Mercedes-Benz Intouro K hybrid intercity bus Compact intercity bus with supercapacitors ("supercaps")

• Hybrid principle: generating braking energy and using it to move 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
• The Intouro K hybrid: versatile equipment and a role model for safety

While the emphasis is on fully electric drive systems for urban traffic, Daimler Buses is relying on the Mercedes-Benz Intouro featuring a hybrid module for intercity transport as well as for a combination of regular and touring bus services in its drive to continue to decrease the already economic fuel consumption. The hybrid drive unit can be supplied for all two-axle Intouro models equipped with an automatic transmission with torque converter. The hybrid module made its debut in the intercity bus programme in August 2022 in the Intouro K hybrid, a versatile, particularly manoeuvrable and highly economical intercity bus providing a wide range of usage possibilities.

Hybrid principle: generating braking energy and using it to move off

The basic function of the Intouro hybrid is extremely simple. The core component is an additional electric motor that acts as an alternator while the bus is braking and decelerating in overrun mode, thereby converting braking energy into electricity. This power is stored and is made available to the electric motor to support the combustion engine especially during high output requests: when it comes to moving off, but also when accelerating and to support idling. However, it is not intended to increase maximum performance.

The electric motor is a disc-shaped major assembly with integrated power electronics and a thickness of eight centimetres which is inserted between the combustion engine and the automatic transmission. Its output is 14 kW with a torque of 220 Nm. 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 of the already low fuel consumption. In the Intouro, this is particularly evident in local and suburban operation, where the driver is constantly alternating between the accelerator and brake pedals. In this kind of operation, a reduction of up to five percent can be achieved.

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

The current generated by recuperation is stored in double-layer capacitors, also known as "supercaps". These electric energy storage units are characterised by a high power density. They are not sensitive to high power peaks and boast a long service life. In contrast to batteries, supercaps are ideally suited for the constant and rapid changes between charge and discharge when stopping and starting. The Intouro hybrid only needs a single braking manoeuvre 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, when seen in the direction of travel, they are mounted at the rear on the left-hand side of the vehicle’s roof in order 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 airstream.

A DC/AC converter, or power inverter, converts the stored direct current into alternating current to drive the electric motor. Both the DC/AC converter 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 below 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 thus avoiding the inherent restrictions and safety requirements that this would entail. The intercity bus has a separate 48-volt network. This is classed as low-voltage technology and is safe to use. The unmodified auxiliary assemblies are driven conventionally. The required installation space is small and the outline remains unchanged, as does the interior. The added weight of the hybrid drive is 254 kg. As a result, the total number of passenger seats is only slightly reduced.

Bus drivers behind the wheel of the Intouro hybrid won't notice any difference when handling the vehicle or driving it in ongoing operation. Even the instrumentation is identical. Therefore no extra training is necessary. Likewise, neither quick driver swaps, often common during regular bus service, nor switches between different buses pose any problem at all.

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

The tried and tested components of the Intouro hybrid are also used in the successful Citaro hybrid, for example, a model that has proven itself splendidly in practice and has been using this technology for many years now. The use of supercaps as energy storage units is derived from the Citaro hybrid, for example. This system is also well-known as recuperation module. However, extensive adaptation measures were required due to the new electric/electronic structure of the Intouro with different control units.

The recuperation module is a prerequisite for the Intouro hybrid. In addition to the vehicle batteries, it stores the current generated by recuperation and makes it available when moving off or on mountainous inclines. This relieves the strain on the alternator and thus on the combustion engine and reduces fuel consumption. The energy storage unit is mounted on the right-hand side of the roof in the direction of travel to save space.

The Intouro K hybrid: versatile equipment, exemplary safety

With a length of 10.75 metres and a turning circle of only 18.34 metres, the compact Intouro K hybrid is particularly manoeuvrable. At the same time, it is a fully-fledged bus with all the outstanding characteristics of the Intouro family. Corresponding to its broad area of application, which extends from trips through mountainous regions and on narrow roads in towns and villages to excursions with small groups, it is available in numerous equipment variants – the range extends from practical, tender-compliant high-floor intercity buses to buses geared towards excursions and weekend trips.

The range of equipment includes destination displays, a single or double-width entrance in the centre and two different lifts for passengers with restricted mobility. The driver's seat of the Intouro K is ergonomically perfect and driver-oriented. From its visual appearance to the controls and instrumentation including a colour display, the high-quality cockpit is as luxurious as in a fully-fledged touring coach.

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

The equipment with its assistance systems is outstanding: The Active Brake Assist 5 (ABA 5) emergency braking assistant is the only system of its kind in buses that can perform maximum full-stop braking manoeuvres even for moving pedestrians. Sideguard Assist warns of people and obstacles when turning. Along with conventional assistance systems, this ensures that the Intouro K meets exemplary safety levels.