Choosing Right Materials Used in Solar Panel production for Backsheet and EVA Encapsulant

The primary defects in solar PV modules can be traced back to the backsheet. Backsheet functions as an insulator and therefore, any fault or failure typically results in a significant negative effect on the performance of the PV module. The backsheet’s fracturing and layer separation can trigger decay and rusting within the internal circuits. This corrosion can result in the formation of hot spots, dissipating heat and leading to power output degradation and safety issues.

Therefore, it is crucial to select the backsheet material carefully for your solar panels. The best approach is to choose a reputed solar panel manufacturer for backsheet needs. This article discusses how low-quality backsheets negatively affect the solar panel’s performance and lifespan. The article further highlights the need for the best quality backsheets and EVA.

Degeneration Problem in Low-Quality Backsheets

Degenerative problems in a solar plant due to poor-quality backsheet installations can happen at any stage in the lifespan of a solar plant.

These failures manifest in the form of:

Cracking (either on the inner or outer layer)
Delamination
Yellowing

Identify Solar Panel Backsheet Failure

In case your manufacturer has used low-grade material for backsheet manufacturing, you will experience a decline in the PV module’s output. You can also evaluate the degradation through a visual examination.

Other methods of finding backsheet failures in solar panel include a chalking observation test, thermal imagery, and FTIR. Based on the severity of the degradation, an insulating material can be used to conduct a chalking observation test. Another method to locate the overheated areas, caused by rusting or delamination from a backsheet flaw, is by using thermal imagery. The kind of backsheet utilized in a PV module and its degradation (if present) can also be determined using field Fourier Transform Infrared (FTIR) spectroscopy, a method used to identify polymeric materials. It employs infrared light to examine samples and ascertain the material’s chemical characteristics.

Benefits of Incorporating High-Quality Backsheet for Solar Panel

High-Quality Backsheet Material Extends the Life of the Solar Panel and has other benefits as discussed below:

Thermal Dissipation

Solar panels generate heat while transforming sunlight into energy. Overheating can detrimentally affect the panel’s effectiveness and durability. The backsheet is essential in regulating this heat. It functions as a heat barrier, enabling the solar panel to shed excess heat, which aids in keeping the temperature of operation lower. By effectively managing heat, the backsheet enhances the overall performance and lifespan of the solar panel.

Protection Against UV Rays

Solar panels are constantly exposed to sunlight, which carries damaging ultraviolet (UV) rays. Extended exposure to UV rays can lead to deterioration and damage to the panel’s sensitive parts, like the photovoltaic cells. The backsheet acts as a protective shield, saving the panel from UV radiation. It blocks UV rays from penetrating the deeper layers, thus minimizing damage potential and guaranteeing the panel’s long-term efficiency.

Guard Against Physical Damage

Solar Panels are regularly subjected to various environmental elements’ stress such as wind, rain, hail, and debris. The backsheet offers mechanical protection, serving as a buffer between the panel’s fragile internal components and the outside environment. It aids in avoiding physical damage due to impact, wear, and tear, or extreme weather conditions. By protecting the panel from external influences, the backsheet ensures the panel’s structural stability and functionality.

Electrical Insulation and Safety

Solar panels create electricity, so maintaining appropriate electrical insulation is crucial for safe operation. The backsheet serves as a safety layer that keeps the solar panel’s conductive components isolated from the outside surroundings. It helps avoid electrical shorts, leaks, or other electric faults that could occur due to exposure to moisture or conductive substances.

Choosing Good-Quality Raw Materials for Solar Backsheet

A backsheet is composed of a single polymer or layers of polymers. Commonly used PV backsheets are layered with polymers like Polyethylene terephthalate (PET), Polyvinyl fluoride (PVF), Polyvinylidene fluoride (PVDF), and Polyamide (PA).

The composition of a backsheet may vary in terms of the number of layers based on the maker and its specific purpose. Thus, the materials selected for solar panels will differ. However, backsheets come in three main variations: Double fluoropolymers, Single fluoropolymers, and Non-fluoropolymers. Each category has its own characteristics and price range.

Double-layered Fluoropolymer Backsheets

These particular backsheets are composed of numerous strata. The exterior layers are commonly crafted from a substance known as Tedlar, a variety of polyvinyl fluoride (PVF), or Kynar, a variety of polyvinylidene fluoride (PVDF). These layers offer superior safeguarding to the inner layers. The interior layer is typically crafted from polyethylene terephthalate (PET).

Note: Fluoropolymers possess a distinctive molecular framework, with carbon atoms encompassed by fluorine atoms, amplifying the preservation of the layers.

Single-layer Fluoropolymer Backsheets

Single-layer fluoropolymer backsheets have a less complex structure compared to their double-layer counterparts. The side exposed to the air is commonly composed of Tedlar or Kynar, while the inner side is made up of PET, accompanied by a primer or an ethylene-vinyl acetate (EVA) layer. Opting for a singular fluoropolymer layer instead of dual layers cuts down the cost.

Non-Fluoropolymer Backsheets

This backsheet variety is made up of two PET layers and one primer or EVA layer. Historically, backsheets without fluoropolymer were less popular because of worries about deterioration due to UV exposure or hydrolysis. But, evolution in polyester chemistry and manufacturing methods have led to the creation of polyester films that are highly resistant to UV. These films have enhanced durability which has made the backsheets without fluoropolymer a more practical and economical option.

Choosing Good-Quality Raw Materials for EVA Encapsulant in Solar Panel

Encapsulants provide adhesion between solar cells, the top surface, and the rear surface of the PV module. Quality EVAs provide electrical insulation, reduce moisture ingress, protect against mechanical stress and corrosion, and hold PV module components in place. Therefore, selecting the right EVAs is also as important as selecting the right backsheets.

The most common encapsulant material is EVA (ethyl vinyl acetate). EVA sheets are inserted between solar cells and surfaces, then heated to 150°C for polymerization and bonding.

Role of EVA Encapsulant

Adhere well to all surfaces
Work amidst exposure to high temperatures and UV radiation
Stability at high temperatures
Provide high optical transmission
Low thermal resistance

High-quality encapsulant requires strict quality control and consistent composition with top-notch raw materials. It must have strong adhesion, sufficient gel content, and low shrinkage.

Test to Ensure High Good-Quality Raw Materials Incorporation in EVA Encapsulant

Adhesive Test for EVA Encapsulat (Checking Peeling Strength in EVA)

Measures EVA’s adhesion to the substrate
Strong adhesion is important for panel longevity
Low adhesion suggests expired EVA, moisture exposure, or improper lamination
Spring balance test with 75 N/cm to 125 N/cm values for quality control

Gel Content Test

Measures cross-linking in EVA polymer
Lower gel content affects long-term mechanical integrity
Variations used for approximate values at the shop floor level

Thermal Shrinkage

EVA films shrink during lamination at high temperatures
Uncontrolled shrinkage causes cell breakage and alignment issues
Manufacturing-induced stresses contribute to shrinkage
Acceptable shrinkage level: 2% or less

Conclusion:

Selecting the right material for PV Backsheets and Encapsulants is critical to keep your solar plant’s output stable and increasing its lifespan. Vishakha Renewables manufactures all types of backsheets ranging from PET, PVDF, PVF, and transparent PVDF. Vishakha is also a reliable supplier of quality solar encapsulants EVA and Polyolefin-based encapsulants. Vishakha deploys the proven extrusion technology to create extremely stable encapsulants with high optical transmission.

For queries related to backsheets and EVAs, please feel free to contact us at info@vishakharenewables.com or alternatively call us at +91 79 6190 7373.