Task 19

Renewable sources

of energyGrade: 6

Presented By: Mrs N Chetty

Pitlochry Primary School Educator 1

Renewable sources of energy

We have learnt that fossil fuels are non-renewable resources of energy.

So, if we are using an energy resource which is non-renewable, then this will be

a problem in the future when these resources run out.

Are there other sources of energy?

Scientists and engineers are looking for ways to harness energy from

renewable resources.

A renewable resource is the opposite to a non-renewable resource. It will not

run out and can be used over. Renewable energy sources include natural

phenomena such as sunlight, wind, tides and plant growth. The energy comes

from natural processes that happen over and over.2

Wind

Examples of Renewable sources of energy are:

Silly

Boys

Go

Hunting

On

Weekends

Solar (energy from the sun)

Biomass (energy from plants and other organic material)

Geothermal (heat energy from below the surface of the earth)

Ocean (tides and waves)

Hydropower (waterfalls or fresh water dams)

3

Wind energy from moving air

Silly

Boys

Go

Hunting

On

Weekends

Solar energy from the sun

Biomass energy from plants and

other organic material

Geothermal heat energy from

below the surface of the earth

Ocean tides and waves

Hydropower waterfalls or fresh

water dams

Renewable sources of energy Anchor Chart

Solar energy is becoming more and more popular amongst regular homeowners. People are beginning to realize that they can save money on their monthly electricity bills by installing solar panels on their roof to capture the sun’s energy.

Solar energy can be converted into electricity in two different ways:One way is using photovoltaic cells. This is the most common way to produce electricity from the sun. There are solar energy plants that span for many acres with hundreds of photovoltaic panels containing many cells. Some common examples are the photovoltaic cells that you see on a calculator.

Solar thermal/electric power plants are the other way of producing electricity from the sun. These plants create electricity by concentrating the sun’s energy/heat to heat up a liquid to its boiling point where it eventually creates steam. The steam spins a turbine in a generator, which createselectricity in the traditional format.

Solar energy:

5

Biomass:

Items such as dead trees, branches, tree stumps, small plants that have died, leaves, grass clippings, wood chips, corn husks and other organic substances that can be burnt to generate heat, are examples of biomass. Biomass can be solids, liquids and gases.

Liquid biofuel can be made from crops such as maize and soybeans.These crops are fermented – the sugars turn into ethanol.Ethanol can be added to petrol and diesel

Methane is a biogas that can be used as a source of energy like natural gases.Humans constantly produce waste. The waste materialGive of biogas as it breaks down in specially designed landfills which collect the methane gas.

6

Geothermal:

Geothermal energy uses the heat from the Earth’s core as a means of generating electricity. Deep in the Earth’s crust the temperature is a constant 55° C. Geothermal power plants produce electricity.These plants use an intricate piping system to absorb the heat from the Earth’s core. This heat energy is used to heat liquids to produce steam which is used to spin the turbines in an electric generator.

7

Many early societies relied on the movement of water to help make their work easier.Wheat mills were often found near rivers because they used the moving water to spin a water wheel that helped drive machines that ground up grain. Rather than having a person grind the grain by hand, they harnessed the power of water.Although water wheels are still used in smaller rural societies, harnessing energy from water has evolved. We now use moving water in dams. The dam takes water flowing from the river and channels the falling water into canals that have turbines stationed at the bottom. The power of theheavy falling water spins the blades of turbines, which power generators that convert the mechanical energy into electrical energy. Some popular hydroelectric power plants around the world are Three Gorges Dam in China, Guri Dam in Venezuela and Grand Coulee Dam in the United States.

Hydropower:

8

Tidal current turbine – A tall turbine (much like a wind turbine) anchored to a base,

is placed on the sea floor. The tidal currents move the rotors, generating electricity.

When the tide goes out, the rotors reverse direction and continue to generate

electricity. Electricity is sent to the grid on shore via a cable.

Disadvantage: Devices of steel or structures of concrete must stand up to the

constant pounding of waves and the corrosion of salt water.

Ocean:

Wind:

Wind energy functions by harnessing the movement of the wind. The blades on the top of the tower catch the wind and spin. These blades are connected to a long shaft, which runs down the tower to a generator that converts the movement of the wind into electrical energy.One of the major problems with using wind as a main source of energy is that the wind does not always blow; for this reason we cannot rely on wind as an alternative energy source 100% of the time.

9

Activity :

1. Tabulate the advantages and disadvantages of the following sources of energy that are used to generate electricity:

Solar energy, Biomass, Hydropower, Wind power, Fossil fuels

10

It is important to save electricity as this reduces the amount of waste

produced when burning fossil fuels to generate electricity.

We can save electricity by:

• Turning off appliances when not in use.

• Using a solar water heater.

• Using a solar panel to power certain appliances.

• Use a gas stove.

• Use energy-saving light bulbs. These light bulbs use approximately 75% less

energy than regular tungsten bulbs.

Saving electricity

11

• A material that allows a path for an electric current to flow is called

an electrical conductor. Most metals are conductors of electricity.

Copper: Copper is the most common material used for wiring.

Silver : Is the best conductor but silver is expensive, so rarely used in wiring.

Gold: Doesn’t rust, is expensive and is only used when high-quality contacts

are needed.

