Comment: Waste heat could hold the key to net zero and beyond

London is looking to become net zero in 2030 under ambitious plans from the Mayor of London, Sadiq Khan. Around two-thirds of the city's current carbon emissions can be attributed to heating and powering London’s buildings. Bill Wilson, from Buro Happold’s energy team discusses the results from its recently published study commissioned by the Greater London Authority (GLA). It shows waste heat could hold help unlock the carbon conundrum.

London offers a range of recoverable waste heat sources that can support the supply of clean heat to homes and businesses. However, these vary considerably by volume and temperature. Consider energy recovery plants, sewage treatment works and data centres which all emit large amounts of recoverable heat daily. Just one mid-sized data centre emits the equivalent amount of waste heat annually to heat around 100,000 homes. 

We identified and implemented improvements to the London Heat Map to include data around available waste heat sources – helping build awareness and identifying opportunities for developing low-carbon heat offtake. Our analysis considered the location and size of waste heat sources across the city. By mapping this data, we highlighted a significant amount of waste heat already available in London. The largest existing waste heat sources contain enough energy to supply up to 12% of London’s heat - the equivalent of heating over 600,000 homes.

The team subsequently developed the London Waste Heat Study. This examined London’s largest, most strategic waste heat sources and modelled the opportunity for strategic multi-borough heat network development. At a high-level feasibility stage, seven strategic heat network areas were identified by running analysis based on clusters of heat demand with size and proximity to these strategic waste heat sources. If these potentially ‘viable’ heat networks were built, following necessary development work, these seven could potentially supply up to 6% of the city’s heating needs. Plus there is expansion potential.

This waste heat, if recovered (and ‘connected’ to heat pumps to lift temperatures where required), could be used to distribute low-carbon heat via district heat networks across multiple adjoining London boroughs simultaneously. This would successfully address one of the major challenges to delivering strategic scale district heat networks i.e. the scale and complexity of providing a multi-borough solution.

These heat networks could:

• cover 25 of the 32 London boroughs and Corporation of London,
• utilise over 7900 GWh/yr of rejected waste heat, meeting up to 3700 GWh/yr of heat demands, with potential for further recovery through infill and/or expansion;
• save over 40 million tCO2e over the next 40 years

To achieve this, considerable investment would be needed. Specifically the installation of around 487 km of pipework. The cost - around £2.3 billion in CAPEX for constructing the primary network in each heat cluster. Yet this investment in local energy provides considerable socio-economic opportunity and social value through associated local growth and jobs.

Additionally, these seven strategic heat networks would provide multi-borough solutions. To date decarbonisation has largely been considered borough-by-borough as large-scale change and establishing the necessary delivery partnerships are both challenging and time-consuming. A strategic heat network programme aligned to waste heat sources and the government’s zoning policy could enable the GLA to lead the way in demonstrating how the best of the public and private sector is brought together. This could further unlock multi-borough zonal scale heat network opportunities for cities globally.

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The UK is currently looking at new Heat Network Zoning policy, aimed at de-risking network development. The abovementioned approach could provide greater confidence in securing heat network connections. Other large heat users including hospitals, universities and social housing providers could also consider these strategic heat networks to help decarbonise their estates.

Yes, the investment looks considerable. Yet this infrastructure has a lifespan of upwards of 60 years. Plus waste heat is often available at lower cost than alternative low-carbon sources. This combines to make heat networks more viable than ever for investors, giving customers more attractive tariffs and simpler technical solutions to decarbonising heat compared with other technologies. Also consider the added value of improved overall air quality, energy security and significant carbon emission reductions.

Yet, more needs to be done to realise these opportunities. At a high level, each of the seven strategic multi-borough heat networks identified were, in the context of a high-level feasibility study, potentially commercially viable and deserving of further development work. The next stage involves looking at the findings in greater detail to better understand the technical and economic opportunities and business case. If these proceeded to commercialisation and construction, investment would be needed. This would likely be sought in partnership with the private sector e.g. the UK’s National Wealth Fund or the GLA’s Green Finance Fund.

None of this can be achieved in isolation. We will need to work closely with the GLA, London Councils, London Boroughs, heat network developers and waste heat sources as well as several other stakeholders to unlock this opportunity fully.

Bill Wilson is associate director at Buro Happold. During its role as lead consultant under the GLA’s Local Energy Accelerator (LEA) programme, Buro Happold was tasked with supporting the GLA in allocating funding to beneficiaries and providing technical, commercial and project management support throughout the project lifecycle to accelerate and de-risk development.