German conference focuses on electric buses – Dresden Conference

Electric Bus Operations

The final two sessions of the conference featured seven presentations on the operational application of electric buses. The high profile system recently launched in Vienna was described by Peter Wiesinger of Wiener Linien GmbH. Vienna’s extensive tram system circles the city centre, the centre itself being served by four localised bus routes which had been mainly operated by midibuses fuelled by LPG like most of the bus fleet. Extensive trials were undertaken prior to the commencement of the procurement process to replace them in 2011. These involved low emission diesel, hybrid and electric vehicles with an outcome that electric vehicles would be ordered for three of the routes and hybrid diesel buses for the fourth. The two midibus routes were the first to be converted to electric operation with the hybrid route to follow in 2014 and the full size electric bus route in 2015.

The chosen midibus is a Rampini product with electric equipment from Siemens, a key factor in Wiener Linien’s choice. The 7.78m long vehicles offer the same capacity (46) as the diesel buses replaced. This is achieved by halving the battery capacity to 96kWh compared with the standard Rampini product to reduce weight, the reduced range (130km) being compensated for by in-day charging at the route terminal. Each terminal is designed to accommodate two vehicles. The charging system is built into the vehicle with power being drawn from a two wire overhead system by a driver controlled pantograph. 90Amps are drawn for a period of up to 15 minutes. The in-service recharging process is also expected to at least double the expected battery life to over four years. 7kW (9.4hp) systems are installed for both heating and cooling within the vehicle whilst a silicon foil resistance heating system is provided between the battery modules to cope with Vienna’s harsh winters. Overnight charging at 25Amps takes place at the depot where twelve charging points are available.

Initial results show that there has been no impact on timetable or capacity and that the terminal recharging time could be reduced to eight minutes. The next steps in the project envisage improvement of the vehicle heating capacity and a water based pre-heating system for use during overnight charging. A further positive step introduced in July 2013 allows passengers to board and alight during the terminal charging process. One of the vehicles has been tested in the neighbouring Czech city of Brno where charging took place from the trolleybus overhead, albeit facing the wrong way to achieve the correct polarity!

The following presentation from Andreas Laske, Vice President eBus/eBRT at Siemens, also referenced the Vienna project after an initial consideration of Siemens’ role in the development of electric mobility since 1879. He produced a chart comparing the costs of electric power with diesel and bio-gas which, although short on actual numbers, indicated a significant whole life operating and maintenance cost benefit from electric vehicles as well as the environmental benefits of low noise and no emissions at the point of use. Siemens have also worked with Cobus to deliver the first electric airside eCobus.

The final presentation of the first day covered the development of the Eurabus project, from Director of GF Euracom Group GmbH, Thomas-Christian Seitz. Eurabus started in 2009 with the objective of developing a full electric 12m bus with all the capability of a diesel bus and the benefits of electric operation. Identifying that Tewoo were delivering a similar concept in China, the company was selected as a partner to develop a European standard vehicle with proven componentry from known suppliers such as ZF, Ziehl-Abegg, Wabco, Continental and Isri. The first vehicle entered service with KViP, Pinneberg in September 2012, gaining predominantly positive feedback from drivers and passengers although an issue was identified of noise from auxiliary equipment. This has been addressed in the recently completed version 2.0 of the vehicle that is expected to receive TUV approval this month.

Key features of the Eurabus are lightweight construction, a heatpump system to minimise energy consumption for heating and cooling and the use of Lithium Iron Phosphate batteries. Whilst the latter do not offer the highest density energy storage, Eurabus claim they are safer, more stable and cheaper than other battery concepts. On a 90% discharge cycle, battery life is quoted as 2000 cycles, giving around seven years of six day week operation. Reduced discharge cycles will significantly increase this life. A range of 200km is expected from a full charge normally delivered overnight at the depot although the Eurabus concept is capable of being equipped for inductive or conductive fast charging.

Opening the session on day two, Bastjan Prenaj of ABB Automation Products presented the TOSA project launched in Geneva during the 2013 UITP congress. The 1.8km TOSA demonstration route at Geneva Airport is expected to continue until March 2014 with full operation on route 5 with twelve flash charging points to follow. The principle attraction of TOSA is the minimised battery installation in the vehicle minimising weight and maximising passenger capacity. Just 38kWh of water cooled LTO battery capacity is installed, the equivalent of two small electric cars. Full day operation includes three charging phases, 30minutes at 50kW in the depot overnight, three to four minutes at 200kW at the terminal points and 15 seconds at 400kW at each of the flash charging points. The vehicle connects automatically via a collector to the overhead flash charging points that only become live when a vehicle is detected as being correctly connected. There is no additional action required by the driver other than to stop the vehicle within the allowable tolerance of the laser aligned collector. ABB have provided the electrical installations for the charging points together with the control system and the two 120kW (161hp) motors installed in the articulated buses built by Hess.

