Types of panels

There are four major types of solar panels available on the market today: monocrystalline, polycrystalline, PERC, and thin-film panels.

Polycrystalline solar panels

As the name implies, these come from different silicon crystals instead of one. The silicon fragments are melted and poured into a square mold. This makes polycrystalline cells much more affordable since there is hardly any wastage and gives them that characteristic square shape.

However, this also makes them less efficient in terms of energy conversion and space, since the silicon purity and construction are lower than monocrystalline panels. They also have lower heat tolerance, which means they are less efficient in high-temperature environments.

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Monocrystalline solar panels

Also known as single-crystal panels, these are made from a single pure silicon crystal that is cut into several wafers. Since they are made from pure silicon, they can be readily identified by their dark black colour. The use of pure silicon also makes monocrystalline panels the most space-efficient and longest-lasting among all the solar panel types.

However, this comes at a cost — a lot of silicon is wasted to produce one monocrystalline cell, sometimes reaching over 50%. This results in a hefty price tag.

Passivated Emitter and Rear Cell (PERC) panels

PERC solar panels are an improvement of the traditional monocrystalline cell. This relatively new technology adds a passivation layer in the rear surface of the cell that enhances efficiency in several ways:

• It reflects light back into the cell, increasing the amount of solar radiation that gets absorbed.

• It reduces the natural tendency of electrons to recombine and inhibit the flow of electrons in the system.

• It allows greater wavelengths of light to be reflected. Light waves over 1,18nm can’t be absorbed by silicon wafers and simply pass through, so they end up heating the cell’s metal back sheet and reduce its efficiency. The passivation layer reflects these higher wavelengths and stops them from heating up the back sheet.

Thin-Film Solar Panel Variations

Unlike crystalline panels above that use silicon, thin-film solar panels are made from different materials. They have lower production costs but require large surface area which is not ideal for the majority of installations.

Efficiency

Among all panel types, crystalline solar panels have the highest efficiency.

• Monocrystalline panels have an efficiency rating over 20%.

• PERC panels add an extra 5% efficiency thanks to their passivation layer. 

• Polycrystalline panels hover somewhere between 15-17%.

• In contrast, thin-film panels are usually 2-3% less efficient than crystalline silicon.

• CIGS panels have an efficiency range of 13-15%.

• CdTe ranges between 9-11%.

• a-Si have the lowest efficiency at 6-8%.

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Degradation rates and lifespan

On average, solar panels degrade at a rate of 1% each year. That’s backed up by the solar panel manufacturer’s warranty, which guarantees 90% production in the first ten years and 80% by year 25 or 30.

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Panel protection

Whichever way you mount your PV system, it’s vital to keep it protected. Birds in particular can be a problem for rooftop installations, as they see the space under panels as an ideal nesting spot. Unfortunately this can cause damage to the system and the roof. You can combat this with specialist PV bird protection - spikes or mesh that deter the animals without harming them.