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This lesson covers non-renewable energy sources — fossil fuels and nuclear power — as required by AQA GCSE Design and Technology (8552), Section 3.1.2. Understanding where energy comes from and how it is generated is essential for evaluating the environmental impact of products and manufacturing processes.
A non-renewable energy source is one that will eventually run out because it is consumed faster than it can be replaced. The three main fossil fuels — coal, oil and natural gas — formed over millions of years from the remains of ancient organisms. Once burned, they cannot be reformed on a human timescale.
The diagram below classifies the main UK electricity sources on two axes — renewable vs non-renewable, and low-carbon vs high-carbon:
graph TD
E["Energy Sources"] --> NR["Non-Renewable"]
E --> R["Renewable"]
NR --> FF["Fossil Fuels\n(high CO2)"]
NR --> N["Nuclear\n(low CO2)"]
FF --> C["Coal\n~0.90 kg CO2/kWh"]
FF --> O["Oil"]
FF --> G["Natural Gas\n~0.35 kg CO2/kWh"]
R --> RW["Wind, Solar,\nTidal, Hydro,\nBiomass\n(low CO2)"]
Coal is a solid fossil fuel formed from ancient plant material compressed under heat and pressure over millions of years. It is burned in power stations to generate electricity.
| Advantage | Disadvantage |
|---|---|
| Reliable — provides a steady base-load supply | Produces the highest CO₂ emissions per unit of energy of all fossil fuels |
| Abundant global reserves (estimated 100+ years) | Mining causes habitat destruction and air pollution |
| Existing infrastructure for coal-fired power stations | Burning releases sulphur dioxide (SO₂), contributing to acid rain |
| Creates jobs in mining communities | Coal ash contains toxic heavy metals |
Oil is a liquid fossil fuel extracted by drilling. It is refined into fuels (petrol, diesel, jet fuel) and is the raw material for most plastics.
| Advantage | Disadvantage |
|---|---|
| High energy density — excellent for transport | Combustion releases CO₂, contributing to climate change |
| Versatile — fuels, plastics, lubricants, chemicals | Oil spills devastate marine ecosystems |
| Well-established global distribution network | Finite resource — estimated 50 years of proven reserves |
| Relatively easy to transport (pipelines, tankers) | Price volatility affects manufacturing costs |
Natural gas (mainly methane, CH₄) is extracted from underground reserves and used for heating, cooking and electricity generation.
| Advantage | Disadvantage |
|---|---|
| Cleanest-burning fossil fuel — lower CO₂ than coal or oil | Still produces CO₂ and contributes to climate change |
| Fast start-up — gas turbines can respond quickly to demand | Methane leaks during extraction are a potent greenhouse gas |
| Efficient combined-cycle gas turbines (CCGT) | Finite resource — estimated 50–60 years of proven reserves |
| Lower SO₂ emissions than coal | Fracking (hydraulic fracturing) is controversial — risk of groundwater contamination |
AQA Exam Tip: When comparing fossil fuels, always rank them by CO₂ emissions: coal (highest) > oil > natural gas (lowest). This is a frequently tested fact.
Nuclear power generates electricity by splitting atoms of uranium (or plutonium) in a process called nuclear fission. The heat produced turns water into steam, which drives turbines connected to generators.
| Advantage | Disadvantage |
|---|---|
| No CO₂ emissions during operation | Produces radioactive waste that remains hazardous for thousands of years |
| Reliable base-load power (runs 24/7) | High construction costs — nuclear power stations cost billions to build |
| High energy density — a small amount of fuel produces a huge amount of energy | Risk of nuclear accidents (e.g. Chernobyl 1986, Fukushima 2011) |
| Long operational life — stations can run for 40–60 years | Decommissioning is extremely expensive and time-consuming |
| Reduces dependence on fossil fuels | Uranium is a finite resource (though reserves are large) |
AQA Exam Tip: Nuclear power is technically non-renewable (uranium will eventually run out), but it does not produce greenhouse gases during operation. Examiners may test whether you understand this distinction.
