In Iceland’s southern Highlands, the Sigalda Power Plant, Sigöldustöð in Icelandic, stands alongside reservoirs and rivers that shape the country’s vast interior. Located near Þórisvatn, the nation’s largest reservoir, Sigalda occupies a strategic spot about 160 kilometres east of Reykjavík. It is the newest in a string of hydroelectric projects lining the region.
Building power in the Highlands
Sigalda Power Plant officially began operation in early 1978, part of a rapid project to increase the nation’s electricity supply. Owned by Iceland’s national power company, Landsvirkjun, Sigalda joined a network of major hydroelectric stations along the Tungnaá River, including Búrfell, Búðarháls, Vatnsfell, Sultartangi and Hrauneyjafoss.
The Sigalda Dam holds back the Tungnaá at a canyon above the hill known as Sigalda. This created Krókslón reservoir, a body of water covering 14 square kilometres. The dam itself is a feat of engineering, built from rock fill, stretching 925 metres in length and standing up to 40 metres high, its surface protected by asphalt. Water from Krókslón is channelled through a one-kilometre canal, reaching the edge of Sigalda Hill.
How the plant works
Three pressure shafts run 216 metres down to the powerhouse, each with a diameter of 4.3 metres. Here, water falls through turbines under a harnessed head of 74 metres. In total, Sigalda has three turbines, each generating up to 50 megawatts, for a total capacity of 150 megawatts.
After powering the turbines, water travels 550 metres through a tailrace canal into the Hrauneyjafoss Reservoir, reinforcing the interconnectedness of Iceland’s hydro infrastructure. Sigalda, through its turbines and the flow of up to 230 cubic metres per second, is capable of generating around 650 gigawatt-hours each year.
Transmission lines from Sigalda connect to other large hydroelectric stations and branch out to southeastern Iceland, weaving the local energy production into the wider national grid. The swift construction and ambitious design of Sigalda reflected the growing need for reliable and renewable energy in the late 20th century, and set the stage for further hydropower development in Iceland’s Highlands.
