Light and shade of 500 W plus solar panels – part I

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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

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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.

In the next article of the series, we will analyze how we got here. Was it by chance that most manufacturers launch these products at the same time?

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