Energy Resources (Renewable & Non-Renewable)
Key idea: Compare renewable and non-renewable energy resources used to generate electricity, focusing on efficiency, cost, reliability and environmental impact (O Level Physics).
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The core idea
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Learning objectives
- Recognise kinetic, potential, nuclear and internal energy stores
- Describe mechanical energy transfer by a force acting over a distance
- Describe electrical energy transfer by an electric current
- Describe energy transfer by heating due to a temperature difference
- Describe energy transfer by electromagnetic and mechanical waves
- Recall and apply Ek = ½mv² in new situations
- Recall and apply Ep = mgh near the Earth's surface in new situations
- State and apply the principle of conservation of energy
- Recall and apply work done = force × distance moved in the force direction
- Recall and apply power = energy transfer / time taken
- Calculate efficiency as useful energy output / total energy input
- Evaluate prescribed electricity-generation resources by efficiency, cost, reliability and environmental impact
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, η, is the useful fraction of the input: η = E_useful/Eᵢₙₚᵤₜ × 100%
- In exam answers, compare resources using the four headings: efficiency, cost, reliability, environmental impact.
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)
| Resource | Efficiency of energy transfer | Cost | Reliability | Environmental impact |
|---|---|---|---|---|
| Fossil fuels (non-renewable) | Heat-engine route; substantial energy is transferred to the surroundings | Ongoing fuel cost; established technology | Fuel can be stored and generation scheduled | CO₂ and air pollutants; finite resource |
| Nuclear (non-renewable) | Heat-engine route; substantial energy is transferred to the surroundings | Very high start-up; waste management | Steady output when operating; shutdowns require planning | Low CO₂ in operation; radioactive waste and accident risk |
| Solar (renewable) | Light → electrical directly; conversion still has losses | High start-up; low running | Varies with day, weather and shading | Low CO₂ in operation; land and materials impacts |
| Wind (renewable) | Wind → turbine → electrical; conversion has mechanical and electrical losses | High start-up; low running | Varies with wind conditions | Low CO₂ in operation; noise, visual and wildlife impacts |
| Hydropower (renewable) | No heat-engine stage; turbine and generator still have losses | High start-up (dams); low running | Reservoir output can be scheduled; rainfall-limited | Flooding and ecosystem disruption; site-dependent |
| Tidal (renewable) | Moving water → turbine → electrical | High start-up; low running | Timing is predictable, but output is cyclic and site-limited | Marine and coastal ecosystem effects |
| Geothermal (renewable) | Thermal route; performance depends on source temperature | High drilling cost; low running | Can provide steady output at suitable sites | Low CO₂ in operation; local impacts |
| Biofuel (renewable if replenished) | Usually a heat-engine route with waste heat | Fuel production, transport and land use | Fuel can be stored; depends on a continuing supply | Emits CO₂ when burned; sustainability depends on production |
Do not mix up efficiency and availability
Efficiency is the fraction of input energy transferred usefully. Availability describes whether the resource is present at a particular time. Weak sunlight reduces a solar panel’s power output; it does not by itself define the panel’s conversion efficiency.
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
Modelled example 1
Compare two resources
Problem
Compare fossil fuels and solar for electricity generation.
Study the worked solution
Compare the transfer routes
Method
Contrast the thermal route with direct light-to-electrical conversion.Reason
The route identifies where substantial non-useful transfers occur without claiming either process is loss-free.Working
Fossil fuel: chemical → thermal → kinetic → electrical. Solar panel: light → electrical.Separate start-up and running costs
Method
State which costs continue during operation.Reason
A single statement that one resource is “cheaper” is incomplete without a cost timescale.Working
Fossil generation has continuing fuel cost; solar has high start-up cost but no fuel cost.Compare availability
Method
Describe fossil generation as schedulable and solar output as variable.Reason
Stored fuel can be used when required, whereas sunlight varies with time, weather and shading.Working
Solar may need storage or backup when its output does not match demand.Compare environmental effects
Method
Include both operational emissions and other impacts.Reason
Renewable does not mean impact-free.Working
Fossil fuels emit greenhouse gases and air pollutants; solar has low operational emissions but land and materials impacts.
Guided practice 2
Compare two renewables
Problem
Compare tidal and wind power for electricity generation, including reliability and one environmental impact of each.
Commit to the reliability comparison first
Hints
Hint 1: separate predictability from constancy
Predictable timing does not mean continuous output.
Hint 2: locate each installation
Consider coastal ecosystems for tidal schemes and landscape, noise or wildlife for wind turbines.
