Facilitating higher power has been the main goal of efforts that have been put into optimizing upstream processes – and larger wafers fit the bill very well in that regard. As with the wafer and cell processing stations, larger wafers increase production capacity (in MW) in module production. This approach brings a better value proposition to the table in terms of utilization rates of process consumables and utilities, while also resulting in less waste and labor costs. The number of electrical connections, mechanical movements on a per W basis, also reduces with larger wafers.
Module BOM
Moving to larger and powerful modules also requires some changes, especially the bill of materials (BOM). These larger modules require larger frames, encapsulation and backsheets, thus a compatible laminator. Glass is an ever more important component that also increases the total module weight considerably; but it should not add to the load stress of the module.
As is common knowledge for the followers of the solar industry, glass was in short supply last year, and larger modules that require glass sheets of different sizes proved a bottleneck for manufacturers, especially the very large G12 formats. While not specific to G12, the bifacial variants of these high power modules that use glass on both sides exacerbated the supply situation further. With these the limitation from the glass side was pronounced in the first months of Q1. The followers of M10 were the first to shout out about debottlenecking the glass supply suitable for the M10 format. At TaiyangNews High Efficiency Conference in Dec. 2020, JA Solar presented its evaluation of the supply chain to support the M10 based production and glass was part of it.
The company emphasized that about 50% of the total available 220 GW glass capacity can support 182 mm based module formats in 2021. The company also provided an update on the supply of encapsulation materials that 58% of over 240 GW total available capacity is compatible with 182 mm module configuration.
At least the solar glass scarcity was a very short-lived phenomena that is already solved with many new production capacities having come online and under development. At the May 2021 held TaiyangNews Very High-Power Module Conference, Trina Solar emphasized that around 50 GW production capacity of glass is suitable for G12 modules with above 600 W becoming available by end of 2021, which is expected to grow to 120 GW by 2022.
Junction boxes are the first casualty in the case of a rise in short circuit current due to larger cell sizes, if proper care is not taken, according to TUV's Joerg Althaus, who has provided an extensive overview on the Quality Aspects of Very High-Power Modules. at TaiyangNews Very High-Power Module Conference. The bypass diodes need to be able to handle such high currents without failure, and the thermal stress on the diodes needs to be alleviated by providing some extra space between diodes without causing shading on the rear-side of the module. Junction box damage may further affect the cables, which might put the entire system's reliability at stake.
Open-circuit voltage also affects the junction box, as it increases the reverse voltage to be handled by the diode, which may lead to high leakage currents. A junction box design that takes all these aspects into consideration is a key factor to ensure stable operation of the PV system.
The text is an excerpt from the TaiyangNews Report on Very High Power Solar Modules: Summarizes Most Notable Developments Along Manufacturing And PV Value Chain for Panels Based on Large Wafers & Provides Overview on Latest Products of Leading Module Suppliers – The TaiyangNews Market Survey Report can be downloaded for free here.
At TaiyangNews' Very High Power Modules Virtual Conference, Joerg Althaus from TUV provided an overview on the Quality Aspects of Very High-Power Modules, the recording can be viewed here.
Building High Power Modules Based On Larger Wafers Impacts Balance of System Components