Can Solar Panels Work Through Clear Plastic?
Can solar panels work with clear plastic? Many people ask this when thinking about putting solar panels on their homes.
Yes, they can! Solar panels can work with see-through materials like plastic and glass.
Most solar panels you find today have a protection layer made of glass or a kind of plastic. This layer keeps the panel safe from damage and lets light go through it.
Solar panel makers know their panels will be covered by a clear material they choose.
But if you add another layer of clear plastic or glass on the solar panel, less light will go through, making the system less efficient.
Depending on the plastic type, how thick it is, and the space between layers, the system could lose up to 10% of its efficiency.
This happens because of the following reasons:
- Glass and clear plastic materials have a different refractive index than air.
- A clear plastic layer adds an extra distance of light path that needs to be traveled, causing the angle of incidence between the sun’s rays and solar panels to change.
- The air gap between the plastic layer and solar panel may encourage water droplets to form creating a barrier that reduces the amount of light passing through and reaching solar cells.
- The additional layer will prevent the Antireflective coating (ARC) of the solar panel to not work efficiently since there is an additional surface that the light is refracted from one to another.
Why would a homeowner want to add clear plastic on top of the solar panel?
To have an additional layer of protection (aka lamination)
A homeowner may want to install clear plastic on top of the solar panel to protect it from shocks and debris. Even though most solar panels are made of tempered glass, it is still possible for something to damage the panel.
A clear plastic layer will provide an additional layer of protection and guard against anything that could cause damage.
To provide clear protection for a roof or on a patio.
In some cases, the homeowner wants to cover the roof or install solar panels on a patio with clear protection.
Clear plastic works well for this type of application because it protects the roof or patio from any debris that may fall on it while also allowing light to pass through and reach the panel underneath.
What factors affect energy efficiency applying a new layer on a solar panel?
The thickness of the plastic layer
The thickness of the plastic layer influences energy efficiency because the thicker it is, the more difficult it is for light to pass through. If an additional layer is planned, it is recommended to get a thin version of the material, such as polycarbonate film.
The thickness of the air gap
Installing the same clear plastic right on top of the panel or a few meters above the panel will result in different light transmissions.
The air gap between the solar panels and the plastic will also have an effect on how much of the sun’s rays can pass through both layers. In order to maximize this, you should put as little space as possible between them.
If you want to cover a solar panel’s surface with clear plastic try not to leave any air gap in between the panel and covering film as it may attract water droplets or fogginess to form reducing the amount of light that can pass through.
The thicker the air gap, in between the panel and the covering film, the higher drop in efficiency the solar panel will experience. Therefore, it is always best to keep the air gap as little as possible.
The surface of plastic material
The surface quality of the plastic material has also an effect on how much light is able to pass through.
For example, a plastic film with a smooth finish will allow more light to pass through as opposed to a film with an uneven finish. This is because the smooth surface will allow for less light reflection and more light transmission, due to its polished nature.
If you are installing clear plastic on solar panels then it is important to consider all of these factors before getting started and working out your installation plan accordingly.
Optical properties of the plastic material
Every material has unique optical properties, and plastic is no exception. Plastics have a refractive index that can change from one material to another.
In addition, their ability to reflect light can also vary depending on which wavelengths are being reflected.
Knowing the optical properties of the planned plastic layer will help you to determine how much light will be able to pass through the material.
As earlier said, not all types of plastics are the same. The plastic that you choose will determine how much light can pass through it and whether or not you’ll get a good performance from your solar panels.
The best types of materials to use when making solar cells out of clear material is polycarbonate, acrylics, glass, Plexiglas™ (PMMA), fused silica glasses(quartz), and sapphire wafers in some cases.
Each one has its own plus and minus depending on what type of application you are looking for, and what environmental conditions your panels will be exposed to.
Test Different Plastic Materials Yourself
You can test the power output of a panel using a digital multimeter by measuring the voltage and amperes generated by a solar panel.
Test these values with and without the cover to see how much power is lost if you laminate your panels with a specific cover.
