Q8Power Generation Sources

Geothermal energy is the natural heat stored within the Earth's interior, arising from the radioactive decay of isotopes such as uranium, thorium and potassium in the crust and mantle, plus residual primordial heat from planetary formation. This heat manifests at the surface in regions of high geothermal gradient as hot springs, geysers, fumaroles and volcanic activity, and can be tapped commercially where hot, permeable, water-bearing rock formations (geothermal reservoirs) exist at accessible depths.

Geothermal power plants extract this heat through production wells drilled into the reservoir. Three main plant types are used depending on the reservoir temperature and phase: (1) Dry-steam plants — used where the reservoir directly produces dry, superheated steam, which is piped straight to a steam turbine-generator; (2) Flash-steam plants — used for high-temperature liquid-dominated reservoirs; the hot pressurized water is 'flashed' (partially vaporized) as pressure drops in a separator vessel, and the resulting steam drives the turbine while the remaining brine is reinjected; (3) Binary-cycle plants — used for moderate-temperature resources; the geothermal fluid is passed through a heat exchanger to vaporize a secondary working fluid with a lower boiling point (e.g., isobutane, in an Organic Rankine Cycle), which drives the turbine in a closed loop, while the geothermal fluid itself is reinjected without direct contact with the turbine.

Beyond electricity generation, geothermal energy is widely used directly for space heating, greenhouse heating, aquaculture, and industrial process heat. Geothermal energy offers high capacity factor (continuous, weather-independent baseload supply, unlike solar/wind) and low emissions, but is geographically constrained to regions with favorable geological conditions and requires careful reservoir management to avoid depletion.