Innovation Energy | High-Density Urban Facade Photovoltaics: Challenges and Breakthroughs

In modern metropolises with towering buildings, rooftops are already occupied by various electromechanical equipment, and the vast urban facades are bathed in sunlight but rarely utilized. Through quantitative assessment, climate coupling analysis, and comfort studies, this research explores whether large-scale application of facades can become the city's "second photovoltaic hinterland," providing decision support for urban energy transformation under the "dual carbon" strategy.

 

Introduction

In recent years, the cost of photovoltaics has continued to decline, and efficiency has continuously improved, making it a key force in promoting energy transformation and achieving the "dual carbon" goal. However, rooftop resources in high-density urban buildings are scarce, while the facade area is 3-6 times that of the roof, hiding huge potential for "vertical power generation." Shading, orientation, climate coupling, and aesthetic conflicts make facade photovoltaics both promising and challenging. This article focuses on typical large Chinese metropolises, summarizing key scientific issues and cutting-edge technological fields from four dimensions: potential assessment, climate impact, power generation stability, and human comfort, providing actionable solutions for policy formulation and industrial collaboration.

 

Figure 1: Graphical Abstract

 

Under the dual pressures of the climate crisis and energy transformation, photovoltaics have become a key technology for achieving the "dual carbon" goal. Over the past decade, the cost of photovoltaic electricity has decreased by 88%, and component conversion efficiency has increased from 8% to 22%, driving a surge in the installed capacity of distributed photovoltaics in China: 21.6 GW was added in 2021, doubling to 43.48 GW in 2023, and exceeding 145 GW by the end of 2024. The rooftops of high-density urban buildings are already occupied by electromechanical equipment, while the facade area is 3-6 times that of the roof, making it a promising "second battlefield" for urban photovoltaics. In mid-to-high latitude regions, the solar altitude angle is lower in winter, and the daily irradiance on south-facing curtain walls can be 15-30% higher than that on rooftops. Building-integrated photovoltaics (BIPV) demonstrate a "zero land occupation" advantage, driving buildings to transform from "energy consumers" to "energy producers."

 

However, large-scale deployment of facade photovoltaics faces four major technical bottlenecks. First, potential assessment: towering buildings, intersecting shadows, and diverse orientations render traditional two-dimensional algorithms ineffective. It is necessary to use unmanned aerial vehicle LiDAR, open-source GIS, and AI shading algorithms to construct three-dimensional point cloud models and couple meteorological data in real time. This requires high data accuracy and computing power. Second, climate coupling: for every 1°C increase in ambient temperature, photovoltaic component efficiency decreases by 0.4%-0.5%; large-area photovoltaics will generate a "photovoltaic heat island effect" (PVHI), leading to a 1.5°C increase in daytime urban temperatures, a 5.6% fluctuation in humidity, and a 1.2 m/s change in wind speed, resulting in significant microclimate disturbances. Third, power generation stability: multi-directional layouts can achieve off-peak power generation in the morning from east-facing and in the evening from west-facing facades, reducing the need for energy storage, but extreme weather such as heavy rain and sandstorms can still cause a sharp drop in power generation. Intelligent grids and demand-side response are urgently needed to achieve dynamic balance. Fourth, human comfort: in summer, photovoltaic curtain walls can reduce air conditioning loads, but in winter they hinder solar radiation, increasing heating needs; semi-transparent photovoltaic windows (STPV), dynamic shading, and colored perovskite components can balance daylighting and aesthetics, but their overall performance still lacks empirical evidence in high-density urban areas.

 

To achieve large-scale application of facade photovoltaics, it is necessary to bridge the "policy-technology-market" triple gap. Current building codes lack standards for BIPV structures, fire protection, and grid connection, and building renovation costs are high; fixed feed-in tariffs ignore the spatiotemporal differences of facade systems, compressing returns; and dispersed ownership leads to a lack of benefit-sharing mechanisms. Facing the national "dual carbon" strategy, future breakthrough paths will focus on AI-driven dynamic shading algorithms for precise potential assessment, quantifying the interaction between photovoltaics and climate to develop climate-adaptive systems, and constructing a multi-objective optimization framework that balances power generation efficiency, building performance, and aesthetics.

 

Life cycle analysis shows that although BIPV systems have higher initial investment, their comprehensive benefits, such as reduced air conditioning loads and participation in carbon trading, can bring considerable returns. When AI algorithms and smart grids are deeply integrated, buildings will no longer be energy consumers but active "prosumers" in the urban power grid—this silent energy revolution is redefining the symbiotic relationship between humans and cities.

 

Summary and Outlook

AI-driven algorithms will enable refined potential assessment of facade photovoltaics, and climate-adaptive materials can simultaneously suppress efficiency degradation and regulate microclimates; multi-objective optimization frameworks achieve optimal balance between power generation, energy saving, and aesthetics. Time-of-use electricity pricing, carbon trading, and revisions to building codes will help unlock economic value and promote BIPV standardization. When technological breakthroughs and institutional innovation work together, high-density urban curtain walls will transform into "breathing energy skins," deeply coupled with smart grids, weaving three-dimensional energy networks in vertical space. The vision of buildings transforming from energy consumers to "producers" will finally be realized.

 

Editor in Charge

Fang Yi, Institute of Process Engineering, Chinese Academy of Sciences

Xia Siyou, State University of New York

 

Original link: https://www.the-innovation.org/article/doi/10.59717/j.xinn-energy.2025.100091

This article is from The Innovation Sister Journal The Innovation Energy Commentary article "Challenges of large-scale facade PV systems in dense urban environments in China" published in Volume 2, Issue 2 of The Innovation Energy (Submission: 2025-02-10; Acceptance: 2025-04-10; Online Publication: 2025-04-12).

 

DOI: 10.59717/j.xinn-energy.2025.100091

 

Citation Format: Liu W., Mao H., Tian Z., et al. (2025). Challenges of large-scale facade PV systems in dense urban environments in China. The Innovation Energy   2: 100091.

 

Author Introduction

Chen Xinyu Professor, Department of Electrical Engineering, Huazhong University of Science and Technology; Adjunct Professor, School of Management, Huazhong University of Science and Technology; Director, Center for Power Energy System Transformation, Huazhong University of Science and Technology; recipient of the National Outstanding Youth Science Fund; Visiting Scholar, Harvard University. Research areas include power markets, integrated energy systems, renewable energy and grid integration, energy policy, and load forecasting. He has published numerous papers as the first author and corresponding author in high-level SCI journals, including Nature Energy, Nature Communications, Science Advances, and Joule.

http://faculty.hust.edu.cn/chenxinyu1/zh_CN/index/2223841/list/index.htm

Tian Zhiyong Associate Professor, Doctoral Supervisor, Huazhong University of Science and Technology; PhD from the Technical University of Denmark, Postdoctoral Fellow from the Norwegian University of Science and Technology; Hubei Provincial Overseas High-Level Talent, "Wuhan Yingcai" (Excellent Young Talent). He has presided over and participated in more than 10 national-level projects. His research group mainly focuses on building energy efficiency and solar energy utilization, green data centers, and cross-seasonal thermal energy storage. He has published more than 20 SCI journal papers as the first author or corresponding author.

http://faculty.hust.edu.cn/zhiyongtian/zh_CN/index/2333697/list/index.htm