Until 2 years ago, the average power of PV modules, even in the high efficiency monocrystalline segment, hardly exceeded 360 W. And at that time, the International Roadmap for PV (ITRPV) was expecting solar modules to touch the 400 W level only by 2029. In the meantime, several PV manufacturers have started mass producing 500 W+ and even 600 W+ panels on a multi-GW scale.
What made this fast development possible? Decoupling of power and efficiency — the 2 most important performance characteristics of PV modules. Historically, module manufacturers have mostly relied on cell-level performance to improve module output power. However, the efficiency potential of today's standard PERC cell technology is mostly exploited. As greater module size can also improve the power level, companies have done exactly that already in the past: 72-cell module formats gained increasing popularity in utility applications. While there are higher cell number products available, such as 78-cell modules (or their half cell equivalents), which is the next level, there are limits owing to the challenges it entails at the inverter level.
Recently, PV manufacturers 'stumbled' upon an easy and effective method to improve module power independent from efficiency – larger wafers.
To understand how it works, it is important to analyze the reason behind the need to increase module power. The main motivation here is not just a sign of improvement ('larger means better') but is strongly backed by economics – enabling reduction of balance of system (BOS) costs
For example, increasing the module power by 50 W from 390 W has the potential to reduce BOS costs by about 5%, according to LONGI Solar while the actual number varies according to the benchmark. Digging deeper shows that the main savings are driven by the fact that string power increases with higher module power, with fewer strings required to get to a specific capacity. And with fewer strings, there is a commensurate reduction in racking / tracker and electrical component costs, which shows up as savings in BOS.
It doesn't end there. Module power has to be augmented without increasing its voltage, because it would not reduce the number of modules per string. Therefore, the benefits of BOS reduction can be realized only if the voltage is kept at the same level, which means the current of the module rises. So, approaches like designing larger modules with a higher number of cells are not as beneficial as increasing the wafer size. On the other hand, a larger wafer size results in a higher cell current, which is a function of the surface area, while the voltage remains the same.
Thus, building larger modules based on larger wafer formats has been a low hanging fruit in manufacturers' reach, especially compared to a move toward the next higher efficient cell technology.The 'larger wafers' concept caught on like wildfire, overshadowing any other development in the PV industry in the year 2020. As a result, the market was flooded with many different wafer sizes from M2 (156.75) all the way up to G12 (210 mm).
Several questions and concerns on the road to larger wafers
There have been several questions and concerns on the road to larger wafers – and on top of the list was and still is: 'What is the optimum largest wafer size?' The major module manufacturers have mainly split into two camps. The leading vertically integrated panel producers went the M10 route with a pseudosquare edge length of 182 mm. Those module manufacturers without big capacities in large wafer production have favored G12, a full-square format with 210 mm side length. A few manufacturers took the middle path by adopting products based on both wafer formats.
Given this size ambiguity, there were several other concerns about the scaling up of production equipment, availability of suitable BOM such as glass, encapsulation and backsheet, compatibility of system components such as inverters and trackers, etc. But the industry again surprised everyone with the pace of development. There are now innovative solutions available for addressing each of these concerns.
Not only that, but the PV industry is making progress in leaps and bounds as manufacturers keep bringing new products to the market with ever increasing power. The first edition of our report on this subject, launched in Aug. 2020, was named TaiyangNews Report On 500W+ Solar Modules – with 500 W being the benchmark at that time. Today, there are modules available with up to 700 W rated power.
So, in keeping with the current trend, this year's edition is named TaiyangNews Very High-Power Modules. The current edition summarizes the most important developments over the last year that have enabled these high-power modules to enter the mainstream. And whatever are these developments, they are bound to show up at the final product level – the solar module. At SNEC 2021 in June, the world's biggest solar trade show, one key trend will be very high power solar modules. This report also provides a preview of products introduced and promoted at SNEC by leading module manufacturers.
The text is an excerpt from the TaiyangNews Report on Very High Power Solar Modules, which can be downloaded for free here.
At TaiyangNews' Virtual Conference on Very High-Power Solar Modules, Shravan Chunduri, Head of Technology for TaiyangNews, emphasized that using larger wafers to attain higher power modules has more or less become a standard; the recording can be viewed here.