Despite the fact that a PV backsheet’s primary purpose is to shield solar PV modules, some solar plants aren’t able to last as long as they were expected to. Backsheet is crucial for shielding delicate solar cells from damaging elements and other potential damage that might happen on the PV module’s back exterior side. So what kind of backsheet is used on solar panels the most frequently? For more information on solar panel backsheet materials, read this article.
What Is A Backsheet
The backsheet, which is the PV module’s outermost layer, is intended to protect the electrical system and inner photovoltaic cell components as well as act as an electrical insulator.
It protects the components from moisture, the elements, and the weather by acting as a weather barrier.
Backsheets are typically made of polymer materials like ethylene chlorotrifluoroethylene (ECTFE), polyvinylidene fluoride (PVDF), polyesters (PET), polyamides (PA), tetrafluoroethylene hexafluoropropylene vinylidene fluoride (THV), and ethylene-vinyl acetate copolymer (EVA).
To obtain the desired properties, a backsheet can also be made from a mixture of various polymers.
There are common backsheets that contain various combinations of polymers, including single fluoropolymers, double fluoropolymers, and non-fluoro polymers.
How Important Is A Solar Panel’s Backsheet
Protects From Mechanical Stress
The backsheet gives the module strength and durability. Without a backsheet, mechanical stress could potentially harm the photovoltaic cells and the electrical system.
Many different factors, including human activity, wind load, snow and ice weight, falling objects like rocks or branches from nearby trees or buildings, earthquakes, and human activity can all cause mechanical stress, which can manifest as pressure, impacts, vibrations, and shock.
If the correct backsheet is not present, each of these elements may harm the PV cells and/or electrical system.
Protects From Water & Dust Intrusion
A strong defense against dust and water infiltration is provided by the backsheet layer. Photovoltaic cells may experience corrosion and pit as a result of water and dust particles, among other problems.
Backsheet aids in shielding electrical connections and components from corrosion, insulation deterioration, and potential short-circuiting, all of which are damages brought on by moisture.
Additionally bothersome are dust particles, which, if they build up on the cell surfaces, can make the system less effective or even stop working altogether. By shielding against those particles, the backsheet aids in preventing this from happening and helps to prevent the buildup or accumulation of those particles on the cell surfaces.
Protects Against Uv Exposure
By shielding the system from solar radiation, the solar panel backsheet also aids in preventing damage brought on by ultraviolet (UV) exposure. The breakdown of the cell’s semiconductor components by UV radiation will have an impact on their effectiveness and performance.
The backsheet helps block UV radiation and shields the cells from its damaging effects. All backsheets, however, will eventually lose their color due to UV exposure, regardless of the material used.
Having said that, a color change isn’t always a sign of a broken backsheet. However, if a color change is significant and the backsheet exhibits signs of deterioration, this might be cause for concern.
Reduces Thermal Stress
The PV module’s thermal stress is lessened by backsheets as well. When it’s too hot or cold, photovoltaic cells can experience stress, which will reduce their effectiveness. The system is protected from thermal stress by a backsheet, which insulates it from both high and low temperatures.
By preventing high-energy photons from reaching the PV cells, the backsheet also aids in reducing solar heat gain, preventing overheating that may result in damage or subpar performance.
Minimizing heat gain is crucial because, as we already know, solar cells’ performance declines as temperature rises above a certain threshold. By minimizing solar heat gain and shielding the cells from overheating, the backsheet is crucial in this regard.
Dielectric Strength
A solar panel is a self-contained energy system that shouldn’t be electrically impacted by anything outside of it. A protective barrier, the backsheet prevents electrical conductivity between the cells and the environment.
A material’s dielectric strength is the highest electric potential that can be applied to it without causing an electrical breakdown or losing its insulating qualities. This is so that high dielectric strength materials can be exposed to high voltage without experiencing a dielectric breakdown.
Features Of A High-quality Backsheet Layer
Low Cost
Backsheets are no different from other types of materials in that cost is the primary consideration. As a result, producers have been known to cut corners on quality and use less expensive materials for the backsheet layers in their solar panels in an effort to reduce costs.
Because it plays a crucial role in the energy system, protecting expensive cells and maintaining their efficiency, the backsheet should be of high quality without being excessively expensive.
The lifespan of a typical solar panel is 25 to 30 years. The ongoing need to replace backsheets and other components that might not last as long, however, makes cheaper PV modules a costly long-term investment.
Solid
The backsheet needs to be sturdy enough to maintain its shape and withstand pressure from the outside elements. Backsheets should be sturdy enough to withstand pressure from the outside even though they are made of polymer material, which is somewhat flexible.
Chemical Inertness
The backsheet must be chemically inert, which means it must not react chemically with its surroundings or other photovoltaic system components in a way that eventually causes harm to them. The ideal material will be stable and won’t change in composition over time.
