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MAN the market leader in natural-gas-powered buses

Natural gas and biogas – the MAN Lion’s City CNG makes highly efficient use of alternative fuels

The world's assured accessible natural-gas reserves are estimated at almost 190 billion cubic metres - at today's rate of extraction that's enough for the next sixty years. If one adds the natural-gas resources (meaning gas that cannot yet be extracted or only with great effort), then the range is around 130 years. At more than 75 billion cubic metres, the world's biggest deposits of natural gas have been found in the Near and Middle East, followed by Eastern Europe / CIS (62 billion), North, Central and South America (17), Far East/Pacific (15) and Africa (14). Security of supply and combustion characteristics are factors in favour of natural gas as an alternative source of energy for both stationary and mobile applications - this is being recognised by more and more countries around the world. This is why the UAE, for example, decided years ago that natural gas was to account for twenty percent of the total amount of fuel consumed on its roads by the year 2012.

Natural gas is an eco-friendly source of primary energy. Extracting, cleaning and transporting the fossil fuel with the lowest carbon content require comparatively little energy. The specific emission of greenhouse gases by natural gas - calculated for the entire chain of supply, i.e. from the well to the tank - is around 65 grams per megajoule of energy, which makes it almost a quarter less than that of diesel. Although this advantage is to a certain extent cancelled out by the lower efficiency of the natural-gas powered engine relative to the diesel engine as well as by the additional weight of the fuel storage, natural gas still boasts the highest CO2 efficiency of all fossil fuels in the "well-to-wheel" comparison.

With the help of bio-natural-gas, the operation of CNG buses can be very nearly CO2 neutral. The biogas resulting from the fermentation of organic substances such as green waste, leftover food or liquid manure is upgraded by means of a special procedure to the quality of natural gas, after which it combusts cleanly and unproblematically in series-produced natural-gas engines without the need for any further technical modifications.

A characteristic of natural gas is that it burns very cleanly by comparison with other fossil fuels, so that gas-powered engines emit low levels of air pollutants such as carbon monoxide (50% less than diesel), hydrocarbons (80% less), nitrogen oxides (70% less) and particulate matter (up to 99% less than a diesel engine without a particulate filter). MAN's natural-gas-powered buses use this to their advantage and have for several years - and without complex exhaust-gas treatment systems - already been considerably within the limits laid down by the EEV (Enhanced Environmentally-friendly Vehicle) standard, currently the most stringent in the EU. CNG buses also tend to be quieter than their diesel-powered compatriots, thanks to the fact that natural gas is combusted in SI engines.

The many years of experience with CNG-powered drives are paying off

MAN Truck & Bus can point to the experience of a quarter of a century in natural-gas-powered buses: as far back as 1972, MAN buses with gas-powered engines were shuttling Olympic athletes and spectators to the stadiums in Munich and its environs. Twenty years later, the MAN SL 202 with CNG-powered engine celebrated its premiere and in 2003, MAN delivered the first EEV-compliant gas-powered buses to its customers. In the meantime, MAN has delivered more than 5,000 gas-powered buses and bus chassis with gas-powered engines. Major markets for these buses and engines are The Netherlands, Turkey, Germany, Sweden, Australia, Austria, Portugal, Iran and Spain. MAN's share of the European market for these buses has averaged 44 percent over the past eight years. In fact, from 2007 to 2009, MAN's share was over half the market.

This success is based solidly on MAN's modern natural-gas-powered engines. There are currently two series of engines (E08 and E28) available for bus and bus-chassis applications in five output classes from 162 kW (220 hp) to 228 kW (310 hp). The MAN E0836 LOH 01 natural-gas engine with a capacity of 6.9 litres and turbocharging is available in three output classes; 162 kW (220 hp), 184 kW (250 hp) and 206 kW (280 hp). In each case, this output is delivered at 2,200 rpm. Thanks to its excellent power-to-weight ratio - dry, the engine weighs a mere 650 kilograms - the E08 engine is particularly suitable for buses operating largely in flat regions or for installation in compact (midi) buses. At the moment MAN is offering this engine exclusively to external bus manufacturers.

