What you'll learn
This topic examines the energy resources used to generate electricity and power transport worldwide. You'll explore renewable and non-renewable energy sources, their advantages and disadvantages, and their environmental impacts. Understanding the UK's energy mix and global trends in energy use is essential for both exam success and informed citizenship.
Key terms and definitions
Renewable energy resource — an energy source that is naturally replenished at a rate equal to or faster than it is being used, so it will not run out
Non-renewable energy resource — a finite energy source that is being used up faster than it is being formed, meaning it will eventually run out
Fossil fuels — coal, oil and natural gas formed from the remains of dead organisms over millions of years; these are non-renewable and release carbon dioxide when burned
Carbon neutral — a fuel or process where the carbon dioxide released when it burns equals the carbon dioxide absorbed when it was formed, resulting in no net increase in atmospheric CO₂
Nuclear fission — the splitting of large atomic nuclei (such as uranium-235) to release energy, used in nuclear power stations
Biofuel — fuel produced from living or recently dead biological material, such as wood, ethanol from crops, or biogas from waste
Reliability — the ability of an energy resource to provide a consistent and predictable supply of energy when needed
Start-up time — the time taken for a power station to increase its electricity output from zero to full capacity
Core concepts
Non-renewable energy resources
Non-renewable energy resources will eventually run out because they are being consumed faster than they are being formed.
Fossil fuels (coal, oil, natural gas)
These formed from organic matter subjected to heat and pressure over millions of years. When burned, they release energy stored as chemical energy.
Advantages:
- Reliable — can generate electricity continuously regardless of weather
- High energy density — relatively small amounts release large quantities of energy
- Existing infrastructure — power stations and distribution networks already established
- Short start-up time (particularly for gas power stations)
Disadvantages:
- Release carbon dioxide, contributing to climate change and global warming
- Release sulfur dioxide and nitrogen oxides, causing acid rain
- Non-renewable — finite supplies that will be depleted
- Extraction damages habitats through mining and drilling
- Oil spills can devastate marine ecosystems
Nuclear fuel
Nuclear power stations use nuclear fission of uranium-235 or plutonium-239. The nucleus splits, releasing energy as heat, which produces steam to drive turbines.
Advantages:
- No greenhouse gases produced during operation
- Very high energy density — small amounts of fuel produce enormous energy
- Reliable baseload power
- Relatively low fuel costs once operational
Disadvantages:
- Produces radioactive waste that remains hazardous for thousands of years
- High initial construction and decommissioning costs
- Risk of catastrophic accidents (though very low probability)
- Long start-up time
- Non-renewable — uranium supplies are finite
- Concerns about nuclear proliferation
Renewable energy resources
Renewable resources are naturally replenished and will not run out with continued use.
Wind power
Wind turbines convert the kinetic energy of moving air into electrical energy. Blades turn a generator when wind passes over them.
Advantages:
- No fuel costs
- No polluting gases produced during operation
- Can be located offshore where winds are stronger and more consistent
Disadvantages:
- Unreliable — depends on wind speed (no wind means no electricity)
- Visual and noise pollution concerns
- Can harm birds and bats
- Requires many turbines to match output of conventional power stations
Solar power
Solar cells (photovoltaic cells) convert light energy directly into electrical energy. Solar heating panels use the Sun's energy to heat water directly.
Advantages:
- No fuel costs or polluting emissions during operation
- Useful in remote locations
- Low maintenance requirements
Disadvantages:
- Unreliable — depends on sunlight (limited at night and in cloudy conditions)
- High initial costs
- Requires large surface areas for significant power output
- Manufacturing solar panels involves some toxic chemicals
Hydroelectricity
Water stored in elevated reservoirs flows downhill, turning turbines. The gravitational potential energy of water converts to kinetic energy, then electrical energy.
