You might think covering a solar panel might affect its abilities! Often it’s believed that solar panels don’t work during cloudy days, but this isn’t the case. The same is true for glass.
Solar panels behind glass will still work! If you happen to be using one behind a window, it will still work. However, it won’t be as effective or efficient than one placed uncovered and outside.
Glass is transparent though, how does it affect solar panels? Well it’s kind of a funny story….
Some Things to Know!
Fresnel Law. What the heck is that? Well. Let’s break it down a little bit.
Light is often described, and shown, as a wave or particle. (Or both!) In our scenario we will use a wave. When a ray of light travels from the sun to the earth it has a specific speed, and direction. So if the light reaches another surface, then part of the ray can be reflected back and it can be refracted on the inside of the surface.
This theory occurs according to the Fresnel Law. The law explains that when light reaches another medium, like water, glass, or another type of surface then part of the light will always be reflected back whilst another part will be trapped within it but with a different speed than it was at when it arrived.
So, how does all of this affect our solar panel?
How Does Glass Alter Solar Panels?
Because reflection will occur within the glass, then the number of photons that travel with the ray of light will decrease and be lost. All of the sunlight that’s reflected is going to be lost and you won’t be generating as much electricity or power as you would normally be without the glass. This will reduce energy output and can slow things down.
This isn’t the only way glass can alter solar panels though.
Glass actually has a tint, if you can believe it. I certainly couldn’t, but there is. The tint within the glass is also used to keep the heat from the sun causing issues within your home. It’s much more commonly found in warmer places, however, glass can often be tinted this way regardless of your environment. This tint makes it harder for solar panels to catch the sunlight.
Another big issue would be that using a solar panel through a window might not catch all of the day’s sunlight. Solar panels need to be placed towards the sun if you want the maximum amount of energy. So if you kept it inside but besides a window, you wouldn’t be catching the most sunlight you could be. In fact putting a solar panel behind a window would hardly get you any sunlight or energy at all!
Placing panels inside a building or behind another window can have bad effects as well. The irradiance will be at its max value when the sun is at its highest, so around noon each day. Since the roof of the house is blocking this path of sunlight, you won’t be able to get the necessary sunlight you need at the best time of day to do it. This will lower your production and any production created will be from something called Diffued Horizontal Irradiance, or DHI.
DHI is when solar radiation is reflected, or retracted, from things like clouds, mountains, lakes, or the ground and atmosphere. So DHI essentially refers to the solar irradiance that impacts the surface of the panel.
By placing a solar panel behind a glass or a window, you are eliminating the natural light component of solar radiation that would directly impact the solar panel. Meaning that your solar panel would be working mostly with DHI components, related to the reflection of sunlight from other sources.
So..Is it Worth It?
In the long run…no? However it really just depends on how much you use this form of energy generation.
It’s important, however, to talk about things you need to keep in mind if you happen to HAVE to keep your solar panels behind a glass pane. Here are a few of them.
One: If they’re inside a home, and moveable, consider moving them with the movement of the sun. This way you’re receiving the optimal amount of sunlight throughout the day. You may still lose some but you’ll have not lost nearly as much as you would have to let it sit in one place.
Two: Try to keep the glass at an angle that isn’t going to strongly affect the solar panel. Your solar panels have to be at a certain angle throughout the day, and if happen to put the glass right on top of the panel, you’re going to consistently reflect sunlight throughout the day. If possible, place your glass either straight above, or at another angle of the solar panels to protect them, whilst still preventing light from bouncing off of them!
Finally: Consider ditching glass altogether and going for a different material to protect your solar panels. If you don’t want them getting damaged, and still want to keep them protected, that’s totally fine! There are other materials that are going to be more helpful, like plexiglass. Plexiglass can be made much thinner than regular glass, and can be placed directly on to solar panels. Plexiglass has been found to reflect less light, allowing your solar panels to absorb much more than they would if they were under glass!
Whether or not you fully decide on how to cover your solar panels, it’s important to remember why you have them. If you’re interested in generating your own power, and maybe have enough solar panels that aren’t covered in glass, then a glass covering should be fine. However, if you find that you’re relying on only a few, glass probably isn’t the best option for you! It all boils down to your preference, and how much sunlight you need!