Sustainable cooling of the London Underground network

Subsurface rail networks across the globe are becoming increasingly overheated because of climate change. More prolonged and extreme summers, combined with a rapidly increasing urban population, has led to devastating impacts on both public health and rail engineering. Surprisingly, little attention has been paid to mitigating this situation, even in major cities like London, whose Underground network currently only uses temporary fans to shift warm air around in summer. At the same time, any proposed cooling scheme should be fully environmentally sustainable and must not contribute towards climate change, so should not contain refrigerants. In this way, this project will elucidate a proof-of-concept scheme that harnesses water from buried rivers and the Chalk aquifer to cool Tube stations via a process of heat exchange (using ground-source heat pumps - GSHPs). Research methodology First, the student will identify feasible locations for the operation of such a proof-of-concept scheme from a hydrological point of view, by mapping subterranean rivers and groundwater levels across central London. Then, the effects of abstracting and re-injecting heated water on the subsurface will be investigated using a variety of numerical modelling tools. An economic cost-benefit analysis will also be undertaken. Field mapping at several proxy Chalk outcrops across southeast England will elucidate fracture patterns, which will allow the numerical modelling to be calibrated. Following the development of self-build water level sensors and GSHPs, the student will conduct field tests, together with a scale model that cools a theoretical subsurface railway station using groundwater and/or subterranean river water that flows through a GSHP.