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P3 Sustainable EnergyP3 Sustainable Energy

M Barker

Shirebrook Academy

(OCR 21st Century)

19/04/23P3.1 How much Energy do we P3.1 How much Energy do we use?use?

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Energy ConsumptionEnergy Consumption

The demand for energy is predicted to rise by a large amount in the next few decades:

What issues will this rise in demand cause?

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FuelsFuelsA “fuel” is something that can be burned to release heat and light energy. The main examples are:

Coal, oil and gas are called “fossil fuels”. In other words, they were made from fossils.

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Some definitions…Some definitions…A renewable energy source is clearly one that can be _______ (“renew = make again”), e.g. _____, solar power, biogas etc.

A ___________ energy source is one that when it has been used it is gone forever. The main examples are ____, oil and gas (which are called ______ ____, as they are made from fossils), and nuclear fuel, which is non-renewable but NOT a fossil fuel.

Electricity is called a “________ source” because it is converted from other forms – what would these forms be in batteries, wind turbines and solar panels?

Words – non-renewable, coal, fossil fuels, wood, renewed, secondary

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PollutionPollutionWhen a fuel is burned the two main waste products are _____ dioxide and ________ dioxide.

Carbon dioxide is a _________ ___ and helps cause _______ _________. This is produced when any fossil fuels are burned.

Sulphur dioxide, when dissolved in ________, causes ______ _____. This is mainly a problem for ___ power stations.

Nuclear power stations do not produce these pollutants because they don’t ____ fossil fuels.

Words – sulphur, coal, global warming, carbon, acid rain, greenhouse gas,

rainwater, burn

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Using ElectricityUsing ElectricityBasically, electrical devices are used to transfer electrical energy to the environment:

-+

This light bulb will transfer light and heat to the

surroundings.

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Energy and PowerEnergy and PowerThe POWER RATING of an appliance is simply how much energy it uses every second.

In other words, 1 Watt = 1 Joule per second

E

TP

E = Energy (in joules)

P = Power (in watts)

T = Time (in seconds)

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Some example questionsSome example questions1) What is the power rating of a light bulb that transfers

120 joules of energy in 2 seconds?

2) What is the power of an electric fire that transfers 10,000J of energy in 5 seconds?

3) Rob runs up the stairs in 5 seconds. If he transfers 1,000,000J of energy in this time what is his power rating?

4) How much energy does a 150W light bulb transfer in a) one second, b) one minute?

5) Jonny’s brain needs energy supplied to it at a rate of 40W. How much energy does it need during a 50 minute physics lesson?

6) Lloyd’s brain, being more intelligent, only needs energy at a rate of about 20W. How much energy would his brain use in a normal day?

60W

2KW

150J, 9KJ

120KJ

630MJ

0.2MW

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PowerPowerPower is “the rate of doing work”. The amount of power being used in an electrical circuit is given by:

P

IVPower = voltage x current

in W in V in A

We can use this equation to analyse power stations:

1) A transformer gives out 10A at a voltage of 50V. What is its power output?

2) An electric fire has a power rating of 2KW. If it runs on a voltage of 230V what is the current?

3) Electricity is transmitted along some lines in the National Grid at 400KV. If the current is 1KA what would be the power through the wire?

500W

8.7A

400MW

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The Cost of ElectricityThe Cost of ElectricityElectricity is measured in units called “kilowatt hours” (kWh). The kilowatt hour is a unit of energy but the Joule is too small to count so we use the KWh instead. For example…A 3kW fire left on for 1 hour uses 3kWh of energy

A 1kW toaster left on for 2 hours uses 2kWh

A 0.5kW hoover left on for 4 hours uses __kWh

A 200W TV left on for 5 hours uses __kWh

A 2kW kettle left on for 15 minutes uses __kWh

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The Cost of ElectricityThe Cost of ElectricityTo work out how much a device costs we do the following:

Cost of electricity = Power (kW) x time (h) x cost per kWh (p)

For example, if electricity costs 8p per unit calculate the cost of the following…

1) A 2kW fire left on for 3 hours

2) A 0.2kW TV left on for 5 hours

3) A 0.1kW light bulb left on for 10 hours

4) A 0.5kW hoover left on for 1 hour

48p

8p

8p

4p

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Reading Electricity MetersReading Electricity Meters

1) How many units of electricity have been used?

