3 Types of Solar Panels (Components of PV System I) – SS1 Solar Photovoltaic Installation & Maintenance Lesson Note (First Term)

Solar panels come in three main types: monocrystalline, polycrystalline and thin-film.

• Monocrystalline: black, the most efficient and the most expensive.
• Polycrystalline: speckled blue, cheaper and needs more space.
• Thin-film: lightweight and flexible, with the lowest efficiency.
• Panel sticker: the label on the back gives the ratings, such as Pmax, Voc and Isc.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Name the three main types of solar panels.
2. Identify each type by its appearance.
3. Compare the types by efficiency, space needed, heat performance and cost.
4. State what Pmax, Voc, Isc and efficiency percentage mean on a panel sticker.
5. Explain why the power a panel gives on a roof is often less than the rating on its sticker.

What are the three types of solar panels?

The three types of solar panels are monocrystalline, polycrystalline and thin-film, and they differ in how they are made and how they look.

• Monocrystalline: made from a single, pure crystal of silicon.
• Polycrystalline: made by melting many silicon fragments together.
• Thin-film: made by layering solar materials on a surface such as glass or metal.
• Main differences: some types are powerful but expensive, while others are cheaper but need more space.
• On Nigerian roofs: you will see panels that are dark black, panels that are blue, and thin sheets that look like plastic.

What are monocrystalline panels?

Monocrystalline panels are the “premium” type, made from one pure silicon crystal.

• Appearance: dark black, often with rounded (cut) corners.
• Efficiency: the highest, usually 18% to 22%, so they turn more sunlight into electricity than other types.
• Space: fewer panels are needed for the same power, so they suit small roofs.
• Heat performance: in Nigeria’s hot sun, they hold their power better than polycrystalline panels.
• Cost: the most expensive to buy.

What are polycrystalline panels?

Polycrystalline panels are the “budget-friendly” type, made from many silicon fragments melted together.

• Appearance: speckled blue with straight, square edges.
• Efficiency: slightly lower than monocrystalline, about 15% to 17%.
• Space: more panels are needed to give the same power as monocrystalline.
• Heat performance: they lose a little more power when the weather is extremely hot.
• Cost: much cheaper because they are easier to make.
• Common use: popular in Nigeria for people with a big roof but a smaller budget.

What are thin-film panels?

Thin-film panels are thin, light panels made by layering solar material on glass, metal or plastic.

• Appearance: a solid, dark sheet without the visible cell lines seen on the other two types.
• Efficiency: the lowest, usually 7% to 13%.
• Flexibility: lightweight and can be bent, so they can be fixed on curved surfaces or a backpack to charge a phone.
• Durability: they do not last as long as the “hard” crystalline panels.
• Light conditions: they work fairly well in low light or cloudy weather.
• Application: portable solar chargers, and large solar farms where space is not a problem.

How do the three types of solar panels compare?

The table below compares the three types using the points explained above.

What do the ratings on a solar panel sticker mean?

The ratings are the numbers on the sticker at the back of a panel, which tell you what the panel can do under test conditions.

• Pmax (Maximum Power): the “wattage” of the panel (for example 250 W or 400 W), the most power it can produce under test conditions.
• Voc (Open Circuit Voltage): the voltage, or electrical “pressure”, the panel shows when it is not connected to anything. It is measured in volts (V).
• Isc (Short Circuit Current): the maximum current, or “flow” of electricity, the panel can give. It is measured in amperes (A).
• Efficiency percentage: the share of the sun’s energy hitting the panel that is turned into electricity.

What does efficiency percentage mean?

Efficiency is the percentage of sunlight energy that a panel changes into electrical energy.

• Example: a 20% efficient panel turns 20 out of every 100 units of sunlight energy into electricity.
• Higher efficiency: more power from the same panel area.
• Lower efficiency: more panel area is needed for the same power.

Why is real-life power lower than the sticker rating?

Real-life power is lower because the sticker rating is measured in a laboratory under ideal conditions, which a roof rarely has.

• Test conditions: panels are rated at a cell temperature of 25°C with very strong, direct sunlight.
• Heat: in places like Maiduguri or Lagos, a panel on a roof can become much hotter than 25°C, and its output drops as it heats up.
• Time of day: sunlight is weaker in the early morning and late afternoon, for example at 4:00 PM.
• Cloud cover: clouds reduce the sunlight reaching the panel.
• Dust: dust, especially in the Harmattan, blocks sunlight from the cells.
• Shade: shadows from trees or buildings cut the output.

Evaluation

1. Why would a family living in a small flat in Lagos prefer monocrystalline over polycrystalline panels?
2. If a panel is labelled 300W, will it give exactly 300W at 4:00 PM in the evening? Why?
3. Which panel type looks blue and is made of many crystals?
4. State what Voc and Isc mean on a panel sticker.

Assignment

Draw a table comparing the three types of solar panels under these headings: appearance, efficiency, space needed, heat performance and cost. Then explain in two or three sentences why a panel on a roof in Maiduguri often gives less power than the Pmax on its sticker.