Scientists at Suzhou Institute of Biomedical Engineering and Technology (SIBET) of the Chinese Academy of Sciences recently developed a LED-based solar simulator for better terrestrial solar spectra and orientations.

Terrestrial solar radiation is greatly affected by atmospheric, temporal, geographical, climatic and other environmental factors. Therefore, it is difficult to obtain stable, repeatable and controllable sunlight in time for quantitative experiment, instrument calibration, performance test.

Solar simulators are thus frequently used as experimental or calibration equipment. Existing LED solar simulators are, however, not capable of simulating the geometric characteristics of sunlight under one solar constant.

The SIBET team adopted a high-power vertical structure narrow-band LEDs, and designed a distributed high thermal conductivity single crystal COB package to achieve high optical power density and stable output.

Fig. 1. Graphical abstract of the solar simulator. (Image by SIBET)

They proposed a method to collect full aperture light with hyper-hemispherical aplanatic lens and built a multi-source integrating collimating system. The terrestrial solar spectra and orientations with spectral fitting under various conditions have been simulated simultaneously.

The team also conducted a control experiment with polycrystalline silicon solar cells under outdoor sunlight with same conditions. The simulator proved to have good spectral accuracy and orientational consistency.

“The proposed solar simulator realizes uniform illumination within the range of volume space,” said SUN Chao, scientist from the research team.

Researchers developed arbitrary solar spectrum fitting and control software, and for the first time, simulated simultaneous terrestrial solar spectra and solar orientations under different conditions.

“The simulator has wide application in photovoltaic industry, photochemistry, photobiology,” said XIONG Daxi, chief scientist of the team.

The team has applied for a patent for related design. The research results have been published in the journal Solar Energy (IF=5.742) entitled "LED-based solar simulator for terrestrial solar spectra and orientations".

Fig. 2. LED arrangement with different peak wavelengths. (Image by SIBET)

Fig. 3. The irradiance distribution on the target surface perpendicular to the beam with 100-mm working distance. (a) Normalized 3D model distribution of measured current value; (b) The class A non‐uniformity distribution of irradiance (yellow region); (c) The class B non‐uniformity distribution of irradiance (yellow region); (d) Photograph of light spots. (Image by SIBET)

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