The test is pretty straightforward to do. Simply place the panel under direct sunlight and measure the voltage of each type of plastic at a certain angle. You can ideally position the solar panel flat position at an angle parallel to the ground.
The best time to do this experiment is on a sunny day at around noontime when the sunlight is coming from right above.
Doing this experiment, attach the plastic layer to the glass of the solar panel with transparent tape leaving as little air gap in between the panel and the plastic as possible.
This is to ensure that the least amount of light energy gets lost on its way through the plastic cover, which would skew your results.
Make sure to take as many measurements as possible to get an overall average.
If you are unable to do the test yourself you can employ a qualified third-party engineering organization that can perform the test for you.
If the power loss is significant you may want to choose an alternative option.
What types of clear covering options are out there?
When selecting a suitable material for solar panel coverings, it’s essential to consider various factors such as durability, light transmission, weight, UV resistance, and impact resistance.
To help you make an informed decision, we have created a comparison table that highlights the key properties and features of four popular transparent materials: polycarbonate, glass fiber-reinforced polyester (GRP), Plexiglas™ (PMMA), and glass.
| Material | Durability | Light Transmission | Weight | UV Resistance | Impact Resistance | Cost | Notable Features |
|---|---|---|---|---|---|---|---|
| Polycarbonate | High | 88-90% | Light | High | 200x glass | Medium | Resists yellowing, maintains clarity over time, good insulator |
| Glass Fiber-Reinforced Polyester (GRP) | High | Lower than polycarbonate/glass | Light | High | High | Medium | Good insulator, resistant to harsh weather, suitable for supporting structures and casings |
| Plexiglas™ (PMMA) | Medium | 92% | Light | High | 17x glass | Medium | Excellent clarity, good insulator, more scratch-prone than polycarbonate |
| Glass | Medium (can be improved) | 80-90% | Heavy | Varies | Low | High | Can be tempered or laminated for increased durability, less impact-resistant than other materials |
Polycarbonate
Polycarbonate is a transparent plastic that offers exceptional chemical resistance, making it a popular alternative to glass in solar panel production.
This material is incredibly durable and capable of withstanding various weather conditions such as storms, snow, and accidental impacts like stray volleyballs.
Remarkably, polycarbonate has 200 times the impact resistance of glass, making it a much stronger material. In addition, it is lighter than glass, which facilitates easier handling and installation.
Polycarbonate’s optical properties are akin to those of glass, providing transparency and an appealing appearance while also boasting increased strength and reduced weight.
One unique aspect of polycarbonate panels is their ability to resist yellowing and maintain clarity over time. This ensures consistent light transmission and maintains solar panel efficiency.
The light transmittance of polycarbonate typically ranges from 88% to 90%, which is comparable to glass. This high light transmittance allows for optimal sunlight absorption by the solar cells, leading to efficient energy production.
Furthermore, polycarbonate exhibits an outstanding UV resistance that helps protect solar cells from harmful ultraviolet radiation, which can cause degradation over time. This property enhances the longevity and overall performance of solar panels.
In terms of thermal conductivity, polycarbonate has a relatively low coefficient, ranging from 0.19 to 0.22 W/m·K.
This low thermal conductivity makes it an excellent insulator, helping to maintain the temperature stability of the solar cells and contributing to more consistent energy production.
Glass fiber-reinforced polyester (GRP)
Glass Reinforced Polyester (GRP), commonly known as fiberglass, is a unique material distinct from ordinary glass.
While glass is an amorphous solid, often transparent, and produced by melting sand with a mixture of soda, potash, and lime, fiberglass is created through a different process.
Fiberglass is a silica-based glass that is extruded into fibers with a length at least 1,000 times greater than its width. This results in a material with a high strength-to-weight ratio, which is ideal for various applications.
One of the notable characteristics of fiberglass is its resistance to harsh weather conditions.
It can withstand the damaging effects of UV rays, oxidation, and corrosion, making it a suitable choice for outdoor installations and products that are exposed to the elements.
In addition to its durability, fiberglass is an excellent insulator, both thermally and electrically.
