Building facade photovoltaic potential has been underestimated for a long time: An assessment analysis of BIPV potential in ten megacities in China

With the global pursuit of sustainable development and carbon neutrality goals, solar energy, as a clean and renewable energy source, is receiving unprecedented attention. In China, with the acceleration of urbanization and the continuous growth of energy demand, building-integrated photovoltaic (BIPV) systems, as an efficient way to utilize solar energy, are gradually becoming an important way to solve urban energy problems.

Graphical Abstract of the Paper

Recently, the Ye Bin team from the School of Environmental Science and Engineering, Southern University of Science and Technology, published a research paper entitled "Energy-economy-environment evaluation of building-integrated photovoltaic considering facade factors for representative megacities in China" in Applied Energy, a top journal in the field of engineering technology. This research developed a comprehensive assessment model for energy saving and carbon reduction of building-integrated photovoltaic systems (BIPV), evaluating the solar energy resources endowment and energy saving and carbon reduction potential of BIPV in ten megacities in representative climatic regions of China. The study innovatively assessed the power generation potential of building facade photovoltaic systems using multi-dimensional images and three-dimensional building footprints. In addition, it also explores the coupling and interconnection of building-integrated photovoltaic systems with electric vehicles to evaluate the role of electric vehicles in reducing the peak-valley difference of the power grid.

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https://authors.elsevier.com/a/1ks0t15eifFubw

This article, based on the research paper published by the Ye Bin team from the School of Environmental Science and Engineering, Southern University of Science and Technology, in the journal Applied Energy, conducts an in-depth assessment and analysis of the BIPV potential in ten megacities in China, aiming to provide valuable reference and inspiration for industry professionals.

Research Framework Diagram

As one of the world's largest energy consumers, China faces enormous pressure to reduce carbon emissions. To meet this challenge, the Chinese government has proposed a series of climate mitigation pathways, aiming to gradually transform the energy structure through the promotion of renewable energy. BIPV systems, as an innovative model that combines photovoltaic power generation with buildings, can not only provide clean power supply but also effectively reduce building energy consumption and carbon emissions. However, due to differences in geographical location, climate conditions, and building types in different cities, the power generation potential of BIPV systems varies significantly. Therefore, this study aims to conduct a comprehensive assessment of the BIPV potential in ten megacities in representative climatic regions of China through multi-dimensional images and three-dimensional building footprints, providing scientific basis for urban planners and decision-makers.

The study shows that the annual average power generation potential of rooftop photovoltaic (RPV) in the ten cities ranges from 14.19 TWh (Lhasa) to 108.92 TWh (Shanghai), covering 29.1%-63.2% of the city's electricity demand. Among them, high-latitude cities (such as Harbin and Urumqi) significantly improve power generation efficiency by optimizing the roof tilt angle (average increase of 24.8% in irradiation absorption). For example, the Harbin RPV system can meet 43.6% of local electricity demand, becoming an important option for energy self-sufficiency in northern cities.

Solar radiation values are lower than the optimal installation surfaces of BIPV on each surface

The potential of building facade photovoltaic (FPV) has been underestimated for a long time. The study shows that the south-facing facade, due to its high irradiation intensity (average 978.8 kWh/m²/year), has a power generation efficiency of nearly 60%-80% of RPV. Taking Beijing as an example, with its dense high-rise buildings, the proportion of south-facing FPV area reaches 25%, and the annual power generation can be increased by 59.77%. However, due to insufficient irradiation (average 454.5 kWh/m²/year), the north-facing facade has poor economic efficiency and needs to be combined with building morphology optimization layout.

Due to differences in climate zones, site-specific installation strategies are needed:

• Cold regions (Harbin): RPV is the main focus, with optimal roof efficiency under low-angle sunlight in winter.
• Hot summer and warm winter regions (Guangzhou): FPV has strong supplementary properties, and the south-facing facade can alleviate the peak electricity demand in summer.
• Plateau regions (Lhasa): The highest irradiation intensity nationwide (over 2000 kWh/m²/year), but low building density requires refined development.

With the popularization of electric vehicles in various cities, their electricity consumption accounts for 6.39%-16.46% of the total power generation. The study found that the synergistic effect of BIPV-EV can significantly improve the proportion of self-generated electricity from building-integrated photovoltaics. Taking Urumqi as an example, the absorption capacity of electric vehicles reduced the surplus electricity of the distributed system by 13.81%. This shows that electric vehicles, as a flexible power load, can effectively absorb the surplus electricity generated by the BIPV system, thereby reducing the surplus electricity ratio and grid resale ratio of the power system.

Building facade area angles in ten cities

Impact of BIPV systems on environmental carbon emissions in ten cities

From the perspective of energy security, BIPV systems can significantly improve the proportion of renewable energy in cities and reduce dependence on traditional energy. From an economic perspective, although the initial investment of BIPV systems is high, with technological advances and cost reductions, its economic benefits are gradually becoming apparent. In particular, rooftop photovoltaic (RPV) systems and south-facing facade photovoltaic systems, due to their better power generation potential and lower power generation costs, have better economic performance. From an environmental perspective, the promotion and use of BIPV systems can significantly reduce the carbon emission intensity of cities and make important contributions to achieving carbon neutrality goals.

Policy and technological suggestions: Breaking through the bottleneck of large-scale application

Policy level: Mandatory standards and market-oriented incentives work together

• New buildings: Mandatory requirements for BIPV coverage (e.g., roof ≥50%, south-facing facade ≥30%).
• Financial tools: Provide 15%-20% installation subsidies for FPV projects and pilot carbon credit trading.

Technology level: Material innovation and digital empowerment

• Photovoltaic building materials: Develop lightweight, light transmittance adjustable FPV products to adapt to glass curtain walls and irregularly shaped buildings.
• Digital twin: Based on a 3D GIS model, simulate the power generation efficiency of BIPV in different climate zones and optimize installation schemes.

The large-scale application of BIPV relies not only on technological progress but also on the linkage of policies, markets, and urban planning. The analysis of the ten cities shows that RPV is currently the most economically viable option, while the potential of FPV needs to be combined with building design and material innovation. In the future, through the construction of a "BIPV+EV+smart grid" ecosystem, megacities in China are expected to take the lead in achieving the goal of "zero-carbon buildings," providing a model for energy transformation in high-density cities around the world.

Information Source: Applied Energy