Energyresources
Where our energy comes from, how each power station turns a store of energy into electricity, and what every choice costs.
What we use energy resources for
An energy resource is a store of energy we can tap into. We use them for three big jobs: transport, generating electricity and heating.
Transport
Petrol, diesel and aviation fuel all come from oil. Some vehicles run on biofuels. Electric cars and trains use electricity, which could come from any resource.
Generating electricity
Every resource in this lesson can be used to generate electricity. Most do it by spinning a turbine that turns a generator.
Heating
Most homes burn natural gas in a boiler. Others use oil, coal, wood (a biofuel), electric heaters, solar water heating or geothermal hot water.
Renewable
A renewable energy resource is one that is being (or can be) replenished as it is used. It will not run out.
Non-renewable
A non-renewable energy resource is used up faster than it is replaced, so it will eventually run out. Fossil fuels took millions of years to form.
Burning fossil fuels to spin a turbine
Coal, oil and natural gas are fossil fuels. Each has a large chemical store of energy. A power station burns the fuel to boil water, and the steam does the rest.
Why we still use them
- Reliable: they generate whenever fuel is burned, whatever the weather.
- Output can be raised or lowered to match demand. Gas-fired stations start up quickly.
- They release a lot of energy from each kilogram of fuel.
The environmental cost
- Burning releases carbon dioxide, a greenhouse gas that contributes to global warming.
- Coal and oil release sulfur dioxide, which causes acid rain.
- Mining and drilling damage habitats, and oil spills harm sea life.
Non-renewable
Fossil fuels formed over millions of years from the remains of plants and animals. We are using them far faster than they form, so supplies will run out and prices will rise as they get harder to reach.
Nuclear power: the same turbine, a different source of heat
A nuclear power station has no furnace. Instead, nuclear fuel such as uranium or plutonium releases energy from its nuclear store inside a reactor. That energy boils water, and from there the station works exactly like a fossil fuel one.
Control rods absorb the neutrons that keep the reactions going. Lowering them slows the reactor. Lowering them fully shuts it down.
Good points
- No carbon dioxide or sulfur dioxide released while generating.
- A tiny mass of fuel releases a huge amount of energy.
- Reliable: steady output day and night, in any weather.
Drawbacks
- Produces radioactive waste that stays dangerous for thousands of years and must be stored securely.
- Very expensive to build, and to decommission (take apart safely) at the end of its life.
- Accidents are rare but can be very serious.
Non-renewable
Uranium is mined from the ground and there is a limited supply, so nuclear fuel is non-renewable, even though it releases no greenhouse gases in use.
Nuclear stations take a long time to start up and shut down, so they run constantly to supply the steady base of demand.
Hydroelectric power: water falling from a height
A dam holds water high up in a reservoir, where it has a large gravitational potential store. Let it fall and that store empties into the water's kinetic store, which spins a turbine. No fuel, no steam.
Good points
- Renewable: rain refills the reservoir.
- No fuel costs and no carbon dioxide while running.
- Reliable and fast: open the gates and it responds to a surge in demand within seconds.
Drawbacks
- Flooding a valley destroys habitats and can force people to move.
- Rotting plants under the new reservoir release methane, a greenhouse gas.
- Expensive to build, needs a mountainous site, and a long drought lowers the output.
Pumped storage
When demand is low, spare electricity can pump water back up to the reservoir. That stores energy in the gravitational potential store of the water, ready to release when demand peaks.
Tidal power: the rise and fall of the sea
Tides are caused by the gravitational pull of the Moon and the Sun. A tidal barrage is a dam across a river estuary. As the tide rises and falls, water is held at different levels on each side and then released through turbines.
Good points
- Renewable, with no fuel costs and no carbon dioxide while running.
- Very predictable: tides happen twice a day, whatever the weather.
- One barrage can generate a large amount of electricity.
Drawbacks
- Changes the estuary habitat for wading birds and fish, and blocks boats.
- Very few suitable sites, and very expensive to build.
- Generates in bursts, and the times shift each day, so they don't always match demand.
Wave power: the sea pushes air through a turbine
Waves are made by the wind blowing across the sea, so the water at the surface is always moving up and down. A wave power station on the shore uses that movement to pump air backwards and forwards through a turbine.
Good points
- Renewable, with no fuel costs.
- No carbon dioxide or other polluting gases while running.
- Useful for islands and coastal communities with rough seas.
Drawbacks
- Unreliable: waves depend on the wind, so a calm sea means no output.
- Each machine has a small output, so many are needed.
- They can spoil the view, be a hazard to boats, and be damaged by storms.
Tidal and wave are different
Tides come from the pull of the Moon and the Sun and are predictable. Waves come from the wind and are not. Don't mix them up when a question asks about reliability.
Wind power: a generator on a stick
Moving air has energy in its kinetic store. The wind pushes on the blades and turns them, and the blades turn a generator sitting in the housing at the top of the tower. There is no steam and no fuel.
Good points
- Renewable, with no fuel costs.
- No carbon dioxide or other polluting gases while running.
