Light and shade of 500 W plus solar panels

Δημοσιεύθηκε από PV Magazine σε Φωτοβολταικά - Διεθνή · Τετάρτη 02 Σεπ 2020
Tags: 500, W, plus, solar, panels

In the three article of a series, pv magazine editor Pilar Sánchez Molina analyzes with industry experts challenges and opportunities created by new panels with power output exceeding 500 W.

In recent months, several Tier-1 module manufacturers have started a race to develop more powerful products exceeding 500 W. This contest has raised widespread enthusiasm, but also skepticism from experts and people involved in the PV sector who are now asking many questions. What’s behind it? Are more powerful modules really more advantageous? Why are they coming now?

pv magazine has spoken with independent power producers, panel manufacturers, investors, EPC contractors, PV product distributors and consultancies to try to understand if we are facing a flash in the pan or a trend that is here to stay. Today we present the first article in the series in which we try to cover all aspects.

Ultra-powerful or ultra-efficient?

The first question we asked ourselves is why are manufacturers improving power instead of improving the efficiency of their products.

“China is betting on the PERC ny-type cell architecture, which provides for a high cell efficiency of between 22-23% in production, but it is not the highest in the market. New technologies such as TOP-Con or old ones known as heterojunction can overcome these efficiencies,” said Eduardo Forniés of Spanish wafer manufacturer Aurinka.

However, with more than 100 GW of production capacity worldwide, PERC dominates the market. Two reasons seem to explain this phenomenon. On the one hand, nobody wants to move to unexplored territory. Certainty implies bankability, since banks accept PERC, and not so much other more efficient technologies that are more expensive. On the other hand, the fact that the entire industry is built around PERC helps lower costs.

“This year, at SNEC there was no one showing off new technologies. Before there was a technological competition between manufacturers to launch the most efficient module on the market,” Asier Ukar from PI Berlin told pv magazine. “Although it is true that the difference in the production capacity of a Top 3 and Top 20 manufacturer was not as abysmal as it is now.”

It seems that nobody dares to innovate and it is easier to follow the market standard, which means PERC in combination with an increase in power, which is being set by the largest panel producers. “The market is like entrenched in a trend that has homogenized the strategies of manufacturers,” added an independent power producer (IPP) who does not want to be mentioned.

However, representatives of German renewable energy company Baywa re are more optimistic: “From our perspective, heterojunction cell technology will be the next technological development,” a company spokesperson explained. “The first pilots are already under construction in China, but the market production capacity will not be large enough before the middle or the end of next year.”

Examining cell and module design

Fournies, from Aurinka, explains that these modules owe their increased power to the following factors:

1. The most obvious is its increase in the area of the solar cells that the module contains. The power of the cell is directly proportional to the area of the cell, which is not the case with efficiency. For example, the 625W SunPower module has the largest cell on the market with a site of 210 mm. Therefore, much of that power is due to the area of the cell, which is larger. This also means that the area of the module will be greater, which has to be taken into account when moving it to the solar plant. The JA Solar 800 W module also has a 210 mm cell, although it is cut into three parts. This module owes its high power simply to its large dimensions (2.2 by 1.7 m), although it incorporates the innovation of dividing the cell into three parts instead of two (half-cut cell).

2. Another factor responsible for the slight growth in power is the increase in the efficiency of the cell, which is why the increase in module power is mainly due to the increase in the area of the cell and the module.

3. At the module level, technologies such as half-cell are being used. If we take into account the JA module, it is no longer a half-cell but a 1/3 cell, or shingled. Half-cell modules employ cells that are cut in half before being welded together to form the string of cells. This increases the power of the module (not of the cell) due to a reduction in the series resistance by reducing the intensity of the cells by half (in half the area we have half the current and double the voltage for having a double number of cells). This module technology is already mainstream and is here to stay.

Shingled cells are cut into five or six parts, and these parts are superimposed on their edges and joined by conductive adhesives. This module offers lower resistance losses and higher power and allows a saving in the cost of copper connectors coated with tin-lead alloy. The problem is that so far it is more difficult to manufacture these cells than the half-cell devices and there are probably economic losses due to a high percentage of cell breakage. If companies succeed in shingled profitably, they may drive the half-cells out of the market.

4. Also, at the module level, every manufacturer will have bifacial technology. This technology is simple to apply at the cell level and even saves costs due to the saving of metals, but at the module level it entails an increase in cost due to the rear glass. When the manufacturers of modules can sell those extra watts that are obtained in the rear side, for which they are working on the IEC 60904-1-2 standard, this technology will also become mainstream.

In summary, it seems that the increase in power is mainly due to a larger size module, which is not exactly a technological advancement (we will develop this point later in another article in the series). “Most of these current developments have nothing to do with the development of technology, just with the expansion of the size of the wafers. This implies that we do not have any efficiency advantage,” a spokesperson for Baywa re told pv magazine.

