| Authors |
Bergur SIGFUSSON, Kevin DILLMAN, Magnus Th. ARNARSON, Marta R. KARLSDOTTIR, Magnea Th. MAGNUSDOTTIR, Ingvi GUNNARSSON, Gretar IVARSSON, Sandra O. SNAEBJÖRNSDOTTIR, EDDA S.P. ARADOTTIR, Holmfridur SIGURDARDOTTIR |
| Abstract |
The Hellisheidi Power plant was commissioned in 2006 and was fully built in 2011. Initially, the majority of non-condensable gas (NCG) emissions from the plant were vented to the atmosphere at selected cooling towers of the plant, resulting in elevated H2S concentration levels in neighbouring communities and considerable CO2 emissions. The total H2S and CO2 discharge from the geothermal reservoir was 10,900 tons/year and 43,000 tons/year respectively in 2014, but had decreased to 9,500 tonnes/year and 37,400 tonnes/year in 2018. In 2014, a capture plant applying the CarbFix process was commissioned and connected to the main turbine hall of the power plant. That same year, 2,400 tonnes of H2S from the powerplant were re-injected back into the geothermal reservoir. The plant capacity was doubled in 2016, resulting in re-injection of 4,500 tonnes of H2S. In 2018, all gas exhaust systems of the power plant were combined into a single system enabling the operation of the capture plant at full capacity resulting in the re-injection of 7,000 tonnes of H2S. With these new installations the H2S emissions have decreased stepwise to 2,500 tons/year in 2018 due to the capture and re-injection activities. Measurements from a network of air quality monitoring stations, located between 600 m to 30 km from the nearest cooling tower, all show a decrease in the mean daily atmospheric H2S concentration in conjunction with degreasing emissions from the powerplant. In 2018, the mean daily H2S concentration at three monitoring stations in communities nearest to the geothermal plant (Norðlingaholt, Lækjarbotnar and Hveragerði) never exceeded the regulatory health limits set in Iceland (50 µg/m3 averaged over 24 hours). Elevated concentrations of H2S in the air quality monitoring station closest to the power plant (about 600 m from the main emission point) have decreased since the capture plant was commissioned. The mean daily H2S concentration at the power plant exceeded 50 µg/m3 12 times in 2018 compared to 106 times in 2014, the year when the capture plant was commissioned. Over the same period, reinjection of CO2 has increased from 4,100 tonnes/year to 12,200 tonnes/year, in 2014 and 2018. This is in accordance with Reykjavik Energy´s (RE) 15-year goal of reducing RE´s and its subsidiaries´ carbon footprint by 60% by 2030. Expansion and continued operation of gas capture and reinjection is seen as a key factor in achieving this goal. |