2) If 1 unit costs 10p how much has this electricity cost?

1 month later…

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The 9 types of energyThe 9 types of energy

Type 3 example sources

Heat

Kinetic (movement)

Nuclear

Sound

Light

Chemical

Electrical

Gravitational potential

Elastic potential

Type 3 example sources

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The Laws of PhysicsThe Laws of PhysicsThere are many laws of physics, but one of the most important ones is:

Energy cannot be created or destroyed, it can only be

converted from one form to another

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Energy changesEnergy changesTo describe an energy change for a light bulb we need to do 3 steps:

Electricity Light + heat

1) Write down the starting energy:

3) Write down what energy types are given out:

2) Draw an arrow

What are the energy changes for the following…?

1) An electric fire

2) A rock about to drop

3) An arrow about to be fired

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Conservation of EnergyConservation of EnergyIn any energy change there is ALWAYS some “waste” energy:

e.g. a light bulb:

In this example HEAT is wasted and it is transferred to the surroundings, becoming very difficult to use.

Electricity Light + heat

Describe the following energy changes and state the “waste” energy or energies:

1) A vacuum cleaner

2) A TV

3) A dynamo/generator

19/04/23EfficiencyEfficiencyEfficiency is a measure of how much USEFUL energy you get out of an object from the energy you put INTO it.For example, consider a TV:

Electrical Energy (200J)

Light (80J)

Sound (40J)

Heat (?)

Efficiency = Useful energy out

Energy in

x100%

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Some examples of efficiency…Some examples of efficiency…

1) 5000J of electrical energy are put into a motor. The motor converts this into 100J of movement energy. How efficient is it?

2) A laptop can convert 400J of electrical energy into 240J of light and sound. What is its efficiency? Where does the rest of the energy go?

3) A steam engine is 50% efficient. If it delivers 20,000J of movement energy how much chemical energy was put into it?

0.2 or 20%

0.6 or 60%

40KJ

19/04/23Energy Transfer (“Sankey”) Energy Transfer (“Sankey”) diagramsdiagrams

Consider a light bulb. Let’s say that the bulb runs on 100 watts (100 joules per second) and transfers 20 joules per second into light and the rest into heat. Draw this as a diagram:

100 J/s electrical energy

“Input” energy “Output” energy

80 J/s heat energy (given to

the surroundings)

20 J/s light energy

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Example questionsExample questionsConsider a kettle:

1) Work out each energy value.

2) What is the kettle’s efficiency?

Sound energy

Wasted heat

Heat to water

2000 J/s electrical energy

Consider a computer:

150 J/s electrical energy

10 J/s wasted sound

20 J/s wasted heat

Useful light and sound

1) How much energy is converted into useful energy?

2) What is the computer’s efficiency?

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Reducing Energy UsageReducing Energy Usage

How can we reduceenergy usage?

19/04/23P3.2 How can Electricity be P3.2 How can Electricity be Generated?Generated?

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Generators (dynamos)Generators (dynamos)Electricity is convenient because it can be transmitted over long distances and can be used in many ways. But how is it generated? We need to use a “generator”:

Basically, a generator works by spinning a magnet near a coil of wire. That’s useful, but how do we get this magnet to keep spinning?

