Residential photovoltaic panels with high partial shading tolerance, high voltage

Scientists led by the Korea Electrotechnology Research Institute have developed new residential small-area high-voltage (SAHiV) solar modules that they said are designed to endure high partial shading.

The researchers designed panels with both rectangular and triangular shapes and solar cells connected in parallel, which have higher partial-shading tolerance compared with cells connected in strings. “However, the module voltage will be very low in a parallel connection,” they also stressed. “Designing a module with parallel connections of high-voltage and low-current cells is a basic solution but is impossible with commercial solar cells.”

The academics divided conventional cells measuring 60 mm × 60 mm into 12 cells with both triangular and rectangular shapes, measuring 15 mm × 20 mm and 30 mm × 20 mm, respectively.

“We connected 12 cells in strings to become one subgroup to form a pseudo-high-voltage low-current cell with the same dimensions as a conventional cell,” they said. “This design differs from that of shingled cells, where a module is divided into four to six pieces arranged in strings lengthwise and connected string subgroups to group with parallel connections to the side.”

Shingled panels feature a busbar-free structure in which only a small proportion of cells are not exposed to sunlight. The cells are bonded with electrically conductive adhesive to form a shingled high-density string and the resulting strips are connected. The reduced number of busbars reduces shadowing losses.

With these cells, the research group built solar modules measuring 240 mm x 180 mm and with an active area of 432 cm2. They also built a shingled module with four subgroup cells, where each subgroup cell consisted of 12 string cells, and a SAHiV module with 12 subgroup cells, where each subgroup cell consisted of 12 string cells. Finally, they also designed a SAHiV triangle module with 12 subgroup cells, where each subgroup cell consisted of 12 string cells.

Through a series of Monte Carlo-based simulations and verification experiments, the scientists tested the performance of all panels under different types of shading patterns and angles, including eight discrete shading scenarios and five continuous shading scenarios. They compared their performance with that of a reference shingled panel.

The researchers said the tests showed that both the SAHiV modules and the SAHiV triangle modules are less sensitive to partial-shading geometries. “We found that the SAHiV triangle module demonstrates better partial shading tolerance under most of the investigated scenarios,” they further explained, noting that this shading tolerance is particularly high under shallow shadowing of up to 50%.

“For the SAHiV and SAHiV triangle modules in the vertical shading pattern, slight changes in the total shading area result in the same power,” the group said. “The SAHiV modules are robust against changes in the shading shape as long as the shading area is similar.”

The scientists presented the novel module architecture in the study “Small area high voltage photovoltaic module for high tolerance to partial shading,” which was recently published in iScience. “The results of this study indicate that the SAHiV module is very suitable for urban applications with unpredictable shadows and limited land,” they concluded. “Under these conditions, the SAHiV module will increase its performance by 1.5–3 times compared to conventional modules, maximizing electricity production.”