1. Alternative drive systems at Daimler AG for the mobility of the future

2. Alternative drive systems at Daimler AG

3. Hybrid vehicles - several drive systems on board

4. Electric motors as an alternative to combustion engines

5. Fuel cell - moving towards a zero-emission future

6. Using better fuels, achieving cleaner combustion and higher performance

7. Advancements with other internal combustion machines

8. Timeline: Alternative drive systems at Mercedes-Benz

Hybrid vehicles - several drive systems on board

• First hybrid drive patent granted to Wilhelm Maybach in 1902
  
  
• Mercedes-Benz OE 302 of 1969 with diesel-electric drive
  
  
• Creation of a variety of research vehicles
  
  

Two of the important aims in developing visionary drive systems are to save fuel and reduce emissions, and Daimler AG is pursuing these objectives in various ways. One approach is that of hybrid drives. This involves installing several power sources in a vehicle that can be used individually or together, depending on the situation. With today’s automobiles, there are generally two systems, an internal combustion engine in combination with an electric motor. A drive of this kind offers benefits not only in terms of economy and environmental compatibility, but also with regard to driving enjoyment, comfort and everyday practicality.

One of the early steps towards the modern hybrid drive was that of the early experiments by Wilhelm Maybach in engine development, which had the aim of optimizing existing gasoline engines by combining them with alternative drive techniques. As early as 1902, he took out a patent for a two-cylinder engine that was to combine the functions of the internal combustion engine and the steam engine in one. His “vehicle drive system, consisting of an explosion machine and a compressed-air machine,” patented on January 29, 1905, was intended, in particular, to remedy the design drawbacks of the combustion engine.

The drive system provided for a compressor driven by the gasoline engine. The compressed air thus obtained was additionally heated by the temperature of the exhaust gases, thus increasing the compression. Two compressed-air machines in the form of horizontally opposed piston engines under the car body converted the pressure into kinetic energy to turn the wheels. With such an unconventional engine, one of Maybach’s aims was to achieve a high torque for starting off from a standstill. However, the main idea behind the system, a serial hybrid drive, was to eliminate the need for heavy engine components: the inventor stressed the “omission of the gear wheel drive, the differential gear, the clutch, and the brakes acting on the transmission, in other words, the elimination of those parts that have caused problems up to now” as advantages of his engine. In addition, the drive system was very easy to operate. Unfortunately, the high cost involved and the low efficiency militated against putting the patent into practice.

The OE 302 marks a new start for hybrid development

The more recent history of hybrid drives at Daimler-Benz began in 1969, when the company presented the OE 302 city bus as an experimental vehicle at the Frankfurt International Motor Show (IAA). The bus carried 66 passengers, and its powertrain was a DC motor with an output of 115 kW (156 hp), that could be temporarily increased to 150 kW (204 hp). This electric motor was powered by lead batteries, for example during zero-emission driving through city centers. For driving in the country, the electric motor fed a generator which in turn was powered by a diesel engine. The latter operated at a constant speed, at a constant load, and with good efficiency, which meant it generated less exhaust gas or noise in comparison with a vehicle diesel engine, and also required less fuel. According to the researchers, the hybrid principle employed in the OE 302 substantially reduced the downside of having a lead battery - high weight and low energy density - at reasonable cost.

“The electric drive will find its application in buses, where noise and emissions from street vehicles must be entirely eliminated from the city center,” according to a somewhat prescient 1971 press release. “Using hybrid energy systems, they can travel through inner-city areas on electric batteries, thus producing zero emissions and very little noise.” At that time, however, the company reached the following conclusion: “The additional cost in comparison with the drive systems already in use and with natural gas drives therefore means that […], for the present, practical application [of electric drive systems] should only be expected in special cases.”

The Mercedes-Benz OE 305, presented in October 1978 at “transport ’78,” the international trade fair for transport technology, was set up on the same principle as the OE 302. With identical output data, however, it was able carry up to 100 passengers. Its range using only batteries was between 50 and 75 kilometers, depending on driving style, and up to 300 kilometers in hybrid mode. In May 1970, as part of a five-year model test, the first four of a total of thirteen OE 305 buses commenced regular duties as public transport vehicles in Stuttgart. Another seven vehicles followed in September in Wesel.

