Assessing the potential and utilization of solar energy at the building-scale in Shanghai

The assessment of potential and utilization of solar energy for each building has become an essential precondition of urban sustainable development. Currently, there are two challenges, namely high computation cost for an assessment within a large city and missing rooftop information for each building. In this study, by taking the downtown area in Shanghai as sample, a grid scheme with buffer was proposed to alleviate the computational burden and successfully estimate solar radiation with an accuracy of 0.91. Also, a quadrant-based segmentation method was developed to classify rooftop types with an overall accuracy of 83.63%, which helps better calculate solar energy utilization cost. Finally, we assumed PhotoVoltaic conversion (PV) systems or Domestic Solar Water Heater (DSWH) systems are installed on all suitable rooftops and analyzed their utilization cost, as well as economic and ecological benefits. The results show that 165,529 and 52,131 buildings are suitable for PV and DSWH systems, respectively. PV system's average payback time is about five years with reducing standard coal consumption of 1.85 × 10¹¹kg. The DSWH system requires three more years to balance the cost and benefits. The criteria of further solar energy planning are also concluded from three perspectives: building height and density, and rooftop structure.