Unit P3:Sustainable Energy

Name: _______________Class: _______________Teacher: ______________

About energy…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.

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.

conserved distributing source transferred oil secondary gas living climate

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.

Units of energy are Joules (1 Watt for 1 second) but this is a very small amount.

We pay for electrical energy in larger ‘units’ of kilowatt-hours (kWh)

The power rating of an appliance relates to the current it takes from the supply

A household electricity meter measures the number of ‘units’ (kWh) used

Examples:1500W (1.5kW) fan heater for 3 hours= 1.5 x 3 = 4.5 kWhIf 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

Power = voltage x currentEnergy = power x time

Q: How much energy is needed to light a 60W lamp for 20 seconds?

Q: How much does it cost to roast a potato? (1 hour in a 3kW oven, electricity price 11p per unit)

Using less energyEverything we do requires energy

This… Needs this energy

Heating a bath 5 kWh

Driving 16km ?

Producing 1 pint milk ?

Making a computer ?

We can use less energy by ____________the number of things we do or use, or by making things more ____________We can show where the energy is going using a sankey diagram – width of arrow shows the proportion of energye.g. for aLight bulb

Country Energy per person per day

USA 250 kWh

_______? 110 kWh

China 50 kWh

_______? 20 kWh

People in different countries use different amounts of energy

Waste(heat)

55J

Useful(light) 5J

Energy in(total) 60J

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.

Useful = total - waste

If you don’t know the useful amount, you can find it from

Complete the table using 1800kWh, 10kWh, 0.8kWh

Draw a Sankey diagram for a motor which uses 120J and wastes 40J as heat.

How efficient is this motor?

Fill the blanks: India reducing efficient UK

What percentage of home energy use is ‘other’ (not electricity or gas)?

Sources of energyWe 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

Electricity is a secondary energy source, we have to generate it using a ________ source.

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)

Draw and label a pie chart showing home energy use

primary voltage petroleum coil

Moving a magnet near a coil produces a voltage

Power StationsPower 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 (____________)

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?

biomass generator geothermal steam turbine

Label the pipe which carries

steam

Nuclear powerNuclear 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 ___________

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.

Nuclear fuel produces about 8000 times the amount of energy as the same mass of coal, and produces less waste.

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

radioactive contamination reactor uranium reduce irradiated

Why are there two separate heating circuits?

Renewable energy sources

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

Renewable energy sources can be used without running out

generator radiation propeller fossil moving reservoir photovoltaic

Distributing electricity

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.

All the power stations are connected together into the National Grid

Electricity is distributed at high voltage in wires supported by p_______. The current is low so there is less waste heat.

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

How do transformers help improve efficiency of electricity distribution?

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

Arguments FOR Arguments AGAINST

Nuclear Power

• They produce no CO2 while operating•

•

• They produce radioactive waste• Construction and decommissioning ……

• Building new reactors …

Renewable energysources

• 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.•

Use the text book to write additional arguments for and against

We use the letter I for

current

You do the math…

Energy (Joules) = Power (Watts) x time (seconds)

Energy (kWh) = Power (kW) x time (h)

Cost of energy (pence) = number of ‘units’ used x price per ‘unit’(a ‘unit’ is 1 kWh)

Power (W) = Voltage (V) x current (A)

Power (Watts) = Energy transferred (J) / time taken (seconds) E

P x t

P

V x IEfficiency = energy usefully transferred x 100% total energy supplied

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

kWh is used for energy in the home because a Joule is a very small unit

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)

Interpreting Pie ChartsThe 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%

16%Efficiency = useful power x 100% total power

Efficiency is always less than 100%

Practice questions …1. List two primary and one secondary energy sources

2. Name two sources of energy which generate electricity without using steam

3. What do we mean by a renewable energy source?

4. What is the power rating of a toaster which uses a voltage of 230V and a current of 4A?

5. Draw and label a block diagram of a thermal power station. What types of fuel could it use?

6. Which uses less energy: a 2000W kettle used for 5 minutes to make tea, or a 10W phone charger left on for 24 hours