Effects of increasing urban albedo in the Greater Toronto Area

Increasing surface reflectivity decreases the skin and air temperature, which potentially reduces cooling energy demands. The state of the art online numerical Weather Research and Forecasting model (WRF) is used to investigate the effect of increasing albedo in Toronto, Ontario, during the 2018 heat wave period (July 2^nd through July 5^th) on urban climate and building energy consumption. The study couples the WRF with a multi-layer of the Urban Canopy Model (ML-UCM) and Building Energy Model (BEM). The ML-UCM is a part of the land-surface parameterization to predict the heat and moisture fluxes from canopies to atmosphere. The BEM is coupled with Building Effect Parameterization to predict the energy consumption of buildings. BEM simulates the effect of heat generation from buildings on urban climate. The reflectivity of roofs, walls and roads are increased from 0.2 to 0.65, 0.60 and 0.45, respectively. Albedo enhancement leads to a decrease in air temperature by around 1°C and an increase in wind speed which induce a reduction in skin temperature. The combined effect of decreased solar heat gain by buildings and decreased air temperature reduced the energy consumption of HVAC systems by 3-5%, confirming the positive effect of increasing the albedo on urban climate. (paper)