Geothermal Power

    OCR
    GCSE

    Geothermal power harnesses thermal energy stores within the Earth, originating primarily from the radioactive decay of isotopes such as uranium and thorium in the mantle. This thermal energy heats underground water, generating high-pressure steam that drives turbines connected to generators to produce electricity, or provides direct district heating. As a renewable energy resource, it offers high reliability and low carbon emissions compared to fossil fuels, though its economic viability is geographically constrained to volcanic regions or areas with accessible hot rocks.

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    Objectives
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    Exam Tips
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    Pitfalls
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    Key Terms
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    Mark Points

    What You Need to Demonstrate

    Key skills and knowledge for this topic

    • Award 1 mark for identifying the heat source as radioactive decay of unstable nuclei (e.g., uranium) in deep rocks
    • Award 1 mark for describing the process: cold water is pumped down, heated by hot rocks to produce steam
    • Award 1 mark for stating steam drives a turbine which turns a generator to produce electricity
    • Credit responses that identify geothermal as a reliable energy source that does not produce carbon dioxide while operating
    • Award 1 mark for noting the limitation that power stations can only be built in specific volcanically active areas

    Example Examiner Feedback

    Real feedback patterns examiners use when marking

    • "You correctly identified the mechanism, but missed the origin of the heat—mention radioactive decay for full credit"
    • "Good comparison of renewables, but ensure you highlight that geothermal is reliable unlike wind or solar"
    • "You mentioned 'pollution'—be more specific. Is it visual, noise, or chemical? Geothermal has low chemical pollution"
    • "Excellent link between location and volcanic activity; now consider the high initial capital costs to reach the top band"

    Marking Points

    Key points examiners look for in your answers

    • Award 1 mark for identifying the heat source as radioactive decay of unstable nuclei (e.g., uranium) in deep rocks
    • Award 1 mark for describing the process: cold water is pumped down, heated by hot rocks to produce steam
    • Award 1 mark for stating steam drives a turbine which turns a generator to produce electricity
    • Credit responses that identify geothermal as a reliable energy source that does not produce carbon dioxide while operating
    • Award 1 mark for noting the limitation that power stations can only be built in specific volcanically active areas

    Examiner Tips

    Expert advice for maximising your marks

    • 💡When asked for the energy source, be specific: specify 'radioactive decay' rather than just 'heat from the earth' to secure Higher Tier marks
    • 💡In 6-mark evaluation questions, contrast geothermal's high reliability (base load) with the intermittency of wind or solar power
    • 💡Ensure you distinguish between the environmental impact of construction versus operation (e.g., CO2 is low during operation but high setup cost)

    Common Mistakes

    Pitfalls to avoid in your exam answers

    • Stating the heat comes from 'the core' or 'magma' without referencing radioactive decay as the origin of the thermal energy
    • Confusing geothermal power stations with ground source heat pumps used for domestic heating
    • Claiming geothermal energy is unreliable or weather-dependent (confusing it with wind or solar sources)
    • Vaguely stating it causes 'pollution' without specifying that it releases fewer greenhouse gases than fossil fuels but can release hazardous underground gases

    Study Guide Available

    Comprehensive revision notes & examples

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    Key Terminology

    Essential terms to know

    Radioactive decay as the internal heat source
    Energy transfers: Thermal to Kinetic to Electrical
    Reliability and base-load capability
    Geographic limitations and environmental impact

    Likely Command Words

    How questions on this topic are typically asked

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    Describe
    Explain
    Evaluate
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