H2 – fuel of the future

In cooperation with OEMs and H2 initiatives, the topic of storage solutions for hydrogen has been intensively pursued at SAG for some time. Thus, various scenarios are being investigated for which the use of H2 could be interesting. The focus is on the development of efficient solutions for cryogenic storage of LH2. The use of liquid hydrogen as a fuel brings significant advantages. Among others: a higher range and payload, shorter refueling times, more transport volume.

Simon Berger
Engineer R&D
Advantages, production and challenges Hydrogen
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SAG is the technology leader in cryogenic storage solutions for LNG and hydrogen.

The extensive know-how is now flowing into the development of the first truck tank system for liquid hydrogen.  Since hydrogen has a low volumetric energy density, it is usually carried in compressed form in cylindrical pressure tanks in motor vehicles. In passenger cars, 700 bar has become the established storage pressure. In buses, on the other hand, storage space (e.g. on the roof) is less limited. Therefore, pressure accumulators with 350 bar can be used. Maintaining the high pressure and the extremely low temperature of minus 253 degrees Celsius over a long period of time is one of the challenges in developing tank systems for liquid hydrogen.

The advantages of LH2 Cryotanks by SAG

Maximum efficiency

Maximum efficiency

Range up to 1000 km, higher payload, more transport volume, maximum hydrogen capacity

Higher capacities

Higher capacities

40 % + at 700 bar
60 % + at 350 bar

For FC & ICE

For FC & ICE

Suitable for trucks with fuel cell OR Hydrogen ICE

Technical details of the LH2 tank solution by SAG

  • Thermo flask principle – inner and outer tank
  • High Vacuum and multi layer insulation
  • Hydrogen storage at – 250 °C and low pressure < 10 bar
  • Density increase gas-liquid at 273 K and 1 bar factor 700
  • 30 % higher volumetric energy density than 700 bar
  • Holdtime 9 days until boil off pressure 5 bar

Tank solutions for hydrogen

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).

10 important questions about 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.

The energy densities of different fuels:

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

The danger posed by spilled hydrogen or accidental burning is no greater than that of gasoline or diesel. It burns without producing smoke and the radiant heat of the fire is low. The safety radius defined for emergency responders is smaller than that of conventional fuels.

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

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

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

The byproduct of conventional engines includes carbon dioxide, nitrogen oxide and fine particulates. Hydrogen-powered systems generate only electricity, water and waste heat.

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

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

Refueling of passenger cars or light commercial vehicles takes 3 to 5 minutes.

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

Yes. Using hydrogen to store and transport energy results in less pollution than traditional fuels or batteries.

Compatibility of cryogenic liquid hydrogen storage, fuel cells and hydrogen internal combustion engines

Amongst zero CO2 transport solutions, liquid hydrogen as a fuel for heavy duty trucks offers advantages in terms of energy storage density and refueling time especially in comparison to battery electric vehicles. In addition, the pressure in the tank can be kept at a low level compared to high pressure gaseous storage. This comes with advantages in terms of weight, sizing, cost and safety of the tank.

Compatibility of cryogenic liquid hydrogen storage, fuel cells and hydrogen internal combustion engines