The Røssåga power plants are located in Hemnes Municipality in Nordland County.
Ownership: 100 %
Production: 830 GWh (900 GWh after upgrading)
Power: 160 MW
Øvre Røssåga power plant uses the height of fall between Lake Røssvatnet and Lake Stormyrbassenget, while Nedre Røssåga power plant uses the height of fall between Lake Stormyrbassenget and the village of Korgen.
Lake Røssvatnet has a reservoir capacity of 2.35 billion cubic metres and is Norway's second largest lake, measured on surface area.
The development of the Røssåga power plants involves the municipalities of Hemnes, Hattfjelldal and Grane. The development, which started already in 1948 and proceeded in stages up to the last generating unit in 1962, was connected to the operation of the Norwegian Ironworks in Mo i Rana. The plant was also to produce power for domestic supply to 19 municipalities in Midt-Helgeland and electrification of the Nordlandsbanen railway. In the 1960s, Elkem's aluminium plant in Mosjøen arrived as a major consumer of power.
Øvre Røssåga power plant has three generating units with Francis turbines and a total installed capacity of 160 MW. Head loss in the water system or loss of energy due to friction of the water against the uneven surface of the tunnel and other obstacles, has meant that full power levels have not been achieved. The planned upgrade will make it possible to utilise this missing capacity.
The gross height of fall is 136 metres.
Øvre Røssåga currently produces about 800 GWh a year. After the planned upgrade production will be around 900 GWh.
In the period 2016-2018, the three generating units at Øvre Røssåga will be rehabilitated and a new parallel tailrace tunnel put into use. Increased power, new tunnels and rehabilitation will increase production by 200 GWh at Øvre and Nedre Røssåga power plants, which together will be able to produce around 2.8 TWh per year.
Architect Hans Grinde drew the plans for and participated in the planning of Øvre Røssåga power plant.