Plexiglass vs Tempered Glass: Which is the better material for solar panels?

Although photovoltaic modules are fantastic at converting sunlight into electricity, they are not resistant to outside elements such as heat, rain, wind, and dust.

They need a certain level of protection from negative environmental impacts. Therefore, these modules are encased in a protective cover that serves as a safety barrier.

A good protective cover serves three main purposes: protection, aesthetics, and function. Therefore the material choice for a protective cover is of utmost importance.

The most common types of protective covers used in the solar industry are tempered glass and Plexiglass. Both of these materials have their benefits and drawbacks, but which one is the better option for your needs?

In this post, we explore each of these materials has to offer so you can make an informed decision on which material works best for your purposes.

Before we get into the comparison, I want to clarify an important point. Plexiglass is simply a brand name, not an actual glass type. It’s important to note that what you actually want is Poly(methyl methacrylate) (PMMA) or acrylic sheets.

Crylux, Acrylite, Astariglas, Lucite, Perclax, and Perspex are some other common brand names used for acrylic sheeting that have similar properties to Plexiglass.

What is Plexiglass?

Plexiglass is a type of acrylic sheeting that is often used in the solar industry due to its transparency, flexibility, and low cost. It is a fantastic material for many applications where transparency is a priority, such as covering solar panels.

It has good impact resistance, is fairly easy to cut, and is especially well-suited for outdoor use since it can stand up to UV rays very well.

Therefore, it is also used as a solar panel glass substitute since it works as a comparable product.

Many people believe that plexiglass is a plastic product that is inferior to glass, particularly when it comes to solar panel manufacturing. The fear stems from the misconception that plastic degrades faster than glass, causing the panels to become less efficient.

This can't be further from the truth, and here is why.

All plastics are petroleum products and they are damaged by sunlight, particularly UV radiation. Some plastics like polyethylene (PE) degrade faster under the sun. Most children's toys are made of PE and they get all warped after a few months under the sun.

Acrylic (Plexiglas®, Lucite®, and Acrylite®) is derived from natural gas and, when solid, is absolutely inert. Acrylic manufactured in the United States doesn't yellow in the sun.

Take a look at the canopies and bubbles on WWII bombers, which are still clear after more than half a century in the sun!

There are three other clear polymers that can turn yellow in the sun and be mistaken with acrylic: Styrene, PETG, and Polycarbonate. Although they have a similar appearance to acrylic, they are not chemically related.

Also, plexiglass is lighter than glass but can be just as strong. In fact, many manufacturers use Plexiglass not because of its strength but because plexiglass is half the weight of glass. Such a large difference in weight allows for a much lighter and cheaper frame.

This means that plexiglass is a great material choice if you want to reduce the overall system cost of your solar panel installation or save on shipping costs due to lower package weights.

What is Tempered Glass?

Tempered glass is an amorphous form of heat-strengthened safety glass, which means it maintains its physical properties after exposure to high temperatures.

It's known for its strength because it can withstand a great amount of force without breaking into sharp pieces that could cut or lacerate a person.

It is also favored for its transparency, which allows light to pass through more easily and generate electricity from the solar cells behind it.

How much stronger is tempered glass than regular glass?

Tempered glass is four to five times stronger than regular float glass. It has increased strength, which makes it more resistant to thermal breakage and mechanical damage.

Tempered glass was originally developed for windshields. However, today it can also be found in other applications such as partitions, doors, tables, and countertops.

Annealed glass can shatter into jagged shards when it is broken. With tempered glass, the glass breaks into small pieces, which are typically less sharp.

Therefore, tempered glass is preferred more often than regular annealed glass where human safety is a concern.

How is the glass is tempered?

The tempering process consists of heating and rapidly cooling flat glass so that it can resist high pressure or force without shattering or breaking. In order to temper glass, it first needs to be cut to the desired size.

The glass is then examined for imperfections that could cause breakage. Once the glass is free of any imperfections, it can be placed into a tempering oven to heat up.

