Can photovoltaic systems still generate electricity on cloudy or smoggy days?

The operating principle of photovoltaic systems

A photovoltaic system converts the energy of photons from sunlight into electrical energy using solar panels. As long as there is light—even if the light intensity is relatively low—the photovoltaic system can still function.

The impact of rainy or foggy days

• Reduced Light Intensity: On cloudy or hazy days, clouds, raindrops, and particulate matter in smog block and scatter sunlight, significantly reducing the amount of light reaching photovoltaic panels. According to studies, on cloudy days, a photovoltaic system’s power output may be only about 10% to 20% of what it would be on a clear day, while on heavily hazy days, the output could be even lower.

• Spectral Changes: On cloudy or hazy days, the spectral composition of sunlight also changes. Photovoltaic panels have varying response efficiencies to different wavelengths of light; therefore, on cloudy or hazy days, the spectral composition reaching the photovoltaic panels may not be conducive to their efficient power generation.

The impact of different photovoltaic cell types

• Single-crystal silicon photovoltaic cells are relatively sensitive to changes in light intensity, and their power generation efficiency drops noticeably on cloudy or smoggy days.

• Polycrystalline silicon photovoltaic cells: Compared to monocrystalline silicon photovoltaic cells, they exhibit slightly better adaptability to changes in light intensity. However, their power generation efficiency will still decline significantly on cloudy or foggy days.

• Thin-film photovoltaic cells—such as amorphous silicon thin-film cells and copper indium gallium selenide (CIGS) thin-film cells—respond relatively well to low-light conditions. Compared with monocrystalline and polycrystalline silicon photovoltaic cells, their power-generation efficiency declines less significantly on cloudy or foggy days; however, their overall power output will still be substantially affected.

Optimization measures in practical applications

• Optimize the installation angle and orientation: By appropriately adjusting the installation angle and orientation of photovoltaic panels, ensuring they receive as much sunlight as possible, it is possible to improve power generation efficiency to some extent even on cloudy or smoggy days.

• Adopting an intelligent tracking system: The intelligent tracking system can adjust the angle of photovoltaic panels in real time according to the sun’s position, ensuring that the panels always face the sun and thereby enhancing power generation efficiency. Although the sun’s position may not be obvious on cloudy or smoggy days, the intelligent tracking system can still make adjustments based on pre-set programs or sensor data to capture more sunlight.

• Energy storage systems: Equipping a system with an energy storage device—such as batteries—enables it to continue supplying power during days with low solar generation, like rainy or smoggy days, by drawing on the stored electrical energy. This enhances the reliability and stability of photovoltaic systems.

In short, photovoltaic systems can still generate electricity on cloudy or foggy days, though their efficiency will be significantly reduced. By optimizing installation and adopting certain auxiliary technologies, it’s possible to enhance their power-generation efficiency and reliability to some extent under these weather conditions.