What Glass is Used for Solar Panels
People tend to ask a lot of questions about solar panels. From what can solar panels power, to whether using a solar panel lowers my electric bill.
But one of the most common questions relates to the materials found in a solar panel.
What glass is used for solar panels and what are the benefits of a glass layer?
Join us as we answer these burning questions. But first, we need to look at what materials make up the different layers of a solar panel.
What Are Solar Panels Made from
The metal used in solar panels has to be durable enough to withstand strong weather, as they’re going to stay outdoors, but also light enough to work with. Most solar panels use silicon cells to generate current and aluminum to make the frame.
Within a solar cell, the semiconductive crystalline silicon is fitted between conductive layers.
Other layers found in solar cells are the bottom metal plate, a metal grid at the top, a layer of antireflection coating, and a piece of glass.
Solar panels contain solar cells gatherers light energy from the sun and convert it into usable electricity. This process is similar to how a leaf goes through the process of photosynthesis, generating food for a plant.
The sun emits waves of energy that range in length from short ultraviolet waves the longer infrared waves. The shorter the wavelength, the more energy it contains, which means solar panel manufacturers want to capture the high-end of the spectrum to generate more electricity.
To achieve this, manufacturers choose materials for Solar panel that capture the high end of the radio spectrum in the glass of the panel. These materials include silicon, which is extracted from silica sand and is used as the primary element in most solar panels.
This element is the second-most abundant element found on the earth’s crust so it’s unlikely that solar panel companies will have a shortage in materials anytime soon.
Different solar panels have different glass widths depending on their goals. A thin-film solar panel is the cheapest type of solar panel on the market so it uses a relatively thin layer of standard glass.
Crystalline solar panels commonly use 4 mm glass, making them more durable and stable.
But what exactly does this layer of glass do? Well, let’s find out.
What Is the Purpose of the Glass?
Since glass is the first layer that the light encounters, it’s important we understand its purpose. Firstly, glass is an insulator, meaning that it won’t conduct any electricity.
Other insulators that have a similar conductivity as glass include rubber and polyester, but glass stands out from those as it's completely transparent. This means that most of the light from the sun simply passes through to the other layers. Glass serves more as a protective measure than anything else.
It keeps everything else away from damaging the inner layers. These include rocks from debris or a branch falling from a tree, hitting the surface of the solar panel.
The other layers within the solar cells are fragile, so having that extra layer of protection prevents those layers from being damaged.
The glass layer however makes up about 97% of a solar panel’s overall weight. It does more than just protect the inner components of the solar cell, it also mirrors the sunlight, allowing the solar panels to concentrate it.
If the semiconductors were exposed, 30% of the light would reflect away from the solar cell. This makes it inefficient and when using solar panels on a large-scale grid, we strive for efficiency. The glass already reflects away 5% of the light coming and certain solar panels lose more light due to heating.
The combination of the glass and antireflection coating allows us to achieve efficiency and prevents us from losing more energy. The antireflection coating is also transparent, but the light doesn’t just pass directly through it as it would glass.
The coating gets a reflection of the top and bottom, and if it’s the right thickness, the two reflections cancel each other out. This makes the reflective light disappear, leaving only the incoming light. The amount of cancellation is more dependent on wavelengths so you will never fully get rid of the reflective light.
Both the glass and anti-reflection coating solves a lot of the practical issues that solar panels face. But we are going to focus on the former, and why so many solar panel manufacturers insist on using it in their solar cells.
What Are the Benefits of Glass in a Solar Panel?
Before we can get into what kind of glass is used in solar panels, we must understand why so many manufacturers use it as a layer in their solar panels.
Transmit and Reflect
As we mentioned earlier, glass is transparent. The reason so many solar panel manufacturers make use of glass layers is that they transmit light without absorbing any of it.
This means that if sunlight hits the surface of the glass, it doesn’t get absorbed, and it instead passes directly through the other side of the glass to make its way to the other layers. The glass acts as a mirror due to it being highly reflective. If applied to the concept of a solar panel, it allows them to concentrate the sunlight coming in.
Certain solar panel manufacturers go the extra mile and laminate the glass.The common coatings are aluminum, gold chloride, and silver nitrate.
The purpose of this coating is to add an extra layer of protection to the semiconductors beneath the layer of glass and add the rigidity of the solar panel itself.
Coating the glass with a polymer back sheet won’t be as effective and will expose the solar cells to environmental moisture.
Glass is much stronger than you might think. Unless heavy amounts of stress are being applied to the glass, causing a shock, the glass will need much more than a falling branch to break it.
Solar panels are made from tempered glass, also known as safety glass. The reason being is that it’s four times stronger than your standard plated glass.
Different types of glass have different strength levels. For example, tempered soda-lime glass has been proven to be stronger and less prone to breaking compared to your everyday window.
Should the glass break, it’ll shatter into smaller pieces, reducing the risk of injury by cuts. We will cover the different types of glass in a solar panel after we have broken down the benefits of glass in a solar panel. But for now, know that glass can bear the stress caused by strong winds and snowfall.
