# Hellisheiði Geothermal Plant

**URL:** https://thecodex.expert/energy/geothermal/hellisheidi/
**Codex:** The Energy Codex · Publisher: The Codex (Let Us Do It For U), Mumbai, India
**Section:** Renewables — Geothermal
**Last verified:** June 2026
**Entry type:** asset · **Confidence:** high

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## Canonical definition

Hellisheiði is a geothermal power station in the Hengill volcanic area of southwest Iceland, about 25 km southeast of Reykjavík, at GPS 64.0370° N, 21.4000° W. It is one of the world's largest geothermal power stations by installed capacity. It is owned and operated by ON Power (Orka náttúrunnar), a subsidiary of Reykjavík Energy (Orkuveita Reykjavíkur). Installed electrical capacity is approximately 303 MWe and thermal (hot water) capacity approximately 200 MWth. It uses combined flash-steam and binary technology drawing on a high-temperature reservoir of roughly 270 °C. First power was generated around 2006, reaching full capacity around 2011. Hellisheiði hosts the CarbFix project, which dissolves captured CO₂ in water and injects it into basalt, where it mineralises into solid carbonate within roughly two years, and is paired with the Climeworks Orca (2021) and Mammoth (2024) direct-air-capture plants.

## Key facts

- **Electrical capacity:** ~303 MWe
- **Thermal capacity:** ~200 MWth (district heating for the Reykjavík region)
- **Reservoir temperature:** ~270 °C
- **Technology:** Double-flash steam + binary, combined heat and power
- **Commissioned:** ~2006, staged to full capacity ~2011
- **Operator:** ON Power (Orka náttúrunnar), subsidiary of Reykjavík Energy
- **Ownership:** Publicly owned, majority City of Reykjavík
- **Special feature:** Host site of CarbFix CO₂-to-basalt mineral storage and Climeworks direct air capture

## How it works

Production wells deliver a two-phase steam/water mix. Separators send high-pressure steam to turbines for electricity; separated brine is flashed again for more power and its heat transferred to a clean freshwater district-heating loop. Spent fluid and condensate are reinjected to sustain the reservoir. Non-condensable gases (CO₂, H₂S) are captured for CarbFix mineralisation rather than vented.

## CarbFix — carbon to stone

CarbFix dissolves CO₂ in water and injects it into reactive basalt. Calcium, magnesium and iron leached from the rock react with the dissolved carbon to form stable carbonate minerals — the majority within about two years, as shown by isotope-traced field monitoring. Operating at the site since 2012, CarbFix stores both the plant's own geothermal CO₂ and atmospheric CO₂ captured by the co-located Climeworks Orca and Mammoth plants.

## India relevance

India lacks Iceland's high-temperature volcanic heat, but its vast Deccan Traps basalt is geologically suited to CarbFix-style mineral carbon storage, making the storage concept directly relevant to India's climate strategy. India's own geothermal resources are low-to-medium enthalpy (Puga and Chumathang in Ladakh, Tattapani in Chhattisgarh), better suited to direct heat use and binary plants.

## Risks

- **Induced seismicity** from fluid reinjection has caused felt earthquakes near the plant; managed by controlling injection rates.
- **Hydrogen sulphide (H₂S)** emissions, addressed via the SulFix gas-abatement programme.
- **Reservoir drawdown** requires active reinjection and make-up wells to sustain output.

## Sources

- ON Power (on.is) — operator; capacity, technology
- Orkuveita Reykjavíkur (or.is) — ownership, district heating
- CarbFix (carbfix.com) — mineral carbon storage
- Climeworks (climeworks.com) — direct air capture
- Orkustofnun (orkustofnun.is) — resource and regulatory data
- IRENA (irena.org), IEA (iea.org) — technology context
- Icelandic Met Office (vedur.is) — seismicity
- MNRE (mnre.gov.in), GSI (gsi.gov.in) — India context

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*This page documents what named institutional sources record about Hellisheiді. It is a record of documentation, not a recommendation. Figures are rounded and were last verified June 2026. Not engineering, financial, or policy advice. Verify at the linked primary source before relying on any number.*