Advantages:
- Reliable — water flow can be controlled
- No fuel costs
- Very fast start-up time (can respond quickly to demand)
- No polluting gases during operation
- Reservoirs can provide water storage and recreation
Disadvantages:
- Requires suitable geography (mountains and high rainfall)
- Flooding valleys destroys habitats and displaces communities
- High initial construction costs
- Can disrupt fish migration
- Limited suitable sites in the UK
Tidal power
Tidal barrages trap water at high tide, then release it through turbines at low tide. The gravitational pull of the Moon causes predictable tidal movements.
Advantages:
- Predictable and reliable tides
- No fuel costs
- No polluting emissions during operation
Disadvantages:
- Very high construction costs
- Limited number of suitable estuaries
- Disrupts ecosystems and shipping
- Only generates electricity when tide is flowing in or out (not continuously)
Wave power
Waves drive floating generators or cause water to flow through turbines.
Advantages:
- No fuel costs
- No polluting emissions during operation
Disadvantages:
- Technology still being developed
- Unreliable — wave height varies
- Must withstand storms and saltwater corrosion
- Limited suitable coastal locations
Geothermal energy
Hot rocks deep underground heat water pumped down to them, producing steam to drive turbines. Available in volcanically active regions or by drilling deep wells.
Advantages:
- Reliable constant heat source
- No fuel costs
- Minimal environmental impact once operational
Disadvantages:
- Only economically viable in specific geological locations (Iceland, New Zealand)
- High drilling costs
- Limited sites in the UK
- Can release some greenhouse gases from underground
Biofuels
Biomass (wood, crops, waste) burns to release stored chemical energy, or produces biogas through anaerobic digestion.
Advantages:
- Can be carbon neutral if replanted at rate of consumption
- Uses waste materials
- Can provide reliable power (unlike wind/solar)
Disadvantages:
- Still releases carbon dioxide when burned (only carbon neutral if sustainably managed)
- Requires land that could grow food crops
- Transporting and processing biofuels requires energy
- Burning wood releases particulates (air pollution)
Environmental and ethical considerations
Climate change
Burning fossil fuels releases carbon dioxide, a greenhouse gas that traps heat in the atmosphere. This causes:
- Global temperature increases
- Melting ice caps and rising sea levels
- More extreme weather events
- Ecosystem disruption
Acid rain
Sulfur dioxide and nitrogen oxides from fossil fuel combustion dissolve in rainwater, forming acid rain that:
- Damages buildings and statues
- Harms aquatic life in lakes and rivers
- Damages forests and crops
Comparing environmental impacts
All energy resources have environmental costs:
- Manufacturing solar panels and wind turbines requires energy and materials
- Hydroelectric dams flood habitats
- Nuclear waste remains radioactive for millennia
- Even "clean" technologies have impacts during construction and decommissioning
UK and global energy trends
Current UK energy mix
The UK generates electricity from:
- Natural gas (largest single source)
- Wind power (rapidly increasing)
- Nuclear power
- Biomass
- Coal (being phased out)
- Solar, hydroelectric and other sources (smaller contributions)
The proportion from renewables has increased significantly since 2010 as the UK aims for net-zero carbon emissions by 2050.
Energy use patterns
Electricity demand varies:
- Daily — peaks during morning and evening, lower overnight
- Seasonally — higher in winter for heating and lighting
- Weather-dependent — heating/cooling needs change
Power stations must match supply to demand continuously. Baseload power (nuclear, fossil fuels) runs constantly, while others respond to peaks.
Global considerations
- Developing nations often rely heavily on fossil fuels due to lower initial costs
- Access to renewable energy varies by geography (solar near equator, hydroelectric in mountainous regions)
- International cooperation needed to address climate change
- Energy security concerns drive diversification of energy sources
Worked examples
Example 1: Comparing energy resources
Question: A country wants to reduce carbon dioxide emissions from electricity generation. It is considering replacing a coal power station with either wind turbines or a nuclear power station. Evaluate the advantages and disadvantages of each option. [6 marks]
Model answer:
Wind turbines advantages:
- Produce no carbon dioxide during operation, reducing emissions (1 mark)
- No fuel costs, reducing long-term expenses (1 mark)
Wind turbines disadvantages:
- Unreliable/dependent on wind speed, so cannot guarantee constant supply (1 mark)
- Would need many turbines to match coal power station output (1 mark)
Nuclear power advantages:
- No carbon dioxide produced during operation (1 mark)
- Reliable baseload power/can operate continuously (1 mark)
Nuclear power disadvantages:
- Produces radioactive waste requiring long-term storage (1 mark)
- Very high initial construction costs (1 mark)
Examiner note: Evaluative questions require balanced discussion of both options. Award marks for valid scientific points with appropriate detail. Maximum 6 marks even though 8 points listed.
