Research vehicle targets sustainable automobility even on long journeys

Research vehicle targets sustainable automobility even on long journeys

Technology News |
With the Interurban Vehicle (IUV), the German Aerospace Center (DLR) research institute has developed a concept for vehicles in the middle and luxury segments. Its combination of hydrogen drive, battery and automated driving shows what sustainable automotive long-distance transport of the future could look like.
By Christoph Hammerschmidt

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The IUV combines fuel cell, battery and new approaches to energy management. In this way, it should enable emission-free and comfortable driving over long distances of up to 1,000 km. Autonomous driving functions relieve the burden on the driver and allow new freedom in the design of the interior.

“For the project, we built the IUV as a rollable body demonstrator. This demonstrator gives a first impression of how the vehicle could look in practice. At the same time, with the help of the demonstrator we were able to better develop central components and technologies, measure them on test benches and test them. It also shows which aspects we can further develop and realise in the future with partners from industry and research,” describes project leader Sebastian Vohrer from the DLR Institute of Vehicle Concepts in Stuttgart, Germany.

Emission-free on the road: fuel cell, battery and smart energy management

With its design concept of a fuel cell plug-in hybrid, the IUV combines a fuel cell with an output of 45 kW, a 700 bar hydrogen pressure tank and a battery with a capacity of 48 kWh. This configuration gives the IUV a total range of up to 1,000 km. The electric motors with a total output of 136 kW accelerate the vehicle up to 180 kmph. The hydrogen refuelling process at hydrogen filling stations takes about as long as with conventional drives with combustion engines, the DLR engineers promise. The battery can also be charged independently at public or private charging stations. The fuel cell is located in the front of the car, the battery in the rear of the five-metre-long vehicle. The hydrogen tank is installed in the underbody and holds about 7.5 kilogrammes of hydrogen.

The more electrification in vehicles increases, the more efficient all electricity, heating and cooling processes must be designed. Otherwise, there is a risk of losses in range or in comfort functions such as air conditioning and infotainment systems. For this reason, the DLR team also dug deeply into the energy management: For the IUV, the researchers took a closer look at metal hydride storage systems. With their help, part of the pressure difference between the hydrogen tank at 700 bar and the fuel cell at 5 bar can be used to generate additional cooling for the vehicle’s air conditioning and to support the conventional refrigeration machine.

In their work for the IUV, the DLR scientists also investigated how autonomous driving would affect the vehicle concept and architecture. To do this, they assumed a high degree of automation at SAE level 4. This means that the car drives itself permanently; only when it can no longer manage a task does it ask the human to take over the controls again. “Especially on long distances, automation can significantly relieve the drivers. At the same time, it allows us to make the interior of the vehicle more open and flexible,” describes project manager Sebastian Vohrer. The IUV team has developed various designs for this purpose and evaluated them for their functional and technical feasibility. One result is the seating arrangement of the IUV, which can be variably adapted to the driving mode: The two front seats can be rotated. In autonomous mode, the occupants can also sit with their backs to the direction of travel. The strict separation of the rows of seats is thus eliminated and a common communication space is created. The dedicated climate control concept adapts to the interior and the respective occupants; it is no longer controlled centrally via the dashboard. Instead, each passenger can control the air conditioning individually via interfaces in the headliner – similar to aeroplanes.

A lightweight vehicle structure is regarded as key to achieving a long range while keeping energy consumption low. By combining various lightweight design approaches and fibre-reinforced plastic, the DLR engineers succeeded in limiting the weight of the vehicle to less than 1600 kilograms when empty, but including the energy storage units. The bodyshell of the IUV even weighs only 250 kilograms, around a quarter less than is currently common in this vehicle segment.

The team built selected components of the IUV as prototypes and tested them in crash tests to verify the calculations and simulations previously made on the computer. These included the side skirt below the side doors. It is a particularly important structure and is intended to protect the hydrogen tank in the vehicle floor and the occupants in the event of a side impact. This is because the IUV does not have a centre pillar, which in conventional car bodies connects the floor and roof of the vehicle and serves as a crash element. Without a centre pillar, there are also large door openings. In combination with sliding doors that open towards each other, they make getting in and out particularly easy.

Wherever possible, the DLR researchers have also worked with functional integration – another lightweight construction approach: “Structures fulfil several functions here, for example the floor structure not only carries all the vehicle’s superstructures, but also conducts electricity or data at the same time. This means that it is possible to partially dispense with additional cable lines and thus further reduce overall weight,” explains Vohrer.

www.dlr.de

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