Lesson Notes By Weeks and Term v5 - Grade 9

Lesson Video

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Performance objectives

• Describe the main components of the electricity supply system.
• Explain how a coal-fired power station generates electricity.
• Discuss the pros and cons of different energy sources.
• Trace the path of electricity from a power station to a home.
• Identify the environmental impacts of generating electricity.

Lesson summary

South Africa relies heavily on electricity to power our homes, schools, businesses, and industries. Understanding where this electricity comes from, how it gets to us, and the challenges facing our national electricity supply system is crucial for every South African citizen. Electricity powers the lights that allow you to study at night, the refrigerator that keeps your food fresh, and the computers that connect you to the world. Our national electricity system, largely managed by Eskom, faces significant challenges like aging infrastructure, increasing demand, and environmental concerns.

Lesson notes

2.1 The National Electricity Supply System: An Overview The South African national electricity supply system is a complex network designed to generate, transmit, and distribute electricity to consumers across the country. It primarily consists of three major components: Electricity Generation: This involves converting energy from various sources (e.g., coal, uranium, sun, wind, water) into electrical energy. In South Africa, coal-fired power stations are the dominant source, followed by nuclear power (Koeberg) and a growing contribution from renewable energy sources like solar and wind.

Electricity Transmission: This is the process of transporting high-voltage electricity over long distances from power stations to substations. High-voltage transmission lines are used to minimize energy loss during transmission. These lines are usually supported by large pylons.

Electricity Distribution: This involves reducing the voltage of electricity at substations and distributing it to homes, businesses, and other consumers through a network of lower-voltage power lines. Transformers play a critical role in stepping down the voltage for safe usage. 2.2 Electricity Generation at a Coal-Fired Power Station Coal-fired power stations are the backbone of South Africa's electricity supply.

The process involves the following steps: Coal Combustion: Coal is burned in a large furnace to produce heat.

Water Heating: The heat is used to boil water, producing high-pressure steam.

Steam Turbine: The high-pressure steam is directed onto the blades of a turbine, causing it to rotate. The turbine is connected to a generator.

Electricity Generation: The rotating turbine spins the generator, which converts mechanical energy into electrical energy using electromagnetic induction. A generator consists of coils of wire rotating within a magnetic field.

Cooling: The steam exiting the turbine is cooled and condensed back into water, which is then recycled back to the boiler. Cooling towers are often used to dissipate the heat. This process requires a significant amount of water.

Emission Control: Exhaust gases from the furnace are treated to remove pollutants like sulfur dioxide and particulate matter before being released into the atmosphere. This is critical for environmental protection.