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Unit P3: Sustainable Energy

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1 Unit P3: Sustainable Energy
Name: _______________ Class: _______________ Teacher: ______________

2 About energy… Energy is ___________ – it is not created or destroyed. It is simply ___________ between different forms. Often energy is transferred to the surroundings as heat, and is no longer in a useful form. We require energy for everything we do. All this energy must come from an energy _______ (e.g. oil, food, sunlight, wind…) A primary energy source is one that is found or occurs naturally e.g. coal. Electricity is a ___________ energy source because it must be generated using a primary source We have to pay for the energy we use. The price depends on how much fuel is used and the cost of _____________ energy. As we use more energy and fuels become scarce, we have to pay more. Fossil fuels (e.g. coal, ____, ____) are formed over millions of years from the decay of dead plants / animals. We are using them up much more quickly than they form. This is not sustainable and they will run out. Burning fossil fuels releases CO2 (which contributes to ________ change and global warming) and other pollutants. Biofuels are formed from recently _______ material (e.g. wood, sugar). They can be replaced quickly but still produce CO2 when burned. conserved distributing source transferred oil secondary gas living climate

3 How much energy do we use?
All domestic appliances use energy, the amount depends on the power rating and the time the appliance is on for. The power rating of an appliance relates to the current it takes from the supply Energy = power x time Power = voltage x current Units of energy are Joules (1 Watt for 1 second) but this is a very small amount. Examples: 1500W (1.5kW) fan heater for 3 hours = 1.5 x 3 = 4.5 kWh If electricity is 10p per kWh ‘unit’, this costs 4.5 x 10p = 45p The current drawn by the fan heater from the 230V mains is power ÷ voltage = 1500 ÷ 230 = 6.5A Q: How much energy is needed to light a 60W lamp for 20 seconds? We pay for electrical energy in larger ‘units’ of kilowatt-hours (kWh) Q: How much does it cost to roast a potato? (1 hour in a 3kW oven, electricity price 11p per unit) A household electricity meter measures the number of ‘units’ (kWh) used

4 Fill the blanks: India reducing efficient UK
Using less energy Fill the blanks: India reducing efficient UK Everything we do requires energy People in different countries use different amounts of energy This… Needs this energy Heating a bath 5 kWh Driving 16km ? Producing 1 pint milk Making a computer Country Energy per person per day USA 250 kWh _______? 110 kWh China 50 kWh 20 kWh Complete the table using 1800kWh, 10kWh, 0.8kWh We can use less energy by ____________the number of things we do or use, or by making things more ____________ The efficiency of a process is the useful output (energy or power) divided by total input (energy or power). Small number divided by bigger number. We can show where the energy is going using a sankey diagram – width of arrow shows the proportion of energy e.g. for a Light bulb If you don’t know the useful amount, you can find it from Draw a Sankey diagram for a motor which uses 120J and wastes 40J as heat. Waste (heat) 55J Useful (light) 5J Energy in (total) 60J Useful = total - waste How efficient is this motor?

5 Sources of energy What percentage of home energy use is ‘other’ (not electricity or gas)? We use different energy sources for different things. In the home we mostly use gas (69%) and electricity (22%) For transport we mostly use _______________ (97%) Industry uses Electricity, Gas and petroleum. Electricity is very useful because it is easy to distribute and can be used for many purposes Draw and label a pie chart showing home energy use Electricity is a secondary energy source, we have to generate it using a ________ source. Moving a magnet near a coil produces a voltage Generators work by electromagnetic induction. A magnet is moved (rotated) near a ______of wire to induce a _________. As the magnet is rotated one way and the other, the generator produces alternating current. (a battery produces direct current) primary voltage petroleum coil

6 Label the pipe which carries steam
Power Stations Power stations are where we generate electricity from primary energy sources. All the power stations are connected together to supply all our homes . Most of our electricity is generated by thermal power stations. These all work the same way: Heat boils water into ______, which drives a _________to turn the electrical ____________. The heat to boil the water may come from a variety of sources: burning fossil fuel (coal, oil, gas); heat from underground rocks (______________); burning wood (____________) biomass generator geothermal steam turbine Label the pipe which carries steam Thermal power stations are not very efficient. Gas is more efficient than coal (about 60% against 45%). Using more gas instead of coal means the UK has reduced the amount of CO2 released. Why is this important?

