In mid-March 2021, the leading global PV and smart energy total solution provider Trina Solar unveiled a new generation of ultra-high power Vertex modules with a single panel power of 670W. Recently, the head of the company’s product strategy and marketing department, Dr. Franck Zhang, was interviewed about several burning questions regarding module technology and products.

Trina Solar released 400W, 500W, 550W and 600W+ modules in 2020. Together with its most recently launched 670W module, they have been recognized by being awarded full-reliability certificates and through solid real-world experience; glass supply has been secured; packaging and logistics solutions have also been verified and approved by leading global logistics companies. The 600W+ module is now fully equipped for industrialization.

Zhang explained the key features of the 670W Vertex module in detail. First, the series inherits the non-destructive cutting, high-density cell interconnection and other high-precision technologies of the 210mm modules; second, with its ultra-high power, the single-string power is 34% greater than that of the traditional 500W+ modules; third, in addition to reliability, the 670W Vertex modules achieve the ultimate use of containers in shipping, as a result of which loading power rises by 12% per container and installation costs fall 5- 7%, creating huge scope for reducing the LCOE and BOS cost. Zhang said that in 2021, 210mm products will account for 70%-80% of Trina Solar's overall modules shipment, and 670W Vertex modules are expected to become the mainstream of 210mm products.

Following is the dialogue between Zhang and media representatives concerning the module’s size, redundancy of the junction box, logistics and transportation, installation and other issues.

Q: How can high power be achieved using the new 670W modules? By making them bigger? It had earlier been said that the maximum module size was about 2.6 m². How does 670W break that limit?

Zhang: The 2.6 m² you mentioned is simply the view of some module manufacturers. It does not align with what customers of Trina Solar believe.
So people should not be misled by any of this. Moreover, modules larger than 2.6m² are already on the market, including the 182mm 78-cells module (2471 x 1135 = 2.8m²).

PV modules are used in a variety of scenarios, each with their unique module type, so there is no such thing as a "single optimal size". Our new module features a 6 x 11 layout of the 210mm module. Vertex S 400W is 5 x 8 and Vertex 500W is 5 x 10, both of which were launched last year. Through the flexible layout, 210 modules can cover various power ranges to meet various needs.

So let's disperse the following misconception once and for all: “The 210mm large silicon wafer is equivalent to a large module”. No, it’s not.

In fact, 210mm wafers do not mean larger modules. We can use 210mm wafers to make 400W modules with a size of 1754mm x 1096mm, and we can make 500W modules. They are both perfectly matched products for commercial, industrial and residential scenarios in terms of size, weight and module power and efficiency. They mostly compete with the 370W and 450W products commonly used in the industry, and have 30-50W more power advantage than those with similar size and weight, which can bring extra value to customers and are thus more competitive. In addition, Trina Solar’s 550W and 600W+ modules are products built for large-scale power plants. Typically, these plants are larger in scale and cover relatively large areas, so the LCOE reduction is significant.

The 670W module we are talking about is also an ultra-high power product for large-scale power plants. With a module size of 2.384m x 1.303m, the 670W module does have an area of more than 2.6m², but this solution works. We have come up with a complete solution reconciling packaging, logistics and installation. As long as it can reduce the LCOE, it is a valuable product. After our new product launch, some companies have said the 670W is worthless. This is misleading to the industry because they have not developed 210mm products at all and lack knowledge of the value of 210mm products. They denigrated the value of MBB (multi-bus-bar), too, and that has become the mainstream interconnection solution today.

In fact, even these very critics are now using MBB.

Q: There are other voices in the industry that says module size is limited by containers. What do you think?

Zhang: I've been asked this question by my peers, who keep claiming that 1134mm is the maximum width for the container. But this conclusion is based on the traditional two-pallet stacking method, which is not the limitation under the innovative packing at all.

For 600W+ series products, Trina Solar innovated with the packaging method to bring in vertical placement, so the placement is no longer limited by the conflict between the width of the modules and the height of the container. Such packaging makes the best use of the container's internal capacity. Compared with other mainstream products on the market, with the standard 40HC (high cube) container, the loading power increases by 12%, which introduces a corresponding 12% cost reduction in logistics.

In terms of safety, first of all, the factory packaging is completed by automatic equipment to ensure safety and efficiency; second, in transportation, the module packages are closely arranged inside the container with less shaking; finally, stable and reliable transfer was achieved at the project site to ensure safe delivery to the customers.

