RETRACTED: Calculating potential of solar energy and CO2 emissions reduction for cityscale buildings based on 3D remote sensing technologies

Abstract

Solar energy utilization will play an increasingly important role in sustainable urban development because it will help motivate low-carbon development. This study proposed a framework that calculates the solar irradiance on roofs and facades of city-scale buildings, as well as the potential reductions in energy consumption and CO2 emissions that can be derived from solar energy utilization. This framework consolidates data acquired using 3D remote sensing techniques (e.g., light detection and ranging (LiDAR) data and digital photogrammetry) with existing 3D building vector models from urban planning and building design. To further the economical use of solar energy, the framework provides a new strategy based on three aspects (threshold, structure, and orientation), for a more realistic analysis of the available area of roofs and facades, by combining street view images and point clouds. Nanjing, China, was selected as a study area for validating and analyzing the proposed framework. The experimental area covers approximately 30 km² and 5216 buildings. The reliability of the proposed method was validated by comparing the results with the computation modules of mainstream commercial programs and previous international studies. The following conclusions were drawn from the experimental area. (1) Annual solar energy on the roofs of all buildings was 9647.89 GWh, corresponding to a PV yield of 1447.18 GWh, which equates to reductions of 584.66 kt in standard coal consumption and 1261.94 kt in CO2 emissions. The annual solar energy on the facades was 5364.63 GWh, corresponding to a PV yield of 804.69 GWh, which equates to reductions of 325.10 kt in standard coal consumption and 701.69 kt in CO2 emissions. (2) Based on the calculated potential solar energy utilization of the building envelopes, it was shown that the utilization of solar radiation on roofs and facades would promote low-carbon urban development. The utilization of solar energy on the facades of high buildings will contribute to the supply of energy for these buildings and help balance their energy consumption. (3) As the solar incidence angle changes over time, the reductions in energy consumption and CO2 emissions related to PV power generation are maximal in summer for building roofs, whereas no significant seasonal differences were observed for facades. (4) Incorporating the available area translates the utilization of solar energy and potential CO2 reductions from theory to practical application by reducing inefficient and invalid areas. The percentages of available area of roof and facade were estimated at 47% and 16% by comprehensive calculations considering three aspects (threshold, structure, and orientation). The corresponding potential of solar energy on the roofs and facades in the validation area B are 167.18 GWh and 53.63 GWh, respectively, compared to the original theoretic values of 316.97 GWh and 237.98 GWh.