Advanced PV Technologies – SS3 Solar Photovoltaic Installation & Maintenance Lesson Note (First Term)

Advanced PV technologies are methods of getting more electricity from solar panels of the same size. Bifacial panels collect sunlight on both the front and the back. Solar trackers are motorised mounts that turn panels to follow the sun. Both can raise output above that of a standard fixed panel, but they cost more.

Behavioural objectives

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

• explain how bifacial panels work;
• describe what a solar tracker does;
• compare both technologies with a standard fixed panel.

What are bifacial solar panels?

A normal solar panel only collects sunlight from the top. A bifacial panel collects from both the front and the back.

How do bifacial panels work?

The back gets light from reflections off nearby surfaces, such as white walls, concrete, sand or a light-coloured rooftop. The more reflective the surface underneath, the more energy the back captures. Scientists call this reflectivity albedo.

Bifacial panels typically produce 10% to 30% more electricity than regular panels of the same size.

Advantage and limitation of bifacial panels

• Advantage: more output without adding more panels.
• Limitation: they need open space and a reflective surface underneath. Mounting them flat on a dark rooftop wastes the rear side entirely.

What are solar trackers?

A standard panel stays in one fixed position all day. But the sun moves. It rises in the east, crosses the sky and sets in the west. When sunlight hits a panel at an angle instead of straight on, the panel produces less electricity.

A solar tracker is a motorised mount that rotates the panel to follow the sun throughout the day, like a sunflower turning toward light.

What are the types of solar tracker?

• Single-axis tracker: rotates east to west, following the sun’s daily movement. It produces about 15% to 25% more than a fixed panel.
• Dual-axis tracker: rotates east to west and also tilts up and down to follow seasonal changes in the sun’s height. It produces up to 40% more than a fixed panel, but costs significantly more.

How do fixed panels, bifacial panels and solar trackers compare?

Worked example

A school has 10 panels, each producing 300 W. They switch to bifacial panels that gain an extra 20% from reflected light. What is the new total output?

• Standard output = 10 × 300 = 3,000 W
• Extra from bifacial = 20% × 3,000 = 600 W
• New total = 3,000 + 600 = 3,600 W

Evaluation

1. Why would a bifacial panel not work well if mounted against a dark wall?
2. What is the main difference between a single-axis and a dual-axis tracker?
3. A 4 kW solar array gains 25% more output after installing a tracker. What is the new output?

Assignment

1. Explain what albedo is and why it matters for bifacial panels.
2. A school has 20 panels, each producing 250 W. They switch to bifacial panels that gain an extra 10% from reflected light. Calculate the new total output.