Solar accessibility in developing cities: A case study in Kowloon East, Hong Kong

Solar accessibility, defined as the solar irradiation received in a spatial and temporal domain, is increasingly becoming a practical demand in a variety of applications, especially in dense and high-rise urban areas where people prefer natural daylighting accommodations and offices and enterprises desire rooftops with high exposure to sun for photovoltaic cells. However, new buildings may substantial alter spatio-temporal solar distribution and obstruct exposure to solar power significantly. Thus, providing an accurate quantification of how solar accessibility is impacted by a developing urban environment is a key step in the development of sustainable cities. Motivated by this observation, a solar irradiation estimation model has been designed, which allows solar radiation from a particular elevation and azimuth to pass through urban surfaces modelled as 3D polygons, resulting in the creation of 3D shadow surfaces. As such, the urban surfaces can also be represented as 3D point clouds of irradiations determined by both solar radiation and shadow. By applying the model to existing and planned urban environment, it is possible to estimate the transformation of solar accessibility at the district scale. As a case study, a master plan for the Kowloon East district proposed by the Hong Kong government has been considered, and an application of the propose methodology found that new buildings to be built in the district can obtain considerable solar energy, while having a marginal impact on existing buildings. This case study suggests that the model can be used in many other cities for a variety proposes.