Revealing the Intrinsic Mechanisms of Hot and Cold Spots within a Locally Shaded Photovoltaic Module Based on Micro-Electrical Characteristics

Zhihan Liu, Yongshuai Gong, Zixuan Wang, Yingfeng Li () and Dongxue Liu ()
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Zhihan Liu: New Energy School, North China Electric Power University, Beijing 102206, China
Yongshuai Gong: Institute of Science and Technology, Three Gorges Corporation, Beijing 100038, China
Zixuan Wang: New Energy School, North China Electric Power University, Beijing 102206, China
Yingfeng Li: New Energy School, North China Electric Power University, Beijing 102206, China
Dongxue Liu: Institute of Science and Technology, Three Gorges Corporation, Beijing 100038, China

Energies, 2024, vol. 17, issue 17, 1-12

Abstract: Hot-spot generation is critical to the performance and lifespan of photovoltaic (PV) modules; however, the underlying mechanisms of hot-spot formation have not been fully elucidated. This work conducted a localized shading test on a PV module, measured the micro-electrical characteristics and temperature distributions of both the shaded and unshaded cells, calculated the heat-source power densities, and then predicted the occurrence and locations of hot and cold spots via numerical simulations. It was found that, under an irradiance of 750 W/m 2 , when one cell in a PV module is shaded by 1/2, the unshaded area within the shaded cell exhibited a hot spot, with the temperature reaching up to 77.66 °C, approximately 22.5 °C higher than the surrounding cells. The intrinsic mechanism for the occurrence of the hot spot is that, compared with the unshaded cells, the unshaded portion of the shaded cell can generate an extra significantly large Joule heat power density, about 1079.62 W/m 2 . The reason for generating such a large Joule heat power density is that this portion is in a reverse-bias state with a high current density flowing through it, according to our measurements. In contrast, the shaded portion forms a cold spot, about 7.5 °C cooler than the surrounding cells. This is because the shaded portion can only generate a Joule heat power density of about 46.98 W/m 2 due to the small reverse-bias current density flowing through it and fails to absorb heat from solar irradiance, which is about 645 W/m 2 . Moreover, this work demonstrates that the hot-spot temperature initially rises and then decreases with increasing shading ratio, with the highest temperatures and the most pronounced temperature changes occurring around a shading ratio of 1/2. The presented method can be also used to evaluate the performance and reliability of various other PV modules under local shading conditions.

Keywords: local shading; reverse bias; heat-source power density; temperature distribution (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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