Dam Safety

Älvkarleby: A pioneering hydropower plant in Sweden

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Älvkarleby: A pioneering hydropower plant in Sweden

The 125 MW Älvkarleby hydro project in Sweden is a historically significant facility, being among the first three built in the country. Learn more about the plant, which was inducted into the Hydro Hall of Fame in 2021.

The three oldest hydropower plants in Sweden – 135 MW Olidan on the Göta Älv River, 417 MW Porjus on the Luleälv River and 125 MW Älvkarleby on the Dalälv River – were built in the early 20th century with the main purpose of supplying power to the railways and local industries. For Sweden, this was the start of hydro power development and a milestone in the country’s industrialization.

Älvkarleby, the third of those pioneering plants, was a 2021 inductee into the Hydro Hall of Fame. It has operated continuously since 1915 except for a span of a few months when a new unit was added during an extension of the then-70-MW plant, from 1988 to 1991. At that time, a new dam was built in a similar location to the old dam.

This article gives the background and history on Älvkarleby, including dam safety work performed in the early 2000s. The plant was one of only four inducted into the Hydro Hall of Fame in 2021.

Hydro Hall of Fame

Background on the plants

Emerging industry and railways played a major role in determining the location of Vattenfall’s first hydropower plants. Over the course of a few years, three gigantic, for that time, and architecturally fascinating plants were built at Trollhättan, Porjus and Älvkarleby.

Construction of the Olidan power plant at the Trollhätte falls began in June 1906, and the plant was in regular operation by March 1910. At that time, it was Sweden’s largest hydroelectric plant. The Olidan plant was built with penstocks embedded into underground rock tunnels, which was unusual at the time.

Olidan was a technical and commercial success for the state. It was decided, therefore, that the state would own resources and produce hydropower itself in the future, rather than lease it out to other operators, as previously discussed. In 1910, the Swedish parliament granted Vattenfall money to construct a power station at Porjus, north of the Arctic Circle.

Porjus was to be built in the middle of the northern wilderness and would be the northernmost power plant in the world. The main purpose of the Porjus plant was to supply the ore railway between Luleå and Narvik with electricity. Statens Järnvägar, the Swedish state railway, had plans to construct a significantly smaller hydropower plant along the Vakkokoski rapids in the Torne River.

But Vattenfall’s dynamic manager Vilhelm Hansen argued his case energetically in parliament. Hansen didn’t just base his arguments on the ore railway. A plant in Porjus would also open the way for new industry. The ore needed to be processed before it could be exported.

The Porjus plant was an exceptional construction. It was built underground with headrace and tailrace tunnels, and hence the machine hall was also underground. It was an enormous size for its time. The hall was 70 m long, 11 m wide and 11 m high. Underground power stations became internationally recognized as a Swedish speciality. Porjus went into operation in 1914 and the ore railway was electrified the following year.

That year also saw Vattenfall’s third hydroelectric plant commence operation – in Älvkarleby. Planning for this power plant assumed that its largest consumer would be industry. There were many important industries north and west of Älvkarleby where steam was the driving force and could be replaced by electricity.

All three plants were designed by the era’s most in-demand architect: Erik Josephson. The buildings were of brick and the “monumental style,” with huge volumes, was intended to reflect their power. The switchgear building at Porjus, which was above ground, was not called the temple in the wilderness for nothing. Josephson was, incidentally, also the person who designed Vattenfall’s very first emblem or logo.

The lighting at Porjus was also special, as many people worked underground. There were lots of electric light bulbs. The fittings for the control room were commissioned from craftswoman Olga Lanner. She also supplied the fittings for Olidan and Älvkarleby.

Building Älvkarleby

The Dalälv River runs through the heart of Sweden’s mining industry. Many mills have been built along the river, which has also been used for log driving on a large scale. Today, Vattenfall has three power plants on the Dalälv River: 24 MW Näs commissioned in 1978, 20 MW Söderfors and Älvkarleby.

The Älvkarleby power plant is located 8 km from the point where the Dalälv River flows into the Baltic Sea. Älvkarleby was already an important settlement back in the Bronze Age. People were probably drawn to the area by its salmon fishing, and the river is still popular for sport fishing, even after construction of the power plant.

The purpose of the Älvkarleby power plant was to supply central Sweden with electricity. Älvkarleby originally had an installed capacity of 70 MW but its capacity has increased over time and is now 125 MW.

The Alvkarleby plant began generating electricity in 1915 in central Sweden.

The Älvkarleby plant began producing power in 1915. The original plant had five Francis turbine-generator units and a total capacity of 70 MW. The development included a 200-m-long intake canal partially blasted in rock and partially lined with concrete walls. The concrete walls were cast in 10- to-15-m-wide monoliths ranging in height from 3 m to 16 m. Drainage pipes were installed in the walls, and the expansion joints were sealed to prevent leakage.

The plant has a head of 23 m and water discharge of 700 cubic meters per second.

The Alvkarleby powerhouse contains five original turbine-generator units

The new power plant

In the late 1980s, Vattenfall added a new 50-MW unit and refurbished the old units. To accommodate the increased turbine flow, the intake walls were raised and reinforced. Design loads considered in raising the walls included water pressure, uplift, ice and load rejection. The left wall was raised about 0.6 m, and a 0.3-m thickness of concrete was cast on the inside of the wall, with reinforcement bars connecting the new concrete, old concrete and rock.

To further stabilize the wall, Vattenfall contracted with a construction company to install 78 36-mm post-tensioned anchors in holes drilled through the old concrete and 6 m to 8 m of the underlying rock. The holes were tested for watertightness before installation of the anchors and, if leaks were detected, were pressure-filled with grout and redrilled. After refilling the holes with grout, the contractor fixed the anchors in the holes, grouted the 5-m anchoring zone, and allowed the grout to cure. The upper anchor plate was then grouted into place and allowed to cure, and the anchor was tensioned to a force of 720 kiloNewtons. The tension force applied to the anchors was 66% of the nominal yield strength and 58% of the nominal ultimate strength for the anchor material. During installation, the anchors’ elongation was also measured at various loads and compared with expected values. Before the installation, the anchors were wrapped in a corrosion-protecting band that would allow some movement inside the concrete. This would enable Vattenfall’s dam safety engineers to measure the actual force in each anchor in the future. Finally, the hole was grouted and the top of the anchor was treated for corrosion protection and capped.

New dams were built in around 1990 in similar locations to the old dams. The concrete in the original dams was badly damaged, and construction of the new dams went hand in hand with expansion of the power plant.

A new dam was built at Alvkarleby in about 1990.

In 2002, a load test of anchors at Älvkarleby revealed that seven of the 78 anchors in the intake canal wall had ruptured. As a result of the investigation, Vattenfall installed a different type of anchor throughout the facility and no longer relies on the remaining anchors.

The ruptured anchors were replaced in 2004, and the remaining new cables were installed in 2005. At that time, Vattenfall said it planned to select a sample group of anchors for testing at five-year intervals. The expected life of the new anchors is about 50 years, and there is ample space to install new ones when needed.

In keeping with the river’s importance as a sport fishery, Vattenfall performs studies of downstream migration of fish at its research facility in Älvkarleby.