A superstrate literally meaning “top layer” is the covering on the upper (sun-facing) side of photovoltaic module. It is a passive but critical part of a solar cell. It is primarily added for the purpose of protection of the cell against various undesirable effects of impact, weather, and other environmental effects. The superstrate material for photovoltaic use must possess a number of properties which we discuss below.
What Qualities Must It Possess?
A solar panel superstrate has to possess the ability for the following functions:
- Impact and Abrasion Protection – The superstrate should provide the front surface of the cell protection against impact and possible abrasion, scratches, etc. Such situation can occur quite often during transportation and maintenance activities.
- Protection against Wind and Sand- Wind and physical handling can cause flexural. This may cause microcracks within the solar cells. Wind can also cause sandblasting of the solar plate. The superstrate will protect the front surface against abrasion in windy and dusty environment.
- Weather Protection: The Superstrate must protect against weather elements. Water and water vapor can both cause rusting of materials. Perovskites are especially vulnerable to water. In addition, smoke and salt (in coastal areas) can harm the solar panel.
- Electrical Shock- The superstrate material must have good breakdown voltage to protect against electrical shock.
- Transparency: It must be as transparent as possible to allow maximum solar energy to pass through to the cell underneath.
- Light Weight– Like most equipment, we want the panels to be light weight. A heavy superstrate can add unnecessary weight to the panel.
- Withstand Ultraviolet Radiation-Ultraviolet radiation with its high energy can cause chemical and physical changes to the superstrate. Opacity and color change are possible.
- Temperature Resistance– the material should be able to withstand extremes of temperature at the location of operation.
- Eco–Friendliness– the material should be recyclable.
- Self-Cleaning– The superstrate is going to be exposed to smoke, dust, silt, snow, etc. It should be self-cleaning (non-stick) or at least easily washable.
Fiberglass and Glass Fiber-The distinction
Glass fiber and fiberglass are two terms which are commonly confused. To explain, glass fiber is fiber made out of glass material, just as glass wool is. Glass fiber is used for multiple purposes, the glass wool being one. Glass wool is as an insulator filling in many thermal applications. It is also used a matting, and as a knit sleeve where it acts as both an electrical as well as heat insulator. Fiberglass, on the other hand, is glass fiber impregnated in a plastic liquid and allowed to solidify. Fiberglass is used as a light weight structural element in outdoor structures, sports equipment, automobiles, and many other applications. Here, we are considering fiberglass for a possible role as a photovoltaic panel superstrate.
Fiberglass Suitability as Superstrate Material
Fiberglass has most of the desirable attributes. But a drawback with veto power is the transparency. It is a translucent material. That makes it unsuitable for use as a superstrate.