Geothermal energy uses heat stored inside Earth to produce electricity and provide direct heating. In a geothermal power plant, wells reach deep underground where hot rock warms water into hot liquid or steam. This energy source matters because Earth’s internal heat is available day and night, unlike sunlight or wind.
A well designed geothermal system can provide steady renewable power with low greenhouse gas emissions.
Key Facts
- Geothermal power converts Earth’s internal heat into usable electricity or heat.
- Thermal energy transfer can be estimated by Q = mcΔT, where Q is heat, m is mass, c is specific heat, and ΔT is temperature change.
- Electrical power output is P = E/t, where P is power, E is energy, and t is time.
- In a dry steam plant, steam from underground directly spins a turbine connected to a generator.
- In a flash steam plant, hot high pressure water rises and partly turns into steam when pressure drops.
- Injection wells return cooled water underground, helping maintain pressure and reduce water loss.
Vocabulary
- Geothermal energy
- Geothermal energy is thermal energy stored inside Earth that can be used for heating or electricity generation.
- Production well
- A production well is a deep borehole that brings hot water or steam from underground reservoirs to the surface.
- Injection well
- An injection well is a borehole that sends cooled water back underground to be reheated by hot rock.
- Turbine
- A turbine is a rotating machine that converts the motion of steam or fluid into mechanical energy.
- Generator
- A generator is a device that converts mechanical energy from a spinning turbine into electrical energy.
Common Mistakes to Avoid
- Thinking geothermal energy comes from sunlight, which is wrong because it mainly comes from heat left from Earth’s formation and radioactive decay inside Earth.
- Assuming all geothermal plants use lava, which is wrong because most use hot rock, hot water, or steam far below the surface rather than molten rock.
- Forgetting the injection well, which is wrong because returning cooled water helps keep the underground reservoir working and supports long term operation.
- Treating geothermal as completely impact free, which is wrong because drilling, land use, mineral-rich fluids, and small induced earthquakes must be managed carefully.
Practice Questions
- 1 A geothermal plant produces 45 MW of electrical power. How much electrical energy does it generate in 6 hours? Give your answer in MWh.
- 2 Water of mass 2000 kg cools from 180°C to 90°C in a heat exchanger. Using c = 4200 J/(kg·°C), calculate the thermal energy transferred.
- 3 Explain why reinjecting cooled water underground can make a geothermal power system more sustainable than simply releasing the water at the surface.