The glass used in solar panels is fire resistant, adding to the solar panel's fire safety and overall protection.
Cheap and Light
Glass requires little to produce compared to other materials. There’s not much science behind it, all that’s required is soda ash and sand. Melting and shaping the glass is a simple process that doesn’t require any fancy machinery to get the job done.
Glass is also light in terms of weight. This makes installation much easier and the overall weight of the solar panel much lighter, making the process of carrying it around hassle-free.
So, if you are wondering if solar panels are safe to install on your roof, the answer isn’t only dependent on your solar panel. As much as having glass on glass solar panels are relatively lighter than your other solar panels, you want to ensure your roof is rigid and well maintained before any installation. A
Solar panels can become dirty, just as any other appliance that’s left outside. What makes having a glass layer on the solar panel convenient is that it’s easy to clean.
Certain materials require certain cleaning methods, but all you need to use when cleaning glass is soapy water and a sponge. That’s it.
Since glass is smooth, dirt normally slides off it, and dust can be wiped away. In other words, you are saving yourself from purchasing special cleaning items or hiring someone to clean them for you.
Another convenience to glass in a solar panel is that it’s easy to recycle. Once your solar panel has seen its days, recycling companies will heat the glass, turning it into a powder that can be used to produce other products.
Now that we’ve covered all the benefits of glass in a solar panel, let’s answer the burning question of what type of glass is used in solar panels.
What Glass is Used in Solar Panels
The glass we’re talking about here is ‘flat glass,’ which is comprised of float, rolled, patterned, and drawn glass.
The Most Common of them all
Float glass is the one that’s commonly used in solar panel production and offers the best quality at a low cost.
Once the raw components are all in one batch, they are taken to a furnace and melted. This molten glass is poured into a bath filled with molten tin.
Inside this bath is a mixture of both hydrogen and nitrogen gas, preventing the tin from oxidizing.
And due to the tin being denser than the molten glass, the glass covers the tin, making for a smooth and leveled surface.
Sometimes manufacturers will also apply an anti-reflection coating after the bath using chemical vapor deposition. This uses thermally induced chemical reactions at the surface of the bath to coat the mixture.
The coating reduces the amount of light being reflected and increases the percentage of the sublight being absorbed from the photovoltaic cells. The glass-tin material is then placed in an oven that allows it to cool and prevent cracking.
Before the glass is incorporated into the solar panel, it’s inspected and coated with lucite, or methyl methacrylate. This prevents the glass from being scratched or damaged when being handled.
Rolled glass is used on surfaces that aren’t flat, for example, the roof of an RV. It’s called rolled glass because it’s pressed through a roller, softening the glass and allowing it to wrap around different surfaces.
These are primarily used for flexible solar panels and are used on smaller surface areas, or if you want a portable panel to take with you on camping trips.
Patterned glass is used to cover the crystalline silicon module. It has a shallow pattern on the surface of the glass that diffuses the reflection on the module’s surface.
The deeper patterns on this type of glass further reduce the reflection, but they also attract water and grime which can damage the glass. Drawn glass also makes use of a roller by rolling the molten glass through it is a much older technique than our previous contenders.
More companies are swaying towards float glass as it’s the cheapest to produce and it provides the best quality out of the lot. However, some companies in China prefer the more traditional methods of production and still use drawn glass.
Soda-Lime is the most common type of flat glass. It sounds like a tasty drink, but that’s not quite the case. It contains sodium, calcium oxide, and silica.
Certain flat glass requires silicon dioxide, which when melting to generate flat sheets, is extremely expensive.
Soda-lime glass reduces the softening point when adding sodium oxide. This however makes the glass water-soluble so adding calcium oxide will help by ensuring that the glass is chemically resistant.
Unfortunately, there are alkali elements in soda-lime glass such as sodium, potassium, and calcium. These can escape from the glass and affect the inner layers of a solar cell.
An alternative to soda-lime that isn’t as prevalent is low-iron. The name comes from the glass having a lower iron content than soda lime. Where soda-lime measures 1,000 ppm, low-iron is drastically lower, measuring 100 ppm.
Glass with a lower level of iron-oxide makes for a solar panel that has a greater sunlight transmission. This means that solar cells protected using low-iron are more efficient than the ones shielded by soda-lime. The solar transmission found in soda-lime glass is around 85%, but in low-iron glass, it’s a whopping 91%, sometimes exceeding that amount.
As you can imagine, the production cost for low-iron glass is much higher than your standard soda-lime glass. However, the better transmission and overall quality of the glass itself justifies its asking price from the more experienced solar panel users.
By now, we can verify that glass plays an important role in keeping a solar panel strong and functional.
Adding that extra layer of protection ensures that you are getting the most out of your solar panel and keeping it safe from any external threats. Whichever glass your solar panel uses, know that it’s an important feature to ensure that your solar panel lasts for years to come.
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