Hot fluid rises from a geothermal reservoir through a production well. Depending on temperature, it is used directly as dry steam, flashed to steam in a separator (flash plants), or used to boil a secondary low-boiling-point fluid across a heat exchanger (binary plants). Either way, the resulting vapor spins a turbine-generator before condensing and returning underground.
η_Carnot = 1 − Tcold / Thot (theoretical maximum)
P = ṁ · Δh · η (turbine power output)
η_actual ≈ 0.5–0.65 × η_Carnot for real plants
- Reservoir temperature — sets the theoretical (Carnot) efficiency ceiling and how much of the fluid flashes to steam.
- Well flow rate — more mass flow means more energy delivered per second to the turbine, raising power output.
- Plant type — dry steam needs vapor-dominated fields (rare, most efficient plumbing), flash works well for high-temperature liquid reservoirs, binary lets even moderate-temperature resources (120–180 °C) generate power via a secondary working fluid.
- Reset — restores default reservoir conditions.
The Geysers field in California is the world's largest dry-steam plant, while binary plants now unlock geothermal power from far more, cooler resources worldwide.