0.01–0.5 sun is a realistic and alternative irradiance window to analyze urban outdoor photovoltaic cells

Vox Kalai Wong, Chujun Zhang, Zhuoqiong Zhang, Mingwei Hao, Yuanyuan Zhou, Shu Kong So*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

1 Citation (Scopus)


Solar cells have penetrated many cities as Building Integrated Photovoltaic (BIPV) or the energy source for standalone Internet of Things (IoT) devices. Traditionally, photovoltaic (PV) cells are evaluated using 1 sun irradiance. However, in a city, factors such as air pollution, cloudiness and cell installation orientation may attenuate the receivable solar energy. Also, the power conversion efficiency (PCE) of a PV cell is highly irradiance-dependent. Evaluating urban outdoor PV cells using 1 sun irradiance could lead to inaccurate prediction of PCE and overestimated output power in actual usage. Herein, we analyzed daytime irradiances of 11 cities located across the globe. Our results show that realistic irradiance (RI) in most cities is between 0.01 and 0.5 sun, reflecting the irradiance under a cloudy to mostly sunny sky. Under such an RI window, the PCEs of 9 different PV technologies were compared. 7 PV technologies have compromised performance. 2 PV technologies, organic and perovskite PVs, show enhanced PCE under the RI window and are favorable for urban outdoor applications. The potential of powering IoT devices by these PV technologies under sub-optimal irradiance conditions in cities is also highlighted.

Original languageEnglish
Article number101347
JournalMaterials Today Energy
Early online date17 Jun 2023
Publication statusPublished - Aug 2023

Scopus Subject Areas

  • Renewable Energy, Sustainability and the Environment
  • Materials Science (miscellaneous)
  • Nuclear Energy and Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology

User-Defined Keywords

  • Cloud cover
  • Internet of Things (IoT)
  • Photovoltaic cells
  • Solar energy and smart city
  • Terrestrial irradiance in cities


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