7 Nuclear power Nuclear power stations work the same way as other thermal power stations, with the heat (to make steam) coming from radioactive decay of __________ (fuel rods) in a nuclear ___________ Nuclear fuel produces about 8000 times the amount of energy as the same mass of coal, and produces less waste. Why are there two separate heating circuits? Nuclear power can help ________ our CO2 emissions, but some people are unhappy because of the potential risks. Radiation is invisible and can cause cancers. Label A,B,C The nuclear fuel does not produce CO2 so does not affect global warming. However it does produce _____________ waste. If you go near to a radioactive substance you may be _________, but you do not become radioactive and irradiation stops when you move away. Contact with a radioactive substance (e.g. inhaling, eating, drinking) causes _______________. This is worse because the radiation will affect you for longer. radioactive contamination reactor uranium reduce irradiated

8 Renewable energy sources
Renewable energy sources can be used without running out Solar power uses __________ (light/heat) from the sun. One way is to use thermal panels to heat water which then heats a house. Another way is to use _____________ panels to directly produce electricity. Hydroelectric power stations use the energy of water in a high ________. The water flows down, driving a turbine on its way out from the dam. The turbine drives a generator. Wind power uses the wind to turn a large __________(wind turbine) which drives a _________. The turbines can be on land or at sea Waves and tides : we can use the energy of _________ water to move specially designed turbines , which drive the generators. Biofuels (such as wood) can be burnt in the same way as ________fuels but are replaced more quickly generator radiation propeller fossil moving reservoir photovoltaic

9 Distributing electricity
All the power stations are connected together into the National Grid Electricity can easily be distributed using wires. However current in the wire causes heat which wastes e_______. To reduce the waste and improve e____________, step-up transformers are used – these change the electricity from a low voltage/high current to a high voltage/low current. Electricity is distributed at high voltage in wires supported by p_______. The current is low so there is less waste heat. How do transformers help improve efficiency of electricity distribution? The high voltage would be far too d__________ to use at home, so a step-down transformer reduces the voltage (and increases the current). Transformers can only work using alternating current, not direct current

10 Which energy source to use?
There are many different energy sources we can use. Or we can try to use less. There are advantages and disadvantages of each. There is no right answer, we must compromise Use the text book to write additional arguments for and against Arguments FOR  Arguments AGAINST  Nuclear Power They produce no CO2 while operating They produce radioactive waste Construction and decommissioning …… Building new reactors … Renewable energy sources Little CO2 or pollution released, even including construction Unreliable – wind doesn’t always blow, or the Sun shine Using less energy Even small energy savings can help Energy is essential to all we do. Reducing energy consumption would take our society backwards.

11 We use the letter I for current
You do the math… E P x t Power (Watts) = Energy transferred (J) / time taken (seconds) Energy (Joules) = Power (Watts) x time (seconds) kWh is used for energy in the home because a Joule is a very small unit Energy (kWh) = Power (kW) x time (h) Cost of energy (pence) = number of ‘units’ used x price per ‘unit’ (a ‘unit’ is 1 kWh) P V x I We use the letter I for current Power (W) = Voltage (V) x current (A) Efficiency = energy usefully transferred x 100% total energy supplied 16% Efficiency = useful power x 100% total power Quantity Units Energy E Joule (J) Kilowatt-hour (kWh) Power P Watt (W) Kilowatt (kW) Time t Seconds (s) Hour (h) Voltage V Volt (V) Current I Amp (A) Efficiency is always less than 100% Interpreting Pie Charts The size of each slice shows the proportion of the whole amount. You can estimate the size of an unlabelled slice by comparing to a labelled slice. E.g. The USA slice is about 4 times as big as the UK slice, so it is about 4 x 16% = 64% Useful facts Mains electricity in the home is 230V 1kWh (1 unit) is 1000W for 1 hour 1kWh = 3,600,000 J Electricity costs about 11p per kWh

12 Practice questions … List two primary and one secondary energy sources
Name two sources of energy which generate electricity without using steam What do we mean by a renewable energy source? What is the power rating of a toaster which uses a voltage of 230V and a current of 4A? Draw and label a block diagram of a thermal power station. What types of fuel could it use? Which uses less energy: a 2000W kettle used for 5 minutes to make tea, or a 10W phone charger left on for 24 hours

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