Gyro drive as a special form of the hybrid drive system

A special form of the hybrid drive is the gyro drive which Mercedes-Benz tested from the late 1970s on. A flywheel operated as a mechanical energy storage unit. Two different forms of gyro drive were developed for two different vehicles: for an O 305 regular service bus (passenger capacity: 113 persons), and for a city bus (carrying 17 persons) based on the 208 van. Both vehicles operated on an identical principle: the drive energy was generated either by a standard diesel engine (O 305: 96 kW/130 hp, city bus: 48 kW/65 hp) or by the flywheel, or by both simultaneously. The flywheel storage unit was charged during braking operations, but additionally by the combustion engine when excess power was available, because only a reduced amount of power was needed to propel the vehicle. A power shift transmission was used in the O 305, and an electric transformer in the city bus.

The gyro drive system allowed a combustion engine to work continually within a low-consumption operating range. This effect, and the partial recovery of brake energy that normally remained unused, had a beneficial effect on fuel consumption and the brakes’ service life. It also meant that the combustion engine could be made smaller and lighter. In certain situations, the combustion engine could also be switched off when the flywheel was charged, so that the vehicle could run up to 1,000 meters at low noise and with zero emissions. As areas of use for vehicles with gyro drive, researchers identified city traffic with a large number of bus stops, and many acceleration and braking operations, and also driving on route sections that were to be kept emission-free, such as in pedestrian precincts.

More recently, the company has been pursuing hybrid technology in a number of different projects, yielding a large number of different vehicles over the years.