Durability
For the backsheet to last for a long time without tearing or breaking, it must be extremely strong. The backsheet should be made of sturdy materials that can withstand weathering, heat, dirt, grease, and other environmental factors.
Resistance To Uv Radiation
UV rays shouldn’t be able to pass through the backsheet because they should be UV resistant. Long-term exposure to UV radiation won’t cause high-quality backsheets to lose their structural integrity or cause the cells behind them to degrade.
Resistance To Moisture
Water must not absorb into or pass through the backsheet, which means it must be water resistant.
As a result, high-quality backsheets are typically made from materials that have the ability to repel water. The backsheet needs to be tough enough to endure being exposed to moisture for a long time.
Resistance To High Temperatures
Extreme high and low temperatures should not cause the backsheet to weaken, soften, or allow the solar cells to suffer other heat-related damage.
Backsheets should retain their structural integrity and not have an impact on the cells behind them when exposed to high temperatures. The backsheet must also be able to endure thermal shrinkage without losing its shape or structure.
Lightweight
The backsheet should be as light as possible to prevent it from increasing the system’s overall weight and impairing its performance.
Because additional weight makes objects more difficult to handle, transport, and install as a whole. The weight of the backsheet should be as light as possible compared to other solar panel components.
Good Adhesion Strength
In order for the backsheet to remain attached to the PV cells even when exposed to strong winds and other weather elements, as well as in situations where there is thermal cycling, it must have a high level of adhesion strength. The backsheet can shield the cells from damage brought on by external forces in this way.
Environmentally Friendly
To prevent long-term harm, the backsheet should be environmentally friendly. The backsheet’s manufacturing process should not use materials that are harmful to the environment or to people’s health, including those that might harm wildlife or other natural resources.
In comparison to fluorinated backsheets, polyethylene (PET) backsheets offer more disposal options. Because the only option for fluorinated backsheets is to be disposed of in landfills, which is not good for the environment.
What Is The Most Popular Backsheet Material For Solar Panels
Polyethylene Terephthalate (pet) Backsheet
Backsheets are frequently made from polyethylene terephthalate (PET) material. Although it has good mechanical qualities, it can’t withstand solar radiation for very long.
When exposed to ultraviolet (UV) light, PET backsheets usually deteriorate and over time, turn yellow. The yellowness index (YI), which depicts a polymer’s change in color and is linked to the chemical transformation brought on by irradiance, high temperatures, and other processes, can be used to identify degradation.
Fluoropolymer Backsheets
The market for backsheets is dominated by fluoropolymer backsheets because of their superior chemical resistance to a variety of harsh elements that can degrade solar cells.
Fluoropolymers are hydrophobic, chemically inert materials that are superior to PET as backsheets because they can withstand UV light and chemical exposure. They can be made very thin yet very durable, and they have good mechanical and thermal stability.
However, due to their intricate manufacturing process, which calls for the use of a variety of different polymers, catalysts, and additives, fluoropolymers are pricy to produce.
Common Backsheet Problems
Peel Off Issue With Eva
Backsheets will gradually deteriorate over time if exposed to the sun’s UV rays. They may peel off as a result of this, losing their adhesive qualities and becoming vulnerable to other issues.
However, backsheet deterioration is not only a result of UV rays. Backsheet peeling can also be caused by high humidity, high temperatures, and environmental chemical contaminants.
Air Side Layer Coating Issue
The air side layer coating issue is one of the backsheet issues that are most likely to come up.
This occurs when there is poor adhesion between the polymer materials on the back sheets on either side, which is typically brought on by humidity or high temperatures during the module manufacturing or installation process.
Layers Crack Issue
When exposed for an extended period of time to high temperatures and moisture, the backsheet layers are more susceptible to cracking. In addition to making them peel off, this may also allow moisture to penetrate the cell side layer, damaging solar cells through exposure.
Yellowing Issue
Moisture and UV rays both have the potential to cause backsheet yellowing. Backsheets gradually start to turn yellow over time when they are exposed to the sun’s ultraviolet rays.
Deterioration of the backsheet typically manifests as yellowing first. Moisture is subject to the same rules. Since backsheets are made of organic compounds that will react to shifting environmental chemistry, they may start to yellow when exposed to high humidity or liquids.
Delamination Issue
When the layers of the backsheet are improperly bonded together, a problem known as delamination arises. When this occurs, any solar cells that are below the surface may sustain damage, which could result in cell deterioration or failure.
This typically happens as a result of poor adhesion between the polymer materials on either side of the backsheets during the assembly process and high temperatures.
Conclusion
The fact that backsheets shield the cell side layers from moisture and other environmental factors makes them a crucial part of photovoltaic solar panels. Backsheet materials come in a wide variety, and newer ones are constantly being created. The cost and impact of systemic degenerative problems like backsheet failure can be significantly decreased by fully digitizing the asset down to the module record.
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