrak Consulting. “But we are behind with heat. Climate Change and the looming energy crisis need to drive planning for low carbon heat sources in new developments.”

Hicks points to warm minewater, sourced from depth in flooded mines, as a promising route for a variety of direct heat applications, particularly for the UK. She also notes that “as well as a negative environmental legacy, former mining areas often experience high unemployment and fuel poverty, so there is a social imperative as well as a spatial synergy between old mine workings and low-cost heat demand.”

A plentiful resource for the UK to tap into Geothermal for district heating is not a one solution fits all or everywhere scenario. Choosing the right system to get the most out of a district heating scheme is location-specific.

But borehole-based systems can be designed to incorporate the local geology or surrounding existing infrastructure (such as flooded mines) to increase their efficiency and carbon savings and reduce running costs. Depending on the thermal conductivity of the ground, the geothermal gradient and the presence of nearby warm water resources, systems can range from pipe loops installed in a network of shallow holes or horizontal trenches, to pairs of medium (500m) or deep (~1000-2000m) wells accessing specific reservoirs for open-loop systems.

The UK has a wealth of natural geothermal resources and flooded mine workings that can be used for both open and closed-loop purposes. The take-up for shallow resources has been relatively good; there are several thousand closed-loop ground source heat pump systems in the UK. But for deeper resources, and mine water resources, we are far behind most of Europe.

There is currently only one operating district heating scheme with a geothermal component; in Southampton. It utilises a deep well drilled for research purposes in the 1980s. However, as GeoScience Limited’s own Ground Source Heat Pump specialist, Dr Robin Curtis argues, the potential in this early advance could and should have been more enthusiastically followed up. “The UK was an early player with the Southampton scheme, commissioned in the 1980s by enlightened members of the city council. We could now be rapidly unlocking similar decarbonised heat potential from the subsurface via indigenous geothermal, minewater and ground source resources”. But the UK largely failed to pursue this early lead.

Incentive and imperative

However, attitudes are changing. There is now a move towards other schemes such as mini-heat networks in Manchester with low temperatures boosted by heat pumps at substations. There are also innovative systems like the proposal for the new Seaham Garden Village development in County Durham that plans to use heat from the Coal Authority’s nearby Dawdon Mine.

Meanwhile, further encouragement in the UK has recently been provided by the delivery of the £1bn Public Sector Decarbonisation Scheme (PSDS), which provides grants for “public sector bodies to fund energy efficiency and heat decarbonisation measures”. Additionally, advice from the Committee on Climate Change last year in their Progress Report to Parliament on “Reducing UK Emissions” recommends heat networks and heat pumps should be supported by tax or levy changes that favour low carbon heating over fossil fuels.

With opinions from influential bodies slowly moving in a more sustainable direction, and targeting decarbonised heat and climate resilient infrastructure, it is clear that a lot could be gained from further interaction between the UK’s geothermal and construction industries to help achieve net zero carbon by 2050.

As Peter Ledingham, GeoScience Limited’s MD says: “If we are to meet the ambitious carbon reduction targets in the UK, one of the most important changes we have to make is to decarbonise our heating. Geothermal energy is one of the very few readily available technologies that can replace fossil fuel heating at any scale from individual houses to large multi-purpose residential and commercial developments. The time is right to harness renewable and sustainable geothermal resources to make a significant impact on the carbon impact of our heating in both existing and yet to be built housing stock.“

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