Q: Are there any special requirements for installation?

Zhang: In terms of installation, our 670W single-glass modules weigh 34kg and the double-glass modules about 38kg. Compared with the 182mm 72-cells, with the single-glass about 32.4kg and the double-glass about 35kg, the weight has increased slightly. According to current global occupational safety requirements, such as the most stringent U.S. and European ones, the carrying weight for one person cannot exceed 23 kg. In today's module installation scenario, no matter whether you lift either a 166mm 72-cells module or a 182mm 72-cells module, two people are required. So it’s within this weight range for two people to lift a 670W module.

In other words, from the weight point of view, module installation is no problem. We have also done simulation experiments to prove that there is no problem for manual installation. We’ve also seen a module weighing about 34.9kg launched by our peers that is handled by two people and installed by three, which has completed the installation more than several gigawatts without any problems.

A lot of empirical evidence proves that 670W Vertex modules can still be installed in the traditional way. However, due to the module power increase of 100W or more, the module quantity in a 100MW power station is reduced by about 20%, so the overall installation cost will drop accordingly. Considering that the increase in module weight may affect some of the module installation cost, it is estimated that the overall installation cost will fall by 5-7%.

In addition, in view of future developments in module installation, we have started to develop an automatic installation machine, retaining only delicate operations, such as fastening screws, for manual work. This will undoubtedly improve installation efficiency, reduce labor costs and drive down the LCOE. I believe this will lead to a revolution in the way modules are installed.

Q: I think you're aware of some of the recent doubts over high currents, such as higher heat generation, the risk of redundancy from junction boxes, etc. How can you explain this?

Zhang: First, the current density of a cell depends on the cell structure and efficiency. With the same PERC structure, large-wafer cells and small-wafer cells have almost the same cell conversion efficiency, the same encapsulation and the same irradiance condition, so there is almost no difference in module current density. So why does the module possess high currents? The higher current is only generated when the current is converged through the cell connector, and then lead to the high current outputs from the junction box, which means that the high current is generated after the cell connection; the per-unit of cell does not involve high current.

Second, given the similar module efficiency, as for 210 modules and 182 modules, under the unit area, the amount of solar radiation not converted into electrical energy are the same.Thus, based on the same installation and heat dissipation conditions, the working temperature of the 210mm high-power module and 182 module tends to be the same, with no risk of increasing working temperature, which have been verified in empirical tests. Some people, holding the view that 210mm module's working temperature is high, actually do not understand the basic principle of photoelectric conversion, and this judgment is not supported by actual measurement data.

In addition, 182mm module uses the 9BB (bus-bar) technique with 20mm spacing between the busbars, while our 210mm module uses the 12BB technique with 17.5mm spacing. Given this difference, the 210mm cell has less resistance in the current transfer path. When the currents converge, the current becomes larger in such areas of bus bars. However, due to our optimized thickness and width of the cell connector, the cross-sectional area of connectors inside 210 modules becomes larger, thus reducing the heat generation and losses in these areas.

The risk of junction boxes has also been mentioned in some articles. But in those articles, I think the calculations are wrong, which is multiplied by 1.3 after already being multiplied by 1.25 in terms of redundancy. It’s totally unnecessary! First, I think the "1.3 times" is basically non-existent, unless both sides are shaded at the same time, definitely with a slight chance. Because when the front side is shaded and the back side is not – it continues to be energized smoothly. Second, although the short-circuit current of our modules is 18.4A, the typical operating current is only about 17A, multiplied by 1.25 equals about 21A. And the current of junction box that has been certified is 25A, which is really more than enough. Moreover, the 30A junction box solution is also mature and certified, ready for mass production, without any technical bottlenecks.

To summarize, there is no need at all to think about margins beyond the safety margin, which only adds the redundancy costs and is simply not economical. By the way, this may also reflect different companies' technical choice and technical judgment ability.

Already eight to nine of the major manufacturers can supply junction boxes compatible with 210 modules. We will carry out a variety of more extended tests in certain extreme scenarios to make sure the 30A junction box can fully meet the needs technically and application-wise.

Q: How about the mechanical performance of Trina Solar's 670W Vertex modules?