The oven heats the glass to over 600 degrees Celsius. The heated glass must remain in this high-temperature environment for several hours so that the atoms in the glass can realign.

After that, the glass is “quenched,” which is a high-pressure cooling process. High-pressure air blasts the glass surface from an array of nozzles in various places throughout this operation, which lasts only seconds.

The outside surfaces of the glass cool significantly faster than the core of the glass when it is quenched. The core of the glass pulls away from the outside surfaces as it cools.

As a result, the center of the tempered glass stays under tension while the surrounding surfaces compress, giving it its strength.

How do Plexiglass and Tempered Glass stack up against each other?

Price

Tempered glass is more expensive than plexiglass. A standard one square foot of plexiglass costs around $10. While the same square foot of tempered glass costs $10 to $55, depending on the product's thickness.

The higher price of tempered glass is due to its high production costs but may be worth the additional cost for some applications.

Impact resistance

Tempered glass is both extremely robust and quite delicate. It might shatter into millions of pieces for no explainable reason. Even with Premium Brands, there have been many examples of tempered glass shattering inexplicably.

Acrylic is not a silica-based glass. It's considerably softer, lighter, more flexible, and workable than tempered glass. As a result, it does not shatter easily. The impact strength of acrylic is greater than that of tempered glass, which implies that cracking will occur before shattering as a built-in safety mechanism.

Weight

Tempered glass is significantly denser and thus heavier than acrylic glass. And, in order to be tougher, it must be thicker, which adds weight. This weight might sometimes be the source of its own demise.

Acrylic differs from silica-based tempered glass in that it has different chemical components in its base. It can be thinner while maintaining a high degree of durability, making it lighter.

Scratch resistance

Tempered glass is significantly stronger than acrylic glass in terms of scratch resistance. This means the tempered glass is more likely to keep its appearance over the life of the solar panel.

However, there is a tradeoff to this resistance. The tempered glass is more likely to shatter from a strong impact, such as when it falls onto a hard surface during installation or shipping.

Also, when exposed to extreme heat or cold, tempered glass can shatter. This makes it unsuitable for use in very hot weather (which would require panels without any breaks) and extremely cold climates (in which case, there's a risk the material could shatter).

Light transmittance

Both materials have good light transmission properties. However, glass transmits 90% of the light, while acrylic transmits 92%.

Tempered glass is often more expensive than Plexiglass and allows less light into the solar panels, lowering cell efficiency. Plexiglass can be a good choice to substitute glass in photovoltaic modules due to its ductile tensile qualities, UV resistance, and thermal resistance.

Insulation

Plexiglass has better insulation qualities than tempered glass. It can be used in more extreme environments while restricting external temperatures to affect the cells. Tempered glass has a tendency to break at lower temperatures, which is why it is often used in warmer climates.

Ease of Fabrication

When it comes to fabrication, plexiglass can also be easily drilled, machined, or sawed while tempered glass cannot be.

Because tempered glass is still a type of glass, it has more limitations when it comes to reworking and reshaping than plexiglass. It is also more expensive to fabricate tempered glass than plexiglass.

Safety

Although tempered glass is safer than regular glass, it is still very dangerous when broken. When tempered glass shatters, it shatters into millions of pieces that can pose a significant risk to workers and the environment.

On the other hand, plexiglass does not shatter very easily when exposed to stress or weight. It also takes longer for plexiglass to break. Before it shatters, it will likely show signs that it is about to break so you have time to do something before the plexiglass actually shatters.

Frequently Asked Questions

Conclusion

Both plexiglass and tempered glass are strong, durable materials that are suitable for solar panel manufacturing.

However, tempered glass usually has a much longer lifespan than plexiglass and is more resistant to yellowing over time.

Tempered glass also provides better protection against non-impact forces such as walking that come from outside the panel. Because it distributes force across its entire surface rather than focusing it on one area.

On the other hand, plexiglass is cheaper and very lightweight, and ideal for certain applications where weight or price is a concern.

Finally, plexiglass has also good insulation properties that make it resistant to cracking in extreme weather conditions such as intense sunlight or cold temperatures.