The Jungfraubahnen AG commissioned construction of today’s hydroelectric power station on the Schwarze Lütschine River in 1906/08 for the purpose of generating electricity for the railway. Over the years, minor and major renewal and modernization works have been carried out without any substantial alteration to the basic building structure. The distinctive machine house, now slightly hidden by the bushes and trees on the river banks, was constructed according to plans drawn up by the architectural offices of Haller& Schindler, Zurich.

Milestones

• On 29 October 1890, Adolf Guyer-Zeller, Zurich received a permit for construction of a water plant on the Schwarze Lütschine in Lütschental

• The construction work began at the end of November 1906. The construction was carried out by the Alioth electricity company in Müchenstein-Basel as general contractor. The architects Haller & Schindler in Zurich were responsible for the design and the construction

• After only two years of construction, the power plant could be commissioned on 3 November 1908. Equipment of the central site: 4 Pelton turbines each with 1,370 HP with generators of 1,000 kV A each, 7,500 volts, 400 rev/Min., 40Hz

• Through the rewinding of the generators 1 through 4 by the Haefely Basel company, the output of the four generators could each be increased to 1,150 kV A in 1916

• In 1923, the four machine groups were rebuilt for frequencies between 40 and 50 Hz, or 400 and 500 rev/min.

• A fifth machine group with a 2,900 HP turbine and 2,500 kV A generator could be put into operation in 1926. The five machines were operational until 2010

• Starting in 1932, the Jungfrau Railways distribution network could be operated with the Bernese power plants BKW in the interconnected system

• In 1960, the final phase of the Jungfrau Railways high-voltage grid at 16 kV and 50 Hz was completed. The frequency converter from 40 Hz to 50 Hz could be permanently shut down

• On 27 October 2003, work began on the new water intake and weir system in Burglauenen. On 19 August 2005, the new weir system had a celebratory inauguration

• Due to the age of the existing machines, the new construction of the production facility was launched in 2008. The work of project "G55" was successfully completed in 2011. Newly in operation are 2 vertical, 6-nozzle Pelton turbines, which together have an installed capacity of 11.5 MW. Each year approximately 55 GWh of electricity is now generated from approximately 35 GWh

Contact:

Jungfrau Railway Power Plant

Phone: 033 828 77 77

The old, in the meantime demolished, weir to dam and regulate the Lütschine River comprised two weir boards, each with 6-metre-wide adjustable toothed racks and a 3-metre -wide bottom outlet. A maximum of 6m3/s process water was drawn from the Lütschine and via sedimentation tanks channelled into approximately 1.5 km-long free-flow tunnels. A surge chamber was located at the end of these tunnels. From there, the water was transported to the power station on an exposed pressure pipe mounted on plinths.

The almost 100- year-old system had operational and safety defects:

• Insufficient sand separation in the shallow, turbulently flowing sedimentation tanks. Loss of too much process water during long flushing operations.
• Danger of weir openings being blocked or weir boards jammed by driftwood carried down the Lütschine when water level is high.
• The slender weir pillars were constructed of lightweight framework filled with concrete. They began to oscillate during high water.
• Operation of the weir was labour-intensive and at times coupled with risks for personnel.

As early as January 1987, these defects led to the Jungfraubahn AG commissioning the Colenco engineering company to carry out a study for a new building. The preliminary project by Colenco was examined and optimized in July 1992 by the Hydraulics Research Institute (VAW) at the Swiss Federal Institute of Technology in Zurich (ETH) using a model to the scale of 1:25.

During the winter of 2002/03, the significant points of the project were again revised and optimized by the power plant engineering department of the BKW Energie AG and subsequently published. The planning-permit process in accordance with the Railway Act was completed without objections. The required official permits have been valid since late autumn 2003, with the concession granted for 80 years.

The main elements of the renewal project are:

• New weir in the Lütschine, comprising two openings, each 7 metres wide, a solid central pier in in-situ concrete and an abutment pier on both river banks. The closure device consists of hydraulically operated radial gates with built-in weir flaps. The new weir bridge also serves local traffic.
• Lowering of the Lutschine river bed in the dam area, in order to match the new, lower-lying bed of the radial gate. Construction of a diverting platform in the dam area.
• Water catchment on the south bank equipped with a coarse bar screen followed by a gravel-trap channel. A fine-screen installed in front of each of the two de-sanding basins. The debris washed down is lifted out of the water using a mobile cleaning machine and deposited in a skip for disposal.
• Two covered de-sanding basins, each with a capacity of 3m3/s with lengthwise flow. Basin dimensions: length approx. 40 m, width 5.6 m, depth approx. 4 m. Sand removal from the basin effected using a method developed at the Rapperswil Technical College (HSR). Sand extraction pipes (800 mm NW diameter) laid horizontally at the bottom of the sloping basin walls. Inlet boxes are welded into these pipes at regular intervals. The tangential placing of these boxes effects transport of sand into the pipes not by transitory inertia but by a horizontally rotating swirling motion. The grains of sand are constantly in suspension and this method offers the following advantages:
  - almost no moving parts subjected to wear and tear
  - reduced construction depth of de-sanding basins
  - basins need only be partially emptied during flushing
• Control building to house required operational systems such as hydraulic drive mechanism and control cabinets. In addition, pipes for superfluous water and a wastewater pumping station for Grindelwald Municipality installed in the basement.
• Facility for releasing a constant surplus water amount of 400 l/s throughout the year.
• Space reserved on the south bank of the Lütschine for potential construction of a fish pass at a later date.

The current permitted dam level at the weir has also been maintained. The amount of water drawn off also remains the same at 6 m3/s. The new weir allows for the safe discharge of a 1,000-year-flood, which equates to 160 m3/s, even if only one weir opening is in operation.

The remaining parts of the facility, such as penstock galleries, pressure pipes and power station building remain in operation with little alteration. A high-capacity siphon has been built into the surge tank to facilitate the fast discharge of subsequent water flow in the event of a fast shutdown. The water discharged flows back into the Lütschine through the old pressure pipe, which is used as an overflow pipe.
In the power station building, the old supply pipes (branch pipes) to the individual machine groups have also been renewed.

The Executive Board of the Jungfraubahn AG approved the necessary renewal credit on 25 September 2003 and simultaneously commissioned construction work to be carried out. The official “cutting of the first sod” took place on 27 October 2003. Work then started on the first phase of the excavation pit in the Lütschine. The entire construction and assembly time took around 18 months. The new weir and water collection system went into operation in June 2005.