MAN Lion’s City Hybrid – the innovative city bus that brings greater ecological balance and economy
The MAN Lion's City Hybrid runs significantly more efficiently than the most modern conventional diesel-powered city bus while being just as safe and reliable. Its 30 percent lower consumption of diesel and emission of CO2 is convincing. Quiet and free of exhaust gases when stationary and when pulling away from bus stops and intersections, this is a bus that protects the environment. After many years of research and development work followed by intensive testing in laboratories and on the road, the MAN Lion's City Hybrid has been available for order by European customers since the IAA Commercial Vehicles 2010. The MAN Lion's City Hybrid is already operating successfully in regular service in various major European cities.
Urban transport is the ideal sphere of operation for buses equipped with 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.
Eco-friendly thanks to serial hybrid drive
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 (around ten years). This is 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 two 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.
The tried and trusted MAN Lion's City
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's own 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. The dashboard's central display 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 Paris and Spain. As of today, the MAN Lion's City Hybrid has done more than 100,000 kilometres. 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 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.
The new MAN Lion’s City Hybrid with its innovative EfficiencyDesign was presented at the UITP Congress at Vienna in June 2009 for the first time. With its serial hybrid technology it saves up to 30 percent of fuel in city traffic and ten tons of carbon dioxide in the course of one year.