Next we will talk about the qualities that solar panels of glass-glass have, how they are manufactured and the advantages they have.

Glass solar panels

Double-glazed solar panels (glass-glass / double glass) are becoming more and more popular. Is it worth paying more for an additional glass panel?

Sales reps will say it’s worth it and list a few reasons. First, they will find that the glass panels are resistant to microcracks. They will also say that the warranty for such modules is 30 years, not 25 years as for standard modules. In short, they will say that these modules are almost indestructible, unlike the cheaper “foil” modules.

But we don’t have to take their word for it. Let’s analyze the data from the leading institutes so you can make the best decision.

In this article, we do not describe bi-facial technology, that is, two-sided modules. As explained in this article .

Glass is a really tough guy

Standard panels are protected from above with tempered glass. Such  glass is a really tough guy  , not a thick layer of snow, not a gusty wind, not hail will hurt him. To break such a glass, you would have to hit it with a hammer.

Unfortunately, the same cannot be said for the silicone plates hidden under the glass. Mono  and polycrystalline cells have many advantages, but one disadvantage: they  are quite fragile  . If you had that bond in your hands, you could easily break it.

Therefore, if you bend a standard module, the glass will hold it without problems, but the cells can have  micro-cracks  , since they are only protected at the bottom with a plastic film, which does not support the cell. Glass panels have an additional glass panel instead of a sheet. These armored links are much more durable  .

Standard module on the left, glass-glass on the right. The second pane of glass “supports” the links from the bottom, so that they do not break under pressure. Property of  SolarWatt  .

Is this a serious problem? Depends. At  best,  microcracks  reduce module efficiency; In the worst case, they can lead to burning of the foil that protects the module from the bottom and corrosion, and if it happened near the frame, it may even cause an electric arc between the frame and the damaged place to light, which at best it will disable a third of the module. At worst, it will start a fire, but you must be very unlucky.

The difference between best and worst case scenarios is module quality, and you can significantly reduce the number of microcracks, for example by  hiring proven professionals  to get the job done without walking through modules and doing other nonsense. But you can also invest in glass panels, which are actually  resistant to  microcracks and  more resistant to installers’ mistakes  .

Furthermore,  glass is more resistant to chemicals in the air  and will not react chemically with any other panel element, even after many years. While plastics are also known to be chemically inert, glass is a very different class.

For this reason, glass-glass modules are especially recommended in coastal areas with high atmospheric pollution. In this case, the minimum is standard IEC61701 salt spray certified PV modules, but if you really want to protect yourself, consider double glazing. 

However, it should be noted that in the case of low-quality components, the chemical resistance of the glass can be a disadvantage, because the chemical compounds formed within the module cannot escape and the entire module does not “breathe”.

Verdict:  Evidence shows that glass-to-glass solar panels are nearly insensitive to microcracks and therefore more resistant to installer negligence, a major cause of microcracks  . However, are all glass panels worth your attention?

Are double glass panels better?

Many will say yes, we will  not necessarily  say  so . The mere fact of having a second pane does not make the panel a reliable module.

The aforementioned many will answer that the ultimate test of longer life is a  longer power warranty  . While the power guarantee for the reed modules is 25 years (even for the high-end ones!), The power guarantee for the glass panels covers 30 years of operation. And it is true that this type of module will maintain its high performance for a longer time.

While the power guarantee for the reed modules is 25 years (even for the high-end ones!), The power guarantee for the glass panels covers 30 years of operation.

So in theory the user gets an additional 5 years of guaranteed operation, right? Yes and no. Well, unfortunately, the  power guarantee is almost useless  , because it only describes the decrease in energy resulting from natural degradation processes and  does not cover failures  . This means that if a module is delaminated, it will corrode and damage the internal cables, in short, if the module breaks, the power guarantee will not help you. The product warranty protects against such accidents  . Are double-glazed modules better in this regard?

Yes and no. Although  the longest product warranty in the world pertains to the Vision series glass-glass modules  produced by  SOLARWATT  , most glass-glass modules do not go beyond the standard product warranty of 10 to 12 years.

Double glass panels do not necessarily have a longer product warranty than standard modules.

What is the conclusion? The second pane of glass is not a magic solution to all problems.

Let’s illustrate this with an example. Last summer, I bought a module for pennies to charge my laptop in a camper. The panel had two panes of glass and a 30-year power warranty, but only a 2-year product warranty. It would be crazy to fool myself into thinking that this product would last 30 years. There is no comparison with the SolarWatt warranty.

The key to quality is the focus of the brand, the choice of materials and the quality of the workmanship.

This is confirmed by research. In the aforementioned document that describes resistance to microcracks, it was stated that “the  results available to date indicate that the selection and combination of materials and the production process of the photovoltaic module have a greater impact on the sensitivity to microcracks than the design of the module itself  “.

Oh, let’s mention one more thing: the use of second panel technology doesn’t change much in terms of performance and efficiency, because it depends more on the cells used.

Verdict:  Good glass-to-glass solar panels  are more reliable than good  glass-to-sheet panels   , but there are also glass-to-glass panels that are equally vulnerable to failure!

Glass-glass module delamination

Due to their structure, glass-glass panels are more resistant to microcracks and chemical agents. But they are also more prone to  delamination  . The  glass  seems to have  less grip and is also heavier  . So if it is not glued properly, the bottom layer may begin to lose contact with the cells, moisture will accumulate, and the corrosion will be done.

The  modules  frameless  are particularly prone to this  , because they have a framework that can hold them together. More about them in the next subtitle.

In a report describing the  Most Reliable PV Panels of 2020,  PVEL stated, “It is a well-documented fact that glass-to-glass modules performed poorly in the moisture and heat test [interlayer bonding test]. However, the results of the newer double-sided glass film and glass panels were similar in the PVEL PQP tests. This is likely due to the use of POE encapsulant instead of EVA in the glass-to-glass modules. “

And what happened to the lower quality glass-glass modules? The American giant DuPont, producer of the film Tedlar, warns with the words of one of the employees, sent to China:

”A common fault in our glass … is corrosion of the busbars and cables in the panel, causing a loss of power. We saw peelable glass, front and back. “According to him, some modules delaminated so much that the glass hung and sometimes broke under its own weight.

So what is the result of all this?

We will repeat again: whether you are buying glass panels or glass sheet,  choose a good brand with a good guarantee  or with good PVEL results.

We have mentioned frameless panels several times in this post. What exactly are they?