Study on the solar energy harvesting potential at urban block level for business districts in Dhaka

Abstract

On-site production of electricity from solar energy using increasingly sophisticated technologies such as photovoltaics (PV) has been recognized as crucial for making cities energy-efficient. Urban configurations, which can be defined by urban design parameters that are governed by building regulations in Dhaka, highly influence the solar energy harvesting potential (or solar potential) of urban areas. This research aims to find out how the combined effect of urban parameters regulates the solar potential of urban blocks in the business districts of Dhaka, and explores the possibilities for the development of urban design strategies from such findings. Methods include an extensive theoretical framework, field investigation, parametric simulation study, and statistical analysis. For simulation, an integrated parametric interface combining Rhinoceros, Grasshopper, and Ladybug Tools was used. Field investigation generated insights about energy consumption in the buildings in an existing business district (Motijheel Commercial Area) in Dhaka, which is largely regulated by the combined effect of weather variables, and shows strong individual correlations with temperature variables. Moreover, airconditioning energy was found to dominate energy consumption in buildings. As such, solar energy can contribute to meeting energy demands in commercial office buildings more efficiently during the cooler and drier months of the year. Monthly Mean Temperature, Monthly Maximum Temperature (extreme variable), Monthly Average Sunshine Hours, Monthly Number of Workdays and Eid-ul-fitr Month (categorical variable) were all found statistically significant predictor variables for generating monthly energy consumption figures. Parametric study and analytics revealed that while the density and the compactness ratio of an urban block had negative and positive impacts respectively on its solar potential per unit floor area, the impact is governed by the combined effect of parameters such as the number of stories, ground coverage, street-to-surface distance, side-to-side distance, and orientation. Facades facing unobstructed south were found to increase solar potential more efficiently than facades facing other directions and with poorer setback conditions. Local building regulations should acknowledge compactness ratio and surface orientation as significant strategies for more efficient solar energy harvesting in the business districts in Dhaka. Urban designers, planners, architects, and engineers will be critically informed by this research about the impact of urban design decisions on the solar potential of urban blocks within the climatic and physical context of Dhaka.