CO2 emissions, material and energy consumption are reduced on the bridges through the use of hydrogen and e-vehicles, lightweight construction and intelligent controls

The innovative forms of drive in combination with autonomous driving on a specially designed route open up new possibilities for making a vehicle particularly sustainable. With a planned durability of 100 years, a significant proportion of CO2 emissions and material can be saved in both production and operation. In addition, the central intelligent control of the vehicles results in a significant reduction in energy consumption.

Content: The bridge fleet is particularly environmentally friendly because the most sustainable solution is always chosen for the propulsion system, the selection of building materials and the frame construction.

There are battery-electric and hydrogen-electric vehicles on the bridges. The required refuelling infrastructure is not only provided by the bridges for their own vehicles; rather, e-cars can also charge their batteries down on the roads, and hydrogen vehicles can fill their tanks at the hydrogen filling stations located on the seven outer arms of the bridges as well as on the bridge ring.

The second major lever for the sustainability of the fleet is to save material through structural optimisation, a significantly lower number of vehicles and the long life cycles of the vehicles.

Furthermore, in the selection of materials, emphasis is placed on sustainable building materials or, where possible, on renewable raw materials.

Both hydrogen tanks and batteries are used in the vehicles on the Frankfurt bridges

When it comes to climate-friendly drives, battery-electric and hydrogen-electric drives are always at odds with each other.

Both are planned for the Frankfurt bridges, because it can be assumed that, depending on the geographical location and the respective transport task, sometimes one technology and sometimes the other is more environmentally friendly and therefore "better" in terms of the overall ecological footprint.

Since the German automotive industry still wants to play a decisive role, not only in Germany but also with exports worldwide, it is logical that in a German "showcase of innovations" such as the Frankfurt bridges, both technologies are planned as promising drive systems for the future.

Both hydrogen tanks and batteries are used in the vehicles on the Frankfurt bridges

When it comes to climate-friendly drives, battery-electric and hydrogen-electric drives are always at odds with each other.

The difference between hydrogen and battery vehicles

First of all: Both types of vehicle are electrically powered. Electric current is therefore always required for locomotion.

The difference: electric cars have a battery that provides the electricity. In hydrogen cars, hydrogen is converted into electricity by a fuel cell. The hydrogen car only has a small battery to store energy temporarily.

Since there will be a lot of green energy on the bridges, it makes sense to run part of the fleet on hydrogen electricity

The production of batteries requires special raw materials, in particular lithium, cobalt and nickel, whose mining conditions and other factors are particularly critical. Hydrogen, on the other hand, can be produced by electrolysers and then stored in tanks, the production of which does not require comparable raw materials for manufacture. Moreover, energy in the form of hydrogen can be stored for longer periods without major losses, whereas storage in correspondingly large batteries is only possible for days or a few weeks.

With the help of the Frankfurt bridges, a surplus of electrical energy is produced, which is stored both for short-term use in redox or lithium batteries and for the longer term in tanks in the form of hydrogen.

The energy surpluses of the bridges will be made available to the citizens of Frankfurt for their e-cars and hydrogen vehicles.

Vehicles can be refuelled not only on the bridges, but also under them

The hydrogen filling stations on the bridges were designed in such a way that all hydrogen-powered vehicles for bridge traffic can be automatically refuelled with them. This means that the autonomous vehicles automatically drive into the hydrogen filling station and remain there until the refuelling process is complete.

But it is not only the bridge vehicles that will be connected; the bridges will also provide Frankfurt's citizens with seven filling stations at various locations in Frankfurt.

The citizens of Frankfurt can fill up their electric cars with green electricity at the bridge's own electric filling stations.

Frankfurt's bridges provide plenty of green energy, as many surfaces are equipped with photovoltaic panels.

This energy is not only used to power the houses and shops on the bridges, but also to power the battery electric vehicles.

In addition, residents can also use the charging points at the pillars of the bridges to charge their electric vehicles.

There are bridge charging stations, but more remote charging stations in the city are also supplied with electricity from photovoltaic surpluses.

Surplus electricity from bridge solar modules and the photovoltaics of the energy belts around Frankfurt will be stored in the form of hydrogen and made available to both the bridge fleet and Frankfurt's H2 filling stations.

There are 100 hydrogen-electric vehicles on Frankfurt's bridges that can be powered using the bridges' energy infrastructure. However, such a high surplus of green hydrogen is produced that around 80 Frankfurt buses operated by the Frankfurt transport company can also be supplied - this corresponds to 20 percent of Frankfurt's bus routes.

In addition, there is the energy surplus from the (bridge-independent) energy belts along the motorways and federal roads around Frankfurt, which also feed their surplus electricity to the electrolysers of the hydrogen filling stations in the extended urban area.

