The solar backsheet is the outermost layer of the solar panel and is a key contributor in ensuring that the power output of the panel is sustained over the system’s lifetime. It acts as the first line of defense for solar cells and encapsulating materials by protecting them from environmental factors while ensuring electrical insulation. If there is a backsheet related problem in the solar panel, it can result in a breakdown of the panels, premature power degradation, and electrical safety hazards.
A poor quality backsheet can cause various problems and result in additional costs as replacements would be required for the same. A high quality solar backsheet protects the panel from various things such as:
- UV rays which are transmitted or reflected
- Moisture problems due to humidity, precipitation or condensation
- Corrosive environment factors such as atmospheric chemicals, ammonia, and coastal environment
- Temperature issues
- Physical threats such as abrasion and impact
- Electrical damage such as shorting or shock
The solar backsheet need to be scratch-resistant as it can get damaged during installation and maintenance. It needs to remain stable at temperatures ranging between -40 to +85 degrees.
In bifacial solar PV panels that are designed to let the sunlight in from both sides of the cell, the backsheet needs to be optically transparent. The development and testing of backsheet film ensure that it will last longer and keep the electrical components inside safe from the environment.
The outer layer is the most critical layer in backsheet as it is directly exposed to the climate in the field. It protects the middle layer of the sheet from environmental stresses without which it would degrade very quickly and lose the properties. It cannot withstand outdoor conditions. It is made of PVDF, PET, PVF films which are of the highest quality. It makes the outer layer more durable against sand abrasion and other factors such as scratches.
Important properties of backsheets
Thickness – The thickness of the middle layer impacts the electrical insulation. When the thickness increases, the electrical insulation value increases, and the water vapor transmission rate decreases. It also needs to be thick enough to withstand cuts and abrasion.
Adhesion strength – It determines the strength between the inner layer and the panel’s encapsulant. The adhesion strength also depends largely on the selection of the inner layer.
Interlayer adhesion strength – It determines the strength between backsheet’s layers. The process and adhesive used by a manufacturer of a solar backsheet is really critical for it.
The types of protective materials
PVDF – They are available in two configurations. The first is a double sided one in which the inner and outer layer are made of PVDF materials. The other is a single sided one, where the outer layer is made of PVDF material. PVDF is a relatively new material for backsheet and cannot be considered as a tried and tested option. The PVDF material used in backsheet contains around 20%-30% acrylic additives. There are many makers of PVDF films and the composition and performance varies according to the suppliers.
PET – The PET is a non-fluorinated material that was first used in the 90’s by manufacturers for top roof panels. The PET backsheets have been around in the market for quite some time now and there are multiple issues with it such as cracking as a result of power loss. There are new versions available that have been modified to be UV and hydrolysis resistant.
To purchase top quality solar backsheet that are durable and affordable, get in touch with Vishakha Renewables.
