Rooftop photovoltaic energy systems are globally recognized as crucial elements for the implementation of renewable energy in buildings, as they act as generators within the framework of smart cities. Photovoltaic modules can be designed as building roofs, and power generation units can be applied to buildings to meet the requirements of various bu. ••A brief overview of previous studies about rooftop photovoltaic at different scales is presented.••Methods to increase PV utilization and reduce emission at the city-scale are settled.••Main influence factors of studies on PV systems at the building-scale are discussed.••The life cycle analysis of PV modules are summarized.••Rooftop photovoltaic generation systemsBIPV/BAPVEnergy performanceCarbon emission reductionThe rapid development of science and technology has provided abundant technical means for the application of integrated technology for photovoltaic (PV) power generation and the associated architectural design, thereby facilitating the production of PV energy (Ghaleb et al. 2022; Wu et al., 2022). With the increasing application of solar technology in buildings, PV modules are being increasingly integrated into new buildings as building materials for facades and roofs (Kwak et al., 2022), or used in the retrofit of existing buildings (Gremmelspacher et al., 2021; Torres-Rivas et al., 2022). Accordingly, PV energy has become a crucial promising future energy source for cities, demonstrating great potential as a tool to help achieve the goal of peak carbon dioxide emissions.In 2021, the global newly installed capacity of solar energy was 137.584 GW, which was far greater than the generation capacity of other sustainable sources. According to international renewable energy agency 2022, the new installed capacity of renewable energy technologies globally from 2011 to 2021 is shown in Fig. 1. Europe and China are the main markets of building PV generation systems. The building sector has emerged as a large energy consumer recently (Guo, 2022), and governments worldwide have introduced various measures to address this issue, including policies to promote energy conservation, reduce. The unique properties of roofs, such as good sunlight incidence, good ventilation conditions, no redundant shielding, and flexible tilt angle for PV panels, are advantageous for solar energy harvesting. Accordingly, roofs present the highest efficiency potential for PV generation systems in buildings (Lin et al., 2014). However, the impact of roof equipment (e.g., water tanks, central air conditioning units, ventilation equipment, communication signal base station) and their shadow must also be considered.BIPV roofing systems adopt one-off construction and investment mode, in which the PV power generation units and other electrical equipment are directly installed on the roof during its construction, so the system can be tightly mounted to reduce the adverse effects of wind. In addition to power generation, BIPV roofing systems also serve as building structures that can replace original roof components. PV modules can also replace the atria shading (James et al., 2009) and heat insulation layer (Shukla et al., 2018). Moreover, the BIPV roofing system can be adapted to a variety of roof types, including zigzag designs to absorb solar energy without affecting daylight. The BIPV system can also be designed as an arc or sphere to absorb more solar energy on the premise of higher artistic quality, and to create a different feeling for indoor people with more spatial significance.
