March 2013Claus BallzusIGC 2013

The Development of the Hellisheiði Power Plant

ExpertiseSuccessValue

Key features

• Capacity 303 MWe and 133 MWt

• Largest geothermal power plant in Iceland

• Second largest power plant in Iceland

• Co-generates electricity and heat• Commissioned in five stages

between 2006 and 2011 • State of the Art Design

Background• Geothermal electricity

generation since 1969• Experience from operating

5 geothermal fields• Development of Icelandic

key components in the steam gathering system

• Experience in producing electricity and hot water for district heating in a combined power plant

Different approaches• Svartsengi since 1976:

Preheating of ground water with second flash steam, final heating with steam from back-pressure units

• Krafla since 1977:Only electricity generation in a double flash system with double pressure units

Different approaches• Nesjavellir since 1990:

Preheating of ground water in turbine condensers, final heating with geothermal water

• Hellisheiði since 2006:Preheating of ground water in turbine condensers, final heating with geothermal water

Hellisheiði – requirements• Main requirements

• Independent heat and electricity production

• Optimal resource utilization• Modular design• Flexibility to meet changes in

the geothermal field• Fulfil environmental

constrains

Modular design – 1st stageTwo 45 MW single pressure units with independent steam gathering systems

Modular design – 2nd stageBottoming plant added: One 33 MW single pressure unit by flashing geothermal water

Modular design – 3rd stageTwo 45 MW single pressure units added, mostly independent steam gathering systems

Modular design – 4th stageThermal heating plant added: 133 MWt thermal output utilizing geothermal water in shell and tube heat exchangers

Modular design – 5th stageTwo 45 MW single pressure units added, mostly independent steam gathering systems

Learning process – expected and unexpected

• Flexibility: Mean enthalpy of the geothermal field has changed from 1200 kJ/kg at design start to the actual value of 1800 kJ/kg – steam/geothermal water portion is now 51/49% instead of 22/78% at design start.

• Flexibility and modular design: The size of the plant could be changed from 3x40 MWe and 400 MWt to 6x45 MWe + 33 MWe and 400 MWt.

• Flexibility and modular design: A bottoming plant could be added to the process increasing the overall efficiency.

• Modular design: Erection and commissioning of new modules of the plant was possible while operating the modules already commissioned.

• Modular design: Steam gathering system could be rearranged when well output of a certain part of the field turned out to be under expectations.

Learning process – successes

Learning process – development speed2002 Exploration wells2002/03: Feasibility studies and environmental assessment2003: Construction design starts2005: Decision for the bottoming plant2006: Commissioning of the first units2006: Decision for the next 2 units2007: Decision for heating power plant2007: Decision for the next 2 units2008: Financial breakdown in Iceland2009: Slow down of stage 4 and 5, project

delayed by appr. one year2010: Commissioning of the heating plant2011: Commissioning of units 5 & 6

• First well location at Gráuhnúkar about 3 km from power plant.

• Turned out to be one of the hottest spots in the geothermal area and a site for make-up wells.

• New location about 1 km from power plant in a fissure zone.

• Good permeability but injection of the geothermal water triggered earthquakes.

To avoid earthquakes a stable operation of the injection wells is preferred.

Learning process – re-injection

• Development speed: If possible have about 3 to 5 years between stages; operation experience from the production wells can give you an important input for the next step in development of the geothermal field.

• Re-injection: During the exploration phase research of the re-injection areas is as important as for the steam fields. Have planes for an alternative sites or solution in your concept.

• Geothermal gas exhaust: In certain weather condition geothermal gas might not dissolve evenly in the air, numerical models may be misleading. Consider costs for an abetment system in the investment plan.

• Have in mind that a geothermal fields are a dynamic creature over the lifetime of the power plant.

• Leave space for future developments at the power plant site to keep flexibility.• Think modular.

Learning process – recommendation

THANK YOU FOR YOUR ATTENTION

Owner:

Orkuveita Reykjavíkur

Design team:

Production wells

Steam separators

Well head silencers

Pressure regulation

Turbines Generators

Mist separators

Condensers

Emergency exhaust

Hot water tank

Cold water pump

Heat exchangers

De-aerators

Condensers

Hot water pups Re-injection wells

Cooling towers

2x45 MWe+2x45MWe

+1x33 MWe

+2x45MWe

+1x133MWt