A geothermal power plant is a renewable energy machine that turns heat from inside Earth into electricity. Deep underground, hot rock warms water stored in cracks and porous layers called geothermal reservoirs. By drilling wells into these hot zones, engineers can bring steam or hot water to the surface.
This matters because geothermal power can produce steady electricity day and night with low carbon emissions.
Key Facts
- Geothermal energy comes from heat stored inside Earth, mainly from radioactive decay and leftover heat from Earth’s formation.
- Thermal energy transfer from hot rock to water can produce steam that spins a turbine.
- A generator converts turbine motion into electrical energy using electromagnetic induction.
- Electrical power can be calculated by P = E/t, where P is power, E is energy, and t is time.
- Plant efficiency can be estimated by efficiency = useful electrical energy output / thermal energy input.
- Common plant types include dry steam, flash steam, and binary cycle geothermal plants.
Vocabulary
- Geothermal reservoir
- A geothermal reservoir is an underground region of hot water or steam trapped in porous rock.
- Production well
- A production well is a drilled passage that carries hot water or steam from the reservoir to the power plant.
- Turbine
- A turbine is a rotating machine with blades that convert moving steam or fluid energy into mechanical motion.
- Generator
- A generator is a device that converts mechanical rotation into electrical energy.
- Injection well
- An injection well returns cooled water underground to help maintain pressure and recharge the reservoir.
Common Mistakes to Avoid
- Thinking geothermal plants burn fuel, which is wrong because they use underground heat rather than combustion to make steam or heat a working fluid.
- Forgetting the injection well, which is wrong because returning cooled water helps keep the reservoir usable and reduces waste.
- Assuming all geothermal plants use the same design, which is wrong because dry steam, flash steam, and binary cycle plants handle underground heat in different ways.
- Confusing energy with power, which is wrong because energy is the amount delivered while power is the rate of energy transfer.
Practice Questions
- 1 A geothermal generator produces 45,000,000 J of electrical energy in 30 s. What is its electrical power output in watts?
- 2 A plant receives 200 MW of thermal power from hot geothermal fluid and produces 28 MW of electrical power. What is the efficiency as a decimal and as a percent?
- 3 Explain why a geothermal power plant can provide steadier electricity than a solar panel system, and identify one geographic limitation of geothermal power.