Optimization of daylight in atrium in underground commercial spaces: A case study in Chongqing, China

Facing urban problems such as rapid urbanization, air pollution, heatwaves, and urban flooding, the underground space, as a significant urban composition, has demonstrated the unique potential. However, the properties of the lighting environment in underground spaces require the consumption of large amounts of energy. An optimal design strategy for natural daylighting in underground commercial spaces with high density, high usage, and high illumination demand can effectively achieve energy savings. In this study, the most common natural daylighting structure, the atrium, was selected. And the orthogonal analysis was used to simulate the lighting environment generated by four influencing factors (shape, number, profile inclination, and skylight aspect ratio) of underground commercial spaces. For an atrium space of two floors, the results show that the case of 1–3 square-shaped atriums, a profile inclination of 5°-10°, and a skylight aspect ratio of 1:6 comprised a suitable combination that can significantly reduce the electricity consumption. Different combinations of the four influencing factors resulted in different energy savings rates, and the highest energy savings rate was 1.2–1.3 times higher than the lowest. This study can be a valuable insight into the energy-saving design of the light environment in underground space.