Energy Resources (Renewable & Non-Renewable)

1. Definition

A. Energy resources

An energy resource is a source of energy that can be used to generate electricity (or other useful energy).

• Non-renewable resources are finite and will eventually run out (e.g. fossil fuels, nuclear fuel).
• Renewable resources are naturally replenished on human timescales (e.g. solar, wind).

2. Key Ideas

• Many power stations generate electricity by converting energy into mechanical rotation (turbine), then using a generator.
• Some resources convert energy directly into electricity (e.g. solar panels: light → electrical).
• Real electricity-generation processes are not perfectly efficient: some input energy is transferred to less useful internal energy stores and by sound waves.
• Efficiency, eta, is the useful fraction of the input: eta = Eᵤₛₑfᵤₗ/Eᵢₙₚᵤₜ × 100\%
• In exam answers, compare resources using the four headings: efficiency, cost, reliability, environmental impact.

Scroll diagram horizontally to read all labels.

3. Detailed Explanations

A. What the four headings mean (exam wording)

• Efficiency: how much of the input energy becomes useful electrical energy rather than being transferred to less useful stores.
• Cost: start-up cost (building) and running cost (fuel/maintenance).
• Reliability: whether it can generate electricity when needed, including predictable variation, fuel availability and planned or unplanned shutdowns.
• Environmental impact: pollution, greenhouse gases, waste, and effects on ecosystems/land.

B. Quick comparison table (revision)

C. Non-renewable resources

Fossil fuels (coal, oil, natural gas)

• How electricity is generated: chemical → thermal (burning) → kinetic (turbine) → electrical.
• Efficiency: limited by waste heat in thermal power stations.
• Cost: fuel costs can be significant; power stations are well-developed.
• Reliability: fuel can be stored and generation scheduled, although maintenance and faults can stop a station.
• Environmental impact: greenhouse gases and air pollutants; non-renewable.

Nuclear fuel (e.g. uranium)

• How electricity is generated: nuclear → thermal → turbine → electrical.
• Efficiency: limited by waste heat (thermal power station).
• Cost: high start-up costs; safety and waste management increase cost.
• Reliability: steady output when operating, but maintenance and shutdowns must be planned for.
• Environmental impact: low greenhouse gas emissions during operation, but radioactive waste and safety concerns.

D. Renewable resources

Solar

• How electricity is generated: solar panels convert light energy directly into electrical energy.
• Efficiency: light is converted directly to electricity, although some input energy is not transferred usefully.
• Cost: high start-up cost; very low fuel cost (no fuel).
• Reliability: intermittent (day/night, weather); needs storage/backup for steady supply.
• Environmental impact: low emissions during operation; land use and manufacturing impacts.

Wind

• How electricity is generated: kinetic energy of wind → turbine → electrical.
• Efficiency: some wind energy is not captured, and further energy is dissipated in the turbine and generator.
• Cost: high start-up cost; low running cost.
• Reliability: intermittent; needs backup/storage for steady supply.
• Environmental impact: low emissions during operation; noise/visual impact; some wildlife impact.

Hydropower

• How electricity is generated: gravitational potential energy of water → kinetic (flow) → turbine → electrical.
• Efficiency: often high because there is no heat engine stage.
• Cost: high start-up cost (dams/reservoirs), low running cost.
• Reliability: can be high with reservoirs; depends on rainfall/water supply.
• Environmental impact: may flood habitats and affect river ecosystems; site-dependent.

Tidal

• How electricity is generated: energy from moving water or a difference in water level → turbine → electrical.
• Efficiency: energy is dissipated by turbulence, friction and electrical resistance.
• Cost: high start-up cost; low running cost.
• Reliability: very predictable, but limited suitable locations.
• Environmental impact: can affect marine ecosystems and coastal processes.

Geothermal

• How electricity is generated: thermal energy from the Earth → steam/turbine → electrical.
• Efficiency: depends on how hot the underground source is.
• Cost: high drilling/start-up cost; low running cost.
• Reliability: steady supply, but location-limited.
• Environmental impact: generally low emissions; may have local impacts.

Biofuel

• How electricity is generated: chemical energy in biomass → thermal (burning) → turbine → electrical.
• Efficiency: limited by waste heat in thermal power stations.
• Cost: depends on producing/transporting the fuel.
• Reliability: controllable, but depends on fuel supply.
• Environmental impact: renewable if managed sustainably, but uses land and produces emissions when burned.

4. Common Mistakes

• Saying renewable resources have “no environmental impact”.
• Mixing up energy and power (see Power).
• Assuming all renewables are unreliable in the same way (e.g. tidal is predictable).
• Writing “efficient” without stating where the non-useful energy is transferred, usually to internal energy stores and by sound waves.
• Comparing costs without stating whether you mean start-up cost or running cost.
• Treating variable output as the same idea as low efficiency.

5. Exam Tips

• Use the four headings explicitly: efficiency, cost, reliability, environmental impact.
• Use short, comparative phrases (e.g. “more reliable because…”, “lower emissions during operation because…”).
• Give both advantages and disadvantages for each resource.
• State the main non-useful transfer in thermal stations: energy transferred by heating to the surroundings.
• Compare like with like: do not use “more sunlight” as proof that one panel is more efficient.

6. Worked Examples

Example 1: Compare two resourcesCore

Compare fossil fuels and solar for electricity generation.

