AESOLAR is developing an upgraded hotspot-free segmented PV module designed for rooftop installations with permanent partial shading
In collaboration with Fraunhofer CSP, serving as the R&D and validation partner, multiple innovative segmented module layouts have been successfully tested and validated
This module, under the Shaded Star brand name, is expected to be launched by next year
AESOLAR, the well-known German PV module manufacturer behind the smart hotspot-free technology featuring bypass diodes for each cell, has now embarked on the development of its next-generation “SegmentPV” project.
Recalling their previous visit to AESOLAR’s booth at Intersolar Europe, where the company showcased its shading-resistant modules, the TaiyangNews team once again stopped by this year to learn about the latest advancements. During a short interview, Hamed Hanifi, Director of Technology and Innovation at AESOLAR, shared updates on the development and reliability of the new segmented PV module.
What is the “SegmentPV” Project?
Hanifi began by outlining the company’s first shade-resistant module, launched in 2018, which has been sold commercially for several years. However, to overcome the limitations of the earlier technology, AESOLAR decided to redesign the module architecture, thus initiating the “SegmentPV” project.
This national-level project is funded by Germany’s Federal Ministry of Economic Affairs and Climate Action in collaboration with the Fraunhofer Center for Silicon Photovoltaics (CSP). According to Hanifi, the collaboration led to the development of a new generation of shade-resistant PV modules offering significant improvements over previous versions. As a testing partner, Fraunhofer CSP has been validating the concept and testing prototypes for durability and reliability.
Advantages of the New Design
Hanifi explained that even if just 5% of a PV module’s surface is shaded, it can cause a complete system shutdown. In real-world rooftop installations, even high-efficiency modules often fail to meet expected energy yields when shaded by structures like chimneys, antennas, or other rooftop obstacles.
With customer expectations for consistent energy generation, even under partial shading, AESOLAR acknowledged the limitations of its earlier design. While previous models incorporated bypass diodes for each cell, the latest approach addresses the higher cell quantity in half-cut cell architecture. Instead of individual diodes per cell, the new segmented layout assigns a bypass diode to each small cell group, improving shade tolerance and operational control. Hanifi also noted that fewer diodes reduce heat buildup under shading conditions, enhancing reliability.
Segmented Module Layout
The segmented PV layout involves dividing the module into small groups of PV cells, each protected by a bypass diode. Hanifi highlighted that AESOLAR faced ‘a lot of challenges’ integrating bypass diodes within the laminate layer of the PV module while ensuring effective hotspot protection.
The team developed simulation models to test various layouts by grouping different quantities of PV cells. These models revealed scenarios where certain configurations could generate significantly more energy and reduce reliability risks. All proposed layouts were thoroughly tested at Fraunhofer CSP’s lab to validate performance under real-world shading conditions.
Cell Technology Selection
AESOLAR evaluated various cell technologies, HJT, TOPCon, PERC, and Back Contact (BC), for their performance, reliability, and market availability. In-house characterization focused on reverse-bias behavior, which determines susceptibility to heat loss and degradation under shading.
Ultimately, TOPCon cells were selected for their durability, performance, and better compatibility with AESOLAR’s supply chain. He further emphasized that compared to the current market available shade-resistant module, typically of BC cell technology, the company’s upcoming product will feature added advantages. In contrast, the BC cell technology, featuring lower reverse breakdown voltage, breaks faster in shading conditions with lower losses, while the TOPCon cell, which doesn’t break down at all, offers even higher advantages, noted Hanifi. Testing at Fraunhofer CSP confirmed that the segmented module with TOPCon cells performed better under real-life shading scenarios than current market offerings.
Economic Benefits
Unlike power optimizer-integrated modules, which balance string current to reduce mismatch losses during shading, the segmented PV module retains power from unshaded segments, eliminating the need for power optimizers. Though slightly more expensive, the module can deliver higher energy output at a similar system cost.
Launch Timeline
This innovative hotspot-free module, to be branded as Shaded Star, is expected to launch by next year.
Insights from R&D partner
Sharing his experience with the ongoing project, Bengt Jäckel, Group Manager at Fraunhofer CSP, said the lab approached the development from multiple angles, starting with the careful selection of PV components during the early stages. This included identifying the most suitable PV cell for a shade-resistant module that also ensures long-term durability. The choice was closely linked to the configuration of the module’s electrical circuitry and its integration with bypass diodes.
For the bypass diode selection, the team addressed challenges related to varying diode geometries and ultimately chose flat types. They also considered each diode’s performance characteristics and manufacturability for mass production.
In terms of long-term reliability, Jäckel explained that the module’s innovative electrical circuitry provides substantial redundancy under shaded conditions, helping to lower the operating temperature and reduce the risk of material failure.
He further noted a shift in perspective among rooftop PV consumers, where partial shading, once considered a fault, is increasingly seen as a normal operating condition. Jäckel said, “Nowadays, PV module is a commodity and you take as much space as you can. And then, in the end, that also poses some risks in terms of quality and long-term reliability of the product. And that's why shade resistance modules also in the future will be of importance.” However, since no international testing standard currently addresses this frequent and expected partial shading scenario, the lab has developed its specialized reliability tests. These simulate daily shading events to assess the product’s durability over an extended lifetime.