Explain geothermal heating and electricity
Use Earth's internal thermal resource while keeping direct heating, turbine arrangements and suitable sites distinct.
Exam scope and assessment notes
Core and Extended · Physics 0625, 2026–2028, section 1.7.3. Resource mechanisms, five comparison factors and qualitative efficiency are Core. Solar origins and exceptions, fusion in the Sun and electricity research, and numerical energy and power efficiencies are Supplement. Written practice is self-checked. Human subject-teacher review, supervised practical experience and cumulative assessment remain pending. Resource comparisons need the supplied site and task evidence; these are teaching models, not a project recommendation or a claim of measured output.
Before you begin
- Identify source stores and transfer pathways.
- Distinguish a rotating turbine from a generator that transfers energy electrically.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which is the source for the stated geothermal account?
What you will learn
- Describe useful heating and electricity from geothermal resources.
- Evaluate local availability, replenishment and environmental effects.
Earth supplies an internal thermal resource
Geothermal energy draws on Earth's internal thermal energy. Hot water or steam from suitable underground conditions can supply useful heating, for example through a heat exchanger. For electricity, a suitable plant uses steam or another heated working fluid to drive a turbine and generator. A heat exchanger can transfer energy between fluid circuits without requiring every plant to burn fuel in a boiler.
Direct heating need not include a turbine and generator. Earth's interior is a different immediate source from current sunshine, and geothermal is one of the syllabus's exceptions to solar radiation as the main origin of the listed resources. The simple chain describes energy transfers rather than prescribing drilling, pressure-system operation or installation.
The local resource matters
Geothermal is generally classified as renewable when extraction and local replenishment are managed, but an individual reservoir can cool or be depleted if used too rapidly. Suitable temperature, depth and accessible fluid vary strongly by location. Where these conditions and the plant are adequate, output can be relatively steady rather than directly varying with daylight; maintenance and reservoir behaviour still affect reliability.
Drilling and infrastructure can be costly and affect land use. Some fluids can release gases or dissolved substances, and some projects can affect local ground conditions. Scale depends on the accessible resource and technology. Do not treat renewable classification as a guarantee that every town can generate large amounts or that the local environmental effect is zero.
Pause and explain
Can a local geothermal reservoir be overused despite the resource's usual renewable classification?
Worked example
Describe direct geothermal heating and geothermal electricity using a suitable hot-fluid resource.
Show the worked solution
- Hot fluid can transfer energy through a heat exchanger for useful heating.
- For electricity a suitable heated working fluid drives a turbine.
- The turbine drives a generator supplying electrical output.
Answer Direct hot-fluid heating, or heated fluid → turbine → generator.
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.
Trace geothermal direct heating and a suitable geothermal electricity chain.
Give me a hint
Use thermal transfer first and identify when rotation is needed.
Compare my reasoning
- Hot fluid can heat another system through an exchanger.
- A suitable working fluid can turn a turbine.
- The turbine drives a generator for electrical output.
Direct thermal transfer; or heated fluid → turbine → generator.
Look for these in your work
- Distinguish the useful outputs.
- Do not require combustion in every plant.
Compare a town with a suitable accessible hot reservoir and one with no such evidence.
Give me a hint
Use local temperature and accessibility rather than renewable status alone.
Compare my reasoning
- The suitable reservoir may support useful geothermal heating or generation.
- The other town lacks the supplied resource evidence.
- Depth, temperature, infrastructure and replenishment are relevant before deciding scale.
The first has a potential local resource; the second needs evidence of suitable access and temperature.
Look for these in your work
- Respect site evidence.
- Address scale and supply conditions.
A project promises endless constant geothermal output with no impacts. State one local supply limit and two conditions to assess.
Give me a hint
Separate replenishment, engineering reliability and local environmental effects.
Compare my reasoning
- Excess extraction can cool or deplete a local reservoir.
- Assess maintenance and accessible temperature or fluid supply.
- Assess drilling, fluid release or ground-condition effects for that project.
Local replenishment, plant reliability and environmental conditions must be assessed.
Look for these in your work
- Avoid an infinite-supply claim.
- Include a concrete environmental consideration.
Common mistakes
- Not all sites have suitable accessible temperatures.
- Direct heating need not generate electricity.
- Local extraction can exceed replenishment.
What can you explain now?
Does geothermal need current sunlight as its immediate energy input?
Compare with the explanation
No.
The listed geothermal resource draws on Earth's internal thermal energy.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Explain geothermal's source, heating and electricity routes, then identify local limits on availability, scale and 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.