Encapsulants are polymer-based sheets used to integrate components (Glass, Cell, Backsheet, interconnects, etc.) in a solar panel.
The solar PV Cell is laminated between 2 layers of the encapsulant to provide passage for light while ensuring electrical insulation to the PV cells. It also provides mechanical integrity by binding various components of the PV modules (solar panels) together as mentioned above.
What are UV Rays?
Ultraviolet radiation (UV light) is an electromagnetic spectrum of light ranging from roughly 100 to 400 nano-meters wavelength. This UV light is a high-energy wave and generates relatively higher energy harmful to humans with a longer duration of direct exposure.
The encapsulant is generally designed to protect/block UV rays of sunlight reaching PV cells, to prevent PV cells and Backsheet from UV degradation. But, the flip side of this feature of an encapsulant makes lesser light reach cells resulting in lesser power generation.
Considerable amount of UV rays are present in sun light, even on cloudy days and during dull and misty weather. UV light ensures that there is no steep drop in power generation even when ambient visible light is low.
What is a UV Transparent Encapsulant?
With the advancement of cell-making technologies, where the cells are made more UV resistant, there has arisen a scope to make the top layer of the encapsulant UV transparent (No blocking of UV rays), which in turn allows UV light to reach the cells generating more power.
A specialized formulation allows the Encapsulant to transmit the UV light, coming from the sun, and through the solar panel's glass, onto the solar cell. This type of Encapsulant is called UV Transparent.
UV Transparency is one of the key features of a High-Performance Encapsulant.
The power generation with UV Transparent Encapsulants is higher than the standard encapsulants with no PID resistance and no UV Transparency. These additional properties ensure that the panel gives maximum power generation throughout the year.
Even on cloudy days or days with visibly lesser light, your panel may be able to generate more power than others that do not have UV transparent encapsulant.
We measure the complex refractive index of conventional encapsulants with enhanced UV transmission based on techniques like spectroscopic ellipsometry transmission, and reflection measurements over the wavelength range of light from 300 - 120 nm.
Ray tracing of the entire solar module (solar panel) using this optical data predicts a 1.3% increase in short circuit current density (Isc) at standard test conditions for EVA Encapaulants with enhanced UV transmission.
This is in good agreement with laboratory experiments of test modules that result in a 1.4% increase in short circuit density (Isc) by using a UV transparent EVA, instead of a conventional EVA.
Suggestions for Solar Panel Manufacturers and Buyers to consider:
Use PID Resistant - UV Transparent EVA on the front side (sun-facing side) of the solar panel, and PID Resistant - UV blocking EVA on the backside (ground-facing side) of the module to harness the maximum power generation.
The UV cut-off of glass should match the UV Transparent EVA being used to receive maximum generation benefits.
A sun simulator having a flashlight from 290 nm onwards is recommended to get maximum power during the flash test with UV Transparent EVA.
However, UV rays can damage the backsheet of the solar panel. Hence it is recommended that the encapsulant above the solar cell should have UV transparency whereas the encapsulant below the solar cell should have UV blocking capability.
This will also ensure that any UV light that was not absorbed by the cell is reflected back to the cells and the backsheet is protected.
Data Credits : https://www.semanticscholar.org
Image Credits : RenewSys