How did we get here?

The manufacturing process based on the wafer sizes of 156mm by 156mm (M1) and 156.75mm by 156.75mm (M2), which became standard in 2017, barely changed until about 2018 and traditional manufacturers have invested many resources in production lines based on this manufacturing process over the past years.

By contrast, new entrants in the solar manufacturing business may benefit from the “late-mover advantage”, which means they can acquire new production lines that result in more efficient modules without having to wait to amortize other older lines.

To address this competitive advantage, one of the traditional manufacturers, Jinko, introduced a module with larger cells (158.75mm by 158.75mm) with a relatively small investment in the second half of 2018. As the cell size increased, the resulting power increased proportionally, without implying an improvement in the module technology itself.

Other manufacturers decided to follow Jinko’s strategy until Canadian Solar made a master move by releasing, at Intersolar 2018, a module with 166mm by 166mm cells, incompatible with the old lines, and thus distancing itself again from the rest of the solar producers. This forced competitors to invest a notable capex in order to launch the same module on the market. More capex, higher price, less competitiveness. Monocrytalline specialist Longi began producing products with cells of the same size in 2019.

At that point, a world leader in wafer production for the semiconductor industry came into play, Zhonghuan Semiconductor, which, in September 2019, launched an even larger cell, the M12, measuring 210mm by 210mm and based on 12-inch wafers, more typical of the aforementioned semiconductor industry.

It was this innovation that most consistently introduced the concept of “half-cut” and “third-cut cells”, two concepts that respond to the need to reduce cell currents due to the wafers’ large site. Why? Asier Ukar, from PI Berlin, explained: “More surface, more current. More current, more losses as long as the busbar section must be kept constant (which is what would be done to avoid increasing costs). So what can be done to cut losses without investing in higher section busbars? Well, split the cells in two or three so that the current per busbar is reduced (the series losses increase and decrease exponentially with the current). In this way, larger modules can be manufactured without the higher series losses reducing the efficiency of the module. And yet the currents are greater than they were.”

A company that does not wish to be mentioned added another reason: “Manufacturers are not very clear about what can happen to the module if very high currents flow, possible degradation or disruptive phenomena are not ruled out, therefore they reduce them as a precaution.”

But it doesn’t end here: Longi, Jinko and JA Solar have launched modules with 182mm by 182mm cells on the market this year to compete against the M12. The advantage of these modules is that they conform well to the standard layout of the 60-cell module (or 120 if they are split) and therefore do not introduce unusual dimensions that generate headaches for manufacturers of mounting structures or trackers.

Advantages… for whom?

We have asked several manufacturers, IPPs, distributors, developers and EPCs if these modules are really more interesting than the standard ones.

Representatives from Chinese panel manufacturer Trina told pv magazine that “these modules, in addition to having a high energy production capacity, provide advantages to the user due to their electrical characteristics. 210mm half-cut cells result in low Voc for a single module, allowing more modules to be installed in strings than conventional panels. Depending on the climatic conditions of a region, we can reach up to 40 modules in a string for 550 W modules and this is reflected in economic advantages for photovoltaic plants, in the optimization of system equipment, in the reduction of capex and in the consequent reduction of the LCOE for a greater return on investment of the project.”

According to Spanish inverter maker Ingeteam, traditional competition for module efficiency has been transferred to the variable of power. “These modules are more powerful, improve energy density and optimize costs. The trend in the market is precisely that, increasing power to reduce manufacturing costs (frames, glass), integration (structure, number of trackers, anchors and wiring).”

Spanish infrastructure project developer Diverxiatells stated that “relatively recently the conventional module was 260 Wp, today we are implementing 400-450 Wp modules in our projects. Therefore, the move to ultra-powerful modules seems to us a natural evolution of technology and its implementation would allow us to reduce the size of the strings, consequently reducing wiring and the number of solar trackers in photovoltaic plants. This reduction will also mean a smaller surface area and a lower rental cost, thus increasing the IRR of the project.”

So, analyzing the responses of all the companies that have responded to pv magazine, we have come to the conclusion that there are two points that motivate manufacturers to launch these ultra-powerful modules:

Long live marketing!

A high power module sells more. It is like a car that goes faster. Many developers think so, because they see a higher power module as more modern. But it turns out that these advances are not seen either in efficiency or in other indicators. The only thing that manufacturers do is increase the surface of the wafer, that is to say: more surface, more power, but not necessarily more efficiency, industry representatives point out. In case any reader still has doubts, here is an apt comparison: Which animal is stronger, the ant (it is capable of lifting up to 50 times its weight) or the elephant (which can carry up to 9,000 kg)? Clearly the ant, right? Conclusion: having more power does not mean a better module.

