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What is hydrogen?

A good understanding of the unique properties and possible applications of hydrogen is decisive for organising the wind to wheel value chain based on hydrogen. 
Hydrogen is:

Hydrogen has both the highest and lowest energy density

Hydrogen has a very high energy density per weight unit. Only forms of energy such as nuclear energy and nuclear fusion have a higher density. As weight is very relevant for the energy demand in case of transport (vehicle efficiency), the high density per kilo of hydrogen is a great benefit for this application.
At the same time, hydrogen is the smallest and lightest molecule that we know. Under normal atmospheric conditions (1 bar), hydrogen has a low energy density per volume unit. In a vehicle, hydrogen is therefore carried under very high pressure (350 to 700 bar), in order not to take up too much space.

Hydrogen is lighter than air and therefore rises into the air very quickly. In case of unforeseen leaks, it will often have disappeared before it can pose a hazard to the surrounding area. This is not the case in an enclosed space. Hydrogen is harmless to the environment and has no impact on the climate.

High quality hydrogen: purity

To a large extent, the quality (purity) of hydrogen determines the cost price and the value. Fuel cells require hydrogen with a very high purity (class 5); the higher the purity, the higher the efficiency and life span of a fuel cell. Production of hydrogen via an electrolysis process yields class 5 hydrogen (the automotive industry requires 4.5). This is one of the reasons why it is appealing to use electrolysis hydrogen in fuel cells for mobility.
When hydrogen is used in the industry or is used as an additive in natural gas, a lower quality of hydrogen will be adequate.