Energy Resources
Non-renewable energy resources
Fossil fuels (coal, oil, natural gas) and nuclear fuel (uranium) are non-renewable — they are being used faster than they can be replaced.
Fossil fuel power station operation:
- Fuel burned → heat energy released.
- Heat boils water → high-pressure steam.
- Steam turns turbine → turbine drives generator → electricity produced.
- Steam cooled in condenser → returned to boiler.
Nuclear power station: same process but heat comes from nuclear fission (controlled chain reaction in reactor using uranium fuel rods), not combustion. No CO₂ emissions during operation, but produces radioactive waste that requires secure long-term storage.
Advantages of fossil fuels: reliable (can generate on demand), high energy density, existing infrastructure. Disadvantages: CO₂ and other greenhouse gases → climate change; air pollution; limited supply; environmental damage from extraction.
Renewable energy resources
Renewable sources will not run out on a human timescale.
| Source | How electricity is generated | Advantages | Disadvantages |
|---|---|---|---|
| Wind | Wind turns turbines → generator | No pollution, no fuel cost | Intermittent (wind-dependent), visual/noise impact, large land area |
| Solar (PV) | Photovoltaic cells convert light → electricity | No pollution, low maintenance | Intermittent, expensive panels, less effective in low-sun countries |
| Hydroelectric | Falling water turns turbines | Reliable, can store energy (pumped storage), fast response | Flooding habitats, limited sites, large upfront cost |
| Tidal | Tidal flow/barrages turn turbines | Predictable, no fuel | High construction cost, disrupts tidal ecosystems |
| Wave | Wave motion drives generators | No pollution | Unreliable, engineering challenges |
| Geothermal | Earth's heat turns water to steam → turbine | Continuous output | Only viable in volcanic regions |
| Biomass | Burning biological material (wood, crops) | Carbon-neutral in theory (CO₂ re-absorbed by new plants) | Land use, deforestation risk, combustion pollution |
The National Grid
The National Grid distributes electricity from power stations across the country. Key features:
- Power stations generate at ~25 kV.
- Step-up transformer increases to 400 kV or 275 kV for long-distance transmission.
- High voltage transmission minimises current → minimises I²R power losses in cables.
- Step-down transformers at local substations reduce to 33 kV, then 11 kV, then 230 V for homes, or higher for industry.
Efficiency of transmission: some energy is always lost as heat in cables. Reducing current (higher voltage) is the engineering solution.
Environmental and social issues
Climate change: burning fossil fuels releases CO₂ (and CH₄ from gas), greenhouse gases that trap infrared radiation → global warming → sea level rise, extreme weather.
Energy security: dependence on imported fossil fuels creates political and economic vulnerability. Renewables can provide domestic, distributed generation.
CCEA 6-mark evaluate question often asks you to compare energy sources on: reliability, cost, environmental impact, land use, energy output. Always address both advantages AND disadvantages and reach a reasoned conclusion.
Efficiency of power stations
A typical coal power station is ~35–40% efficient. Nuclear ~33%. Gas turbines can reach ~55% (combined cycle). Improvements: combined heat and power (CHP), combined cycle gas turbines (CCGT).
⚠Common mistakes
- Saying renewables are 100% efficient — they still have energy losses; PV cells are typically 15–25% efficient.
- Saying nuclear is "clean" — no CO₂ during operation, but radioactive waste is a significant problem.
- Confusing power and energy — a power station has a rated power (MW); energy = power × time (MWh).
- Forgetting that high voltage reduces current — students sometimes say "high voltage is dangerous for cables" — dangerous to humans, but reduces cable losses.
AI-generated · claude-opus-4-7 · v3-ccea-physics