| Impact | Description |
|---|---|
| Climate change | Burning fossil fuels releases CO₂, trapping heat in the atmosphere |
| Acid rain | SO₂ and NOₓ from coal and oil combustion dissolve in rainwater, damaging buildings, forests and lakes |
| Air pollution | Particulate matter from combustion causes respiratory diseases |
| Oil spills | Tanker accidents and pipeline leaks contaminate oceans and coastlines |
| Radioactive waste | Nuclear waste must be stored securely for thousands of years |
| Habitat destruction | Mining, drilling and infrastructure construction destroy natural habitats |
As a D&T student, you should consider:
AQA Exam Tip: A common 4-mark question asks you to compare two energy sources. Structure your answer as a table with advantages and disadvantages for each, then state which is more suitable for a given scenario and why.
Scenario: Two UK power stations are compared — an older coal-fired station and a modern combined-cycle gas turbine (CCGT) station. The designer needs to compare their efficiency, fuel consumption and CO2 emissions for generating the same electrical output of 500 MW continuously for one hour (i.e. 500 MWh).
Step 1 — Apply the efficiency formula. Power station efficiency is:
efficiency = (useful energy output / total energy input) x 100%
A typical coal-fired station runs at around 35% efficiency. A modern CCGT runs at around 60% efficiency because it uses both a gas turbine and a steam turbine driven by the waste heat.
Step 2 — Calculate fuel energy input for 500 MWh of electricity.
For coal:
Fuel energy input = Output / efficiency
Fuel energy input = 500 / 0.35
Fuel energy input = 1,428.6 MWh of chemical energy in coal
For CCGT:
Fuel energy input = 500 / 0.60
Fuel energy input = 833.3 MWh of chemical energy in gas
The coal station needs 71% more fuel energy than the CCGT to produce the same electricity.
Step 3 — Estimate CO2 emissions. Using standard grid emission factors:
| Fuel | Emissions | CO2 for 500 MWh electricity |
|---|---|---|
| Coal (at 35% efficiency) | ~0.90 kg CO2/kWh | 450,000 kg (450 tonnes) |
| CCGT (at 60% efficiency) | ~0.35 kg CO2/kWh | 175,000 kg (175 tonnes) |
The CCGT station emits less than 40% of the coal station's CO2 for the same electrical output. This is why the UK closed its last coal-fired power station in 2024 and replaced coal's role on the grid with a mixture of gas, wind and nuclear.
Step 4 — Systems block diagram of a thermal power station.
INPUT: Chemical energy in the fuel (coal or natural gas)
|
v
PROCESS: Combustion in the boiler/turbine converts chemical
energy into heat. Heat turns water into high-pressure
steam. Steam drives a turbine, converting thermal into
mechanical energy. The turbine spins a generator,
converting mechanical into electrical energy.
|
v
OUTPUT: Electricity is stepped up by transformers and fed to
the National Grid at 400 kV for long-distance
transmission.
|
v
FEEDBACK: Grid frequency (50 Hz) is monitored continuously; the
control room adjusts fuel flow to match demand,
forming a closed-loop control system across the
entire grid.
Step 5 — Design and technology context. Every product that uses mains electricity carries the CO2 footprint of the generating mix. A product designer evaluating a new appliance's environmental impact must multiply the product's in-use electricity consumption by the grid carbon intensity (in kg CO2 per kWh), which in the UK has fallen from ~0.52 kg/kWh in 2012 to ~0.18 kg/kWh in 2023 as coal was phased out and renewables grew. This is why electric vehicles have shrinking lifetime emissions year on year, even without redesign — the grid they charge from is decarbonising around them.
Misconception: "Nuclear power is classed as a renewable energy source because it produces no CO2."
Reality: Nuclear power is a low-carbon energy source, but it is not renewable. The uranium or plutonium fuel is a finite resource extracted from the Earth, just like coal or natural gas — once used, it is gone (though reserves are large enough for centuries at current consumption). The AQA specification expects you to classify nuclear as non-renewable but low-carbon. Students who lump nuclear with wind and solar lose marks because they confuse two different classification axes: renewability (does the resource replenish on a human timescale?) versus carbon intensity (does operating it emit CO2?). Wind, solar and hydro are both renewable and low-carbon. Nuclear is non-renewable but low-carbon. Fossil fuels are non-renewable and high-carbon. Use both axes when classifying any energy source.