19/04/23Using primary energy sources in power Using primary energy sources in power stationsstations

1) A fuel is burned in the boiler

2) Water turns to steam and the steam drives a turbine

3) The turbine turns a generator – if you want more electricity you have to burn more fossil fuels4) The output of the generator is connected to a transformer

5) The steam is cooled down in a cooling tower and reused

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Efficiency of Power StationsEfficiency of Power Stations

100J Boiler 85J Turbine35J

Generator30J

15J 50J 5J

Heat

Heat Kinetic

Heat Heat

Electrical

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Nuclear power stationsNuclear power stationsThese work in a similar way to normal power stations:

The main difference is that the nuclear fuel is NOT burnt. This means that they produce less pollution but they do produce radioactive waste

instead.

19/04/23Radioactive Waste - Radioactive Waste - IonisationIonisation

Radiation is dangerous because it “ionises” atoms – in other words, it turns them into ions by “knocking off” electrons:

Alpha radiation is the most ionising (basically, because it’s the biggest). Ionisation causes cells in living tissue to mutate, usually causing cancer.

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Radioactive ContaminationRadioactive Contamination

Timeline of Events

Video of risks from polonium 210

Simply being “irradiated” by a radioactive material doesn’t have to be dangerous – for example, we have background radiation around us all the time. However, being “contaminated” is far more dangerous. Consider the example of Alexander Litvinenko who was poisoned with polonium-210:

19/04/23Other ways of generating Other ways of generating electricityelectricity

Can we drive the turbine directly without burning any fossil fuels?

Here are some examnples...

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Wind PowerWind Power

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Wave PowerWave Power

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Hydroelectric PowerHydroelectric Power

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The National GridThe National GridElectricity reaches our homes from power stations through the National Grid:

If electricity companies transmitted electricity at 230 volts through overhead power lines there would be too much energy loss by the time electricity reaches our homes. To ensure this doesn’t happen, electricity companies transmit electricity at higher voltages instead.

Power stationStep up

transformerStep down

transformerHomes

19/04/23P3.3 Which Energy source should we P3.3 Which Energy source should we use?use?

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Which power station?Which power station?Type of power station

Commiss-ioning costs

Running costs

(p per KWh)

Decommiss-ioning costs

Life span (years)

Coal £650 million 4 £100 million 40-80

Oil £700 million 12 £100 million 40-80

Gas £800 million 6 £100 million 30-40

Nuclear £2 billion 3 £500 million 30-40

1) Which power station is the most expensive to build and why?

2) Give one advantage of coal power stations

3) Why is nuclear fuel cheaper than oil?

4) Overall, which power station is the most expensive?

19/04/23Matching supply and Matching supply and demand…demand…

“Baseline” power stations

Hydroelectric power station might “kick in” here

19/04/23Solar Panels and Thermal Solar Panels and Thermal TowersTowers

What are the advantages and

disadvantages of solar power?

19/04/23Using Solar Energy in remote Using Solar Energy in remote placesplaces

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Geothermal EnergyGeothermal Energy

Geothermal energy can be used in _______ areas such as ______. In a geothermal source cold water is pumped down towards ____ _____. The water turns to steam and the steam can be used to turn ______. In some areas the _____ rising at the surface can be captured and used directly.

Words – steam, Iceland, volcanic, turbines, hot rocks

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Non-renewable energy sourcesNon-renewable energy sources

Coal, oil, gas and nuclear

Advantages Disadvantages

Cheap fuel costs

Short start-up time for gas and oil

Good for “basic demand”

Fuel will run out

Costs a lot of money to

decommission a nuclear plant

Pollution – CO2 leads to global warming and SO2 leads to acid rain

Reliable

Nuclear produces little pollution

19/04/23Renewable energy sources Renewable energy sources summarysummary

Wind, tidal, hydroelectric and solar

Advantages Disadvantages

Zero fuel costs

Hydroelectric is good for a

“sudden” demand

Don’t produce pollution

Tidal barrages destroy the habitats of wading birds and hydroelectric

schemes involve flooding farmland

Unreliable (except for

hydroelectric)

Expensive to build

Solar is good for remote locations (e.g. satellites)

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Electricity Supply in the UKElectricity Supply in the UKNotice that, due to all these advantages and disadvantages, we use a variety of sources of energy in the UK: