Practical step towards e-mobility with intercity buses: IAA premiere of the Mercedes-Benz Intouro hybrid

• The hybrid principle: Generating braking energy and using it for moving off
• Supercapacitors (“supercaps”) serve as short-term energy storage units
• 48-volt network, low added weight, unmodified operation
• Tried and tested components, new: Recuperation module for the Intouro
• Intouro K: A genuine all-round talent, even on narrow streets
• Premiere model: Versatile equipment, a role model in safety

Electromobility comes in many shapes and sizes. While the emphasis is on all-electric drive systems for urban traffic, for its first step toward e-mobility, Daimler Buses is relying on the Mercedes-Benz Intouro with its hybrid module for intercity transport as well as for a combination of regular service and touring coach routes in its drive to continue to decrease the already economic fuel consumption. The hybrid module is available for all two-axle models with automatic transmission featuring torque converter from the ample Intouro family. At the IAA Transportation 2022 Press Days, Daimler Buses will be showcasing this technology using the compact Intouro K intercity bus, a versatile, particularly agile and economical bus with a wide range of applications.

Hybrid principle: Generating braking energy and using it for moving off

The basic function of the Intouro hybrid is extremely simple: An additional electric motor acts as an alternator when the bus brakes and coasts, converting braking energy into electricity. This electricity is stored and is made available to the electric motor to support the combustion engine, especially when moving off, but also when accelerating.

The drive technology behind it is simple. One core component of the hybrid drive is the electric motor. The disc-shaped major assembly with integrated power electronics and a thickness of eight centimeters is installed between the combustion engine and the automatic transmission. Its output is 14 kW with a torque of 220 Nm.

The electric motor primarily assists the combustion engine in the case of high output requests, especially when moving off. However, it does not serve to increase the maximum output, which is why the specifications for the bus’s performance and torque remain unchanged. Rather, the electric motor relieves the strain on the combustion engine and increases the moving-off performance. The combustion engine’s speed is not reduced, the peak power is only held back imperceptibly and replaced by the electric motor.

Hybrid technology can lead to noticeable fuel consumption advantages

In addition, a slight boost by the electric motor at idle speed improves the efficiency of the combustion engine. Both of these factors together result in a reduction in the already low fuel consumption. In the Intouro, this is particularly evident in inner city and suburban traffic, where the driver is constantly alternating between the accelerator and brake pedals. The reduction is up to five percent in suburban and inner city traffic.

Supercapacitors (“supercaps”) serve as short-term energy storage units

The electricity generated by recuperation is stored in double-layer capacitors, also known as supercaps. These electric energy storage units are characterized by a high power density. They are not sensitive to high power peaks and have a long service life. In contrast to batteries, supercaps are ideal for the constant and rapid changes between charge and discharge when stopping and moving off. The Intouro hybrid only needs a single braking maneuver from 50 km/h to a standstill to charge the energy storage units.

The power storage system of the Intouro hybrid consists of two modules. Each module contains 16 supercaps. Both modules together have a total capacity of 88 Wh and are mounted on the rear left-hand side of the roof (in the direction of travel) to save space. A cover protects the modules from external influences and sunlight. At the same time, a perforated side panel ensures the necessary cooling by the headwind.

An inverter, or power inverter, converts the stored direct current into alternating current to drive the electric motor. Both the inverter and the electric motor are water-cooled. The additional cooler for this low-temperature cooling unit with a maximum of 65°degrees Celsius is located beneath the vehicle radiator to save space.

48-volt network, low added weight, unmodified operation

Another key advantage: The Intouro hybrid does not need a complex high-voltage network bringing about its own, necessary restrictions and safety requirements. The intercity bus boasts a separate 48-volt network. This is classed as low-voltage technology and is safe to use. The unmodified auxiliary assemblies are driven conventionally. Further advantages of the compact and uncomplicated technical body of the additional hybrid drive: The required installation space is small, the outline remains unchanged, as does the interior – no passenger seats are lost. The added weight of the hybrid drive is 254 kg. As a result, the total number of passenger seats is only slightly reduced and is insignificant in practice.

Bus drivers behind the wheel of the Intouro hybrid will not be able to tell the difference when handling the vehicle or even during operation. Even the instrumentation is identical. Training is therefore unnecessary. Likewise, neither quick driver changes, often common during regular-service bus service, nor switches between different buses pose any problem at all.

Tried and tested components, new: Recuperation module for the Intouro

Developers of the Intouro hybrid rely on tried and tested components. They are already used in the successful Citaro hybrid, for example, a model which has proven itself splendidly in practice, using this technology for many years now. The use of supercaps as energy storage units is derived from this model, for example. Citaro enthusiasts already are already familiar with them as recuperation modules. However, extensive adaptation measures were required due to the new electric/electronic structure of the Intouro with different control units.

This recuperation module is now also available for the Intouro for the first time, regardless of the hybrid module. In addition to the vehicle batteries, it stores the current generated by recuperation and makes it available when moving off or on inclines. This relieves the strain on the alternator and thus on the combustion engine, reducing fuel consumption.

The°energy storage unit is also mounted on the right-hand side of the roof (in the direction of travel) to save space. The recuperation module is a prerequisite for the Intouro hybrid.

Intouro K: A genuine all-round talent, even on narrow streets

The new hybrid module is enjoying its debut in the compact Intouro K within the Intouro model series. It is particularly agile with a length of 10.75 meters and a turning circle of just 18.34 meters. This makes it ideal for trips through mountainous regions, on winding roads or for excursions with small groups.

At the same time, the Intouro K is a fully fledged bus with all the outstanding characteristics of the Intouro family. In line with its broad scope of application, it is available in a wide range of equipment variants – the range extends from matter-of-fact, tender-compliant, high-floor inter-city buses to excursion vehicles.

The range of equipment includes destination displays, a single or double-width entrance in the center and two different lifts for passengers with reduced mobility. There is a large choice of seating and luggage shelf options for the interior. The Intouro’s driver area, which has also been completely redeveloped, is ergonomically perfect and driver-oriented, typical for Mercedes-Benz buses. From its visual appearance to the controls and instrumentation including color display, the high-quality cockpit is as luxurious as in a fully fledged touring coach.

The engine output of the Intouro K is optionally 220 kW (299 hp) or 260 kW (354 hp). Enterprises can even choose from four transmission variants: Six-speed manual transmission, fully automated Mercedes-Benz PowerShift transmission or automatic transmission with torque converter from Voith and ZF.

The new hybrid module and recuperation module, which is available as special equipment, further reduces fuel consumption and thus emissions from this powerful and equally economic drivetrain.