Research status and application of rooftop photovoltaic Generation Systems

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 building components. Their incorporation into building roofs remains hampered by the inherent optical and thermal properties of commercial solar cells, as well as by esthetic, economic, and social constraints. This study reviews research publications on rooftop photovoltaic systems from building to city scale. Studies on power generation potential and overall carbon emission reduction of rooftop photovoltaic systems are summarized at the macro level. The installation angle, tracking system, mechanical properties, shielding effects, indoor effects, and the life cycle of photovoltaic modules were sorted at the micro level, including their development process, advantages and disadvantages. In terms of battery materials, cadmium telluride batteries stand out among new materials with a short payback period of less than one year and a carbon dioxide emission of as little as 19 g CO₂ eq/kWh. Besides, the differences between building-integrated photovoltaic and building-applied photovoltaic are described in light of recent studies. Moreover, the application of photovoltaic rooftops, which is crucial to achieve the carbon emission peak, is also discussed. It can be found that the use of crystal silicon cells in public buildings is still the main approach of rooftop photovoltaic projects, and the maximum installed capacity of single building has exceeded 10,000 kWp. Finally, on the basis of summarizing the previous achievements, the future research focus and directions are predicted.