Rånåsfoss I

Rånåsfoss is a run-of-river power station on the Glomma River Basin in Sørum Municipality. The power station was built in the period 1918-1922.
Prior to the development, the waterfall itself was a 1.5 km long rapid. The monumental building and the dam in faced granite rule the landscape. Through the exhibition “Energy Forum”, thousands of pupils visit the power station each year.

A large installation and many workers

During the construction period, as many as 1200 men worked at the site. In total, 3500 persons worked at the site over the four-year period.
In addition to the barracks and housing facilities, a small society was founded in and around the construction site. During the construction period a post office, a telegraph, a hospital, a grocery- and hardware store and a city hall were established.


After a production period of almost 60 years, the management decided to build a new power station with a large generator with a higher efficiency factor on the opposite side of the river. It was economically correct to increase the machine installations in order to exploit a larger part of the flow of water throughout longer periods of the year. At the same time, it would decrease the running time of the old turbines. Rånåsfoss II was therefore built in the period 1980-1983.

The dam

No changes were made to the dam when the new power station was built. The dam comprises a 45 m long, 6.5 m high cylinder gate and two sector gates, each 50 m long and 3.75 m high. These gates were the largest of their kind in Europe. In 1924-1925 the authorities permitted the water level to be raised by 1 m. Liftable gate elements were installed on the two sector gates.

The absorption capacity at Rånåsfoss I

The absorption capacity of the six aggregates in the old power station at Rånåsfoss is 540 m3/sec., which is equivalent to the volume of a detached house. The flood diversion capacity of the dam is approximately 4400 m3/sec.