This property makes it particularly valuable in the construction and electrical industries, as it can provide insulation without adding significant weight to a structure or system.
GRP’s unique combination of strength, lightweight, and resistance to environmental factors also makes it an ideal material for use in the renewable energy sector, particularly in wind turbine blades and support structures.
Its versatility allows it to be molded into complex shapes and designs, while its strength ensures it can handle the stresses associated with wind energy generation.
When considering solar panels, fiberglass can be used as a protective casing or supporting structure.
However, it is essential to note that the light transmission properties of GRP may not be as high as those of other transparent materials, such as glass or polycarbonate.
This factor should be taken into account when selecting the appropriate material for a solar panel installation.
Plexiglas™ (PMMA)
Plexiglass, also known as Poly(methyl methacrylate) or PMMA, is a type of clear acrylic sheet that offers excellent properties for outdoor applications.
It is a thermoplastic polymer derived from the polymerization of methyl methacrylate monomers, resulting in a transparent and versatile material.
One of the main advantages of Plexiglas™ is its outstanding optical properties.
With a light transmittance of approximately 92%, PMMA allows for excellent visibility and clarity, making it an ideal choice for various applications where transparency is crucial.
Additionally, PMMA demonstrates impressive resistance to degradation over time, owing to its inherent UV stability.
This characteristic ensures that Plexiglas™ maintains its clarity and does not become brittle or discolored when exposed to sunlight for extended periods.
Its weather resistance also extends to other environmental factors, such as temperature fluctuations and moisture, making it suitable for outdoor installations.
Plexiglas™ is approximately half the weight of glass while providing 17 times the impact resistance, which makes it a safer and more manageable alternative to traditional glass. This lightweight nature allows for easier handling, transportation, and installation.
From a thermal perspective, PMMA has a relatively low thermal conductivity of about 0.19 W/m·K, which means it acts as a good insulator. This property can help maintain temperature stability within enclosed systems or structures, contributing to energy efficiency.
Regarding solar panel applications, Plexiglas™ can be used as a protective cover or casing, offering excellent light transmission and durability.
However, it is essential to note that PMMA’s scratch resistance is lower than that of polycarbonate, which may be a consideration when selecting the appropriate material for solar panel installations.
Glass
Glass is a well-known material that provides excellent light transmission properties and can be sufficiently durable when specifically manufactured for solar panels.
The optical properties of glass are generally good, with light transmission rates ranging between 80% and 90%, depending on the glass type and manufacturer.
While not as high as acrylic, which can transmit up to 92% of visible light, glass still offers suitable performance for many applications, including solar panels.
However, glass has some disadvantages compared to other materials like polycarbonate and acrylic.
First, glass is more expensive, which can be a significant factor when selecting materials for large-scale installations or projects with budget constraints.
Second, glass lacks the impact resistance of polycarbonate. While glass can be made more durable through specific manufacturing processes, such as tempering or laminating, it is still more likely to break or shatter under stress or impact than polycarbonate, which boasts 200 times the impact resistance of glass.
Lastly, the optical properties of glass are generally inferior to those of acrylic, which offers better light transmission.
This difference may be important in situations where maximizing light transmission is essential for optimal performance, such as solar panel installations.
In summary, while glass provides good light transmission properties and can be made durable through specific manufacturing processes, it has higher costs and is less impact-resistant than polycarbonate.
Additionally, its optical properties are not as impressive as those of acrylic. These factors should be considered when selecting a material for solar panels or other applications where durability and light transmission are crucial.
Conclusion
Solar panels can work through clear plastic or glass. However, the additional layer between the light source and the solar panel will reduce the amount of light that reaches the solar cells. This will inevitably cause a reduction in energy production.
If you are considering an additional layer on top of your solar panel, or maybe a transparent roof above your solar panels you should consider if the benefits of this outweigh the loss of energy efficiency.
but acrylic has better optical properties and is lighter. Glass can transmit more visible light than most types of plastics and offers high durability if it is manufactured for solar panels.