Where more power and torque are required, the 12.8-litre OBD2-enabled MAN E2876 LUH natural-gas-powered turbocharged engine is called for. This engine is available in two output classes, 200 and 228 kW (272 and 310 hp) and is the standard engine in MAN's natural-gas powered buses.

The range of natural-gas engines that comprehensively covers the power spectrum is paralleled by MAN's range of complete buses which admits no compromise: Natural-gas-powered drives can be ordered as alternatives for just about every model in the new generation of Lion's City modern, low-floor city buses as well as the latest derivation, the new low-entry variant - from the 12-metre long solo bus to the 18.75-metre long articulated bus. For individual adaptation of the fuel storage to the required range of the vehicle there is a comprehensive selection of roof storage modules to choose from. Starting with a standardised aluminium frame, between six and ten gas cylinders can be arranged under the harmoniously designed roof fairing. There is a choice of various types of cylinder for storing the gas, so that almost any wish in terms of individual range can be fulfilled. Of course, MAN's city-bus chassis, renowned for being easy to build on, are also available with gas-powered engines.

The enormous experience MAN has had with gas-powered buses benefits the customer not only when it comes to getting advice on purchasing, but also in the planning and development of the fuel and service infrastructure. It goes without saying that MAN Service is completely familiar with the maintenance and repair of the high-pressure gas systems and that the global supply of spare parts for gas-powered buses is assured. If the customer requests it, training courses will ensure that MAN's know-how is competently transferred to the customer's own service personnel or an external service team. This ensures the smooth operation of the gas-powered buses made by MAN.

Moreover, natural gas is an economical alternative for public transport companies: in many countries, gas is cheaper than diesel, in addition to which operators of gas-powered buses can often profit from state-funded incentives aimed at increasing the percentage of natural gas in the fuel mix.

Finally, natural gas pioneers the way towards a later move to a supply system for gaseous, regeneratively-produced fuels such as synthetic gas or hydrogen.

MAN Lion's City CNG version for hot countries

MAN Truck & Bus, the market leader in gas-powered city buses, unveiled a new version of its Lion's City CNG designed especially for very hot countries earlier this year. The vehicle is driven by a turbocharged six-cylinder engine powered by natural gas and delivering 228 kW (310 hp) with emissions way below the limits set for EEV, currently the most stringent emission standard. The engine's exhaust gases are especially low in nitrogen oxides (NOx) and particulates. Applications for hot countries such as a pre-separator for the air-intake system ensure reliable operation in very dusty regions where temperatures are high. Power from the natural-gas engine is transmitted to the driving axle by means of an automatic six-speed gearbox equipped with intarder. The gearbox software detects up- and downhill gradients, automatically adjusting the gearshift points as it does so. This reduces fuel consumption.

The natural gas is carried in a total of eight aluminium composite cylinders (rated for a pressure of 200 bar), each with a volume of 214 litres or 1,712 litres in all. The gas cylinders are stored under the attractively designed roof fairing, which can be folded open on both sides, making for good accessibility. Storage volume is calculated on the basis of typical inner-city demand, so that the uncomplicated refill procedure can be carried out at the depot in the evening or at night. Alternative packages of cylinders are available on request.

The bright, friendly interior of the Lion's City is kept at a temperature that passengers experience as pleasant by a tropical air-conditioning system delivering a maximum of 44 kW cooling performance. Air curtains on the doors prevent the hot outside air getting in when passengers board and alight at the bus stops – this system has already proven itself on the more than 800 buses from MAN Truck & Bus operating in regular service in Dubai and Abu Dhabi.

MAN produces modern engines for efficient operation using natural gas and biogas. They cover a range of outputs from 220 to 310 hp. The gas-powered engines installed in the MAN Lion’s City CNG are from the E28 range and deliver 272 or 310 hp.