The UK is shifting to renewable energy sources, with emissions from electricity generation falling by 69% since 2010. But the current rate of change is too slow to meet the government’s net zero commitments; as the Climate Change Committee states “a reliable secure and decarbonised system by 2035 is possible, but not at this pace of delivery”.  Imported energy is generally sourced from fossil fuels and, as has recently been shown reliance on imported energy exposes us to extreme price spikes driven by world events. 

WCS is passionate about supporting clients with work that contributes to achieving net zero including renewable energy generation, rail electrification, and electric vehicle (EV) charging networks. As well as investment in projects like these, it is clear that investing in a more efficient energy network is vital if we are to secure a sustainable future. 

Major goals like net zero may involve more than one response

Globally electricity demand is growing faster than the supply from renewable energy sources, driving an increase in generation from fossil fuels. To help bridge this gap a switch to low-carbon energy sources must be accompanied by measures to reduce demand, and investment aimed at creating smarter networks, so more of the energy produced is available when and where needed. This topic was discussed in our recent article on battery energy storage systems

Innovative ways to increase efficiency will also be needed. WCS was the consultant engineer in the SELCHP project, where rubbish collected by Westminster City Council’s electric refuse collection fleet will be incinerated within a waste-to-energy facility; the very waste collected will power the collection vehicles and also street cleaning vehicles. Thinking about making better use of waste, but not just through incineration, has the potential to be part of the long-term solution. Utilising waste heat across the energy network could help deliver efficiency, reduce demand from other energy sources, and create joined-up solutions to power a more sustainable future. 

What is waste heat?

Waste heat is heat produced by machinery or other energy-using processes, which is then not utilised, either dissipated into the atmosphere or actively cooled. Nuclear power stations, for example, have an efficiency of about 35%, meaning that for every watt of energy produced, about 2 watts are lost in the form of heat sent into nearby bodies of water and air. 

How can waste heat be used? Waste heat to power is a solution in which such heat is used to turn turbines or otherwise generate further electricity. The other way to make waste heat useful is to leave it as heat but capture it, for example by heating water or air, and pipe it to where it is needed. Heat networks, also referred to as district heating, are systems where the heat is sent as hot water through insulated pipes to buildings where it can meet demand for heating or hot water. In principle, this is a more efficient use of waste heat than generation, though the ideal option is to do both, which is called combined heat and power (CHP), as in the SELCHP project. 

In the UK almost 50% of the final energy consumed is currently used for heating.  In fact, a study by the Institution of Civil Engineers and the University of Southampton noted that 25% of all energy used for our heating could be saved if we could capture and reuse merely half of the heat that is currently lost from power stations alone. 

Transformers are an especially promising source of waste heat 

Power stations are typically far from towns and cities, and therefore largely not suitable for local piping of district heating, so instead this heat could be converted back to electricity. But there are many other sources of waste heat, and one typically close to population centres is transformers. WCS works regularly with substations and transformers, and is routinely asked to consider the issue of heat from these vital pieces of electrical equipment, but in a traditional method, which is to ensure appropriate venting so that no overheating issues occur. 

Capture of this heat has many advantages. Transformers can weigh hundreds of tonnes and generate a great deal of heat. Insulating oil and / or blasted air is typically needed to cool them. Heat capture allows the use of the heat and increases the efficiency and safety of the equipment from which it is removed. Since 2021, SSE and The National Grid have been exploring how waste heat from transformers can be used in district heating for British towns and cities.   

Other sources of waste heat 

Manufacturing and many industrial processes also produce waste heat in various ways, while at the same time requiring cooling systems to ensure continued operation. Globally, an estimated 10% of electricity is currently used for industrial cooling, and this produces a lot of waste heat which could be captured.  

This is also the case for data centres, and many operators are exploring how to increase the efficiency of their sites, including how to use waste heat.  WCS has experience providing dedicated substations for data centres. Our client Telehouse, which shares our commitment to sustainability, has been pioneering this approach for over a decade. In 2010, it opened a data centre in the London Docklands which uses a waste heat exchange system to supply energy to the neighbouring community and businesses, and for cooling of the facility.  

In the rail sector, potential sources of waste heat include substations dedicated to rail electrification and also busy rail stations, with Stockholm’s Central Station used to warm a nearby office building. This has potential applications across the UK, and with our experience in rail civils projects, including substations and railway stations, WCS would be well placed to support our clients with similar projects. 

Waste heat is just part of the puzzle 

Shifting to a more sustainable energy model will require investment in a variety of innovations, the capture of waste heat being just one of them. WCS continues to work on solar and wind farm projects, rail electrification, and other exciting projects like Welborne Garden Village, where ambient heat in the local reservoir will be used to heat homes. The heat captured from transformers and other devices may be just one aspect of the solution, but it clearly has the potential to contribute significantly to our Net Zero goals and should certainly not be overlooked. 

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