Spanish researchers assembled an experimental solar simulator for vehicle-integrated and curved solar panels. They found that the short-circuit current measurements of the cells followed the ideal cosine response of curvature with differences of less than 0.5%.
“We are considering commercial production in the future,” said corresponding author Guido Vallerotto pv magazine. “At the moment we are still developing several aspects of the simulator. The version we used in the paper’s characterization is not ready for commercialization, even if in practice it is fully functional and functional.”
In a test of a module with a radius of curvature of 1 meter, the research team found that their solar simulator’s cell short-circuit current measurements followed the ideal cosine response of the curvature with differences of less than 0.5 percent.
It also ensured that a non-collimated light source, typically used in conventional solar simulators for flat modules, had a non-uniformity increase of 2-20% depending on the module. The inherent non-uniformity in normal radiation due to the curved shape is amplified when illuminated by a non-collimated light source, the researchers said.
The researchers tested their solar simulator solution with one flat panel and three curved modules with radii of curvature of 3 m, 2 m, and 1 m, respectively. The modules were equipped with 32 metal wrap-through (MWT) cells with eight 4 cells. Each string was measured independently and compared to the expected cosine response.
The team determined the location of the light source, the type of light source and the length of the pulses. They selected the Helios 3198 solar simulator, originally developed to characterize concentrator photovoltaics (CPV), and adapted it to the proposed design. The light pulse power source and electronics were modified to adapt to the slower time response of conventional silicon cells.
The setup included a black tunnel to reject stray light, including baffles and a light trap box and chambers. Tunnel design is critical to achieving better than 1% radiation inhomogeneity, the researchers said. Light stopping chambers closer to the lamp and guide plates along the tunnel are needed to effectively prevent stray light and ensure that only the light reflected by the collimating mirror reaches the measurement plane.
The simulator is based on a multi-flash approach, where the Xenon flash lamp fires when the module is biased to a different voltage with each flash pulse, recording different current-voltage point pairs during pulse decay. The illumination system consists of a circular collimator with a diameter of 2 m and a focal length of 6 m, and a small toroidal flash lamp with a diameter of 65 mm, which produces a collimated beam with a dispersion of 0.3 degrees, which resembles direct normal radiation. (DNI) in outdoor conditions.
The design, installation and test results of the solar simulator are presented in the publication “Collimated solar Simulator for curved PV module characterization”, published in Solar energy materials and solar cells.