The construction of hydropower plant Augand in the Swiss canton of Berne marked the utilisation for a green-­energy project of a stretch of the river Kander that had never before been used for hydropower generation. The Augand facility is a joint project of BKW Energie AG and Energie Thun AG, the co-founders of Kraftwerk ­Augand AG. The power house is home to two horizontally aligned Kaplan turbines by Global Hydro Energy. When under full load, they provide a bottleneck capacity of 8.3 MW. ­Optimised specifically for efficiency, the synchronous generators of both machine units are provided by hydropower specialist KONČAR – Generators and Motors Ltd.. The facility was officially inaugurated in September 2023, after three years of construction.

From 2020 to 2023, a new hydropower plant was constructed on the river Kander, to the southwest of Lake Thun. Initially, two competing license applications were submitted for the energetically unexploited stretch of the river upstream of the Spiez hydropower station. After the projecting ­phase, which took around 10 years to complete and included the assessment of various implementation versions, BKW Energie AG and Energie Thun AG finally joined forces to get the project underway. As a result, Kraftwerk Augand AG was founded to provide the legal framework for the project.

Challenging conditions
Hydropower plant Augand was essentially designed as a diversion plant on the river Kander, upstream of the existing Spiez facility. As Patrik Eichenberger, BKW’s project manager and representative of the owner, explains, ecologic considerations were a major factor in selecting the site for the water chamber next to the BLS railway tracks. “We had to comply with environmental regulations, which eventually ­limited our possibilities for the plant layout to a single option for the site of the water chamber. The Lötschberg line, which is operated by BLS, is one of the most essential transalpine railway lines. Planning our hydropower facility right next to the railway tracks turned out to be extremely challenging, due to the con­strained spatial conditions.” To support the required outflow of up to 30 m³/s of motive water, which crosses under the railway tracks straight after the water chamber, the engineers opted for a 1.4 km non-pressure tunnel, which runs underground to the surge tank.

Railway tracks crossed under without interrupting train services
One of the most challenging tasks of the project was the construction of the culvert under the double-track Lötschberg railway line ­while train services continued as normal ­above ground. The construction work to ­culvert the river was completed within three weeks in late summer 2020. While construction work was going on, the tracks and railway poles, as well as the embankment within the range of the underpass had to be moni­tored geodetically for safety reasons. The ­motive water from the Kander is dammed up by means of a two-part weir baffle and flows out by way of a collateral intake. From there it is guided through two upstream basins, where the floating debris is removed from the outflow reach by a rack cleaning machine mounted in front of a vertically aligned fine mesh grating. Ensuring full continuity for fish migration at the weir gate also required con­siderable constructional effort. To enable aquatic animals to overcome the 7 metres of difference in altitude between the down­stream and upstream end water, a fish ladder was installed in the form of a vertical slot pass consisting of a series of 49 individual basins. The residual water flow at the water chamber was regulated primarily to suit the life and migration cycles of the local brownie trout population. Allowing for seasonal fluctuations, the flow volume varies between 1.5 and 4 m³/s.

Working underground for 1½ years
Excavating the 1,360 m horseshoe-profiled non-pressure tunnel was done in classic ­miner’s fashion by means of tunnel heading and cutting machines with milling attachments and demolition hammers, complemented by protective construction measures. The tunnel passes over a frequently used railway tunnel of the BLS line, as well as another, ­disused tunnel, at distances between 1.9 and 5.9 m. This part of the project required comprehensive advance planning, calculations and proof of safety. “We had to install a tachymeter inside the double-tracked tunnel to be able to constantly monitor the tracks, the tunnel crown and the tunnel floor. This tachymeter was in constant operation from the start of the excavation work until after the final stress tests. We also had to monitor the geodetics along the crown of the second one, the un­used Hondrich tunnel,” as Patrik Eichenberger explains. The breakthrough, which the miners had been working towards from both sides for around 18 months, was finally ­achieved in March 2022.

Turbines shine with record performance
Located at the end of the underground ­conduit is the plant’s water reservoir, which houses the probes of the level-controlled turbines. From the water reservoir, a GRP-based DN2400 double penstock leads directly to the machine building. Delivered as part of an electromechanical all-in-one package, the two Kaplan bulb turbines by Austrian hydropower specialist Global Hydro Energy form the core elements of the machine house. Each of the two horizontally aligned turbines is con­figured for a design flow rate of 15 m³/s and a net head of 30 m. This allows them to achieve a bottleneck capacity of 4,150 kW under full load. Since the machines are equipped with adjustable gate operating mechanisms and runner blades, they are able to provide a consistently high level of efficiency across a wide operational bandwidth even when the avail­able water volume happens to fall below normal levels. Complementing the machine units are two synchronous generators, manufactured by KONČAR – Generators and Motors Ltd. in a water-cooled design, including the corresponding equipment, i.e., butterfly valves, turbine governors, and cooling and greasing aggregates. With its custom-crafted generators, both of which are designed for ultimate efficiency, KONČAR has earned an excellent reputation in the renewable-energy industry. To meet the requirements of the Augand project, the Croatian specialists custom-built two high-efficiency machines, each of them designed to deliver 6,300 V of voltage and 5,200 kVA of rated apparent power. The energy generated by the machine units is conducted from the medium-voltage switchgear to the transformers. Near the plant’s down­stream weir gate it is fed into BKW’s grid.

A power station for many generations
In June 2023, hydropower plant Augand was ready for its first trial run. In September it was finally time to take the joint power plant project of BKW and Energie Thun AG into ­operation at an official inauguration ceremony. The new facility represents an investment of around 68 million Swiss Francs. In a normal year it generates approximately 35 GWh of green energy – enough to supply around 7,700 average four-person households with clean energy. As Patrik Eichenberger explains, the facility was completed in time without any major incidents, despite adverse circumstances ranging from the COVID-19 pandemic and the resulting supply shortages to rising prices, time pressure and two major flood events. Besides ensuring the unimpeded passage of fish, Kraftwerk Augand AG was also able to adjust a stretch of the Kander downstream of the ­power station in cooperation with the local community of Aeschi near Spiez and the Schwellenkorporation Wimmis, with the federal and cantonal governments providing financial support. After the completion of this revitalisation project from the Cantonal Structure Plan for Water Bodies, the Kander is to regain as much of its original riparian terrain as possible along a stretch of about 450 metres. As a further measure, Kraftwerk Augand AG has added a stream ramp to an existing flood barrier to ensure that the fish are also able to find their way upstream of the river weir.