Question (9 marks): Evaluate the UK's reliance on non-renewable energy sources for electricity generation. Discuss the environmental, economic and social impacts, and justify what should happen to this mix over the next 20 years.
Grade 3-4 response: "Non-renewables make lots of pollution. Coal is the worst because it makes the most CO2. Gas is cleaner than coal. Nuclear is cleaner than both but it makes radioactive waste. The UK should stop using non-renewables and use more wind and solar because they are better for the environment."
Why Grade 3-4: Correct surface points but no figures, no discussion of costs or reliability trade-offs, no staged plan.
Grade 5-6 response: "The UK has reduced its coal use massively, closing its last coal power station in 2024, because coal emits around 0.90 kg CO2 per kWh — the highest of any fuel. Natural gas in a modern combined-cycle turbine emits about 0.35 kg CO2 per kWh and also starts up quickly, making it useful for balancing renewables when the wind does not blow. Nuclear produces no CO2 during operation and provides reliable base-load power, but leaves radioactive waste that must be stored safely for thousands of years. Economically, nuclear is expensive to build (Hinkley Point C is estimated at £32bn+) but cheap to run. Socially, closing coal mines caused unemployment in mining communities, but new jobs were created in offshore wind and grid upgrades. Over the next 20 years, the UK should phase out gas by 2040, expand offshore wind, and keep existing nuclear running while building new stations to cover the gap."
Why Grade 5-6: Quantified emissions, named a specific project (Hinkley Point C), discussed social impact, and reached a supported plan.
Grade 7-9 response: "The UK's grid has already undergone a dramatic transition: grid carbon intensity fell from ~0.52 kg CO2/kWh in 2012 to ~0.18 kg/kWh in 2023 as coal (CO2-intense, 0.90 kg/kWh) was phased out and offshore wind (~12 g/kWh over lifecycle) scaled up. Gas-fired CCGT (~0.35 kg/kWh) remains the dispatchable backstop for windless periods. Nuclear power (~6 g/kWh lifecycle) supplies ~15% of UK electricity and provides the inertia and base-load that variable renewables cannot. Economically, the strike price paid under Contracts for Difference illustrates the shift: Hinkley Point C is indexed to £92.50/MWh (2012 money, so ~£128/MWh today), while recent offshore wind CfD strike prices have been ~£40/MWh. This has made offshore wind the cheapest new generation available. Socially, the coal phase-out displaced mining jobs, but well over 30,000 UK jobs now exist in offshore wind manufacturing, installation and maintenance, with Humber, Teesside and Grimsby rebuilt as wind hubs. Over the next 20 years, the rational mix is: (1) eliminate gas by 2040 except for a small strategic reserve; (2) keep existing nuclear running past design life where safe, and commission Hinkley Point C + Sizewell C to replace retiring AGR stations; (3) triple offshore wind to 50+ GW; (4) invest heavily in grid-scale storage (pumped hydro, Li-ion, green hydrogen) because intermittency is the binding constraint once renewables exceed ~50% of supply; (5) interconnectors to Norway, France and the Netherlands for cross-border balancing. The key trade-off is that nuclear is expensive per MWh but delivers the firm capacity that makes a renewables-heavy grid stable. Evaluating the whole: non-renewables should be reduced to a minimal strategic reserve role, nuclear maintained as a low-carbon firm supply, and renewables plus storage scaled to displace the remaining fossil share — because only the full portfolio delivers both decarbonisation and grid reliability simultaneously."
Why Grade 7-9: Quantified emissions and strike prices, referenced real projects and job figures, identified storage as the binding constraint, and reached a systems-level conclusion that weighs decarbonisation against reliability. This is exactly the evaluative rigour AQA's top mark band rewards.
This content is aligned with the AQA GCSE Design and Technology (8552) specification, Paper 1: Core technical principles — Energy, materials, systems and devices. For the most accurate and up-to-date information, please refer to the official AQA specification document.