A few months back, I asked the question: are bifacial modules taking over the market? Another time I pointed out a shift from full cell to half-cut cell modules, notes Martin Schachinger of pvXchange. Now, both trends seem to have been a harbinger of the developments currently unfolding. I cannot exactly call this progress, as current developments driven by the big Asian manufacturers certainly involve points that warrant a critical eye, but more on that later. Just a few months ago, talk was that the 500-watt limit could only be cracked, if at all, by adding together both sides of a bifacial panel's output. Now we are now seeing products nearing market launch that have monofacial output of more than 500 W. How was this achieved so quickly?
Along with new innovations and the renaissance of well-known cell technologies such as heterojunction and n-type, which are increasingly finding their way into the products of ambitious manufacturers, we are also seeing an increase in module surface area with the introduction of ever larger cells. Just a year or two ago, modules on the market were almost exclusively made from so-called M2 wafers, in both full and half-cell variants. For more than 10 years, the classic six inch cell with its 150mm and later 156mm edge length was the industry standard, having replaced the five inch cell with an edge length of 125mm. Now we seem to be entering the era of XXL cell formats. Yet, this development is taking place almost exclusively with monocrystalline cells – there have been hardly any advances in multicrystalline products.
Jinko Solar, for instance, has been using wafers and cells with an edge length of 158.75mm for about two years in its Cheetah series, available either with 60 full cells or 120 half-cut cells. Trina Solar uses this cell format in its products, such as the Honey DE06M series, while JA Solar uses it in the S09 and S10 series. The output of modules using these cells ranges from 325 to 345 W, and the dimensions are about 10 to 30mm larger than those of a conventional 60-cell module, depending on the version – which means they are still very easy to handle and process.
The transition to the M6 class with an edge length of 166mm takes place at the expense of usability. Longi Solar manufactures this wafer and cell size, using it in its LR4-60HPH and LR4-72HPH series, among others. Contrary to what the type designation suggests, these are 120-cell panels typically rated at 350 to 380 watts, or 144 cells at 425 to 455 watts, because this size cell can only be processed once they are sliced in half. If whole cells were used, the current would be so high that currently available inverters would not be able to handle it. Trina Solar also offers products such as the Honey DE08M with half-cut cells in this format, as does Hanwha Q-Cells with its Q.Peak DUO G8 series. Modules of these types are as wide as 1030mm to 1040mm and 1750mm to 2100mm long, depending on the version.
It remains to be seen whether modules of this scale will become established in the market. From today's perspective, however, the latest products in the race for most powerful module, recently introduced by Jinko Solar and Trina Solar and scheduled to be launched in the fall, are likely to prove unwieldy. Trina Solar unveiled its Vertex 500 W class panel this spring. It apparently uses the M12 wafers manufactured by Zhonghuan Semiconductor with a whopping 210mm edge length. The resulting cells each have an output of more than 10 W at a rated current of 18 amperes. Trina Solar simply divides the cells into thirds and incorporates 150 of them into its module, five columns side by side, which delivers 480 to 505 W modules. With a sixth column, the manufacturer wants to break the 600-watt barrier in the future. This would result in a module measuring some 2176x1310mm and tipping the scales at around 32 kilograms, or 37 kilograms for the glass-glass version - who would be capable of handling and processing such a module?
Jinko Solar followed suit with its own giant module using a somewhat smaller, yet more exotic cell format of around 180 by 9mm. The brand-new series, called Tiger Pro, offers a version with 144 shingled cells, which should generate 510 to 530 W, and 555 to 575 W in the 156-cell version. With dimensions of 2385mm x 1122mm, this product is probably aimed squarely at the ground-mount market, where the bifacial version will likely be particularly attractive – a bifaciality of only 6% would be sufficient to exceed the 600-watt mark.
From a manufacturer's point of view, this development may be correct and reasonable. Apparently, the market is demanding ever cheaper modules. For years, price reduction has been achieved by optimizing and scaling production. Now, however, we have reached a point where it is scarcely possible to save costs by optimizing production. Also, the capacities of individual companies are now so huge that even in terms of scale only slight cost reduction potential can be expected. The production of a reasonably durable module has its price, just like the production of a crystalline wafer or a solar cell.
Since the market does not pay for the module per se but for its average power output, it makes sense to continue to increase the peak power per module. This means that more and more money can be demanded per individual module at the same unit cost, which in turn increases the return on investment, which has been extremely meager in recent years. This of course pleases manufacturers. In fact, after nearly a year of stagnation, we can see that the prices for highly efficient modules are slowly starting to fall again. At present, this is still influenced by the difficult supply situation, but it is already making itself felt in contract prices with longer lead times. However, producers are still reluctant to pass on all of the cost advantages of the new module types with higher rated output to the market.
The up-sizing development is less pleasing for installers however, who have to adapt to new module formats that change in rapid succession. Handling in accordance with the manufacturer's installation instructions is just one aspect that needs to be considered. Larger module surfaces with the same or smaller frame thicknesses also place new demands on the substructure, which may have to be designed and built completely differently. Also, inverter design sometimes changes fundamentally in response to the constantly shifting electrical specifications.
It does not always have to be cheaper! Many people may find it strange to read this coming from me. Nevertheless, I'd like to make a brief appeal for proven technology with consistent quality, reliability and ease of maintenance. These are also values that need to be taken into account for sustainable PV market development and which determine overall cost – the so-called levelized cost of electricity (LCOE) of a project – of an installation over its lifetime. Some technological concepts advocated on the basis of reduced LCOE can become a one-way street in the medium to long term.
Overview of the price points by technology in May 2020 including the changes over the previous month (as ofMay 27, 2020):