Increasing production capacity

The largest and most powerful module manufacturers can announce loudly that their production capacity in MW or GW is increasing. Manufacturing a 600 W module costs you the same time as manufacturing a 420 W one, with which you can get much more power in the same time and thus reduce specific operating costs in $/Wp, respondents explained. In other words, it represents a saving for the manufacturer which, by the way, is not reflected in the cost of the module. “Very smart,” they agreed.

Reasonable doubts

Every time we write about the launch of one of these supermodules at pv magazine, the number of readers skyrockets.

However, in our round of questions we have found many experts who have told us about numerous disadvantages: some have wanted to do so openly, while others have asked us not to publish their names. We have asked them to clarify their doubts. Their answers were grouped and summarized in an overview of all the collected information. PI Berlin has helped us analyze most of the reported potential issues.

In the case of large modules, the first issue pertains to mechanical properties, which can be condensed into three problems:

Modules with large cells of 182 mm / 210 mm continue to use double glass with a thickness of 2 mm / 2 mm, which means that, although the module is much larger, its rigidity does not increase proportionally, since the glass continues to have the same thickness as that of smaller panels. Specifically, the module has grown from 1970 mm x 998 mm to 23XX mm x 11XXmm, with an increase in length and width of 15% and 10% respectively. Even if the module passes the MLT test (mechanical load test, which is part of the IEC norm), the torsion and bending of the module will be greater than that of smaller modules, thus increasing the risk of cell breakages under operating conditions (and more if they are mounted on trackers and in areas with relevant wind loads).

The second problem is related to the headaches that they generate among manufacturers of mounting structures due to static issues. These modules, in fact, are going to suffer much higher wind loads due to their larger surface. If they can already fly from a plant while having smaller dimensions, imagine what can happen with these super modules! This implies that the structural analysis will be more complex with special attention to the clamp that joins the module to the profile of the structure. The ideal at a static level is that the module is as square as possible, as highly stretched geometries, as is the case with these modules, increase the perimeter and complexity of the fastening.

If the structural designer wants to continue providing a safe structure, especially against aeroelastic effects, we may start to see a possible increase in prices, which would eat the supposed reduction of the BOS costs that manufacturers of these high-power modules announced. If the structures are not designed properly because they must be cost-competitive or extra costs to minimize the risk are not considered, then it is very possible that we will begin to see how more and more accidents will be reported due to weak static.

The third problem is logistical and relates to packaging, more expensive insurance due to the increased fragility of the merchandise, more weight of the module and less comfort for installers.

Having seen the mechanical issues, we are going to analyze the electrical part.

These modules have different voltages and currents than the previous generation. Manufacturers basically have two options when designing the internal circuitry of the module. The first one consists of increasing the open circuit voltage (Voc) and lower the short circuit current (Isc). In this case, the number of serial modules per string is reduced, which increases the costs for wiring, combiner boxes, inverters and other small components. Ultimately, the BOS costs increase (and with this, there are already two factors that contribute to the increase of the BOS, as this joins the higher cost of the module architecture mentioned above).

The second option is lowering the open circuit voltage (Voc) and increasing the short circuit current (Isc). This variant makes it possible to connect more modules in series and reduce BOS costs (it is more noticeable in the case in which string inverters are used), just the opposite of the previous case. An example is Trina’s Vertex module with a short circuit current of over 18A, which is quite a big jump. But this also has a negative part, which is the increased risk of fire, increased series losses in the busbars and the increase in temperature in the junction box and connectors, which also leads to efficiency losses. To all this we must add that, due to lack of experience with these modules, it is not known how the cables, connectors, junction boxes and inverters are going to behave. The IEC also does not have specific tests that shed light on the possible behavior of these modules.

As they are very new, most of these modules have not passed the extended durability tests offered by PQP, TÜV, RETC, etc., therefore, there are still questions to be answered.

Diverxia adds: “Module manufacturers are betting on power, which is positive in principle. However, the photovoltaic technology has many other variables in which it must evolve. Aspects such as tracker efficiency, inverter efficiency, and more advanced plant control methods must advance at the same pace if you really want to have a competitive photovoltaic plant. The growth and evolution of the module must go hand in hand with the growth and evolution of the rest of the technology that makes up a plant.”

Conclusions

The advantages of these modules are mainly focused on a reduction in the capex of the BOS costs due to the increase in power and current density. But, today, to really quantify the capex reduction requires a very detailed study of each project considering the reductions in DC cabling, playing with cable sections, aluminum and copper prices, testing with fewer modules per string, fewer junction boxes and adjusting the inverter’s DC/AC ratio.

In other words, there are sufficient elements to doubt that the supposed reduction of the BOS costs that accompanies these modules actually occurs due to the additional investment necessary to mitigate the mechanical and electrical risks that these modules bring with them.

