Energy sources: renewable vs non-renewable

· Energy sources can be classified as renewable or non-renewable depending on whether they can be replaced on a human timescale.
· Renewable energy sources include wind, solar, tidal, wood/biomass, geothermal and hydropower.
· Non-renewable energy sources include fossil fuels (coal, oil, natural gas) and nuclear fuels such as uranium or plutonium.
· Most energy released from these sources is converted into electricity, but some is used directly for heating, transport or industrial processes.
· Renewable does not automatically mean sustainable: construction, mining, transport, land use, maintenance and end-of-life disposal/recycling all create environmental costs.

This image category provides labelled diagrams of renewable energy technologies and energy storage systems. Use one that clearly shows how energy is captured or converted into electricity. It is useful for comparing renewable sources visually. Source

Global energy consumption and demand

· Global energy consumption is rising because of population growth and increasing per capita demand.
· Most global energy is still supplied by fossil fuels, although the contribution from renewables is increasing.
· Fossil fuels remain important because they support electricity generation, transport, and energy-intensive industries such as steel, concrete and synthetic fertilizer production.
· A key sustainability challenge is meeting rising demand while reducing greenhouse gas emissions, pollution, resource depletion and energy inequality.
· Exam focus: compare global and local/national changes in energy use, then explain causes such as economic development, technology, policy, resource availability and energy security.

Sustainability of energy sources

· Sustainability depends on environmental, social and economic impacts across the whole life cycle: extraction, processing, construction, use, decommissioning and restoration.
· Fossil fuels: high energy density and established infrastructure, but cause CO₂ emissions, air pollution, habitat damage from extraction and long-term climate impacts.
· Solar power: low operational emissions, but requires land, rare earth elements/metals, manufacturing energy and recycling systems for panels.
· Wind power: low operational emissions and scalable, but output is intermittent and may affect landscapes, birds/bats and local communities.
· Hydropower: reliable electricity and potential storage, but dams can alter river flow, sediment transport, fish migration, local ecosystems and human settlements.
· Tidal power: predictable but location-specific; construction can disrupt coastal ecosystems and is expensive.
· Geothermal power: reliable in suitable locations, but geographically limited and may involve gas release, water use or seismic risk.
· Wood/biomass: renewable only if harvest is matched by regrowth; can become unsustainable through deforestation, land-use change or inefficient burning.
· Nuclear power: low-carbon electricity during operation, but depends on non-renewable fuels and creates issues of radioactive waste, high construction costs and accident risk.

Factors affecting national energy choices

· Countries choose energy sources based on availability, cost, technology, infrastructure, policy, energy efficiency, pollution, energy security and public perspectives.
· Resource-rich countries may rely on domestic fossil fuels because they are available and economically valuable.
· High-income countries may invest more easily in renewables, grid upgrades, nuclear power or energy storage.
· Emerging economies may prioritize affordable and reliable energy to support industrialization, even if fossil fuel use increases.
· Island or import-dependent states may prioritize energy security by diversifying sources or developing domestic renewable energy.
· Strong exam answers compare two named countries, linking choices to physical geography, economic development, political priorities and sustainability trade-offs.

Intermittency and energy storage

· Some renewables are intermittent: solar depends on sunlight; wind depends on wind speed; tidal varies with tidal cycles.
· Intermittency creates a mismatch between energy supply and energy demand, especially during peak use.
· Peak-shaving means reducing or levelling peaks in demand so supply can meet demand more reliably.
· Storage solutions include batteries, pumped hydroelectricity storage (PHS), fuel cells and thermal storage.
· Pumped hydroelectricity storage uses surplus electricity to pump water uphill; during high demand, water flows downhill through turbines to generate electricity.
· Storage systems improve reliability but create their own impacts through mining, construction, land use, cost and pollution.

The diagram shows how pumped-storage hydroelectricity stores energy as gravitational potential energy in an upper reservoir. It helps explain why energy storage is important when electricity from wind or solar is intermittent. It also links energy management to systems thinking: inputs, storage, flows and outputs. Source

Energy conservation and energy efficiency

· Energy conservation means changing behaviour to reduce total energy consumption.
· Examples of conservation: turning off lights, lowering heating, reducing air conditioning, travelling less by fuel-driven vehicles and reducing unnecessary consumption.
· Energy efficiency means using technology or design to provide the same service with less energy input.
· Examples of efficiency: insulation, passive cooling/heating design, low-energy intelligent lighting, efficient appliances, public transport systems and efficient shipping design.
· Circular economy design can improve efficiency by making goods easier to repair, reuse, remanufacture or recycle.
· Conservation and efficiency can reduce dependence on imported resources, improve energy security and lower emissions.
· Evaluation tip: the best answers judge effectiveness, cost, scale, equity, public acceptance and possible rebound effects where efficiency lowers costs and increases use.

Exam command terms: how to score highly

· Describe: identify the energy source and give clear characteristics, e.g. renewable/non-renewable, intermittent/constant, high/low emissions.
· Explain: link cause and effect, e.g. intermittent wind power creates a need for storage because supply may not match demand.
· Compare: use the same criteria for both sources, such as cost, reliability, pollution, availability, efficiency and energy security.
· Evaluate: make a balanced judgement using benefits, limitations and context; avoid one-sided answers.
· Discuss equity: consider how access to energy differs between countries and within societies due to income, infrastructure and political power.

Common mistakes to avoid

· Do not write that all renewable energy is automatically sustainable; extraction, construction and disposal still matter.
· Do not describe nuclear power as renewable; it is non-renewable because uranium/plutonium fuels are finite.
· Do not ignore energy storage when discussing solar or wind power.
· Do not evaluate energy sources only by CO₂ emissions; include pollution, cost, reliability, land use, resource security and environmental justice.
· Do not compare countries without naming them and linking their choices to real contextual factors.