Preparation for SSCE – SS3 Solar Photovoltaic Installation & Maintenance Lesson Note (Second Term)

SSCE questions on solar photovoltaic installation and maintenance cover panels, inverters, batteries, load calculation, IoT maintenance, environmental policy and safety.

Behavioural objectives

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

1. explain the photovoltaic effect and the job of an inverter;
2. compare monocrystalline and polycrystalline panels;
3. explain deep cycle, State of Charge (SoC) and Depth of Discharge (DoD);
4. calculate a load in watt-hours using Watts × Hours;
5. describe how IoT supports remote monitoring, fault detection and proactive maintenance;
6. state the environmental, policy and safety points that SSCE questions often ask about.

What is the photovoltaic (PV) effect?

The photovoltaic effect is the process by which a solar cell turns sunlight into direct current (DC) electricity.

How does a solar cell produce electricity?

1. Sunlight hits a silicon solar cell.
2. The light energy knocks electrons loose inside the silicon.
3. The loose electrons are made to flow in one direction.
4. This flow is DC (Direct Current) and leaves the panel through its wires.

What are the types of solar panel?

There are two common types of silicon solar panel: monocrystalline and polycrystalline.

• Monocrystalline panel: made from a single silicon crystal, dark black in colour.
• Polycrystalline panel: made from many silicon crystals, speckled blue in colour.

What are the main parts of a solar PV system?

A solar PV system is a set of parts that collect, control, store and convert solar energy for use.

• Solar panel: collects sunlight and produces DC electricity.
• Charge controller: controls the current going into the battery and protects it from overcharging.
• Battery bank: stores the energy for use at night or on cloudy days.
• Inverter: changes DC to AC for household appliances.
• Appliances (load): bulbs, fans and TVs that use the electricity.

What does an inverter do?

An inverter is a device that changes DC electricity from panels or batteries into AC electricity.

• Why it is needed: panels and batteries give DC, but TVs, fans and most household appliances work on AC.
• Simple way to remember: the inverter is a “translator” between the battery and the appliances.

How does the battery bank store energy?

A battery bank stores the DC energy from the panels so that it can be used when there is no sunlight.

What are the important battery terms?

• Deep cycle: a battery built to give steady power for many hours. A car battery gives a short, strong “kick” to start an engine.
• State of Charge (SoC): how full the battery is, as a percentage.
• Depth of Discharge (DoD): how much energy has been taken out of the battery, as a percentage.

How are SoC and DoD related?

• Formula: SoC = 100% − DoD.
• Example: if 80% of the energy is taken out (80% DoD), the battery is 20% full (20% SoC).

What is the difference between lithium and AGM/Gel batteries?

Lithium batteries are the modern choice, while AGM and Gel batteries are lead-acid types that need gentler use.

How do you calculate a load?

A load is the electrical energy that appliances use, and it is calculated in watt-hours (Wh).

• Formula: Watts × Hours = Watt-hours (Wh).
• Total power: add the watts of all the appliances.

Worked example

A student has 2 bulbs (20 W each) and uses them for 5 hours.

1. Total power = 2 × 20 W = 40 W.
2. Total energy = 40 W × 5 hours = 200 Wh.
3. Safety margin of 20% = 20/100 × 200 Wh = 40 Wh.
4. Energy to design for = 200 Wh + 40 Wh = 240 Wh.

Why add a safety margin?

• No shortfall: a system that gives only 150 Wh would let the lights go out before 5 hours are up.
• Less strain: a margin (usually 20%) stops the system from struggling.

How does IoT help with modern maintenance?

The Internet of Things (IoT) is a network of devices that connect to the internet to send and receive data, so a solar system can be checked from far away.

What should you explain in an essay?

• Remote monitoring: using an app to check the system from a distance. A technician does not have to travel just to read a battery level.
• Fault detection: the system sends an “error code” to a phone if a fuse blows or a panel is shaded.
• Proactive maintenance: early warnings let the technician fix a problem before it causes a breakdown.

Why do environmental impact and policy matter?

Solar power matters because it is a renewable, low-emission energy source that can reach places the main grid does not.

What are the key policy points?

• Renewable energy: sun and wind never run out.
• Non-renewable energy: petrol, diesel and coal will eventually finish.
• Climate change: burning fuel releases carbon dioxide, which traps heat around the Earth and adds to our “carbon footprint”.
• Solar and emissions: solar panels produce no emissions while in use.
• Rural electrification: the Rural Electrification Agency (REA) is the government agency that supports solar mini-grids for villages far from the main grid (formerly called NEPA or PHCN).

What safety points should you mention in the exam?

Safety in solar installation means protecting the worker and the equipment from electric shock, falls and damage.

• Rubber (insulated) gloves: protect the hands from electric shock.
• Multimeter: use it to test voltage before touching any wire.
• Dry weather: never work on a roof when it is raining, because surfaces are slippery.
• Switch off first: turn off breakers and isolate the battery before working on the system.
• Correct polarity: connect positive to positive and negative to negative.

Evaluation

1. Explain the photovoltaic effect.
2. State two differences between monocrystalline and polycrystalline panels.
3. A battery has an 80% Depth of Discharge. What is its State of Charge?
4. Explain the difference between reactive and proactive maintenance.
5. List three safety precautions to mention when answering a question on installation.

Assignment

Answer both parts.

1. A student uses 3 bulbs (10 W each) for 4 hours. Calculate the total power and the total energy needed in watt-hours.
2. In a short essay, explain how remote monitoring and fault detection help a technician maintain a solar system.