Orders for new MAN Lion’s City Hybrid from eleven public transport companies in northern and eastern Germany
A saving of up to 30 percent on fuel and CO2 plus very quiet pulling away from bus stops and crossings with no exhaust gases: these are good arguments for the innovative new city bus, the Lion’s City Hybrid from MAN. They convinced ten public transport companies in the state of Saxony, who have now ordered a total of 24 hybrid buses from MAN Truck & Bus. The companies, who together form the ARGE RegioHybrid, will be putting the MAN Lion’s City Hybrid into service in major cities, secondary centers and on the regional lines of several transport associations (VVO, VVG, MDV and MVS) during the course of this year.
The Luebeck transport authority, Stadtverkehr Luebeck GmbH, has also ordered five MAN hybrid buses in order to further improve its efficiency and environmental friendliness. The particular objective of hybrid bus operation in this instance is to reduce the impact of air and noise pollution on Luebecks' Old Town Island, a UNESCO World Heritage site.
The purchase of the MAN hybrid buses by the ARGE RegioHybrid and Stadtverkehr Luebeck GmbH is being subsidised by the German Federal Ministry for the Environment with funds for the promotion of electromobility from the government's second package of economic stimulus measures. The Ministry made the subsidy conditional on very high environmental standards. For example, the hybrid buses must prove that they are least 20 percent more efficient than comparable diesel buses and that they comply with strict noise- and air-pollution standards. Moreover, they have to be equipped with a closed particulate filter system. The new MAN Lion’s City Hybrid, which has been on the market since the IAA Commercial Vehicles in September 2010, not only fulfils these conditions: in the most important aspects, it more than fulfils them.
The MAN Lion’s City Hybrid in detail
Urban transport is the ideal sphere of operation for this bus with its serial hybrid drive. These solo vehicles of up to 18 tonnes are driven at low average speeds, accelerating no end of times to between 40 and 50 km/h, only to slow down again shortly afterwards for a stop. When they decelerate, conventional buses transform their great kinetic energy to heat: the energy is thus lost. The innovative low-floor bus with serial hybrid drive on the other hand recuperates its braking energy and transforms it into drive energy. With the automatic start-stop system, the Lion's City Hybrid is able to reduce its fuel consumption and emissions even further. After all, city buses spend 25 to 40 percent of their operating time standing at bus stops or red lights.
The MAN Lion's City Hybrid is driven by two electric motors delivering 75 kW each, coupled by a summation gearbox. Together, the two motors produce a maximum torque of 3,000 Nm. This is why the MAN Lion's City Hybrid can do without conventional stepped transmission. The advantages: the bus accelerates powerfully from a standing start without any interruption of tractive force until it reaches the desired speed – this makes the ride more comfortable for the passengers and driving even simpler for the driver.
When the bus decelerates, the electric motors function as generators, transforming the braking energy into electrical energy. This is stored in so-called traction energy storage, consisting of six ultracap modules mounted behind attractively formed and aerodynamically optimised panelling on the roof of the Lion’s City Hybrid. Ultracaps, also known as high-power capacitors, have a number of advantages relative to the battery systems currently available: high power density, extremely fast power input, long cycle life, constant reliability and a high degree of efficiency. Unlike batteries, no chemical conversion is involved in charging and discharging - electric charges are simply shifted. The absence of moving parts and freedom from maintenance add to the high cost-effectiveness already being achieved. Memory effects and loss of power due to ageing are considerably lower in ultracaps than in lithium-ion or nickel-metal hydride batteries. Ultracaps have a much longer service life than battery systems. Operators of MAN Lion's City Hybrids will be spared the complicated and expensive process of exchanging the energy storage unit during the usual service life of a city bus - one of the great advantages that the MAN system has over hybrid buses that use batteries for transaction energy storage. The fact that batteries deliver considerably less power at low temperatures than ultracaps is another aspect in favour of the MAN system.
When running on energy from its ultracap modules, the MAN Lion's City accelerates quietly and without emitting exhaust gases: depending on the operating conditions, this can be for a distance of up to several hundred metres. Once the energy storage is empty, the eco-friendly MAN diesel engine mounted at the rear of the bus cuts in automatically and with the help of a generator, produces the current needed for the electric traction motors. The Lion's City Hybrid uses a small-volume MAN six-cylinder diesel engine with a capacity of 6.9 litres and an output of 184 kW (250 hp) to produce electricity. This economical diesel engine with modern common-rail injection complies with the voluntary EEV emission standard and is equipped with a controlled CRTec® particulate filter that cleans the exhaust gas of up to 99 percent of its soot. The diesel engine is operated mainly in its optimum speed range with reduced dynamic performance.
Intelligent energy management is responsible for the efficient and reliable interaction between the electric motors and the diesel engine, and between the generator and the energy storage as well as the auxiliary units. This control system was developed by MAN engineers and was continually optimised during the test phase. It controls the operation of the diesel engine and the automatic start-stop system, monitors the charge status of the ultracaps and regulates the operation of auxiliary units such as the power-steering pump and the air-conditioning system. Thanks to intelligent management, the system doesn't need to be configured especially for different routes or driver profiles: this guarantees that all potential efficiency is always utilised to the full.
As far as the passengers are concerned, the MAN Lion's City Hybrid offers all the advantages in terms of comfort and safety for which the conventionally powered low-floor buses from MAN are renowned. Despite its additional technological components, the Lion's City Hybrid has the same number of seats. The air-conditioning system of the Lion’s City Hybrid is electrically operated and regulated by demand, so that even when the bus is stationary and the diesel engine is switched off, passengers will not swelter in the summer heat.
Intelligent energy management keeps the driver continually informed of the system's charge status and its readiness for operation. A central display in the cockpit shows all the data needed for efficient, stress-free and economical operation. These include instruments showing the charge status, the current degree of energy recuperation and general diagnostic information. The only difference in the hardware is an emergency cut-off switch, whose installation is required by Directive 2001/85/EU on buses. MAN offers special introductory courses and training for MAN Lion's City Hybrid drivers so that they can fully utilise the energy advantages of the vehicle in day-to-day operation.
One of the first prototypes of the MAN Lion's City Hybrid was tested as early as 2001 on regular bus routes in Nuremberg, followed by practical operation in various major European cities. To produce exact data, conventional vehicles of similar performance and the same payload operated a reference service. The results showed savings of up to 30 percent in when operating on real bus routes. Moreover, the MAN Lion's City Hybrid had to pass the entire program of tests and trials that all MAN commercial vehicles have to pass in order to obtain series approval.
Infographics: The technology and units of the MAN Lion´s City Hybrid
City traffic is the ideal application for the MAN Lions City Hybrid with its serial hybrid drive. The repeated braking and pulling away from bus stops and traffic lights on scheduled routes is an optimum condition for the recuperation of braking energy.