View solution step by step
Compare the conversion routes
Method
Recognise that both drive turbines and generators.Reason
Both routes have turbulence, friction and electrical losses even though no fuel is burned.Working
Moving water or air → turbine → generator → electrical output.Compare cost and reliability
Method
Separate high construction cost from low fuel cost, then distinguish predictable tides from changing wind.Reason
Both resources are variable, but their variation is not equally predictable.Working
Tidal timing is predictable but cyclic; wind output depends less predictably on local wind conditions.Name site-specific impacts
Method
Link each impact to the installation.Reason
“Renewable” describes replenishment, not absence of environmental effects.Working
Tidal schemes may alter marine or coastal ecosystems; wind farms may create noise, visual or wildlife impacts.
Common misconception 3
Why thermal power stations are not 100% efficient
Learner response
A student says, “A fossil-fuel or nuclear power station can be 100% efficient if its generator has no electrical resistance.” Locate the first error and repair the explanation.
Identify the missing energy pathway
View solution step by step
Locate the first error
Method
Reject the assumption that generator resistance is the only source of non-useful transfer.Reason
A thermal station loses useful availability at several stages, especially through the cooling system and exhaust.Working
The claim ignores substantial heating of the surroundings before and around the generator stage.Repair the energy account
Method
Account for useful electrical output and non-useful transfers.Reason
Conservation of energy requires all input energy to be transferred, but not all of it reaches the useful electrical output.Working
Non-useful transfers include heating through exhaust and cooling systems, friction, heating of components and sound.State the conclusion
Working
The useful electrical output is less than the input energy, so efficiency is below 100%.
Examiner practice 4
Compare nuclear and wind
Examination question
Compare nuclear and wind power for electricity generation. Include efficiency, cost, reliability and environmental impact. [4 marks]
Make one paired comparison under each heading
View solution step by step
Compare efficiency
1 markMethod
Contrast a thermal cycle with a wind turbine and generator.Reason
Nuclear stations transfer substantial energy to the surroundings through their thermal cycle; wind has no heat-engine stage but still has mechanical and electrical losses.Working
Neither route is loss-free.Compare cost
1 markMethod
Separate construction and running costs.Reason
Nuclear construction, safety and waste management are costly; wind has high start-up cost but no fuel cost.Working
Nuclear also requires continuing fuel and waste-management provision.Compare reliability
1 markMethod
Contrast steady scheduled output with weather-dependent output.Reason
Nuclear can provide steady output when operating, whereas wind output changes with wind conditions.Working
Wind may require storage, backup or a wider resource mix.Compare environmental impact
1 markMethod
Give a qualified impact for each resource.Reason
Both have low operational carbon dioxide emissions, but their other impacts differ.Working
Nuclear produces radioactive waste and carries accident risk; wind can create noise, visual and wildlife impacts.
Self-mark with the mark scheme
Compare your response with each mark point. Select a point only when your response contains that evidence.
Self-mark one explained, paired comparison under each required heading.
Challenge 5
Choosing resources for a city
Planning transfer
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 it using efficiency, cost, reliability and environmental impact.
Commit to a mix and defend its trade-offs
Hints
Hint 1: meet both constraints
Your mix must address low operational carbon dioxide emissions and supply when variable resources are unavailable.
Hint 2: qualify every advantage
For each resource, include at least one cost, reliability or environmental limitation rather than presenting it as ideal.
View solution step by step
Choose a complementary mix
Method
Use steady scheduled generation alongside variable renewables and storage or backup.Reason
No single listed resource automatically satisfies every cost, reliability and environmental constraint.Working
One defensible mix is nuclear plus solar and wind, with storage or backup for low-output periods and peaks.Compare conversion and cost
Method
Distinguish the thermal cycle from direct or mechanical renewable routes, then separate start-up from running costs.Reason
The comparison must not equate absence of a heat engine with perfect efficiency or zero total cost.Working
Solar and wind avoid a thermal cycle; nuclear transfers substantial energy to the surroundings. All have high start-up costs, while solar and wind have no fuel cost.Test reliability and environmental trade-offs
Method
Explain how the mix covers variable output and identify remaining impacts.Reason
A recommendation is justified only when it addresses the stated city constraints and acknowledges disadvantages.Working
Nuclear supplies steady output; storage or backup covers low wind and sunlight. Operational emissions are low, but nuclear waste and renewable land, materials, noise or wildlife impacts remain.
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.
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Course and syllabus information
- Course
- SEC G3 Physics
- Edition
- SEC G3 Physics 2027