Show Answer

• Efficiency
  • Fossil fuels: thermal power station → a substantial energy transfer by heating to the surroundings.
  • Solar: direct light → electrical conversion avoids a steam-turbine stage, but some input energy is still dissipated.
• Cost
  • Fossil fuels: ongoing fuel cost.
  • Solar: high start-up cost, low running cost (no fuel).
• Reliability
  • Fossil fuels: controllable; can generate when needed.
  • Solar: intermittent; needs backup/storage.
• Environmental impact
  • Fossil fuels: greenhouse gases and air pollutants.
  • Solar: low emissions during operation, but land/materials impacts.

Example 2: Compare two renewablesCore

Compare tidal and wind power for electricity generation.

Show Answer

• Efficiency
  • Both use turbines and generators, with losses due to turbulence, friction and electrical resistance.
• Cost
  • Both have high start-up costs and low fuel costs.
• Reliability
  • Tidal: very predictable (tide times are known).
  • Wind: less predictable; depends on wind conditions.
• Environmental impact
  • Tidal: may affect marine/coastal ecosystems.
  • Wind: noise/visual impact; may affect wildlife.

Example 3: Why thermal power stations are not 100% efficientCore

Explain why a fossil-fuel or nuclear power station cannot be 100\% efficient.

Show Answer

In a thermal power station, not all input energy becomes useful electrical energy. A significant part is transferred to the surroundings through exhaust gases and the cooling system. Smaller transfers occur through friction, heating of components and sound. Therefore, efficiency is less than 100\%.

Example 4: Calculate efficiency and dissipated energyCore

A thermal power station receives 1.2 × 10⁹ J of input energy and transfers 4.2 × 10⁸ J as useful electrical energy. Calculate its efficiency and the energy dissipated to the surroundings.

Show Answer

Efficiency:

efficiency = 4.2 × 10⁸/1.2 × 10⁹ × 100\% = 35\%

Energy dissipated:

Edᵢₛₛᵢₚₐₜₑd = 1.2 × 10⁹-4.2 × 10⁸ = 7.8 × 10⁸ J

Check: useful output plus dissipated energy equals the input energy.

Example 5: Compare nuclear and windCore

Compare nuclear and wind power for electricity generation.

Show Answer

• Efficiency
  • Nuclear: thermal power station stage → lots of waste heat.
  • Wind: no heat-engine stage, but the turbine and generator still dissipate some energy.
• Cost
  • Nuclear: very high start-up + waste/safety costs.
  • Wind: high start-up, low running (no fuel).
• Reliability
  • Nuclear: steady, scheduled output when operating, with maintenance shutdowns planned for.
  • Wind: intermittent; needs backup/storage.
• Environmental impact
  • Nuclear: low CO₂ during operation, but radioactive waste/safety concerns.
  • Wind: low CO₂ during operation, but noise/visual/wildlife impact.

Example 6: Choosing resources for a cityCore

A country wants to reduce CO₂ emissions but needs a reliable electricity supply for a large city. Suggest a suitable mix of resources and justify using the four headings.

Show Answer

Example answer:

• Mix: nuclear (steady scheduled output) + solar/wind (renewable supplements) + storage/backup for periods of low renewable output and for peaks.
• Efficiency: solar and wind avoid the heat-engine stage; nuclear uses a thermal cycle and transfers substantial energy to the surroundings.
• Cost: high start-up for nuclear + renewables, but lower fuel costs for solar/wind.
• Reliability: nuclear provides steady power; storage/backup covers intermittent renewables.
• Environmental impact: lower greenhouse gas emissions in operation, but manage nuclear waste and renewable land/material impacts.

7. Mind Stretchers

Mind stretcher 1: Choosing resources for an islandExtension

A small island needs electricity. It has strong winds, lots of sunlight, and limited space. Suggest a suitable mix of energy resources and justify using the four headings.

Show Answer

Example answer:

• Solar + wind as main sources (renewable, low emissions during operation).
• Reliability: both are intermittent, so include storage (batteries) or a backup generator for nights/no wind.
• Cost: high start-up cost for solar panels/wind turbines + storage, but low running cost (no fuel).
• Environmental impact: low greenhouse gases during operation; manage land/visual/noise impacts.

Mind stretcher 2: Hydropower vs nuclear in a countryExtension

A country wants a steady supply of electricity with low greenhouse gas emissions. It has many rivers but limited land for reservoirs. Compare hydropower and nuclear and choose one.

Show Answer

Example answer:

• Hydropower can be efficient and low-emission, but large reservoirs need land and can flood habitats.
• Nuclear provides steady output with low emissions in operation, but has high start-up cost and radioactive waste/safety concerns.
• With limited land for reservoirs, nuclear may be more suitable for steady supply, but the decision depends on safety policy and cost.

8. Practice, Quiz and Next Step

Close your notes and use Energy Resources (Renewable & Non-Renewable) in the supplied context below. This requires a constructed explanation or working, not recognition of an option.

Fresh context: An island needs reliable electricity at night, has strong daytime sunlight, limited land and no local fossil fuel.

1. Retrieve: define energy-resource evidence and trade-offs in your own words, including units, sign or conditions where relevant.
2. Represent: Create an evidence table with reliability, environmental effect and site constraint for two plausible resources.
3. Apply: Recommend a resource mix and justify it from the supplied constraints while naming one limitation that remains.

Check the response before looking back

• The chosen system and transfer pathway are stated before applying conservation.
• Energy and power are not used interchangeably, and all quantities use compatible units.
• The numerical result is checked against the physical situation and any efficiency limit.

If one check fails, name that exact gap, revisit the matching explanation or worked example, and redo the task with different values or a different situation. Then use theO-Level topic checks orpractice browser for an independent re-test.