Aluminium: Is not a very good conductor but is sometimes used when a light-

weight material is needed as it is not as heavy as copper wire.

REVISION: Electrical Conductors

• Some materials do not allow electricity to flow through them. These materials are

know as electrical insulators.

• Plastic, wood, glass and rubber are good electrical insulators. They are often

used to carry materials that carry electricity.

• Electrical insulators are used whenever there is a danger of someone getting an

electric shock from a conductor.

• Electricity can be very dangerous and people can die from touching a live wire.

Our bodies conduct electricity, so if we touch a live wire, the electricity will flow

through us. Insulators act as a shield for us when we work with electricity.

REVISION: Electrical Insulators

• Insulators are non-metals, for example; plastic, rubber, wood, ceramic

• Plastic as an insulator – Electric wires are always covered in plastic or other

insulators that doesn’t allow electricity to flow through them. We say that these

wires are insulated.

• Examples of insulated items:

Rubber gloves, plastic-coated pliers, plastic-coated adaptors, ceramic

insulators

KINETIC ENERGY ACRONYM

Sound Energy

Electrical Energy

Light Energy

Mechanical

Energy

Thermal Energy

ME

L

TS

All electrical systems have an input source, a device/load + process and an output

energy.

A system will not work without these stages:

Input source : Electrical energy

Device/Load : Lamp

Process : Electricity flows through filament causing it to glow.

Output energy : Light energy

Complete the systems diagram for the illustration below

A moving car

Input Device Process Output

Chemical

Energy

(Fuel)

Car

motor

Burning of fuel causes

the components of the

motor to move.

Mechanical

Energy

Complete the systems diagram for the illustration below

A toaster

Input Device Process Output

Electrical

Energy

(mains)

toasterElectricity flows into the

element causing it to

heat up.

Thermal

Energy

What are Fossil Fuels• Fossil fuels are non-renewable resources that formed more than 300 million years ago.

• They were made of plants and animals remains.

When the plants and animals died, their bodies were buried under layers of earth.

Over time, these layers built up and became very deep and they pushed down with a great

pressure on the layers below it.

• The remains of those plants and animals were exposed to great pressure and heat.

• Millions of years later, those animals and plants turned into three forms of fossil fuel: Coal, oil and natural gases.

Different types of fossil fuels were formed depending on different factors.

For example:

• whether it was the remains of plants or animals or a combination.• how long the remains of the organisms had been buried for. • the temperature and pressure conditions during the decay of the

organisms.

• Over millions of years of being under heat and pressure, the dead plants and animals changed into a thick liquid, called crude oil. Oil is a dark, thick liquid that can be used to make petrol to burn in vehicles, such as cars, buses and trucks.

• In deeper, hotter places tiny bubbles of natural gas formed. These were trapped under the rocks. Natural gas is colourless and it is used mostly in homes for heating and cooking food.

• Over time, some of the oil and natural gas began to work its way up through the rock and to the Earth's crust and into rock formations called "caprocks". Today, most of the oil and natural gas is collected from these caprocks by drilling down through the layers of rock.

• Oil and natural gas formed from organisms (plants and animals) that lived in the oceans

before there were dinosaurs.

• When these organisms died, they settled on the bottom of the river bed or ocean floor and

the layers built up under mud and sand (silt).

• The mud and sand slowly changed into rock and the rock and water pressure pushed down on

the remains of the dead plants and animals.

The formation of oil and natural gas

The formation of coal

• Coal is a black rock that can be burnt to produce energy in power stations all over the world.• Coal was formed from the dead remains of trees, ferns and some other plants that lived 300

to 400 million years ago. • Over time, the layer of dead plants at the bottom of swamps was covered with layers of

water and mud. The top layers squashed down on the dead plants. • Over millions of years the heat and pressure turned the plants into the coal that we mine

today.• The energy in coal originally comes from energy from the Sun.• Plants on Earth used the energy of the Sun for photosynthesis and to grow. This energy was

stored in the leaves, flowers and stems of the plants. • As the plants died the energy was trapped.

Fossil fuels and electricity

The main supplier of electricity in South Africa is ESKOM. ESKOM uses mainly coal to produce energy for industrial and household use.Let's look at a power station to find out how coal is used to produce electricity.

7. Step-up

transformer

1. Coal mine 2. Pulverizer

3. Incinerator

4. Boiler 5. Turbine

6. Generator

8. Step-down transformer

in a substation

1. Coal is transported

from a coal mine to a

power station.

2. At the power station,

the coal is ground into a

fine powder(pulverised)

3. The ground coal then goes

into a container(incinerator)

where it is burned.

4. The heat generated

from the burning coal is

used to boil water in a

huge boiler.

5. The boiling water

produces steam that

turns a turbine (a

turbine is a big wheel

with blades, which

turns).

6. The turbine is

linked to a generator

which uses a coil to

produce electrical

energy.

7. Electricity is

transferred to a

step-up transformer

to increase the

power of the

electricity allowing it

to travel long

distances.

8. The electric

current is

transported

("carried") by a

system of

electrical

transmission

lines (also called

power lines) to

step-down

transformers in

substations.

9. Electricity is carried to our homes

1. Coal mine 2. Pulverizer 3. Incinerator 4. Boiler

5. Turbine6. Generator7. Step-up

transformer

8. Step-down

transformer in a

substation

9. Home