7.2 Energy sources—uses and management
- Syllabus
- First assessment 2026
- Topic
- 7.2
- Level
- SL
Renewable Is About Replenishment
Renewable energy sources are replenished or recur on a useful human timescale; non-renewable sources depend on finite stocks.
| Renewable sources | Non-renewable sources |
|---|---|
| wind, solar, tidal, wood, geothermal, hydropower | fossil fuels (coal, oil and natural gas), nuclear fuels |
Most energy released from these sources is converted to electricity. Judge the source separately from the turbines, dams, panels, reactors, power lines and other infrastructure used to capture and deliver it.
Sunlight recurs, but a solar farm still uses land and manufactured panels; nuclear generation is low-carbon in operation but uranium or plutonium fuel is non-renewable.
Renewable does not mean impact-free, and low-carbon does not mean renewable.
A Growing Share Is Not a Falling Total
Global energy consumption rises when population grows and when average energy use per person increases.
Fossil fuels still provide most global energy, while renewable supply is growing. Steel, concrete and synthetic-fertilizer production remain strongly dependent on fossil fuels, so changing supply and reducing consumption must occur together.
A country can add renewable generation while total demand grows so quickly that absolute fossil-fuel use does not fall; compare total energy, source shares and absolute amounts over the same period.
A rising renewable percentage shows a changing mix, not by itself a decline in fossil-fuel consumption.
Share, absolute amount and per-capita use answer different questions.
Judge the Whole Energy Life Cycle
Energy-source sustainability must be judged across extraction, processing, construction, operation, restoration and end-of-life—not only while electricity is generated.
| Source or material | Main lifecycle questions |
|---|---|
| Fossil fuels | mining or drilling, crude-oil refining, gas liquefaction, combustion emissions and site restoration |
| Rare-earth elements | finite mining and processing, pollution, recovery and recycling |
| Nuclear | uranium mining, reactor construction, low-carbon operation, radioactive waste and decommissioning |
| Solar | panel materials, land, transport, intermittent output, recycling and disposal |
| Wind | turbine materials, roads and grid links, intermittent output, dismantling and recycling |
Wind avoids fuel combustion during operation but still requires steel, concrete, transport and end-of-life management; environmental restoration may be required for both renewable and non-renewable systems.
Compare the same lifecycle stages, timescale and criteria before ranking sources.
Low operational emissions are not zero lifecycle impact, and one impact cannot stand in for total sustainability.
Energy Mixes Fit Constraints
A country's energy mix reflects its resource geography, infrastructure, policy and demand, so the same source can have different advantages in different places.
| Criterion | China | Iceland |
|---|---|---|
| Availability | large coal reserves; imports some oil and gas; very large wind and solar capacity | abundant hydropower and geothermal resources |
| Cost and infrastructure | coal supports an established, industrial-scale system; transition requires major grid and generation investment | existing hydro and geothermal systems already supply most domestic energy outside transport |
| Pollution and sustainability | coal combustion produces major GHG and air-pollution pressure; renewables are expanding | renewable supply avoids most fossil combustion, while dams and geothermal plants still have local impacts |
| Efficiency and reliability | controllable coal output is reliable, while variable wind and solar require grid balancing and storage | geothermal can provide steady output and hydropower can respond to demand |
| Energy security | domestic coal reduces one import risk, but oil and gas imports create exposure | domestic renewable resources reduce fuel-import dependence, though transport remains a separate constraint |
China's choices balance industrial demand, existing coal assets, pollution and rapid renewable expansion. Iceland's geology and water resources support a contrasting hydro-geothermal mix.
Compare both countries against the same criteria and timescale; a benefit under one criterion can create a cost under another.
There is no context-free 'best' energy source, and a national average can hide transport or local environmental impacts.
Store the Surplus, Release the Shortfall
Storage shifts surplus energy to a later shortfall; it does not create energy.
Intermittent output must be charged when supply exceeds demand and discharged when demand exceeds output, with losses.
A battery charges from midday solar and discharges during the evening peak.
What job does storage perform? timing and balancing, not generation.
Storage is not a new energy source.
Less Service or Less Energy Per Service?
Conservation reduces the service used; efficiency delivers the same service with less energy.
Both can lower demand, but rebound behaviour can consume part of an efficiency gain.
Turning off an unused lamp is conservation; an LED giving the same light with less electricity is efficiency.
Which is efficiency? same light, lower electricity per light-hour.
Efficiency is not identical to using less service.
Objective notes
6 learning objectives7.2.1Energy source types• Renewable: wind, solar, tidal, wood, geothermal, hydropower• Non-renewable: nuclear, fossil fuelsView7.2.2Global energy consumption rising• Population increase, per capita demand• Fossil fuels dominate, renewables increasingView7.2.3Energy source sustainability• Varies significantly• Both types have environmental costsView7.2.4Country energy choices• Factors: sustainability, cost, pollution, efficiency, availability, securityView7.2.5Intermittent energy production• Some renewables require energy storage• Solutions: batteries, pumped hydroelectricity, fuel cells, thermal storageView7.2.6Energy conservation and efficiency• Reduce dependence on imports• Behavioural changes, efficient technologiesView