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	Group photo: In the 1970s and 1980s, Mercedes-Benz tested different propulsion concepts – with a correspondingly large fleet of test vehicles. The photo was taken on the test track in Stuttgart-Untertürkheim in 1981.
	Group photo: In the 1970s and 1980s, Mercedes-Benz tested different propulsion concepts – with a correspondingly large fleet of test vehicles. The photo was taken on the test track in Stuttgart-Untertürkheim in 1981.
	Mercedes Electrique: “The most reliable, quietest and most modern electric city car.” Advertisement of 1907.
	Rapid start: In 1908, the Berlin fire brigade opted for the Mercedes Electrique with electric drive and purchased a fleet consisting of four vehicles. The wheel hub motors in the front wheels are clearly visible.
	Mercedes Mixte on the front cover of the magazine “La France Automobile”, edition of November 9, 1901.
	Environment-friendly electric drive: The Mercedes-Benz LE 306 of 1972 featured a battery exchange system which accelerated the “refueling”. The vehicle was extensively tested.
	Environment-friendly electric drive: The Mercedes-Benz LE 306 of 1972 featured a battery exchange system which accelerated the “refueling”. The vehicle was extensively tested.
	Environment-friendly electric drive: The Mercedes-Benz LE 306 of 1972 featured a battery exchange system which accelerated the “refueling”. The vehicle was extensively tested.
	Environment-friendly electric drive: The Mercedes-Benz LE 306 of 1972 featured a battery exchange system which accelerated the “refueling”. The vehicle was extensively tested.
	Ready for boarding: Mercedes-Benz city bus with hybrid electric drive of 1979. The internal combustion engine powered a generator which produced electricity for the traction motor.
	Ready for boarding: Mercedes-Benz city bus with hybrid electric drive of 1979. The internal combustion engine powered a generator which produced electricity for the traction motor.
	Ready for boarding: Mercedes-Benz city bus with hybrid electric drive of 1979. The internal combustion engine powered a generator which produced electricity for the traction motor.
	Diesel-electric operation in cities: In the Mercedes-Benz Cito (1998), a four-cylinder engine powered a generator which produced electricity for the traction motor. Purely electric operation was possible over short distances.
	Diesel-electric operation in cities: In the Mercedes-Benz Cito (1998), a four-cylinder engine powered a generator which produced electricity for the traction motor. Purely electric operation was possible over short distances.
	Energy providers: The Mercedes-Benz OE 302 electric test bus (1969) needed five battery modules which were installed underneath the floor.
	Diesel-electric: The Mercedes-Benz OE 302 test city bus was powered by electricity, its batteries being charged by a diesel engine. This vehicle marked a new start in hybrid drive development in 1969.
	No clutch pedal: The driver of the Mercedes-Benz OE 302 electric test bus (1969) only had to actuate the accelerator and brake with his feet.
	Diesel-electric: The Mercedes-Benz OE 302 test city bus was powered by electricity, its batteries being charged by a diesel engine. This vehicle marked a new start in hybrid drive development in 1969.
	Early example of an electric car: The chassis of the 30/35-hp Mercedes with wheel hub motors (built from 1905 until 1909).
	Refueling at the mains: Two Mercedes-Benz test vehicles with electric drive, photographed in 1995.
	Testing in the early 1990s: Mercedes-Benz MB 100 D van with electric drive; a city bus version of this model was also set up.
	Large-scale electric-drive test on the island of Rügen in 1992: Mercedes-Benz contributed ten 190 cars and ten MB 100 D vans.
	Large-scale electric-drive test on the island of Rügen in 1992: Mercedes-Benz contributed ten 190 cars and ten MB 100 D vans.
	Emissionsfrei unterwegs: Der in Serie gefertigte Duo-Bus, hier ein Exemplar aus dem Jahr 1993, hat einen reinen Elektroantrieb mit doppelter Energiezufuhr. Die Antriebsenergie kommt entweder aus einer Unterflur-Batterie oder gelangt per Oberleitung ins Fahrzeug („O-Bus“). Das bringt Flexibilität abseits des Leitungsnetzes.
	Transparency: The X-ray picture of a Mercedes-Benz C-Class with electric drive of 1993 shows the layout of components.
	Large-scale electric-drive test on the island of Rügen in 1992: Mercedes-Benz contributed ten 190 cars and ten MB 100 D vans.
	Test car with ZEBRA battery: Mercedes-Benz 190 with electric drive, 1993.
	Large-scale electric-drive test on the island of Rügen in 1992: Mercedes-Benz contributed ten 190 cars and ten MB 100 D vans.
	Novel electric drive: The Mercedes-Benz 190 used as a test car in 1991.
	Novel electric drive: The Mercedes-Benz 190 used as a test car in 1991.
	Large-scale electric-drive test on the island of Rügen in 1992: Mercedes-Benz contributed ten 190 cars and ten MB 100 D vans.
	Zero-emission motoring in the city: In July 2006, the smart brand launched a pilot project in London. The fortwo ed (electric drive) generates an output of 30 kW (41 hp) for adequate performance and has a range of some 100 kilometers (62 miles).
	Zero-emission motoring in the city: In July 2006, the smart brand launched a pilot project in London. The fortwo ed (electric drive) generates an output of 30 kW (41 hp) for adequate performance and has a range of some 100 kilometers (62 miles).
	High level of ride comfort: In early 1982, Mercedes-Benz began testing electric drive systems in passenger cars. The station wagon from the 123 series largely corresponded to the production version but its load compartment was reduced in size by the fact that it accommodated the battery.
	High level of ride comfort: In early 1982, Mercedes-Benz began testing electric drive systems in passenger cars. The station wagon from the 123 series largely corresponded to the production version but its load compartment was reduced in size by the fact that it accommodated the battery.
	High level of ride comfort: In early 1982, Mercedes-Benz began testing electric drive systems in passenger cars. The station wagon from the 123 series largely corresponded to the production version but its load compartment was reduced in size by the fact that it accommodated the battery.
	Testing in city traffic: Mercedes-Benz 307 E van with electric drive (1980).
