Scania presents the bus of the future: Innovative hybrid concept from Scania improves fuel-efficiency by at least 25%

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1 PRESS info P07502EN / Per-Erik Nordström 21 May 2007 Scania presents the bus of the future: Innovative hybrid concept from Scania improves fuel-efficiency by at least 25% Scania presents a unique hybrid-electric powertrain. Thanks to advanced electronic control and efficient energy recycling, fuel economy is at least 25 percent better than a regular city bus and with similar improvements in exhaust emissions. Fuelled by ethanol, fossil CO 2 emissions to atmosphere are cut by up to 90 percent compared to diesel. All parts used, including the energy storage modules, have a design life of years. Debuting at the UITP public transport congress in Helsinki May 2007, Scania's new hybrid powertrain is the result of a three-year development project conducted at the Scania Technical Centre in Södertälje, Sweden. Supercapacitor module Electric air conditioning Fuel Engine Generator Power electronics and 650 V grid Motor Axle gear Resistor unit Scania series-hybrid powertrain 24 V grid Design brief The development of the new powertrain technology is based on an overall perspective of the public transport system. Besides the design of the bus itself (see separate release), the factors influencing performance in the design brief include: At least 25% improved fuel economy and emissions in urban stop-and-go operation. Added comfort with smooth stepless acceleration and low noise. High-output powertrain and better manoeuvrability than a conventional bus contribute to driver appeal. Storage module (supercapacitors), heating and ventilation and electrical air conditioning roof-mounted. Scania Corporate Relations Telephone S Södertälje Telefax Sweden

2 2 (5) Possibility to adapt the powertrain to renewable fuels such as ethanol, which potentially cuts fossil CO 2 emissions by up to 90%, as well as gas (biogas or natural gas), for which tank space is available on the roof. Compatibility with potential future propulsion concepts such as advanced engines, batteries and fuel cells. Uptime and quality guaranteed through exclusive use of components designed for heavy-duty operation. The concept should be commercially viable both for Scania and its customers. Series hybrid Prestudies clearly showed a series-hybrid platform to be most suitable for city operation with a lot of stop-and-go driving due to the high degree of regenerative braking possible. This results from the powerful electric propulsion motor, which supplies all the propulsion power, but also regenerates the same power when braking. The main components of the powertrain are shown in the figure. The engine is a regular Scania engine running on diesel, ethanol or gas. A powerful electric generator is mounted on the engine. A similar unit is powering the rear axle, doubling as a motor for propulsion and generator for braking. In addition there are auxiliaries that are driven mechanically or electrically. Flexible design A series-hybrid powertrain is characterised by the fact that there is no mechanical connection between the engine and the propulsion motor. This gives considerable freedom in vehicle design and packaging. Powertrain components can be located almost independent of each other, for example to optimise weight distribution. This means that Scania's hybrid powertrain can be used in various bus and truck applications, including double-deckers and other types of buses, as well as trucks for refuse collection and various types of distribution applications. Efficiency at least 25% fuel saved To match the high power and torque of the Scania engine, high-output electric motors/generators had to be chosen. The energy storage module with supercapacitors is also designed for high output and high cycle efficiency. Besides the axle gear, no additional reduction gears are required due to the wide operating range of the propulsion motor ( r/min, full torque from start). The acceleration of the vehicle is only dependent on the output of the electric propulsion motor and hence independent of the power provided by the internal combustion engine. Indeed, the operation of the engine can be optimised for maximum efficiency, minimum noise and minimum emissions instead of a trade-off between those parameters and the torque requested by the driver. Not only is the operation of the engine independent of the power demanded by the driver, the engine s operating range can also be chosen freely in the series hybrid powertrain, which makes it possible to optimise operation even further.