Zhang: We offer the same mechanical performance guarantee as other products in the industry. We have been tested and certified by a third party. We took a series of measures and did design optimization. On one hand, the optimized frame design and material selection prevents the deformation even when the module area increases, and reduces the risk of microcracks. On the other hand, the non-destructive cutting ensures that each cutting surface of the cell is smooth and microcrack-free, keeping the same bending strength as full cells. Owing to these measures, the loading capacity of the 670W Vertex module can adhere to the industry mainstream standard of 5400 Pa positive and 2400 Pa negative.

Q: What is the voltage for 670W modules?

Zhang: About 45V. 49.5V for the 182mm 72-cells module (53.2V for the 182mm 78-cells module). Vertex modules are always designed with low voltage.

As for 670W, a single string can connect 28 modules based on a 1500V system at -20℃, while a string of 182mm connects roughly 26 modules. Sowe have two more modules on a string, string power is 34% higher than with the 182mm 540W modules. Increasing the power of a single string is a key factor in reducing the BOS cost of the system. The savings mainly come from the number of modules, amount of steel used for the tracker, piles, DC cables, combiner box, PEX, MC connectors, clamp and corresponding reduction in installation labor costs. The approximate saving is more than $0.01 per watt. Of course, the exact amount of savings depends on the country and region where the project is located, but the underlying logic of BOS reduction remains the same.

Q: The 210 module is still employing wafers of 175μm-thickness, right?

Zhang: Yes, this is the thickness for mass production, which is directly compatible with 175μm. We want to go further down to, say, 170mm. This will take a little bit of time, mainly because of the automation, progressive optimization and improve the yield gradually.

Q: What progress have you made in high-density encapsulation technology in 670W?

Zhang: We use the superior 0.5 to 0.8mm cell spacing technology as always. We will not use the overlapping technology, nor go back to the original 2mm technology. The concept of high-density cell interconnection is implemented through all 210 series products to increase module efficiency by about 0.2-0.3% while ensuring high yields.

Q: Upon mass production, does Trina Solar have a forecast for 670W module shipments this year? Also, how many 210mm modules will be shipped in total?

Zhang: First, Trina Solar's overall target for this year is 30 GW+, of which 210mm modules will account for 70%-80%. The 670W modules sale volume depends on the progress of promotion in the whole market. We expect to reach 8-10 GW this year.

Q: According to the National Energy Administration, the layout of large clean energy bases will be more extensive during the 14th Five-Year Plan period. Does this drive the development of higher power and larger size modules?

Zhang: Yes, because the core value of the 670W module is to drive down the LCOE. 670W modules are targeting for large-scale solar power plants just to further reduce the LCOE. Compared with 182mm modules, we have at least $0.01 per watt of cost reduction, that's the value of it. In addition, 670W also enlarges the room for manufacturing cost reduction. So the purpose of promoting 670W modules is to accelerate the progress of peak carbon dioxide emissions and carbon neutrality. This is very much in line with the main trend of the times and Trina Solar’s vision.

Q: In the industry chain, what progress has been made with adapting inverters, mounting systems and glass supply?

Zhang: I guess everyone has seen the related news. For example, inverters. Huawei Smart PV, Si-Neng, and SUNGROW launched 600W+ inverter products, and TBEA, GOODWE, Ginlong, KSTAR, SMA and some other inverter manufacturers announced that they had completed the delivery solutions of inverters that perfectly match ultra-high-power 210mm modules. Obviously these inverters will also be fully compatible with 670W Vertex modules as the current is also 18.4-18.5A.

Almost at the same time, eight world-leading PV tracker manufacturers – Arctech Solar, Array Technologies, GameChange Solar, IDEEMATEC, Nextracker, PVH, Soltec and TrinaTracker – announced trackers with full compatibility with 210mm ultra-high power modules.

In terms of glass supply, glass manufacturers such as Xinyi, Flat, CNBM, Kibing and China Southern Glass also announced that the production of PV glass had broken through the width bottleneck and started to fully adapt to the large-size 210 modules.

We expect that with ultra-high power 600W+ modules becoming an unstoppable trend in the PV industry, the industry will continue to deliver more support to the innovative 210mm modules from upstream to downstream.

Q: One last question, will the significant increase in raw material prices affect the shipments of 670W modules?

Zhang: The impact is felt throughout the industry, including with 166mm and 182mm modules. So the industry will work together to solve this problem as soon as possible.

Want a further analysis on the core values of 210 modules and the continually evolving 210 industry chain? Download Trina Solar's 210 Special Edition here:

https://pages.trinasolar.com/TrinaSolar210-APAC.html