1. P3 Sustainable Energy (OCR 21st Century) W Richards The Weald School
22/09/2018
P3 Sustainable Energy
(OCR 21st Century)
W Richards
The Weald School

2. P3.1 How much Energy do we use?
22/09/2018
P3.1 How much Energy do we use?

3. What issues will this rise in demand cause?
Energy Consumption
22/09/2018
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?

4. Fuels
22/09/2018
A “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.

5. Words – non-renewable, coal, fossil fuels, wood, renewed, secondary
Some definitions…
22/09/2018
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

6. Pollution
22/09/2018
When 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

7. This light bulb will transfer light and heat to the surroundings.
Using Electricity
22/09/2018
22/09/2018
Basically, electrical devices are used to transfer electrical energy to the environment: - +
This light bulb will transfer light and heat to the surroundings.

8. In other words, 1 Watt = 1 Joule per second
Energy and Power
22/09/2018
The POWER RATING of an appliance is simply how much energy it uses every second.
In other words, 1 Watt = 1 Joule per second E T P
E = Energy (in joules)
P = Power (in watts)
T = Time (in seconds)

9. Some example questions
22/09/2018
What is the power rating of a light bulb that transfers 120 joules of energy in 2 seconds?
What is the power of an electric fire that transfers 10,000J of energy in 5 seconds?
Rob runs up the stairs in 5 seconds. If he transfers 1,000,000J of energy in this time what is his power rating?
How much energy does a 150W light bulb transfer in a) one second, b) one minute?
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?
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
0.2MW
150J, 9KJ
120KJ
630MJ

10. Power
22/09/2018
22/09/2018
Power is “the rate of doing work”. The amount of power being used in an electrical circuit is given by: P I V
Power = voltage x current
in W in V in A
We can use this equation to analyse power stations:
A transformer gives out 10A at a voltage of 50V. What is its power output?
An electric fire has a power rating of 2KW. If it runs on a voltage of 230V what is the current?
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

11. The Cost of Electricity
22/09/2018
Electricity 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

12. The Cost of Electricity
22/09/2018
To 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…
A 2kW fire left on for 3 hours
A 0.2kW TV left on for 5 hours
A 0.1kW light bulb left on for 10 hours
A 0.5kW hoover left on for 1 hour
48p 8p 8p 4p

13. Reading Electricity Meters
22/09/2018
How many units of electricity have been used?
If 1 unit costs 10p how much has this electricity cost?
1 month later…

14. Gravitational potential
The 9 types of energy
22/09/2018
Type
3 example sources
Type
3 example sources
Heat
Kinetic (movement)
Nuclear
Sound
Light
Chemical
Electrical
Gravitational potential
Elastic potential

15. The Laws of Physics
22/09/2018
There 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

16. Electricity Light + heat
Energy changes
22/09/2018
To describe an energy change for a light bulb we need to do 3 steps:
1) Write down the starting energy:
3) Write down what energy types are given out:
2) Draw an arrow
Electricity Light + heat
What are the energy changes for the following…?
An electric fire
A rock about to drop
An arrow about to be fired

17. Conservation of Energy
22/09/2018
In any energy change there is ALWAYS some “waste” energy:
e.g. a light bulb:
Electricity Light heat
In this example HEAT is wasted and it is transferred to the surroundings, becoming very difficult to use.
Describe the following energy changes and state the “waste” energy or energies:
A vacuum cleaner
A TV
A dynamo/generator

18. Efficiency
22/09/2018
Efficiency 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:
Light (80J)
Electrical
Energy (200J)
Sound (40J)
Heat (?)
Efficiency = Useful energy out
Energy in
x100%

19. Some examples of efficiency…
22/09/2018
5000J of electrical energy are put into a motor. The motor converts this into 100J of movement energy. How efficient is it?
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?
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

20. Energy Transfer (“Sankey”) diagrams
22/09/2018
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:
“Input” energy
“Output” energy
20 J/s light energy
100 J/s electrical energy
80 J/s heat energy (given to the surroundings)

21. Example questions Consider a computer: Consider a kettle:
22/09/2018
Consider a computer:
150 J/s electrical energy
10 J/s wasted sound
20 J/s wasted heat
Useful light and sound
How much energy is converted into useful energy?
What is the computer’s efficiency?
Consider a kettle:
Work out each energy value.
What is the kettle’s efficiency?
Sound energy
Wasted heat
Heat to water
2000 J/s electrical energy

22. Reducing Energy Usage
22/09/2018
How can we reduce
energy usage?

23. P3.2 How can Electricity be Generated?
22/09/2018
P3.2 How can Electricity be Generated?

24. Generators (dynamos)
22/09/2018
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?

25. Using primary energy sources in power stations
22/09/2018
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 fuels
4) The output of the generator is connected to a transformer
5) The steam is cooled down in a cooling tower and reused

26. Efficiency of Power Stations
22/09/2018
Heat
Heat
Heat
15J
Boiler
Turbine
Generator
100J
50J 5J
85J
35J
30J
Heat
Kinetic
Electrical

27. Nuclear power stations
22/09/2018
These 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.

28. Radioactive Waste - Ionisation
22/09/2018
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.

29. Radioactive Contamination
22/09/2018
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:
Timeline of Events
Video of risks from polonium 210

30. Other ways of generating electricity
22/09/2018
Can we drive the turbine directly without burning any fossil fuels? Here are some examnples...

31. 22/09/2018
Wind Power

32. Wave Power
22/09/2018

33. Hydroelectric Power
22/09/2018

34. The National Grid
22/09/2018
Electricity reaches our homes from power stations through the National Grid:
Power station
Step up transformer
Step down transformer
Homes
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.

35. P3.3 Which Energy source should we use?
22/09/2018
P3.3 Which Energy source should we use?

36. Decommiss-ioning costs
Which power station?
22/09/2018
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
Gas
£800 million 6
30-40
Nuclear
£2 billion 3
£500 million
Which power station is the most expensive to build and why?
Give one advantage of coal power stations
Why is nuclear fuel cheaper than oil?
Overall, which power station is the most expensive?

37. Matching supply and demand…
22/09/2018
Hydroelectric power station might “kick in” here
“Baseline” power stations

38. Solar Panels and Thermal Towers
22/09/2018
What are the advantages and disadvantages of solar power?

39. Using Solar Energy in remote places
22/09/2018
Using Solar Energy in remote places

40. Words – steam, Iceland, volcanic, turbines, hot rocks
Geothermal Energy
22/09/2018
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

41. Non-renewable energy sources
22/09/2018
Advantages
Disadvantages
Cheap fuel costs
Costs a lot of money to decommission a nuclear plant
Good for “basic demand”
Coal, oil, gas and nuclear
Reliable
Fuel will run out
Short start-up time for gas and oil
Pollution – CO2 leads to global warming and SO2 leads to acid rain
Nuclear produces little pollution

42. Renewable energy sources summary
22/09/2018
Advantages
Disadvantages
Zero fuel costs
Unreliable (except for hydroelectric)
Don’t produce pollution
Wind, tidal, hydroelectric and solar
Expensive to build
Hydroelectric is good for a “sudden” demand
Tidal barrages destroy the habitats of wading birds and hydroelectric schemes involve flooding farmland
Solar is good for remote locations (e.g. satellites)

43. Electricity Supply in the UK
22/09/2018
Notice that, due to all these advantages and disadvantages, we use a variety of sources of energy in the UK: