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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.

1. ___________________________________________________
2. ___________________________________________________
3. ___________________________________________________
4. ___________________________________________________
5. ___________________________________________________
6. ___________________________________________________
7. ___________________________________________________
8. ___________________________________________________

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

Coal is mined and transported
Coal is ground
Coal is burned
Water in pipes is heated to provide steam
Steam drives the turbines
Turbines turn the rotor of the generator
The rotor is an electromagnet that generates electricity
Electricity is carried away by means of copper wires

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.

Questions & Answers

what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
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Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
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Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
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what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
how to synthesize TiO2 nanoparticles by chemical methods
Zubear
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Jordan
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what chemical
Jordan
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Natural sciences grade 8. OpenStax CNX. Sep 12, 2009 Download for free at http://cnx.org/content/col11050/1.1
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