Additional wells required to maintain output Hellisheidi geothermal plant

Hellisheidi geothermal power plant by Reykjavik Energy, Iceland (source: flickr/ thinkgeoenergy, creative commons)
Avatar Hákon Skúlason 21 Nov 2016

ON, the operator of the Hellisheidi geothermal power plant in Iceland expects additional investment need of $221 million over the next 6 years, to maintain operating at the installed capacity of 303 MW electric.

Already planned in the overall set up of the 303 MW Hellisheidi geothermal power plant, ON – the operator – now needs to actually drill additional wells to maintain its operating capacity.

The steam supply in the Hengill geothermal area that fuels the plant is decreasing at around 2.3% every year. With an installed capacity of 303 MW the plant is currently operating with an output of 276 MW.

ON (Reykjavik Energy) has an overall installed geothermal power generation capacity of 423 MW, of which 120 MW come from the Nesjavellir plant and 303 MW from the Hellisheidi plant, both fuelled by geothermal resources in the same area of Hengill near Reykjavik, Iceland.

ON now expects to have to invest up to $221 million over the next six years to drill additional wells.

Power production of hydro power plants depends primarily on stream flow availability and water reservoirs, while power production of geothermal power plants depends on steam availability from multiple boreholes. In the Hengill geothermal area the recent decrease in boreholes performance has resulted in less power production and underperformance of the Hellisheidi power plant.

Steam supply in the Hengill geothermal area was in 2013 deteriorating by an estimate of 2.3% per annum and the decline has even accelerated until now Nov 2016.

The Hengill area was initially intended to supply sufficient steam to the Hellisheidi power plant, but the boreholes are currently not as productive as before and decrease in performance more rapidly than originally assumed. There are indications that the power plant has been expanding too rapidly. In 2012 Reykjavik Energy initiated work on connecting the high temperature area in Hverahlid to the Hellisheidi power plant. The project was commisioned earlier this year. The steam pipes are unprecented 5 km long and require sophisticated moisture separators.

The Hellisheidi power plant are with installed capacity of 303 Mwe, but at the end of 2013 was only showing output of 276 MWe. Additional steam from Hverahlid only increases production of Hellisheidi power plant by 45 MWe. Previous plans assumed to build a new power plant at Hverahlid but these plans have now been abandoned. The decision to transport steam from Hverahlid and reinject additional water output at the power plant site, will result in an estimated capital cost of 221 MUSD for the next six years.