All about Hydrogen Trucks: The Future of Sustainable Transportation

Since hydrogen is both inexhaustible and non-polluting, it has a role to play in the transition to a low-carbon emissions economy – or even a zero-emissions economy in the case of renewable hydrogen. But can this energy-carrying gas explode? What risks are involved in using hydrogen, and what solutions exist to limit these risks in the field of transportation?

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Hydrogen: A brief reminder of the basics

With its simple atomic structure, hydrogen is the lightest atom in Mendeleev's periodic table. It is the most abundant chemical element in the universe. As well as being colorless and odorless, H2 or dihydrogen, consisting of two hydrogen atoms, is a highly energetic molecule. The combustion of 1 kilogram of H2 releases approximately three times more energy than the same mass of petroleum fuel.

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Understanding the properties of hydrogen to ensure its safe use

Like any fuel, hydrogen presents a risk of ignition or explosion in contact with air and a spark or source of heat. Its extreme lightness – it is 14 times lighter than air – and speed of diffusion give it the disadvantage of being able to escape through the slightest gap but also the advantage of dissipating rapidly into the atmosphere, thus limiting the risk of fire in open areas.

Due to its small atomic size, hydrogen can diffuse into metal and modify the crystal lattice, causing the embrittlement of metallic materials, known as the hydrogen embrittlement phenomenon. It is therefore important to select appropriate materials for the design of safe hydrogen systems.

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Hydrogen vehicles: Innovatively designed to ensure safety

The interest in low-carbon energies has prompted manufacturers to develop systems that enable hydrogen to be produced, transported, stored, and used in complete safety. For example, in hydrogen vehicle tanks, everything is designed to avoid or control gas leaks and to reduce the risk of ignition in the event of an accident:

• Heavy-duty sealing: A polymer liner surrounded by a thick layer of high-strength composites seals the fuel tank and can withstand impacts of 5,000 joules.
• Fully controlled system: Vehicles are embedded with strategically placed sensors to check for leaks in the system and a circuit breaker to cut off the gas flow if a leak is detected.
• Fire precautions: Valves allow the hydrogen to be safely evacuated out of the vehicle and thus avoid overpressure in the tank.

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A battery of tests to ensure the safety of hydrogen vehicles

Hydrogen systems are subject to strict safety standards, requiring them to undergo a whole series of tests to verify their resistance to extreme temperatures, chemicals, falls, shocks, and so on. They even undergo ballistics testing to test their resistance to ultra-powerful impacts.

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View all hydrogen cars on Lhyfe Heroes

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To fill the tanks of clean, zero-emission vehicles, such as cars, forklifts, tractors, buses, trucks, refuse collection trucks, boats, trains, etc., filling stations must be supplied with hydrogen that is processed, compressed and delivered to them from a production site.  

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Filling up with hydrogen, as simple and quick as filling up with petrol

Let’s start by highlighting what doesn’t change! Filling up a new Mirai car in a hydrogen station is just as straightforward as refuelling a conventional combustion engine car. Only the filling unit is really different – hydrogen comes in kilograms rather than litres, but everything else is similar. You still have your pump, nozzle, terminal keypad and information screen, and above all the charging time is no different – in less than five minutes the tank is full, and the Mirai can set off again for around 650 kilometres.

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Behind the scenes at a hydrogen station

Before being able to distribute fuel, a hydrogen station must first complete several processes:

• First, the hydrogen must be stored in cylinder racks, tanks or tube trailers,
• It needs to be compressed (to 500 bar for vehicles that run on 350-bar hydrogen and to 900 bar for vehicles that run on700-bar hydrogen, which depends on the vehicle type),
• Then it must be stored again in tanks known as buffers.
• Before being distributed, the hydrogen must be cooled using an exchanger and a cold unit (for 700-bar stations only).
• Only then can the hydrogen be used to fill a tank via the hose and nozzle of the dispenser.

Hydrogen station infrastructure is built above ground and is simple to install, repair and upgrade.

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Who installs hydrogen stations?

In addition to developers and operators of service stations – who are diversifying their offer and promoting clean mobility with hydrogen – local authorities, companies, manufacturers or operators of vehicle/bus fleets can also install their own hydrogen stations for refuelling their fleet. Some such private operators also open their stations to the public.  

In some areas, ecosystems have been set up to co-develop stations that meet the needs of all local users.  

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What do the current hydrogen stations offer?

