Hellisheidi Geothermal Power Plant

Hellisheidi geothermal power plant is a flash steam, combined heat and power plant (CHP) located in SW-Iceland, on one of the largest geothermal systems (high-enthalpy) in Iceland.  The plant's purpose is to meet increasing demand for electricity and hot water for space heating.  The development plan was an incremental expansion from 2006 to 2018 to an output of 303 MWe and 200 MWth, making it the largest geothermal combined heat and power plant in Iceland and one of the world's largest geothermal power plants. The installed heat capacity is planned to be 400 MWt as demand for heating increases in the Reykjavik capital area. Overall, 61 wells were drilled, from 1,000-2,200 meters, 44 production and 17 reinjection wells. The plant owner is ON (formerly Orkuveita Reykjavíkur). 

Mannvit services

Project management	Mechanical design
Overall plant design	Document control
Environmental Impact Assessment	HVAC systems
Design management	Site supervision
Technical supervision	Supervision for turbine and cold end installation
Well design	Steam gathering system supervision
Drilling bid preparation and tender evaluation	Electrical work supervision
Inspection of rigs, equipment, materials	Control system supervision
Supervision for drilling operations	Civil work supervision
Process and system design	Mechanical work supervision
Detailed plant design	Supervision of construction work
Construction drawings	Commissioning work and start-up
Preparation of bid documents	Acceptance testing
Bid evaluation	Training of operators
Design of control systems

Plant details

Phase 1: 2006, 2 x 45 MWe - high pressure turbines.

Phase 2: 2007, 33 MWe - low pressure turbine (bottoming plant).

Phase 3: 2008, 2 x 45 MWe - high pressure turbines

Phase 4: 2010, 133 MWth - thermal power plant

Phase 5: 2011, 2 x 45 MWe - high pressure turbines

Phase 6: 2015, connection of four production wells

Phase 7: 2018, expansion of the heating plant to 200 MWth

Phase 8: 2030 (planned) - 133MWth

 

Process

Geothermal fluid from production wells is gathered in central separation stations.  The separated water is flashed and the steam is used in the low pressure turbine but the water is used in heat exchangers to heat the preheated water up to the required temperature.  Electricity is generated with condensing steam turbines, six high pressure turbines and one low pressure turbine.  The condensers from four turbines are used to preheat fresh water.  The heated water is treated in de-aerators to suit the requirements of the distribution system. The separated water is diluted with condensate and then pumped into re‐injection wells.  Co-generation of electric and thermal power is thus utilized in the most economical way possible.

 

Transmission of energy

Electric energy is transmitted to the substation which is directly connected to the national grid. The line voltage from each unit is 220 kV. The hot water is pumped from the plant to a tank at the highest point of the transmission pipe. From there the water flows by gravity to the storage tanks of the district heating system from where it is distributed to the consumers in Reykjavik.