Basics of Solar Energy – SS1 Solar Photovoltaic Installation & Maintenance Lesson Note (First Term)

Solar energy is energy that the sun sends to Earth as light and heat, called solar radiation.

• Source: the sun, which gives light and heat to Earth every day.
• Use in electricity: a solar panel turns sunlight into electricity through the photovoltaic (PV) effect.
• Key material: silicon, where sunlight knocks electrons loose so that they flow in one direction.

Behavioural objectives

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

1. define solar radiation;
2. distinguish between direct and diffuse radiation;
3. explain the photovoltaic (PV) effect in simple steps;
4. name the main parts of a basic solar PV system;
5. state the advantages of solar energy;
6. state the disadvantages of solar energy.

What is solar radiation?

Solar radiation is the energy the sun sends to Earth as light and heat.

• Everyday example: at 12:00 PM, the heat you feel on your skin outside is solar radiation.
• How it travels: it moves through space as light and heat.
• Simple picture: the sun is like a broadcasting station and the Earth is like a radio receiving the signal.

What are the two types of solar radiation?

There are two types of solar radiation: direct radiation and diffuse radiation.

Direct radiation

• Meaning: light that reaches you straight from the sun without being scattered.
• Feel: very strong and hot, as on a clear sunny day.

Diffuse radiation

• Meaning: light that reaches you after clouds, dust and air have scattered it.
• Feel: weaker and softer. On a cloudy day you can still see, but the light is not as “sharp” as direct sunlight.

What is the difference between direct and diffuse radiation?

How much solar radiation does Nigeria get?

Nigeria receives a high amount of solar radiation because it is near the equator.

• Solar irradiance: the power of sunlight falling on a surface, measured in watts per square metre (W/m²).
• Strong signal: the sun’s “signal” is strong in Nigeria almost all year round.
• Result: Nigeria is well suited to solar technology.

What is the photovoltaic (PV) effect?

The photovoltaic (PV) effect is the process by which light is turned into a flow of electrons (an electric current).

• Photo: means “light”.
• Voltaic: means “electricity” (voltage).
• Example of use: charging a phone from a solar panel.

How does the PV effect work?

A solar panel contains layers of a special material called silicon.

1. Sunlight hits the silicon, like a person throwing a ball at a pile of cans.
2. The “ball” (sunlight) hits the “cans” (electrons) and knocks them loose.
3. The panel is built with a set path, so the loose electrons must move in one direction.
4. This flow of moving electrons is electricity.

Shutterstock

What are the main parts of a basic solar PV system?

A basic solar PV system has five parts: the solar panel, charge controller, battery, inverter and load.

What are the advantages of solar energy?

Solar energy has five main advantages, which Nigerian shop owners often give as reasons for buying panels.

• Zero fuel cost: sunlight is free once the panel is bought. There is no queue at a filling station and no worry about the price of PMS or diesel.
• Silence: generators are loud and can cause headaches. Solar panels make no noise.
• Low maintenance: a generator has moving parts such as pistons, plugs and filters that wear out. A solar panel has no moving parts, so you only wipe off dust occasionally.
• Environmentally friendly: there is no smoke, no smell and no fuel emission while the panel is working.
• Renewable: the sun is a source of energy that does not get used up.

What are the disadvantages of solar energy?

Solar energy has four main disadvantages.

• The “night time” problem: panels make power only when the sun is out. For light at 9:00 PM, you need expensive batteries to store daytime power.
• High setup cost: sunlight is free, but panels, inverters and batteries cost a lot to buy at the start.
• Space requirements: big loads such as a pumping machine or deep freezer need many panels. A small roof may not have enough space.
• Weather dependency: on very rainy or dusty days (Harmattan), clouds and dust block sunlight, so panels produce much less power.

Evaluation

1. What is solar radiation?
2. State the difference between direct and diffuse radiation.
3. What do “photo” and “voltaic” mean in the term photovoltaic?
4. Describe how sunlight produces electricity in a solar panel.
5. Give two advantages and two disadvantages of solar energy.

Assignment

Imagine your family wants to switch from a generator to solar. Do the “audit” below.

1. List 3 things in your house that solar can easily power (for example, bulbs).
2. List 1 thing that might be too “heavy” for a basic solar setup (for example, an old air conditioner).
3. Explain why dust is a bigger problem for solar panels in Kano than in Lagos. (Hint: think about the Harmattan.)