Example 2: Energy reliability
Question: Explain why the UK uses a variety of different energy resources to generate electricity rather than relying on a single source. [4 marks]
Model answer:
- Different resources are reliable at different times/some are unreliable (1 mark), so using multiple sources ensures continuous supply/meets varying demand (1 mark)
- Renewable sources like wind and solar depend on weather conditions (1 mark), so backup sources are needed when conditions are unsuitable (1 mark)
- Using multiple sources increases energy security/reduces dependence on imported fuels (1 mark)
- Different resources suit different locations/geographical features in the UK (1 mark)
Examiner note: Four marks available; two well-developed points would earn full marks. Link reliability to practical consequences.
Example 3: Carbon neutrality
Question: Explain what is meant by a biofuel being 'carbon neutral'. [3 marks]
Model answer:
- Carbon dioxide is absorbed from the atmosphere when the plants/trees are growing (1 mark)
- The same amount of carbon dioxide is released when the biofuel is burned (1 mark)
- So there is no net increase in atmospheric carbon dioxide (1 mark)
Examiner note: Must explain both absorption and release, plus the net result, for full marks.
Common mistakes and how to avoid them
Confusing renewable with clean or environmentally friendly — all energy resources have environmental impacts. Renewable means naturally replenished, not zero-impact. Hydroelectric dams flood habitats; manufacturing solar panels requires mining and energy.
Claiming renewable resources produce "free energy" — while fuel costs are zero, construction, maintenance and decommissioning require significant investment. State "no fuel costs" rather than "free energy."
Forgetting that biofuels only carbon neutral if sustainably managed — if forests are cleared faster than replanted, or if fossil fuels are used to process biofuels, they contribute net carbon dioxide. Always specify the conditions for carbon neutrality.
Mixing up reliability and availability — reliability means consistent supply when needed. Nuclear and fossil fuels are reliable; wind and solar are unreliable because weather varies unpredictably.
Stating nuclear power is renewable — uranium is a finite resource mined from the Earth, making nuclear power non-renewable despite producing no carbon dioxide during operation.
Vague environmental statements — instead of "damages the environment," specify: "releases carbon dioxide contributing to climate change" or "destroys habitats through flooding valleys."
Exam technique for "National and global energy resources"
"Evaluate" questions require balanced arguments discussing both advantages and disadvantages, or comparing multiple options. Present points for and against, then may need to reach a justified conclusion. Typically worth 4-6 marks.
Use scientific terminology precisely — distinguish between "carbon dioxide emissions," "greenhouse gases," "acid rain," and "radioactive waste." Each has different environmental consequences.
Link points to consequences — don't just state facts. "Wind power is unreliable" is incomplete; add "so backup power sources are needed when wind speeds are low" to show understanding of implications.
Extended response questions may ask about trends in energy use or environmental impacts. Structure answers logically, use data if provided in the question, and ensure scientific accuracy throughout.
Quick revision summary
Energy resources divide into non-renewable (fossil fuels, nuclear) and renewable (wind, solar, hydroelectric, tidal, wave, geothermal, biofuels). Non-renewable sources are finite; fossil fuels cause climate change and acid rain. Renewables won't run out but many are unreliable and all have environmental costs. The UK uses a diverse energy mix to ensure reliable supply while reducing carbon emissions. Reliability, start-up time, costs and environmental impact all influence energy choices nationally and globally.