Cooling and recovery of heat from underground railway tunnels for district heating

Temperatures in London’s underground railway tunnels are rising year on year and new energy efficient, cooling solutions are needed. The MICAH (Metropolitan Integrated Cooling and Heating) project involves investigating the feasibility of combining cooling and ventilation of London’s underground tunnels with recovering and reuse of the waste heat to supply a district heating network (DHN). A suitable site from the underground network has been identified, close to a DHN, to which the heat can be transferred. The temperatures of the ventilation shaft air are quite low i.e.17-28°C, so the recovered heat needs to be upgraded e.g. to 70°C using a heat pump, before delivering it to the DHN. A model has been developed which incorporates the proposed design and operational parameters for the combined cooling and heat recovery system, together with specifications for the heat pump and the equipment needed to transfer the heat to the DHN. The model permits evaluation of the performance of the system under a wide range of design, operating and environmental conditions, and for a number of configurations, enabling the model to be used to investigate the potential for waste heat recovery at a range of sites. Preliminary results from the model are presented and the potential benefits, limitations, and the effects of key design and operating parameters are discussed.