A St John’s academic has warned that the UK is wasting one of its biggest potential energy sources – the excess heat produced in factories and other industrial sites.
Industrial heating accounts for around 14 per cent of UK emissions, yet approximately half of the energy used in industry is lost as waste heat and should be reused to reduce business costs and improve the drive towards net zero, according to the new study.
It outlines how this is largely due to unavoidable losses in processes that require extremely high temperatures, which represents a significant efficiency and cost challenge for UK businesses.
Professor Andy Woods, St John’s Fellow, Supervisor in Applied Mathematics and Tutor, led the expert group behind the newly published Royal Society study, Unlocking thermal energy: Capture, storage and re-use of industrial waste heat, which finds that finds that capturing and re-using this heat could help decarbonise industry, reduce overall energy demand, improve productivity, and provide new, local sources of heat for communities.
He said: “If the UK is serious about reaching net zero, dealing with the vast amounts of industrial waste heat needs to be integrated into decarbonisation strategies now, and not as an afterthought.
“As industry makes the switch from fossil fuels to cleaner alternatives, we have a huge window of opportunity to integrate systems to capture and reuse industrial waste heat into future infrastructure. This would strengthen long-term industrial competitiveness and provide a cost-effective way of decarbonising industry.”
“Heat tends to be invisible in energy debates, because it’s not as easy to trade or transport as electricity. But from a systems perspective, it’s hugely valuable”
Industries including steel, cement, glass and chemicals routinely heat materials to temperatures of up to 2000°C before cooling them again, resulting in large amounts of valuable thermal energy being lost to the environment.
Even as these sectors transition away from fossil fuels towards cleaner sources of energy such as hydrogen and electricity, significant amounts of heat will continue to be lost unless new systems are put in place to capture, store and reuse it.
Instead of allowing that heat to dissipate, Professor Woods argues that it should be captured and reused – first within industrial sites, then shared across industrial clusters, and ultimately fed into heat networks serving homes and other buildings.
Professor Woods said: “Heat tends to be invisible in energy debates, because it’s not as easy to trade or transport as electricity. But from a systems perspective, it’s hugely valuable. Even in a low-carbon future with more electrification, there will still be significant amounts of unavoidable heat. The question is whether we continue to waste it or build the infrastructure and policies to use it productively.”
The academic proposes an approach to thermal energy efficiency based on heat cascades, where high temperature waste heat is captured at source and reused at progressively lower temperatures.
He stresses that the issue is as much economic as environmental. “Improving thermal efficiency is not just a climate measure,” he says. “If industry can get more output from the same energy input, that lowers costs and improves competitiveness. At a national level, using energy more efficiently also reduces pressure on the wider energy system.”
The report calls for the Government to build on existing assessments to develop a detailed understanding of where waste heat is generated and where heat demand exists across industry.
“By reimaging waste heat as a valuable resource, rather than an unavoidable loss, the UK could unlock a substantial energy resource”
This would support the development of heat capture, transport and storage technologies along with the necessary regulatory and financial frameworks to enable investment.
The St John’s academic is also the Head of the Institute for Energy and Environmental Flows (IEEF). IEEF researchers work with academic and industrial collaborators from around the world, using fluid mechanics, thermodynamics and surface science to help with some of the major challenges of decarbonisation, including geological carbon storage, geothermal heat storage, energy efficient building design, and superfast battery charging.
“Many of the challenges we face in energy and climate come down to understanding flows – of heat, fluids and energy – and how to manage them better,” Professor Woods said.“That’s something mathematics and physical science can contribute to in a very direct and practical way.”
With industry under growing pressure to decarbonise while remaining competitive, the report positions waste heat not as an inconvenience, but as a resource waiting to be used.
Professor Woods concluded: “By reimaging waste heat as a valuable resource, rather than an unavoidable loss, the UK could unlock a substantial energy resource that would strengthen industry and help in the transition to net zero.”
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