Challenges of large-scale facade PV systems in dense urban environments in China

The world is facing growing challenges posed by climate change and resource depletion. In response, the Paris Agreement has prompted countries to pay great attention to climate issues by setting carbon peak and carbon neutrality goals and accelerating energy transition. Simultaneously, the Russia-Ukraine war has triggered sharp fluctuations in global energy prices, exacerbating the energy security crisis and underscoring the urgent need to develop renewable energy sources.

Solar energy, as a clean and renewable resource, is widely recognized as a key solution to mitigating climate change. Over the past decade, photovoltaic (PV) technology has advanced rapidly, with substantial reductions in cost. From 2010 to 2021, the average cost of PV systems decreased by 88%, making PV power generation cheaper than traditional fossil fuels in some regions.1 From 2021 to 2025, solar PV prices transitioned from subsidy dependence to fully market-driven pricing. Meanwhile, the conversion efficiency of PV cells has improved significantly, rising from an average of 8% in the 1990s to over 22% in 2018,2 demonstrating remarkable progress in both the economic and technical aspects of PV systems.

Amid the global energy transition, China's photovoltaic industry has experienced rapid growth, particularly in residential distributed photovoltaics. In 2021, China added 21.6 gigawatts of residential photovoltaic capacity, equivalent to the total capacity installed during the entire 13th Five-Year Plan period. In 2023, the newly installed capacity further increased to 43.48 gigawatts, more than double that of 2021. The cumulative installed capacity exceeded 100 gigawatts.3 By the end of 2024, China's cumulative installed capacity of residential distributed photovoltaic power generation had reached over 145 gigawatts. This demonstrates that distributed photovoltaics have achieved record-breaking growth and large-scale development.

Building-integrated photovoltaics (BIPV) is a form of combining photovoltaics with buildings by directly integrating PV modules into facade and roof. This allows power generation without using extra land and is gradually becoming a mainstream trend in future building design. With the acceleration of urbanization, high-density and high-rise buildings have become the norm in cities, where rooftops are often occupied by air conditioning units, elevator shafts, and other equipment. This limits the space available for rooftop photovoltaics. In contrast, facade areas in cities are significantly larger than rooftops, offering greater potential for facade photovoltaics. In addition, in high or low latitude regions, during cold seasons or under specific sunlight conditions, facade photovoltaics show better power generation efficiency than rooftop photovoltaics.

Photovoltaic research and applications currently focus primarily on rooftop systems, while urban facade photovoltaics remain underexplored. Facade photovoltaics involve complex issues such as light angles, shading effects, and dynamic energy optimization, requiring further targeted research.