Urban Albedo Computation in High Latitude Locations: An Experimental Approach

The proposed research will develop a novel experimental and modelling study for the computation of urban albedo in high latitude locations, using London as a representative urban environment in the UK. This work is primarily motivated by the need to provide accurate albedo estimates for urban configurations, as such calculations are lacking in most Urban Heat Island (UHI) models used to mitigate its effects.

The research will investigate the seasonal effects of albedo on urban temperature. Albedo intervention can bring substantial positive effects during the summer while marginal negative effects are expected in winter. In mild climates such a negative effect might out-weigh summer benefits. It is possible that seasonal intervention on the urban fabric could give an overall positive impact but for this, accurate computation of urban albedo is required at urban design or intervention stage. These issues will be investigated in the proposed study which has three aims; (a) to investigate experimentally the impact of urban fabric on urban albedo; (b) to develop a catalogue of urban albedo for various material and geometrical combinations and (c) to develop an empirical model to predict changes in urban albedo in relation to changes in urban fabric and solar altitude with a specific focus on advanced materials. This aim will be achieved through an extensive experimental study that includes field and laboratory scale measurements, computer modelling, and followed by the development of an urban albedo calculator that is able to explore seasonal variations. The Urban Albedo Calculator values could be used to predict the urban heat island with greater confidence.

The urban albedo project will lead to a step-change advancement in the understanding of the photometric phenomena of urban surfaces in the context of complex urban geometries. The research will have an impact on UK policy makers in DBEIS, DCLG, DEFRA, GLA and in many local authorities. The policy makers in these organisations can develop urban environment related guidelines that have an impact on façade characteristics more confidently, especially guide lines to mitigate the UHI. Advanced knowledge of urban albedo will lead to better management of UHI. The research will help designers to ensure that new and refurbished façades will have a low impact on outdoor overheating in the summer, which is likely to become more prevalent with future climate change. Planning, urban design, architecture, civil engineering and environmental practices could use the research findings as well as the urban albedo calculator in their day to day consultancy work. Planners and designers could use the urban albedo values from the catalogue to evaluate alternative schemes at early stages. Currently, planners and designers on most occasions carry out urban albedo evaluations based on subjective judgement. Overall the urban albedo calculator will reduce the uncertainties associated with reflective radiation in predicting urban heat island intensity (UHII) and building energy performance. Public understanding of the impact of infrared radiation in the urban environment will be enhanced, through the involvement of school children with the experiments, inspiring students to study STEM subjects. The findings could point the façade material manufacturers towards new directions especially in terms of high urban albedo materials. Further, manufacturers could test these products in different urban geometries using the Urban Albedo Calculator, as well as through the test site which will be set up at University of Kent. Developers of free-ware software focusing on urban climate will have the opportunity to integrate the Urban Albedo Calculator into their model.