3 3 (5) The efficiency of the generator is typically more than 90%, peaking at over 94%. The engine operates according to the diesel principle with a typical efficiency between 40 and 45%. The efficiency of the propulsion motor is similar to the generator and slightly lower at very low speed. Compared to conventional buses, overall fuel savings of at least 25% are achieved in urban operation as a result of the regenerative braking and optimised engine operation. Robustness and quality to secure uptime To live up to Scania customers expectations regarding product quality, the components including the energy storage module have a design life comparable to that of the vehicle, i.e. a full years. All components are also designed to have low maintenance requirements. The motor and generator share most components, a factor that facilitates parts supply. Furthermore, only suppliers that can provide worldwide service backup have participated in the project. Driving such systems as the air conditioning, alternators and water pump electrically provides significant advantages. Robust electric solutions for other auxiliaries like power steering and air compressor are likely to appear within a few years. Components have also been chosen to fit into Scania s modular product system. As far as possible, standard components have been retained to secure maximum reliability and the lowest possible cost for the customer. This also gives a flexibility to make step-by-step improvements to powertrain, components and auxiliary systems, as well as to the complete vehicle as new and improved systems enter the market. Performance The electric propulsion motor provides full torque (2750 Nm) from start and the drive is completely stepless. The powertrain offers the possibility to tailor performance to customer needs. An acceleration limiter is included to minimise the driver s influence on comfort and fuel use. Reduced noise The objective was to lower external noise to 75 dba. However, more important is to reduce the noise in situations where it is considered a problem in city centres. This is mainly at bus stops and when accelerating away, as well as noise from roof-mounted systems like the air conditioning. The engine-generator unit is located in its own encapsulated compartment with noise absorbents. A specially designed noise-insulated wall separates the passenger compartment from the rear module. Air for the cooling systems is transferred in separate noise-absorbing ducts. The operating strategy for the engine-generator unit is optimised for low noise. This means that it is operated at the lowest possible engine speed. An important factor for achieving this is the well-matched torque curves of the engine and generator, both

4 4 (5) having a maximum torque of approximately 1250 Nm. Engine shut-off at standstill is another possibility. Prepared for the future The hybrid concept is compatible with future, environmentally oriented engine technologies like HCCI (Homogeneous Charge Compression Ignition) engines. Here, the series hybrid powertrain offers the possibility to overcome some of the technical challenges for example with fast speed and torque transients and high power peaks. The compatibility with fuel cells is more or less plug-and-play. Thus, it is also fully adapted for plug-in hybrid or purely battery-electric powertrain solutions. Fuel cells, battery-electric or plug-in hybrid electric vehicles are several years from becoming a commercially viable. Current pilot installations are research projects, usually prohibitively expensive to operate in heavy-duty urban transport. Combining hybrid technology with renewable fuels is an important step for long-term sustainability. With an ethanol engine, for example, Scania's hybrid-drive concept not only saves 25% fuel, it also reduces fossil CO 2 emissions by up to 90%, depending on the way the ethanol is produced. It is also compatible with other fuels, e.g. synthetic diesel, RME and gas. Naturally, fossil fuels like diesel and natural gas can be used. Combining the hybrid-electric drive system with a heavy-duty diesel engine fuelled with ethanol currently the most attractive and readily available renewable fuel will constitute an affordable and realistic sustainable city bus powertrain for many years to come. Extensive real-life testing The concept bus will be thoroughly tested and evaluated during Powertrain control strategies will be optimised and assessed in cooperation with selected key customers. In 2008, extended operational trials on the hybrid-electric powertrain will start in conventional 3-axle 13.7-metre Scania OmniLink city buses with Scania ethanol engines. Two buses will start operating in Stockholm in early 2008 and another 10 will follow later that year and in The trials will take place with partial support from the Swedish Energy Agency and in collaboration with Storstockholms Lokaltrafik (SL), the regional public transport authority in Stockholm.

5 5 (5) Technical highlights of Scania's series-hybrid powertrain Engine Scania 9-litre diesel, ethanol or gas engine Power 198 kw (270 hp) at 1800 r/min (concept bus) Torque 1250 Nm at r/min (concept bus) Generator Voith ELVO Drive, TFM Generator, water-cooled Continuous torque 1250 Nm Continuous power: 220 kw mechanical from engine Maximum speed: 2400 r/min Propulsion motor Voith ELVO Drive, TFM Motor, water-cooled Maximum torque: 2750 Nm, continuous torque: 1800 Nm Continuous power: 150 kw mechanical Maximum speed: 2400 r/min Energy storage Supercapacitors: 4x125-Volt Maxwell BOOSTCAP modules, air-cooled Energy available: >400 Wh Control system Standard Scania CAN-architecture with added functionality for hybrid control Maximum speed 78 km/h, depending on final-drive ratio Development partners Voith (hybrid-drive system) Carrier-Sütrak (electric air conditioning) Sponsors Vinnova, Den Gröna Bilen (support for two prototypes) Swedish Energy Agency (support for 10 test buses) PFF For more information, please contact: - Lars Overgaard, Bus Predevelopment, tel , lars.overgaard@scania.com - Anders Folkesson, Bus Predevelopment, tel anders.folkesson@scania.com - Per-Erik Nordström, Product Affairs, tel , per-erik.nordstrom@scania.com