Compare resources using five separate factors
Make an evidence-based comparison without treating renewable, reliable and environmentally harmless as synonyms.
Core and Extended; Physics 0625, 2026–2028, section 1.7.3. Resource comparison and qualitative efficiency are Core. Solar origins and exceptions, fusion and its electricity research, and numerical efficiency are Supplement. Compare the same useful task, consistent system boundary and stated interval. Written work is self-checked.
Before you begin
- Describe the listed resource mechanisms.
- Distinguish an energy resource from the intended useful output.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which factor asks whether the source is replenished on a human timescale?
What you will learn
- Compare renewability, availability, reliability, scale and environmental impact.
- Use supplied site and task evidence rather than a universal ranking.
Ask five different questions
Renewability asks whether the resource is replenished on a suitable human timescale. Availability asks whether an accessible resource exists at the required place and time. Reliability asks whether output can meet the task when needed, considering variability, stocks, maintenance and any supplied balancing equipment. Scale asks how much output a suitable installation can supply relative to demand; environmental impact concerns extraction, construction, operation and disposal or decommissioning.
These factors are related but not identical. Solar radiation is renewable yet unavailable directly at night. A stocked fuel station may be controllable but non-renewable. A predictable tide varies through a cycle. A large dam can store water but still face drought and river impacts. Use a specific example for each claim rather than attaching one positive or negative label to the whole resource.
Start with the task and evidence
For an isolated clinic needing nighttime electricity, supplied daytime solar exposure alone does not establish demand coverage. If a stated option includes adequate storage and maintained backup, that new evidence changes the reliability comparison. For a hot-water task near an accessible geothermal reservoir, direct heating can avoid an unnecessary electricity conversion; it does not imply the same choice suits every town.
A reasonable comparison states the advantages, limitations and what is unknown. If output, costs, demand or environmental data are missing, do not invent a numerical ranking or claim one option has been approved. Scale and resource suitability can also make a combination useful when evidence supports it. No resource has zero impact merely because its operational mechanism does not burn fuel.
Pause and explain
Does a renewable label alone prove a source is locally available, reliable and harmless?
Worked example
An isolated site needs electricity at night and has daytime solar exposure, but no storage is supplied. Which factors remain unresolved?
Show the worked solution
- Sunlight is renewable and available during suitable daytime conditions.
- Nighttime demand coverage is not established without storage or another supplied input.
- Required output scale, equipment reliability and lifecycle/site impacts also need evidence.
Answer Renewability is established; nighttime reliability, required scale and impacts still need evidence.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Assess daytime solar for an isolated nighttime electricity demand with no stated storage.
Give me a hint
Separate a replenished resource from the timing of the task.
Compare my reasoning
- Sunlight is renewable.
- Its direct input is not supplied at night.
- Demand coverage needs further storage or supply evidence.
Renewable resource; nighttime supply is unproven.
Look for these in your work
- Use the stated demand interval.
- Avoid inventing equipment.
Compare predictable tides, stocked fossil fuel and a stored-water dam using renewal and reliability separately.
Give me a hint
Describe the different supply conditions rather than ranking without data.
Compare my reasoning
- Tides are renewable and predictably variable, not constant.
- Fossil stock can support controlled output while remaining non-renewable.
- Dam storage can improve control but depends on replenished water and operation.
Renewal and delivery reliability differ for each resource; no universal ranking follows.
Look for these in your work
- Name a condition for each option.
- Do not equate predictable, stored and unlimited.
A town requests hot water near a suitable geothermal resource but has no stated electricity demand data. Explain why recommending the largest generator is not justified.
Give me a hint
Match the useful transfer and required scale before selecting conversion hardware.
Compare my reasoning
- The stated task is hot-water heating.
- A suitable direct geothermal transfer may serve that task without a turbine.
- Generator scale and electricity demand evidence are missing, so a largest-generator recommendation is unsupported.
Compare suitable direct heating for the task; electricity scale is not established by the supplied evidence.
Look for these in your work
- Use the actual useful output.
- State the missing scale and demand evidence.
Common mistakes
- Keep five factors distinct.
- Do not invent storage, demand or output data.
- Compare the same useful task and site.
What can you explain now?
Does predictable tidal timing mean constant generation?
Compare with the explanation
No.
Predictability and constant magnitude are different properties.
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Make it stick
Name all five comparison factors and give a resource whose renewability does not alone settle its reliability or impact.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.