Harald Ludescher of Ziehl-Abegg Automotive GmbH opened his presentation with views of some of the 38 electric battery buses featuring at terminal recharging in use in Germany in the 1970s, questioning what had happened in the intervening years. Ziehl-Abegg, a family firm with over a century of history in the electrical industry, produced its first hub motor for transport application in 2004, forming the Automotive subsidiary in 2012 to focus on the further development and application of the concept. The ZAwheel was initially tested in retrofit applications to Volvo and VDL products in the Netherlands. Subsequently the company has partnered with VDL for the western Europe market and AMZ (Poland) for eastern Europe and Scandinavia. Examples of both partners’ products were shown at Kortrijk with the demonstration VDL Citea providing an extremely smooth and quiet riding experience. Ziehl-Abegg quote just 53dBA when installed in the VDL product.

The ZAwheel reduces the number of moving parts in the vehicle drive train by 80% and, at 0.9kWh/km, is 90% efficient in translating battery power. The ZAwheel is available as a single unit or as a complete axle module compatible with ZF’s AVE130, AV132 and AVN132 units. Utilising the second generation ZAwheel launched at Kortrijk, Ziehl-Abegg will have a new demonstration vehicle built by AMG available from early 2014.

It was quite a surprise when the penultimate presentation was given in English without subtitles. Hopefully the audience will have understood this fascinating overview of comparative trials of diesel, hybrid and electric buses carried out by the VTT Technical Research Centre in Finland. Project Leader E-Bus, Kimmo Erkkila, described VTT’s ‘heavy duty’ laboratory opened in 2002 where dynamometer testing of buses is possible under a range of operating conditions. Since 2002, a database of some 300 vehicle tests has been built up covering fuel usage and environmental performance under a wide range of conditions.

VTT has also developed its own test ‘mule’ battery bus used to shadow operations around Helsinki. Based on a Kabus lightweight 12m citybus shell, the ‘mule’ will test a variety of components and systems for comparison with the electric buses being trialled in Helsinki. Caetano was the first participant announced, subsequently BYD, eBusco and VDL have been added. Laboratory tests have already been undertaken using operating cycles from cities worldwide including London and New York.

Kimmo finished his presentation with a wider overview of the environmental impact of electric buses, taking into account the sourcing of electricity. This showed that under the best conditions with renewable source electricity, zero green house gas operation could be claimed but in other countries with electricity mainly from coal fired power stations such as Australia, Euro6 buses would offer better green house gas performance.

The conference concluded with a presentation from Prof Dr.-Ing Matthias Klingner, Principle of the Fraunhofer IVI, on the AutoTram® Extra Grand which was to be visited later in the day. Development work at Fraunhofer IVI has focussed on the mass transportation market in the crossover between economic tram and bus operation. The first AutoTram®, an 18m hybrid, was completed for test purposes in 2003. The specification included a BMW diesel engine and 70kw (94hp) fuel cell for power generation together with super-cap, lithium iron battery and flywheel energy storage systems, with provision for rapid recharging. This supported extensive testing of the components in varied combinations. Additional a guidance control system was developed to ensure accurate tracking.

Recognising the potential need for larger vehicles in growing cities, particularly in Asia, experience from the first vehicle was applied to the construction of the AutoTram® Extra Grand which was launched in August 2012. Billed as the largest bus in the world, it was shown at the 2012 IAA where its ability to turn within its own length was regularly demonstrated to visitors. The vehicle was built in conjunction with Goeppel Bus GmbH, the basic structure being a Go4City artic into which has been inserted a trailer from the Maxi Train product. Specific development work was required, both with Huebner for the second (double) articulation and for the rear steered axle that is powered by one of the two 160kW (214hp) Wittur electric motors installed. The primary power pack is an Iveco 5.9-litre Euro5 diesel engine driving a PSM generator rated at 220kW (295hp) with secondary power from an IVI developed 235kW (315hp) generator pack with Mercedes 4-litre diesel engine. A dual power storage system is employed with 35kWh in Lithium Ion batteries and 0.94kWh in fast discharge super capacitors. A gross vehicle weight of 44.7tonnes is quoted with a full complement of 96 seated and 160 standing passengers. The vehicle has received specific approval for trial on public roads and a number of overnight trials have taken place along some of Dresden’s bus routes.