	On the test track in Stuttgart-Untertürkheim: Mercedes-Benz 307 E van with electric drive (1980).
	Propulsion energy at times of hardship, available ex factory: Mercedes-Benz 170 VG (1935) with wood gas burner.
	Mercedes-Benz L 307 van of 1975: Test vehicle with hydrogen propulsion and hydride storage unit.
	Test bus of 1971: The six-cylinder spark-ignition engine of the Mercedes-Benz OG 305 operated on natural gas – with very low pollutant emissions.
	Prototype with electric drive: The Mercedes-Benz A-Class (W 168 series) of 1998 derived its energy from a ZEBRA high-performance battery on a sodium/nickel chloride basis.
	In 1992, Mercedes-Benz presented a “Flexible Fuel” test car based on the 300 SE S-Class model (140 series). It engine management was designed for variable mixed methanol/ gasoline operation with a methanol proportion of up to 85 percent.
	Adjustable engine management: In 1990, Mercedes-Benz presented the 300 E-24 for variable mixed methanol/gasoline operation.
	Special setup: The Mercedes-Benz 450 SL test car (R 107 series) of 1974 had a spark-ignition engine optimized for operation on methanol. The engineers used the console and additional switches for controlling and monitoring the fuel system.
	Three test vehicles from Mercedes-Benz (from left to right): LE 306 electric van (1972), OE 302 electric test bus (1969), OG 305 natural-gas test bus (1971).
	Energy carrier for the future: In 1988, hydrogen was tested as a fuel in Mercedes-Benz vans and passenger cars.
	Mercedes-Benz 200, 1981: Test car for the combined supply of the internal combustion engine with gasoline and liquefied gas.
	Methanol operation and energy recuperation: The Mercedes-Benz O 305 test city bus on the test track in Stuttgart-Untertürkheim (1981). The vehicle was also tested in regular service.
	Environment-friendly vehicles: Mercedes-Benz city bus with electric drive, van with electric drive and passenger car (123 series) for mixed methanol/gasoline operation. The photo was taken around 1980.
	Methanol as a fuel: In 1979, the Federal German Ministry of Transport launched a research project named “Alternative Energies for Road Traffic”. Mercedes-Benz participated in a field test in Berlin with different vehicles, among them the 230 model (123 series).
	Methanol as a fuel: In 1979, the Federal German Ministry of Transport launched a research project named “Alternative Energies for Road Traffic”. Mercedes-Benz participated in a field test in Berlin with different vehicles, among them the 230 model (123 series).
	Gratifyingly low emissions, more efficient power output: The Mercedes-Benz 450 SL test car (R 107 series) with a spark-ignition engine optimized for operation on methanol was presented to the public in 1974.
	B-Class F-Cell
	NECAR 1, 2 and 3: From van to A-Class.
	Mercedes-Benz Concept Vehicles, NECAR 1: An MB 100 van served as basis.
	Mercedes-Benz Concept Vehicles, NECAR 1: The cargo space is packed with equipment. The stacks are arranged beneath the yellow hydrogen flask.
	The Technology of the Fuel Cell and its Operating Systems, The operating principle of the fuel cell.
	Matured: After the completion of the test stage, several units of the NGT Sprinter (Natural Gas Technology) were put into service, for instance by RHENAG in April 1996.
	Matured: After the completion of the test stage, several units of the NGT Sprinter (Natural Gas Technology) were put into service, for instance by RHENAG in April 1996.
	In 1992, Mercedes-Benz presented a “Flexible Fuel” test car based on the 300 SE S-Class model (140 series). It engine management was designed for variable mixed methanol/ gasoline operation with a methanol proportion of up to 85 percent.
	Hydrogen testing: Mercedes-Benz also investigated the suitability of hydrogen as an energy supplier for internal combustion engines in vans.
	On the way into the future: Different vehicles – the photo shows a Mercedes-Benz 230 E – were used in 1993 for testing hydrogen as a fuel for the internal combustion engine.
	On the way into the future: Different vehicles – the photo shows a Mercedes-Benz 230 E – were used in 1993 for testing hydrogen as a fuel for the internal combustion engine.
	Production car: In March 2006, smart presented the forfour lpg (liquefied petroleum gas) with a liquefied-gas tank in addition to the gasoline tank. In combined operation, the car has a range of 1,300 kilometers (over 800 miles).
	Production car: In March 2006, smart presented the forfour lpg (liquefied petroleum gas) with a liquefied-gas tank in addition to the gasoline tank. In combined operation, the car has a range of 1,300 kilometers (over 800 miles).
	Production car: In March 2006, smart presented the forfour lpg (liquefied petroleum gas) with a liquefied-gas tank in addition to the gasoline tank. In combined operation, the car has a range of 1,300 kilometers (over 800 miles).
	Spectacular test car: The Wankel or rotary-piston engine was tested in the Mercedes-Benz C 111-I (1969, shown in the photo) and C 111-II (1970).
	Spectacular test car: The Wankel or rotary-piston engine was tested in the Mercedes-Benz C 111-I (1969, shown in the photo) and C 111-II (1970).
	On the way into the future: Different vehicles – the photo shows a Mercedes-Benz 230 E – were used in 1993 for testing hydrogen as a fuel for the internal combustion engine.
	V8 gasoline engine with cylinder shutoff, six-cylinder diesel engine with turbocharger, gas turbine: The Mercedes-Benz Auto 2000 research car (1981) was used for testing these three propulsion systems.
	V8 gasoline engine with cylinder shutoff, six-cylinder diesel engine with turbocharger, gas turbine: The Mercedes-Benz Auto 2000 research car (1981) was used for testing these three propulsion systems.
	V8 gasoline engine with cylinder shutoff, six-cylinder diesel engine with turbocharger, gas turbine: The Mercedes-Benz Auto 2000 research car (1981) was used for testing these three propulsion systems.
	V8 gasoline engine with cylinder shutoff, six-cylinder diesel engine with turbocharger, gas turbine: The Mercedes-Benz Auto 2000 research car (1981) was used for testing these three propulsion systems.
	V8 gasoline engine with cylinder shutoff, six-cylinder diesel engine with turbocharger, gas turbine: The Mercedes-Benz Auto 2000 research car (1981) was used for testing these three propulsion systems.

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