Frankfurt hydrogen filling stations will probably be located at the major exit roads, because the most important clientele will be heavy goods vehicles.

As no other services are expected to be offered apart from refuelling and the H2 tanks, like the electrolysers, will be installed underground, i.e. in a very space-saving manner, the proximity to the current existing filling stations is an advantage.

Anticipatory driving is not only pleasant, but also saves energy

The central organization ensures that vehicles run smoothly and generally only stop when necessary. In addition, they do not have to brake and restart pointlessly, which consumes the most energy in urban traffic.

Vehicles on Frankfurt bridges brake less frequently, and when they do, they do so with recuperation.

In electric driving, energy is fed back into the battery by the engine during braking: This so-called recuperation is already used in today's vehicles and significantly increases energy efficiency.

Experts on the Topic

BAM Bundesanstalt für Materialforschung und -prüfung - TU Dresden Professur für Elektrische Maschinen und Antriebe - ZSW Zentrum für Sonnenenergie und Wasserstoff Forschung - Forschungszentrum Jülich IEK Institut für Energie und Klimaforschung - Forschungsnetzwerke Energie - DWI Leibnitz-Insittut für Interaktive Materialien

The centrally controlled vehicles on the Frankfurt bridges offer significantly reduced CO2 emissions through demand-oriented route planning

No journeys "for free": no detours, no empty journeys, not one vehicle too large for just a few or one passenger - this too is only possible with central organisation of transport

A centrally optimised system with vehicles in the Car-Sharing model requires fewer vehicles and resources, which saves energy

Intelligent, demand-oriented fleet planning means that fewer vehicles are needed, as individual vehicles do not have to be kept on hand for each person.

A car is stationary for up to 90% of its lifetime, i.e. it is only used for 10% of its time (if a study by the Institute of Social and Economic Research at the University of Cologne is to be believed, a car is actually only used for 5% of its time).

With autonomous driving on bridges, many people are transported by the same vehicles, both buses and trains, and cars. So you don't have to own the vehicles for comfortable usability, but can call them as needed via app.

Since this system is attractively priced, it is expected that more and more people in the city will no longer see a need for their own car. This reduces the demand for cars in general - and thus also the demand for lithium batteries and other materials. To achieve this goal, particular attention was paid to the cleanliness of the vehicles and ease of booking.

Sustainability means fewer car replacement cycles on Frankfurt bridges due to appreciation

Vehicles are valued through craftsmanship and attention to detail

Car bodies are to be partially handcrafted in the master academy. Decorative elements and the attention to detail typical of classic cars are intended to showcase the beauty of the vehicles again and again. The aim is to get away from the throwaway culture and back to an appreciation of things. This significantly saves material and energy.

Fewer accidents mean that vehicles only need to be replaced very rarely

The central control and the autonomous driving mode prevent accidents very reliably. Vehicles cannot usually be destroyed by accidents or carelessness, as the autonomous system controls reliably and correctly at all times. Overconfidence and negligence can be ruled out. The vehicles on the bridges can be designed accordingly elaborately.

Due to the longevity of the vehicles on the bridges, there is no need to constantly buy new cars, buses and trains - against the background of increasingly scarce resources, this is an important factor in the city of the future.

For the vehicles on Frankfurt's bridges, a service life of one hundred or more years is the target. The fact that an astonishing longevity is also possible for regularly used vehicles is still demonstrated today by roadworthy cars from the fifties, sixties or seventies, as seen for example in countries such as Cuba or Morocco.

The longevity of the vehicles must be ensured by regular maintenance and care as well as, quite classically, by rapid repairs when necessary: Through "predictive maintenance", the vehicles know when it is time for a check-up or repair and drive to the workshop. There they are checked, parts are repaired shortly before they become defective or - if this is not possible - replaced. The modular design of the vehicles makes it possible to replace individual parts. This means that an entire complex does not have to be replaced - as is so often the case today - even though only a single element is defective.

Experts on the Topic

Fraunhofer ISI Institut für System- und Innovationsforschung - Hyson - Zentrum für Brennstoffzellentechnik ZBT - DVGW Forschungsprojekte zu Wasserstoff - FFE Forschungsstelle für Energiewirtschaft - Rainer Lemoine Institut

When selecting the materials for the vehicles on the bridges, environmental compatibility - from extraction to disposal - was taken into account.

The materials from which the vehicles are made are consistently designed with environmental compatibility in mind - both in extraction and processing as well as in disposal - even if this is only to take place in 100 years or more. The aim is to consider the complete life cycle of all materials, i.e. from extraction to disposal and possible reuse. If you look at old wooden tracks, it is impressive how long they serve.

Wherever possible, renewable and recyclable materials are used for the vehicles on the bridges.

Wherever possible, renewable raw materials are used, such as wood in the construction of the tracks, or hemp, flax and other natural fibres in the interior panelling and fittings.

Popcorn, for example, can be used for insulation. Many different sustainable input materials can be tried out on the Frankfurt bridges.

As far as possible, at the end of their useful life, all materials should either be returned to the raw material cycle or be able to be reused by up-, down- or recycling.

Extremely durable materials have the advantage of longer life cycles, but the disadvantage that they are not recyclable or degradable without leaving residues.

Fibre composites, which are problematic in terms of their recyclability, are largely dispensed with in the construction of vehicle bodies on the Frankfurt bridges:

In fibre composites, glass or carbon fibres are woven into a carrier material and then bonded with resin. This makes the material high-strength and durable. However, the two components can no longer be separated from each other.

Unfortunately, it does not make sense to completely dispense with fiber composites. For example, the hydrogen tanks are made of fibre composite material. Their poor recyclability is compensated for by the long service life of the vehicles.

Experts on the Topic

DECHEMA - Fraunhofer IFAM - Deutscher Wasserstoff- und Brennstoffzellenverband - Mission Hydrogen - TU Chemnitz Institut für Automobilforschung - DWI Leibnitz-Insittut für Interaktive Materialien

Vehicles on the bridges are of lightweight construction

The most important framework condition for the vehicles on the bridges: they have to be light! There are several reasons for this. On the one hand, lighter vehicles can save materials in bridge construction, because they are not subjected to so much additional stress by the vehicles. On the other hand, the heavy crash structure in the vehicle body can be dispensed with due to the autonomous system and the "biotope environment".

To achieve this goal, all "masses", i.e. weights of the individual vehicle parts, were compiled in a "mass balance". In the next step, each component was checked to see whether and how it could be made lighter than before.

While the oldtimers still drove with the heavy combustion engine and had heavy steel bodies, today there is fuel cell technology as an alternative and a wide range of lightweight materials for the construction of the body.

Over the past decades, cars have become heavier and heavier on average - only in recent years has lightweight construction come into focus

Yet one has caused the other: Anyone who drives faster is exposed to greater force in the event of an accident. In order to protect the occupants, the manufacturers strengthened the bodies and packed numerous safety equipment into the cars.

The result: the cars became even heavier. This led to both material and energy waste: On the one hand, the production of raw materials for car manufacturing increases, and on the other hand, a heavier vehicle requires more energy to accelerate.

Since the vehicles on the Frankfurt bridges are manufactured in lightweight construction, a lot of drive energy is saved

Whether buses, trains or passenger cars - the entire vehicle fleet is manufactured in lightweight construction, which is made possible by the significantly reduced risk of accidents and reduced impact force. This is because all vehicles are networked via a central control system, through which information about the positions, speeds and next manoeuvres of all vehicles is constantly exchanged, thus preventing accidents. In addition, the vehicles do not travel faster than 30 kilometers per hour, so that the reinforcements of the bodywork that are customary today are also unnecessary to a large extent.

And with every gram less, drive energy is also saved: the vehicles on the Frankfurt bridges weigh around 20 to 40 percent less than conventional cars. This results in around 10 percent lower energy consumption.

A lightweight model has been developed for the longest bus and the longest train on the bridges as an example (more ->....)

The German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) has already developed a number of lightweight body structures - e.g. this multi-material body structure with a high proportion of fibre-reinforced plastics

In order to be able to implement lightweight construction, the component weights of the "Neoplan NH 6/7" vehicle were documented in a mass balance.

The weights of the main vehicle components were entered in a mass balance table. This allows a relatively accurate weight estimate of the vehicles to be made.

For a better overview, the weights are divided into different categories: "Frame, bodywork and chassis", "Autonomous system, climate, light elements", "Powertrain" and "Passengers".

For each category there are extensive individual lists with the respective components and weights.

Savings potentials: Optimization of the frame structure, FEM analysis of the axle beams

An extract from the mass balance shows the individual weights of components

The weights of the areas "Frame", "Interior" and "Exterior: Planking outside" are shown in simplified form as an extract from the original mass balance file.

The most important weight components of these ranges can be taken from the list.

Conclusion: Optimizing the vehicle fleet for sustainability serves as a model for the vehicle world of the future

Due to the "track biotope" that can be realized on the bridges, the bridge vehicles are exposed to significantly reduced loads: The driving speed is low, the crash risk is close to zero, and the risk of tipping over is also virtually non-existent - all factors that favor a sustainable choice of materials and low material consumption (and thus low weight).

Even though it will probably be decades before comparable traffic can be realized on the roads, the right characteristics for the vehicle world of the future can be developed and applied here in advance.