PI Berlin recommends waiting at least a year for the main manufacturers to send their modules to laboratories that carry out the necessary extended duration testing. “This will give us an idea of their long-term durability, robustness and electromechanical integrity. We must wait to see what this open fight between manufacturers leads to and how and when the market stabilizes,” the experts from the testing institute said.

Eternal love or a summer romance?

As we reported in the first article of this series, many players in the sector think that, with 500+ W solar modules, we are not facing a technological advance, but rather a trend that has been established among manufacturers to homogenize the market.

We have also seen that this strategy of pushing super powerful modules is relatively safe for manufacturers as, in principle, it allows them to reduce costs without introducing major technological innovations and “the risks that may arise are sufficiently diffuse so that the marketing department can mask them and only those who really know about the subject, who are not always the same people who buy the modules, are aware of them,” one of the companies that prefers not to be cited told pv magazine.

We have mentioned that this trend benefits mainly large or very solvent manufacturers, which means those that already have production lines allowing them to manufacture these types of modules or those that have resources to invest in them. The remaining panel makers are forced to increase expenditures to be able to join this new trend imposed by the big players and which has led to a certain monopoly.

“If we start to compare the typical quality indicators of a module from the point of view of performance (NOCT, efficiency, temperature coefficients …) we can see that the +500 Wp modules are not necessarily better than those of 400 W. Many improve only minimally in aspects that manufacturers can modulate at will due to a commercial interest, such as annual degradation, product guarantee and performance guarantee, that is to say, nothing tangible that can be verified in a laboratory,” Asier Ukar from PI Berlin told pv magazine.

The question then is: are we facing a trend that could be seen as the result of a commercial war seasoned with a lot of marketing, or a product that is here to stay?

A Trina representative said, “They are here to stay. The 210mm cells derived from 12-inch monocrystalline silicon ingots are the largest in the industry, they are a reality, and their production capacity grows more each year.” According to the panel manufacturer, the low open-circuit voltage that this module has, in addition to allowing the integration of a high number of modules per string, also brings a high short-circuit current that creates the need to develop other system components, such as solar trackers and inverters. “For this reason, the entire industry has mobilized to develop optimal compatibility with this new panel model in an alliance that involves companies such as nClave, Nextracker, ArcTech, Sungrow, Huawei, SMA, JA Solar, Risen, DNV GL and TUV Rheiland Group, among others, to extract all the benefits of an optimized photovoltaic system and offer greater integration to the photovoltaic source in the energy network of any country in the world,” it further explained.

Spanish inverter producer Ingeteam also believes we are seeing a positive trend: “Since these panels allow you to increase energy density and efficiency even more, they offer better costs per kWp,” a company’s spokesperson told pv magazine. “This trend will end up being a standard until there is another turning point in cost optimization.”

A representative from Spanish wafer manufacturer Aurinka said that the half-cell and the bifacial are here to stay, while making larger wafers was still a matter of discussion. “Few companies are capable of making wafers above 166mm and below (or just one) at 210mm,” he stated. “These wafers are more fragile so the percentage of breakages in the manufacture of cells and modules will be higher. That is the main drawback of making cells bigger and bigger.” Another drawback, he added, is that most cell and module production equipment is not capable of processing those wafer sizes, so companies that have already made their investment in equipment are limited in that regard. “From our point of view, today, this responds more to a marketing strategy than to a real production scenario. As the cell and module manufacturers claim, none of these modules is mass-produced, and it seems more like a race for a headline than a real market strategy,” he concluded.

German module maker Solarwatt believes that “these modules are here to stay, but they will have their specific market, like all other technologies. There is and will be an increasingly specific range of modules for each client.”

Baywa re also believes that they will stay: “Since the beginnings of the solar photovoltaic industry more than 20 years ago, module manufacturers through investment in R&D have achieved continuous improvements in the efficiency of photovoltaic cells as well as in module technologies. This trend has been maintained in recent years and it is to be expected that many of these modules that are currently being launched will demonstrate their technical quality and suitability for their installation and will be massively manufactured in the future.”

Spanish developer Diverxia clarifies: “We believe that they are here to stay, but we must not forget either that the technology of the modules can advance in other aspects, not only in power.”

German PV product distributor Krannich is also optimistic: “All manufacturers seek to innovate and advance with the technology they produce. The logical thing is to think that what is now a trend is here to stay.” According to the company the production costs associated with ultra-powerful modules can be reduced later, but the current situation – marked by the coronavirus crisis and various accidents in some of the large factories that supply polysilicon wafers – is preventing that from happening. “Today there are certain supply problems that have caused a general increase in prices,” a company spokesperson told pv magazine. “Looking to the end of the year, there is a high demand for high-power panels due to the large projects that are pending, especially in China.” According to Krannich, the demand for these types of modules is higher than current production capacity, and this is resulting in an increase in prices. “Once these stabilize, we can see that this technology is here to stay,” the spokesperson concluded.