| Work Detail |
Researchers at Miyazaki University in Japan have published a white paper on test protocols to address the unique challenges posed by vehicle-integrated photovoltaic (VIPV) modules. It presents the background for a new numerical probability model that incorporates shading, partial shading, dynamic shading, terrain irregularities, and module curvatures.
Researchers at Miyazaki University in Japan have published a report on advances in reproducible testing and protocols that address the challenges of measuring the performance of curved vehicle-integrated photovoltaic (VIPV) modules.
In the study, “ Testing and rating of vehicle-integrated photovoltaics: Scientific background ,” published in Solar Energy Materials and Solar Cells , the research team says their work addresses unique aspects of VIPV modules, such as curvature and irradiation impact caused by shading, partial shading, dynamic shading, and uneven ground conditions.
“Standard calculations for PV systems are often based on simplified assumptions such as no shadows, flat terrain, static installations, and uniform solar irradiation,” Kenji Araki, co-author of the paper, told pv magazine . “However, these assumptions do not accurately reflect real-world conditions. It is essential to take into account real imperfections such as shadows, uneven terrain, mobile PV systems, and non-uniform solar irradiation. Although these factors are not often taken into account, in practice they significantly affect the performance of PV systems.”
The team conducted initial testing of the new protocols and validation in geographically diverse laboratories and research institutes, as well as tests in solar simulators using the agreed protocols and the same calibration data, in addition to blind tests. For round-robin testing, Nanjing AGG Energy (China) provided rigid glass-coated modules with four levels of curvature radii.
The group noted at least eight key differences that need to be addressed to achieve accurate models and measurements of VIPV products. For example, the use of a local coordinate system that includes 3D rotation, capturing the shadow areas of the vehicles doors, hood, bumper and rear windshield.
Vector calculations based on a shading matrix, rather than a shading ratio or angle, are required. Tensor forms, 4-Tensor, are used for the angular response to incident light, rather than the lambarian curve, and instead of the cosine loss by PV panel angles, the differential geometric description using the vector expression of a unit element is used, the researchers noted.
Araki outlined some of the differences. “In the new model, a shading matrix takes into account non-uniform shading in the hemispherical sky. In contrast, classical analysis relies on a scalar shading relationship,” he explained, adding that the new method considers solar cells with curved surfaces and analyzes them using principles of differential geometry, “unlike classical calculation, which assumes solar cells have a flat surface.”
Additionally, the new model uses “vector-based” ray tracing rather than a cosine approach, and instead of representing the angular response and incident angle modification (IAM) as curves based on the incident angle, “the new calculation represents them as four tensors.”
Looking ahead, the researchers plan to develop a “fuel savings estimation tool” for trucks and buses with PV panels. Validation based on tracking 130 trucks is, so far, underway, according to Araki. In addition, other projects are planned to address the challenges of testing modules developed for agrovoltaics, building-integrated PV, as well as alpine PV and aircraft-integrated PV, such as high-altitude pseudosatellites (HAPS).
The research work is the result of the collective contribution of the members of the IEC TC82 PT600 initiative, which aims to establish standards for VIPV systems. |
