Utility Week

UTILITY WEEK | SEPTEMBER 2021 | 29 tion, they also want to know for sure that it will work. Changing that attitude to accept known risks and factor those into investment decisions is a necessary step, he added. Spreading the risk became a clear theme throughout the event, with participants acknowledging the greater gains that could be made through collaboration and support from regulators. Partnerships outside the water sector open up opportunities to recycle byproducts from treatment works. At Thames Water, teams have been working with the Greater London Author- ity (GLA) to see where and how waste from the Hogsmill Sewage Treatment works in southwest London can heat 2,000 homes in Kingston. The site could generate up to 7 gigawatt-hours of low carbon heat per year supplied via a sealed network of pipes to the district heating system at a new housing estate. The project with Kingston Council and Kingston University was driven by the need to decarbonise heat at the housing estate with the chance to save around 105 kilo- tonnes of carbon dioxide equivalent in emis- sions over 30 years. The Climate Change Committee has fore- cast a need to increase district heating net- works by nine times to satisfy 18 per cent of the nation's heat demand in this way in the future. Aram Wood, director of renewables at Thames, said the company was "on the cusp" of this important step towards decar- bonising heat but several challenges remain. The project uses energy recovered from the sewage treatment process and if success- ful could be scaled up to heat homes across the country from other treatment plants. Wood pointed to the multiple benefits of the approach – allowing water companies to extract the heat from wastewater treat- ment and, because sewage water is so warm, leaving heat pumps or heat exchangers with less work than from a cold source. The heat pump concentrates thermal energy and sup- plies it to the district heating system via an on-site energy centre. The GLA, which funded the feasibil- ity study, is mapping where sources of heat from industrial processes such as the sew- age treatment works can be matched with demand. Thames calculated that there's a mas- sive opportunity of around 5TWh in treat- ment and sewer networks annually, which is broadly equivalent to heating around 350,000 homes in London. Wood explained that the displaced gas would equate to 900,000 tonnes of carbon dioxide being saved each year, if those 5TWh could be recovered. "That is a massive opportunity, prob- ably the greatest untapped resource Thames Water has, and can play a significant role in contributing to the decarbonisation of heat in an urban area like London," he said. The motivation has grown in recent years as a wide range of organisations, includ- ing local authorities, have declared climate emergencies. These activities are trickling through to regeneration schemes, hous- ing development and municipal or public buildings. Thames is in discussions with multiple groups to use effluent from its assets in such a way. "It's an extremely exciting time. The question is how to make it happen," Wood said. Before being able to scale up, the pilot scheme in Kingston is "trying to make the economics stack up". The cost remains a stumbling block because heat recovered from effluent through heat pumps is currently more expensive than combined heat and power from traditional gas supplies. Although a project like this cannot com- pete on price, it can help these organisa- tions with their climate targets by recycling heat that is being generated anyway. Clos- ing loops like this has societal and environ- mental benefits but resolving the cost issue would require government support in the form of subsidies or grants to get such pro- jects off the ground. Wood described it as an untapped resource, which extrapolated across the whole industry soon adds up to considerable carbon savings. As well as cost considerations, there are regulatory issues, such as whether an efflu- ent permit would be required and whether Ofwat or Ofgem would be the body to over- see the energy produced from such a project. Circular economy Cost is not the only factor, however. The soci- etal benefits of a scheme that closes the loop on emissions can't be calculated. In Scotland, the government is working continued overleaf

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