A hydrogen station’s offering can be defined based on a few main criteria:

• Compression: 350 bar and/or 700 bar ( or 35 and/or 70 MPa). Some hydrogen stations only deliver 350 bar, some only 700 bar, and others deliver both.
• Storage capacity: This ranges from a few kilos – for supplying a small light vehicle fleet – to several tonnes of hydrogen a day for refuelling trucks, boats, planes, trains, etc.
• Flow rate: Fuelling time will vary depending on the station’s flow rate, the vehicle and the vehicle’s fuelling protocol.

One sign that the sector is already mature is that there is a standard for hydrogen stations – the SAE J2601 standard establishes the protocol and process limits for supplying hydrogen to light fuel cell electric vehicles.

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Where are the first hydrogen stations?  

See the collaborative map of stations‍

France – which plans in its Hydrogen Plan to install more than 100 hydrogen stations in 2023 – must accelerate its network to allow individuals and professionals to fuel their vehicles within a timeframe that matches the plans of vehicle manufacturers and fuel distributors.

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What happens under the bonnet of a hydrogen vehicle? Although many people use the term “hydrogen engine”, in reality, hydrogen vehicles use electric engines powered by hydrogen. Hydrogen trucks, cars, tractors and so on are indeed electric vehicles or more precisely Fuel Cell Electric Vehicles (FCEV).

However, unlike the “conventional” electric vehicle (which should really be referred to as a battery electric vehicle or BEV) – whose electricity is stored in the battery during charging – the “hydrogen electric vehicle” generates its own electricity using a hydrogen fuel cell.

To use a hydrogen vehicle, the user must fill the hydrogen tank rather than recharging the battery.

There are two types of hydrogen engine technology:

• The FCEV: an electric vehicle with an electric engine powered by a fuel cell – most hydrogen vehicles available today use this technology,
• The ICE: A vehicle with a hydrogen internal combustion engine. This technology, which is not yet on the market, is in the R&D phase and interests manufacturers such as Toyota, Porche, and MAN. This type of engine would keep much of the current engine’s operating system the same and would require minimum adjustments to vehicles.

What defines the power of a hydrogen engine?

FCEVs have several design parameters that define a vehicle’s power:

• Battery capacity (in kWh)
• Fuel cell power (in kW)
• Hydrogen storage capacity (in kg)
• Overall engine power in (kW)
  

Depending on the vehicle’s purpose, manufacturers design various configurations of these four elements.

Gas or liquid hydrogen?

These are the two means of storing hydrogen and each has its advantages and disadvantages, depending on the vehicle’s purpose. Liquid hydrogen allows you to store four times more hydrogen but liquefying hydrogen results in a lower energy yield due to the additional liquefaction operation. What’s more, once it is in the car, it must be used very quickly before it turns back into gas and expands. This means it must be used or evacuated ... and lost!

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How exactly does a fuel cell work?

There are several types of fuel cells, which convert fuel into energy. The most common is the hydrogen fuel cell, which converts hydrogen (the fuel) into electricity (the energy), through the electrochemical reaction of hydrogen and oxygen.
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This process, which occurs instantaneously, powers the electric engine while releasing only water.

Technically, the fuel cell uses a “redox” reaction to produce electricity. It comprises two electrodes: an oxidising anode (emitting electrons) and a reducing cathode (collecting electrons), separated by an electrolyte, which directly conducts the ions from one electrode to the other and blocks the electrons, forcing them to pass through the external circuit of the battery.

The tank continuously supplies the anode with hydrogen, while the cathode receives oxygen (from the air).

The anode causes the fuel to oxidise and release electrons, which are forced by the ion-charged electrolyte (which separates the two electrodes) to pass through an external circuit. This external circuit therefore provides a continuous electric current which powers the engine.

Once reunited in the cathode, the ions and electrons recombine with oxygen. This combination causes reduction, which – in addition to the electric current – generates heat and pure water vapour, which escapes in the form of gas through a small tube placed under the vehicle, either while driving or by pressing a button at the end of the trip.

• The tank continuously supplies the anode with hydrogen, while the cathode receives oxygen (from the air).
• The anode causes the fuel to oxidise and release electrons, which are forced by the ion-charged electrolyte (which separates the two electrodes) to pass through an external circuit. This external circuit therefore provides a continuous electric current which powers the engine.
• Once reunited in the cathode, the ions and electrons recombine with oxygen. This combination causes reduction, which – in addition to the electric current – generates heat and pure water vapour, which escapes in the form of gas through a small tube placed under the vehicle, either while driving or by pressing a button at the end of the trip.

Running a hydrogen engine therefore emits only pure water and is completely clean, provided that a completely clean hydrogen fuel is used.

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