4 Types of Solar Panels

Solar panels for roofs are available in various types and energy-efficiency levels. They not only look different but also perform differently under exposure to the sun. The four major types of solar panels are monocrystalline, polycrystalline, PERC, and thin-film solar panels.

Every type of solar is made out of solar cells. Each solar cell is made from layers of silicon, that create electrical fields from the electrons inside the solar panel. This creates a direct current (DC). This conversion of electrons from solar power to electricity is called photovoltaics. This is why solar panels are called Photovoltaic panels or PV panels. A typical solar panel consists of 60, 72, or 90 individual solar cells.

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Types of Solar Panels for Buildings

The four major types of solar panels used for buildings are:

1. Monocrystalline
2. Polycrystalline solar panels
3. PERC solar panels
4. Thin-film solar panels

1. Monocrystalline Solar Panels

• Single-crystal panels made from a single pure silicon crystal
• These silicon wafers are assembled in rows and columns to form a rectangle, covered with a glass sheet, and framed together
• Pure silicon crystal solar panels are identified easily by their dark black color.
• It is the most space-efficient and longest-lasting solar panels
• It consumes a lot of silicon to make.
• These crystalline solar panels give 15 to 20 % efficiency
• Monocrystalline solar panels have black cells.
• They are the most expensive solar panels, as they are made from a single silicon crystal and a unique manufacturing process called the Czochralski process, which is very energy-intensive and costly.
• Monocrystalline solar panels are a good choice when limited space is available for installation and are looking to maximize electricity bill savings.

Image Courtesy: American Solar Energy Society

2. Polycrystalline Solar Panels

• A crystalline type of solar panel, made from different silicon crystals, instead of one crystal.
• Silicon crystals are melted and poured into a square mold to make polycrystalline cells.
• The production faces hardly any wastage and provides a characteristic square shape.
• They possess less efficiency compared to monocrystalline cells.
• They have low heat tolerance, hence less efficient in high-temperature environments.
• They are cheaper than monocrystalline solar panels.
• They give an efficiency between 15 to 17 percent.
• Polycrystalline solar cells tend to have a bluish hue due to the light reflecting off the silicon fragments in the cells. This is different in the way the light reflects from a monocrystalline silicon wafer.

3. Passivated Emitter and Rear Cell (PERC) Panels

• PERC is an improvement of monocrystalline cells. 
• A passivation layer is added to the rear surface of the cell that would enhance the efficiency of the monocrystalline cell panels.
• A PERC panel increases reflects back the light into the cell, which increases the amount of solar radiation that gets absorbed.
• The natural tendency of electrons to recombine and inhibit the flow of electrons in the system is reduced. 
• The passivation layer in the PERC panels, reflects a higher wavelength of light and stops the cell's metal back sheet from heating up ( Heating up of metal black sheet reduces the efficiency of solar panels).
• Slightly expensive than monocrystalline cells.

4. Thin-Film Solar Panels

Thin Film Solar Panels

• A very thin and low-profile solar panel technology.
• They are roughly 350 times thinner than crystalline wafers used in monocrystalline and polycrystalline solar panels.
• They are made from a variety of materials, commonly cadmium telluride (CdTe). A CdTe layer is placed between the transparent conducting layers that help to capture sunlight. A glass layer is placed on its top for protection.
• Other materials used for its manufacture are amorphous silicon (a-Si), and Copper Indium Gallium Selenide (CIGS).
• These come in blue and black hues.
• They have low efficiency and power capacity compared to the above panel types.
• Their efficiency is around 11 percent.
• Thin-film solar panels do not come in uniform sizes.
• The power capacity is highly dependent on the physical size of the thin-film panels.
• Cost less compared to other types and are less labor intensive.
• Applied for large commercial lightweight construction is required, RVs or boats (as portable solar systems).

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Solar Roof Tiles/ Solar Roof Shingles

Cool Roofs for Buildings | US EPA