Use the simulation in your science or Physics class to illustrate conversion of geothermal energy resource to electricity
Overview
This interactive simulation models how geothermal energy is used to generate electricity. It presents a cross-sectional view of the Earth, showing the complete energy transfer chain from deep underground heat reservoirs to powered homes at the surface.
Students control three variables — reservoir temperature, drill depth, and generator efficiency — and observe in real time how these affect steam flow rate, thermal power, electrical output, and the number of homes that can be supplied. The scene responds dynamically: rock strata glow hotter as temperature increases, the turbine spins faster as more steam is produced, the power cable to the house activates, and windows illuminate as electricity flows.
How the System Works (as modelled in the simulation)
Cold water is pumped down an injection well deep into hot permeable rock or a magma-heated reservoir. The rock heats the water, converting it into high-pressure steam or superheated fluid. This rises back to the surface through a production well, where it drives a steam turbine connected to a generator. The spent steam is cooled in a cooling tower, condensed back into water, and re-injected — completing a closed loop. Electrical energy is then transmitted via cable to homes and the national grid.
GCSE Curriculum Links
AQA Physics & Combined Science — Topic 1: Energy
Geothermal energy sits directly within the Energy topic as one of the key renewable energy sources students must evaluate at GCSE. The simulation makes visible the full energy transfer chain:
Thermal energy (Earth’s interior) → Kinetic energy (steam/turbine) → Electrical energy (generator) → Useful energy (homes)
This maps to the AQA specification requirement that students describe how energy is transferred between stores and through pathways, and identify where energy is usefully transferred and where it is dissipated (wasted) as heat.
The simulation also illustrates why geothermal is considered a renewable source: the Earth’s internal heat — generated by radioactive decay in the mantle and residual heat from planetary formation — is continuously replenished on human timescales, unlike fossil fuels.
AQA Physics & Combined Science — Topic 1: Efficiency
The Efficiency slider directly models the core GCSE equation:
$$\text{Efficiency} = \frac{\text{Useful power output}}{\text{Total power input}} \times 100%$$
Students can observe how reducing efficiency from 95% to 30% dramatically cuts electrical output even when thermal power remains constant. This reinforces the concept that no energy transfer is perfectly efficient — energy is always lost, primarily as heat in the condenser and turbine bearings.
The simulation uses a Rankine cycle approximation (the real thermodynamic cycle used in geothermal plants), with efficiency capped by the Carnot limit — a higher-tier physics concept that students can explore through discussion even if the mathematics is beyond the specification.
AQA Physics — Topic 2: Electricity
The generator component links directly to electromagnetic induction, the process by which a rotating turbine shaft causes magnets to spin inside a coil, inducing a voltage (Faraday’s Law). At GCSE, students must understand that:
- Generators convert kinetic energy into electrical energy
- This is the same principle used in coal, gas, nuclear, and hydroelectric power stations
- The difference between energy sources is simply what heats the water (or what drives the turbine directly)
This comparison — geothermal vs. fossil fuels as heat sources for the same type of turbine-generator system — is a powerful teaching moment for students who tend to think of renewables and non-renewables as completely different technologies.
AQA Physics & Combined Science — Topic 4: Electricity Generation and the National Grid
The simulation’s power cable and illuminated house represent electricity transmission to consumers. This links to:
- The role of transformers in stepping voltage up for efficient transmission and stepping it back down for safe domestic use
- The concept of power rating — the electrical output display (in MW) shows why large-scale generation is needed to supply thousands of homes
- The idea of baseload power — unlike wind or solar, geothermal produces electricity continuously regardless of weather, making it valuable for grid stability
AQA Physics — Topic 4: Uses of Radioactivity (Cross-link)
For higher-tier students, a valuable cross-topic link: the Earth’s internal heat is partially maintained by radioactive decay of isotopes such as uranium-238, thorium-232, and potassium-40 deep in the mantle and crust. This means geothermal energy has an indirect connection to nuclear physics — the same process that makes radioactive materials hazardous is also responsible for keeping the Earth’s interior molten.
Working Scientifically
The simulation supports the following Working Scientifically skills from the AQA specification:
- Variables: Students identify independent variables (temperature, depth, efficiency), dependent variables (electrical output, homes powered), and control variables (the physics model itself)
- Relationships: Students observe how changing one variable affects the output, and consider whether relationships are linear or non-linear
- Evaluation: Students evaluate the limitations of the model (e.g., no transmission losses, idealised geology) and discuss how real-world conditions might differ
Suggested Classroom Activities
Starter — Predict Before You Explore (5–10 minutes)
Before touching the sliders, ask students to predict:
- If you drill twice as deep, does electrical output double? Why or why not?
- Which single change will have the biggest impact on homes powered — increasing temperature by 100°C, increasing depth by 2 km, or increasing efficiency by 20%?
Students write predictions, then test them using the simulation. Discuss why results may differ from intuition (e.g., deeper drilling increases flow rate and temperature, making it a compound effect).
Main Activity — Virtual Investigation (15–20 minutes)
Students treat the simulation as a controlled experiment. Working in pairs, they:
- Set efficiency to 80% and depth to 3 km. Record electrical output at temperatures: 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C.
- Plot a graph of temperature (x-axis) vs. electrical output in MW (y-axis). Is the relationship linear?
- Repeat with depth as the variable (hold temperature at 250°C, vary depth from 1 to 6 km in 1 km steps).
- Compare the two graphs. Which variable gives the greater rate of increase in output?
Expected finding: Both relationships are non-linear. Temperature has an exponential-style effect because power scales with both flow rate and the temperature difference available for the thermodynamic cycle.
Discussion — Why Isn’t It Used Everywhere? (10 minutes)
The simulation shows impressive output at high temperatures, prompting the natural question: if geothermal is renewable and continuous, why doesn’t the UK rely on it?
Discussion points:
- Suitable geological conditions are rare — Iceland, Kenya, New Zealand, and parts of the USA sit on tectonic boundaries where heat is close to the surface
- The UK has some potential (Cornwall has deep geothermal projects underway), but depths needed to reach useful temperatures are much greater — increasing drilling cost significantly
- Drilling failures and reservoir depletion are real risks not visible in the simplified model
- Compare to wind and solar: geothermal is consistent but geographically limited; wind and solar are widely available but intermittent
Efficiency Challenge — Higher Tier (10 minutes)
Give students the following values from the simulation at a specific setting and ask them to verify the efficiency calculation manually:
Thermal Power = 18.5 MW, Electrical Output = 4.2 MW
Calculate efficiency. Compare to the slider setting. Why might there be a small discrepancy?
Students apply: Efficiency = (4.2 ÷ 18.5) × 100% = 22.7%
This reinforces the efficiency equation and prompts discussion of rounding, real-world losses, and the Carnot limit.
Extension — Energy Mix Research Task
Students use the simulation as a springboard to research the UK energy mix. They find the current proportion of electricity from:
- Geothermal
- Wind
- Solar
- Gas
- Nuclear
They then write a short paragraph evaluating whether the UK should invest more in geothermal energy, using evidence from both the simulation and their research.
Key Equations Referenced
| Equation | Where it Appears |
|---|---|
| Efficiency = P_out ÷ P_in | Efficiency slider vs. output display |
| P = IV | Electrical power output (linked concept) |
| Energy = Power × Time | Homes powered calculation (3.3 kW average UK home) |
| Carnot efficiency = ΔT ÷ T_hot | Upper efficiency limit (extension discussion) |
This simulation is designed to support GCSE Physics and Combined Science delivery, with particular relevance to AQA specifications. It is suited to classroom projection, paired investigation tasks, and independent revision.