1.1 Present energy sources

Natural sciences

Grade 8

Energy: electricity, heat and light

Module 2

Present energy sources

• At present, most of our energy is derived from fossil sources (coal, oil, natural gas with secondary products e.g. liquid petroleum) and nuclear sources. Fossil sources are not renewable and are becoming fewer. Utilising them also causes pollution. Although we may find it difficult to imagine a world without electricity, this energy source is not available in many parts of South Africa and the African continent.
• In South Africa, energy is provided in different forms, the most important being electricity and liquid fuels (refined from crude oil and coal), coal and biomass (firewood).

The main sources of energy for generating electricity in South Africa are:

burning of coal;

hydroelectricity;

nuclear power.

Coal-burning and power stations

Activity:

To understand and evaluate coal burning as a a source of energy

[lo 2.3, lo 2.4]

At present, coal is the most generally used source of energy, to produce electricity, as South Africa has vast coal reserves. ESKOM coal power stations produce roughly 90% of the country's electricity. We have 18 of these large power stations.

Assignment 1:

Visit the Eskom website to find more information about this type of power generation.

What you mainly need is information on the basic operation of a typical power station.

What does the acronym ESKOM stand for?

To whom is the electricity supplied?

Assignment 2:

Complete the following table to represent the power-generating process by placing the different steps of this process in the correct order.

Turbine turns the rotors of the generator.

Coal is burnt.

Steam drives the turbines.

Electricity is carried away through copper wires.

Coal is ground finely.

Water in pipes is heated to provide steam.

The rotor is an electromagnet that generates electricity.

Coal is mined and transported.

Assignment 3:

Answer the following questions, making use of the information you have gained concerning the process.

1. What eventually happens to the steam that drives the turbines?

2. How much water is needed to operate this system for a day?

3. Name one place in South Africa where you can see high cooling towers.

4. Name any other waste that is formed during the generation of electricity.

5. Is burning coal for the generation of electricity regarded as “clean” with regard to nature?

Assessment of the steps that are followed in the process of generating electricity:

Were you able to place the steps in the correct order and answer the questions correctly?

[LO 2.3; LO 2.4]

Assessment

LO 2: Constructing Science Knowledge:

The learner will know and be able to interpret and apply scientific, technological and environmental knowledge.

This is evident when the learner:

• categorises information;
• interprets information;

2.4 applies knowledge.

Memorandum

PRESENT ENERGY SOURCES

• In South Africa the main sources of energy used to generate electricity are:

• Burning of coal
• Hydroelectricity
• Nuclear power

COAL-BURNING AND POWER STATIONS

Assignment 1

• At present, this is the most generally used source of energy, and therefore of electricity, as South Africa is blessed with vast coal reserves. The ESKOM coal power stations produce roughly 90% of the country's electricity. We have 18 of these large power stations.

ESKOM — ELECTRICITY SUPPLY COMMISSION

• This organisation provides 95% of South Africa and more than half of Africa with electricity.

In brief, a coal-firing power station operates as follows:

Assignment 2

Assignment 3:

The steam that turns the turbines has to escape somewhere - It has to be condensed through cooling, and this requires water!

Each power station requires approximately 150 million litres of water per day. Most of this is lost through evaporation!

Typical cooling towers can be seen along the N2 just outside Cape Town and elsewhere in South Africa.

Waste that is formed during the process comprises harmful gases like sulphur dioxide, carbon dioxide, and nitrogen dioxide – these can bind with moisture in the air and cause acid rain.

Burning coal to generate electricity cannot be seen as a "clean" method and is harmful to nature because of the resultant air pollution, acid rain and particles of ash pumped into the air.