Geothermal
Tapping the Earth's heat to produce both electricity and direct heat. Unlike sun and wind, geothermal runs around the clock, as baseload, day and night. But it depends on the resource underground: the main risks sit at the drilling, fluid-chemistry and induced-seismicity end, not in the power block.
The main families
Dry steam, flash, binary (ORC)
Three plant families: dry steam (reservoir steam drives the turbine directly), flash (pressurized hot water vaporizes by flashing), and binary organic Rankine cycle (ORC) for low-to-medium-temperature resources, where a secondary low-boiling fluid drives the turbine.
District heating, deep, shallow, heat pumps
Direct thermal use: urban district heating fed by deep geothermal, shallow geothermal coupled with heat pumps for buildings, and shallow vertical boreholes. Extracted heat serves space heating, hot water and some industrial processes.
Enhanced geothermal systems, deep drilling
Enhanced geothermal systems (EGS) create or open fractures in hot dry rock by injecting pressurized water, where no natural reservoir exists. Combined with deep drilling, they aim to extend geothermal beyond volcanic zones — at the cost of induced-seismicity risk.
Key challenges
- Resource & drilling — exploration risk dominates the project: until you have drilled, you do not know whether the reservoir delivers the promised flow and temperature. The cost of deep, uncertain wells dominates the budget.
- Fluid chemistry — geothermal brines are aggressive: steel corrosion, scaling of pipes and heat exchangers, and non-condensable gases — including toxic, corrosive hydrogen sulfide (H2S) — that must be managed.
- Induced seismicity — reservoir stimulation, especially in EGS, can trigger felt earthquakes. The Basel project (2006) is the reference case: microseismic monitoring and traffic-light stop protocols have become mandatory.
- Binary-cycle process safety — in a binary (ORC) plant, the organic working fluid is often flammable: leak control, explosive-atmosphere zoning and safety instrumented systems (IEC 61511) govern the power block.
- Resource management & reinjection — to last, a geothermal field must be operated in balance: reinjection of the cooled fluid to support reservoir pressure and avoid premature depletion or cooling.
See also
Geothermal-specific standards
- Process safety & pressure equipment — There are few dedicated international geothermal standards: plants apply general process-safety and pressure-equipment rules (vessels, steam, turbine, heat exchangers).
- IEC 61511 — Functional safety of safety instrumented systems (SIS): relevant to the process safety of a binary-cycle (ORC) plant, whose working fluid is often flammable.
- IEC 60079-0 — Explosive atmospheres: zoning and equipment for flammable gases and hydrogen sulfide (H2S) present in some geothermal fluids.
Related standard pages on IndustryHub
Major players
Turbines & binary cycle
Ormat, Toshiba, Mitsubishi Power.
Operators & developers
Enel Green Power, Calpine (The Geysers), Ormat.
Drilling
Baker Hughes, SLB.
Heat pumps & shallow geothermal
Vaillant, Viessmann, Bosch.
Landmark facts
| Fact | Year | Location | Lesson |
|---|---|---|---|
| "The Geysers" — the world's largest geothermal field | 1960s | California, USA | In operation since the 1960s, "The Geysers" is the world's largest geothermal field and a long-running example of baseload renewable power running day and night for decades. |
| Basel EGS — induced seismicity | 2006 | Basel, Switzerland | A deep-geothermal stimulation (EGS) project induced felt earthquakes and was halted. It is the reference case for induced-seismicity risk in EGS. |