The Hellisheidi power plant ranks sixth among the world’s biggest geothermal power plants by installed capacity. It is a flash steam combined heat and power plant (CHP) generating 303MW of electricity and 400MW of thermal energy. The plant is located at Hengill, about 11km away from the existing Nesjavellir geothermal power station in south-west Iceland.
The plant was commissioned in five phases from 2006-2011, and is owned and operated by Orkuveita Reykjavíkur.
The power output of the plant is primarily supplied to the aluminium refineries of the capital city Reykjavik, which is located 20km west of Hellisheidi.
Orkuveita Reykjavikur decided to build the geothermal power plant in 2002, based on the conclusions of research drilling that was completed in 2001. The first phase of the project included installation of two high-pressure 45MW turbines and commenced production in 2006. A low-pressure steam turbine of 33MW capacity was added to the plant in 2007, as part of the second phase of development.
The third phase, commissioned in 2008, involved the installation of two more high-pressure turbines of 45MW capacity each. Steam from Skarðsmýrarfjall Mountain is used for power generation in the third phase.
The geothermal plant started producing hot water in its fourth phase of development which was completed in 2010. A hot water main pipeline for district heating purpose was also installed in this phase.
The fifth and final stage of development comprised of the installation of two 45MW turbines in 2011.
The Hellisheidi geothermal power plant was developed in an area of 13,000m2 near Mount Hengill in the Hengill geothermal area, one of the largest high temperature geothermal fields in Iceland covering an area of 110km2. Power is generated using a combination of six high-pressure and one low-pressure steam turbines.
Hot fluid is extracted through 30 wells at a depth of 2,000m to 3,000m. The extracted fluid passes through steam and mist separators. The separated hot steam propels the turbines for electricity generation. The plant uses about 500kg/s of geothermal steam at 180°C for producing electricity.
The electrical system of each generating unit of the power station comprises of a 50MVA generator, a 50MVA/220kV step-up transformer, and an 11/11 kV transformer for connection to the 11kV station service system.
The power generated from the plant is transmitted to the national grid’s substation located 1km away from the power plant.
Fresh ground water is heated to 50°C with the steam from the turbines. The water is heated again by heat exchange up to 83°C.
The reheated water is pumped to a 950m3 capacity hot water storage tank at the plant site via a 1m wide and 360m long pipe. The hot water is further supplied to the Reykjavík city via a 19.5km long pre-insulated underground pipe line with diameter of 0.9m to 1m.
Construction of the Hellisheidi hot water main pipeline started in 2008. The pipeline was brought into service towards the end of 2010 and has a maximum flow rate of 2,250l/s.
The Hellisheidi power plant design and construction contract was awarded to Mannvit Engineering.
Verkís Engineering was awarded the design and construction contract for the Hellisheidi hot water main pipeline.
Mitsubishi supplied six 45MW high-pressure steam turbines and Toshiba provided one 33MW low-pressure steam turbine for the power plant.
The counter-flow wet cooling system used at the power plant was supplied by SPX Cooling Technologies. Siemens supplied control and protection system for the power plant.
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