District Energy Networks Lowering return temperatures as the key to lower flow temperatures in DH systems. What effect this creates for energy efficiency, material selection and whole life cost efficiency Andy Watts - Flexenergy Ltd District Energy Networks

Why lowering network temperatures? Low Flow temperatures (max 70°C) allow much more useage of renewable energy as well as residual heat from industry

Low temperature solution for Hot water Typical flow below 55°C Typical flow (UK) 80°C + Reason why DH schemes perceive they can’t go lower than 40⁰C return temperatures is because they operate at higher flow temperature and they usually have a bypass built in, so if there is no demand the flow goes over the bypass into the return subsequently maintaining it at a higher temperature

What does it mean 98 YEARS Material selection opportunities Life Expectancy For plastic materials, lower temperatures are key to enhancing the life of systems. Plastics operate better at lower temperatures so this significant change promotes longevity in use. Eg; Where 70⁰C is used as the optimum flow temperature PB (Polybuteleyne),will provide a life calculation even based on 24hrs/ 365days 98 YEARS Describe how variable flow and continuous now most common because of HW at lower temperature

What does it mean Reduce investment costs (Low lifetime costs) Reduce energy losses (Improve energy efficiency) Smaller pipe diameters (improve installation time) Less repairs/maintenance Plastics do not rust or corrode. Bore remains the same through the life of the product Reduced energy through the life of the system Higher ΔT

Mayor of London Study At 70°C Flow temperature the entire heat demand (66 TWh/a) of London can be covered with Heat Pumps

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Questions Andy Watts Andy.watts@flexenergy.co.uk WWW.FLEXENERGY.CO.UK