Funicular railways have been an important transportation method in Switzerland for more than a century. They remain so today in connecting people and places, but to continue their importance for the next century, these railways must become more energy efficient.
The Sierre – Montana (SMC) funicular, connecting two municipalities in the Valais region of Switzerland since 1911, is doing just that. Harnessing motor, drive and energy storage technology from ABB allows system integrator, Frey AG Stans to install a solution that efficiently generates, stores and uses a combination of solar and braking energy on the renovated funicular. The sources are both very different, but when combined, can save up to 50 percent of energy on a sunny day.
Originally divided into two sections with a transfer station, the winding railway was rebuilt in 1997 and combined into a continuous funicular with a length of 4.2 kilometers, covering an altitude difference of 930 meters. This makes the Sierre – Montana route the longest open-terrain funicular railway in Europe.
It was another 25 years until the railway undertook another major change with a comprehensive update to bring it up to modern operational and environmental standards. The renewal included multiple individual but connected projects such as the replacement of the more than century-old tracks, an expansion of the stations, the purchase of two new wagons, and the important integration of an energy storage system that is manufactured locally in Baden, Switzerland.
"This comprehensive modernization project was achieved in just nine months, but was preceded by years of preparation," explains Patrick Cretton, Director, SMC. This included incorporating the requirements of the Energy Strategy 2050 in Public Transportfrom the Switzerland Federal Office of Transport which supports projects that reduce CO₂ emissions. "It was clear that the energy efficiency of our railway had to be increased with the renewal," says Cretton.
Managing supply peaks
Frey AG Stans had already implemented a new energy storage solution at another funicular, Magglingen Railway in the west of Switzerland. This solution, also leveraging ABB components, helped convince operator SMC of the environmental and financial benefits.
“An onsite energy storage system makes sense for many operators as it allows storage of recuperated braking energy and not have it fed back into the electricity grid," says Aleksandar Veliimirovic, Sales Engineer, ABB. “That stored electricity can be used to smooth out supply peaks which delivers lower overall energy used and significant cost savings in times of high energy prices.”
The carriages of the funicular are permanently connected to a wire rope (44 mm diameter), which is guided over a sheave in the mountain station, whilst a thinner and correspondingly lighter counter rope (22 mm) runs over a sheave in the valley station. The heavier the wagon on the valley side is loaded, the greater the current peak required when starting off, which can now be cushioned via the local energy storage system automatically via software.
Having locally stored and available energy also improves safety. The energy storage system not only supplies the propulsion engine of the railway – a powerful 1000 kilowatt motor and frequency converter combination from ABB - but also the necessary auxiliary operations such as lighting and communications.
Therefore, power can always be provided for emergency operations if and when required. For example, in the event of a failure of the electricity network, the locally stored energy can continue operation sufficiently to bring the vehicles with passengers safely to the next stop. Before the renewal, a diesel generator was installed for emergency propulsion. Maintenance costs and space requirements have been eliminated with the new solution.
Generating the required energy
Once the uphill carriage has reached half of the 4.2 kms distance, an ideal funicular railway theoretically no longer requires an energy supply, as its downhill counterpart now pulls it up via the permanently connected pull rope. In practice, factors such as the rolling resistance, load of the wagons, relative weight of the pulling and counter ropes, and the gradient difference must be taken into account.
Looking more closely at the calculation of required energy: each trip on the Sierre – Montana funicular railway consumes around 40 kilowatts. As the train runs every 20 minutes, the energy demand corresponds to 120 kilowatts per hour. Around 10 percent of that demand can be stored through recuperation. When the sun is shining, the photovoltaic system (solar energy generation) produces around 60 kilowatts per hour.
Combining solar generation, recuperated braking energy and the energy storage system means that up to half of the energy required can be produced or recycled on a sunny day and used on site.
Further to the substantial gains realized in energy efficiency, SMC also operates its railway with zero emissions. The railway still does draw energy from the electricity network but “what we use is 100 percent electricity from renewable hydropower – generated here in Valais,” concludes Patrick Cretton. “This means that our funicular is truly a zero-emission operation."