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Hydrogen

Hydrogen (H2) as fuel of the future

In cooperation with individual OEMs and various H2 initiatives, the topic of hydrogen is currently being pursued by SAG in many respects, e.g. the topic of H2 tanks is obvious. At the same time, various other topics are being investigated for which the use of H2 could be of interest. The initiatives will be pursued with Open Innovation in order to sound out as broad a spectrum as possible at the beginning.

The efficient storage of hydrogen is seen as an important prerequisite for the dissemination of fuel cell technology in the transport sector. Since hydrogen has a low volumetric energy density, it is usually carried in compressed form in cylindrical pressure vessels in motor vehicles. In the meantime, 700 bar have established themselves as the storage pressure for passenger cars. For buses, on the other hand, storage space (on the roof) is less scarce. As a result, buses can still use pressure accumulators with only 350 bar.

The range of fuel cell cars today is about 500 km. For this, approximately 4 to 6 kg of hydrogen are required, depending on the current vehicle technology, vehicle, driving style and driving conditions. In order to store 4 to 6 kg of hydrogen at 700 bar for a passenger car, about 100 to 150 litres of tank volume are required. Otto- or petrol tanks for compact and medium-sized passenger cars today have a tank volume of 50 to 60 litres, while luxury and light commercial vehicles have a tank volume of 70 to 80 litres.

In addition to the volume and weight of the fuel, the weight of the tank system is also relevant, because heavy tank systems increase the rolling resistance, gradient resistance and acceleration resistance and thus the fuel and energy consumption of a vehicle. Vehicle tanks for liquid fuels have a very favourable ratio of transported energy content to the total mass of the tank system plus content. A 55-litre tank for a current compact/medium-class vehicle has a tare weight of only 15 kilograms. The storage density of petrol to the entire tank system, including its energy content, is therefore over 30 MJ/kg. With smaller storage volumes and vehicle tanks for more efficient drives (Otto hybrid), the ratio would be (somewhat) less favourable in the future (JEC 2013).

FAQ Hydrogen

Hydrogen is a chemical element, at standard conditions (20 °C and atmospheric pressure) it is a light gas (7 % air density). 1,000 liters have only 0.09 kg.

However, it can be compressed (350 or 700 bar) or liquefied (-253°C) to increase density.

No. Hydrogen is the most abundant element in the universe and is easily accessible on the earth’s surface.

The energy densities of different fuels:

  • Liquid natural gas = 39MJ / kg
  • Petrol = 41MJ / kg
  • Diesel = 43MJ / kg
  • Liquid hydrogen = 120MJ / kg

The risk of spilled hydrogen or accidental combustion is no greater than that of petrol or diesel. It burns without generating smoke and the radiant heat of the fire is low. The safety radius defined for emergency services is smaller than for conventional fuels.

Another important aspect of safety is that hydrogen does not spread on the ground but rises into the air due to its low density.

No. Hydrogen has long been safely stored in industrial and mobility applications.

The atomic and molecular size of hydrogen is small and easily diffuses into many solids and liquids, but there are many materials with very low permeability that are taken for storage. For example, many steel and aluminum alloys, but also polymers, have long been used to store hydrogen.

In contrast to petrol and natural gas, hydrogen gas has a considerable buoyancy under atmospheric conditions due to its low density. The escaping hydrogen gas rises immediately and is distributed, which reduces the risk of ignition in the air.

On the other hand, hydrogen forms a flammable mixture with air in a wide percentage range. The ignition limit values for hydrogen, petrol and natural gas are 4-75% (1.4-7.6%) and 5.3-15% (air volume %) respectively.

No. Hydrogen-air mixture is flammable but does not explode. A mixture of hydrogen and pure oxygen (oxyhydrogen gas) is explosive.

No. Hydrogen is a non-toxic, clear gas. It is non-toxic, has neither taste nor smell. The use of hydrogen as a fuel source with fuel cells produces no vapours, does not pollute the atmosphere with carbon dioxide and does not emit nitrogen oxides.

Yes. Unlike crude oil, which is an energy source, hydrogen is an energy vector. Oil production involves political and ecological risks. Hydrogen can be produced where electricity and water are available.

The by-products of conventional engines include carbon dioxide, nitrogen oxide and fine particles. Hydrogen-powered systems only generate electricity, water and waste heat.

Yes. Since conventional fuels are produced on a large scale, the production of hydrogen on a small scale is hardly comparable. According to most predictions, large-scale hydrogen production is only slightly more expensive than conventional fuels.

Hydrogen can be produced in different ways. Currently, more than 95% of the world’s hydrogen is produced from hydrocarbons, producing and emitting harmful CO2. A more modern and environmentally friendly technology for CO2-neutral production of hydrogen can be provided by electrolysis of water.

It takes 3 to 5 minutes to refuel passenger cars or light commercial vehicles.

Yes. Hydrogen containers generate electricity like batteries together with fuel cells. A hydrogen system can store more energy and it is much less weight than batteries.

No. Hydrogen is becoming an essential and permanent element of a sustainable energy economy.

The main advantage of conventional fuels is their ease of use, high energy density and controllability. They are liquid at room temperature and normal atmospheric pressure due to the binding forces on carbon atoms.

Hydrogen, however, requires high pressure or very low temperature to achieve sufficient energy density, which requires a more complex container system than a single-walled thermoplastic or metal container.

Yes, using hydrogen to store and transport energy results in less pollution than using conventional fuels or batteries.

120 Jahre Innovation und Nachhaltigkeit
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