- Quick to build, and the land between turbines can still be farmed.
Drawbacks
- Unreliable: no output when the wind is too light, and turbines shut down in storms to avoid damage.
- Some people find them noisy or think they spoil the landscape.
- Each turbine has a small output, so you need hundreds to replace one power station.
Where they go
Turbines are put where it is windy: on hills, on the coast and out at sea. Offshore wind is steadier and stronger, but turbines at sea cost more to build and maintain.
Solar power: electricity straight from light
Solar cells transfer energy from sunlight directly into electricity. It is the only resource in this lesson that generates electricity with no turbine and no generator.
Good points
- Renewable, no fuel costs, no carbon dioxide while running.
- Silent, with no moving parts, so very little maintenance.
- Ideal for remote places and small devices: road signs, satellites, calculators.
Drawbacks
- Unreliable: nothing at night, less on cloudy days and in winter.
- Output peaks at midday, but demand peaks in the early evening.
- Large solar farms cover a lot of land, and panels take energy to manufacture.
Solar heating panels
A different kind of panel heats water directly. Water flows through black pipes on the roof. Black surfaces absorb radiation well, so the water warms up and is stored in a hot water tank. No electricity is generated at all.
Geothermal power: steam from hot rocks
In volcanic regions, hot rocks lie close to the surface. Radioactive substances decaying deep inside the Earth keep them hot. Pump cold water down, and steam comes back up to spin a turbine.
The rocks stay hot whatever the weather and whatever the time of day, so the output only depends on how much water is pumped through them.
Good points
- Renewable: the energy comes from inside the Earth and will not run out.
- Reliable: the rocks stay hot day and night, in any weather.
- Very little carbon dioxide, and the hot water can also heat homes directly.
Drawbacks
- Only works in a few places where hot rocks are near the surface, such as Iceland and New Zealand.
- Drilling several kilometres down is expensive.
- Small amounts of gases from underground can be released.
Spot the pattern
Hot rocks boil water, steam spins a turbine, and the turbine turns a generator. From the steam onwards it is the same as a fossil fuel or nuclear power station. Only the source of the heating is different.
Biofuels: fuel you can grow again
Biofuels are fuels made from recently living things: wood, crops such as sugar cane and oilseed rape, and animal waste. They are burned just like fossil fuels, in power stations, boilers and engines. The big difference is what happens to the carbon dioxide.
1. Growing takes carbon dioxide in
As the crop grows, it absorbs carbon dioxide from the air for photosynthesis. The carbon becomes part of the plant.
2. Burning gives it back
When the biofuel is burned, that carbon joins with oxygen again and carbon dioxide is released back into the air.
3. So the overall change is zero
The amount released by burning is the same as the amount absorbed while growing. Nothing extra has been added to the atmosphere. That is what carbon neutral means.
Good points
- Renewable: new crops can be grown in months.
- Reliable: the fuel can be stored and burned when needed.
- In theory carbon neutral: the plants absorbed as much carbon dioxide while growing as is released when they burn.
Drawbacks
- Needs large areas of land that could be used to grow food.
- Clearing forest to plant fuel crops destroys habitats and releases carbon dioxide.
- Expensive to refine into fuels suitable for vehicles.
Is it really carbon neutral?
Only if crops are regrown at the same rate as they are burned. Fertiliser, harvesting, processing and transport usually rely on fossil fuels, so in practice there is a net release of carbon dioxide.
Comparing resources side by side
No resource wins on everything. Questions usually ask you to weigh reliability, environmental impact and cost against each other for a particular situation.
Reliable
A reliable resource generates when we need it, not just when conditions are right. Fossil fuels, nuclear, biofuel, geothermal and hydroelectric are reliable. Tidal is predictable. Wind, solar and wave are not.
Environmental impact
Think beyond carbon dioxide. Include acid rain, radioactive waste, flooded valleys, damaged habitats, noise, visual impact and land use.
Cost
Separate the cost to build from the cost to run. Renewables usually cost a lot to set up but have no fuel bill. Fossil fuel stations are cheaper to build but the fuel must be paid for every day.
All eleven at a glance
Which resource fits?
How our use of energy resources is changing
For most of the last century, almost all of the UK's electricity came from burning fossil fuels. That has changed quickly, and the last coal-fired power station in the UK closed in 2024.
Rounded shares of the electricity supplied to the grid in each year. "Imports" is electricity bought from neighbouring countries through undersea cables.
Why the change?
Scientists have shown that burning fossil fuels is driving climate change, and that these fuels will run out. Governments have set targets to cut carbon dioxide emissions, and wind and solar have become much cheaper to build.
Electricity is only part of it
Most cars still burn petrol or diesel and most homes still burn gas for heating. Transport and heating are changing more slowly, through electric vehicles and heat pumps.
Why not switch overnight?
New power stations cost billions and take years to build. Wind and solar are unreliable, so they need backup or storage. People object to turbines or reactors near their homes, and jobs depend on existing industries.
Where the marks are won and lost
Practice questions
Write your answer first, then open the mark scheme and tick off each point you made.