Energy efficient district heating - the importance of achieving low return temps

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Session 16 Paper 1, Heriot-Watt University Edinburgh, 14-15 April 2016

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The paper quantifies the benefits of low return temperature to reduce both the capital and operating cost of district heating (DH) schemes. The key benefits are reduction in network heat losses, smaller pipe sizing and improved boiler and CHP efficiency. The paper uses energy centre and HIU data from a number of operating DH schemes in London that serve newly built flats. The data presented includes flow duration curves that indicate the long duration of periods with very low load and return temperature data that shows the impact of incomplete commissioning. The paper discusses how designs can be improved to lower the DH return temperature at all operating conditions. The issues considered include, impact of over estimating peak load, impact of additional heat exchangers in system, pump selection and control, HIU and secondary system selection.