Located in the scenic, mountainous Valais region of Switzerland, the city of Sierre may be small, but it places great importance on sustainability and air quality. Sierre is proud to hold a “Gold Label” European Energy Award, the highest accolade of its type in recognition of the community’s environmental initiatives, which include its increased use of renewable energy.
On the narrow streets of this compact city, a Volvo 7900 full hybrid is quietly transporting passengers in electric mode on the busy main bus route through the centre. The bus does not rely on the electricity grid — its extensive electric behaviour is possible thanks to its high-power electric machine, coupled with the innovative use of geofencing. The former allows the batteries to be charged via kinetic energy recovery, while the latter optimises energy usage to specific bus routes, effectively tailoring the vehicle’s performance.
The optimisation resulted in part-time electric performance, allowing us to further reduce greenhouse gas emissions from our fleet, as well as to make the buses quieter for both passengers and pedestrians.
Public transport operator Bus du Soleil has been operating in the city for the past 20 years. In 2015, it renewed its fleet with four Volvo 7900 full hybrids to meet new environmental requirements. In 2020, Bus du Soleil took another step towards more sustainable public transport: it optimised the environmental performance of the buses by implementing one of Volvo’s Zone management services, the Environmental Zones.
Nicolas Melly, director of Bus du Soleil, says: “The optimisation resulted in part-time electric performance, allowing us to further reduce greenhouse gas emissions from our fleet, as well as to make the buses quieter for both passengers and pedestrians. As there is no need for battery charging infrastructure, this makes the enhanced hybrids an excellent bridging technology on the path to full electrification.”
At the time, the application of geofencing technology, designed to boost the performance of full hybrid Volvo buses, had already been successfully developed and trialled in Luxembourg, but Sierre is the first city to apply the technology to all of its bus lines.
The deployment process was conducted in three steps. Firstly, an analysis of the bus routes was carried out to determine their characteristics, such as speed profile, distribution of energy recovery and noise impact. These unique characteristics were then used to determine the optimal locations for additional electric drive.
In almost any urban area, the opportunity to optimise where buses can drive in extended electric mode is an attractive proposition. It is exactly what we have provided in Sierre and I am delighted with the results.
The last step was to implement a set of environmental zones to tailor the overall performance of the buses. These zones extend the default decision-making process of a hybrid (for example electric departure from bus stops) with additional pre-defined locations for electric drive.
Since its implementation, the new tailoring solution has seen very positive results. Energy consumption and C02 emissions on all the routes in Sierre have been lowered by 10 percent compared to before, allowing the bus to reduce CO2 emissions by 35 tonnes per year/vehicle in comparison to a diesel bus.
The average electric operating time of each bus is now an impressive 50%. The electric driving distance however does depend on the route. In Sierre, it ranges from 22% on the flattest route to 50% on the hilliest route. On a typical day, one bus can drive 60 km in electric mode, which represents an average of 30% of the distance. The reduced noise levels are very apparent on the city’s narrow, residential streets. The maximum speed of the buses in electric mode have also been significantly boosted from 20 km/h to 50 km/h.
Nicolas Melly says: “Overall, the upgrade of our hybrids with the latest technologies has exceeded our expectations. Not only have we lowered our carbon footprint, we have also substantially increased quiet electric drive where it counts for the people that live and work here – at bus stops, on busy streets and in noise-sensitive residential areas.”
Jean-Pierre Roemer, Volvo Buses Switzerland, says: “In almost any urban area, the opportunity to optimise where buses can drive in extended electric mode is an attractive proposition. It is exactly what we have provided in Sierre and I am delighted with the results.”
Business type: Public Transport
City fleet: 5 buses in total; 4 Volvo 7900 full hybrids
Route conditions: Narrow streets with frequent pedestrians, numerous stops, hilly topography, speeds of up to 50 km/h
Tailored routes: 4 lines covering suburbs and crossing the city centre
Number of environmental zones: 22
Longest zone: 1.1 km
-The route analysis identifies its unique energy recovery profile and determines the optimal locations for electric drive
-The objective is to use the recovered energy efficiently to maximise electric drive
-The Volvo Environmental Zones automatically manage the performance of the hybrid system with a predictive approach that considers what will happen later on the vehicle’s route
-The result is a tailored solution that optimises electric drive and offers significant environmental benefits