Hydrogen is the most abundant element in the universe. However, it is always found combined with other elements (for example, with oxygen to form water H2O, with carbon to form methane CH4 …). To obtain it in its pure form, H2, it must undergo processing. In other words, the bonds which link it to other elements must be broken. That is why we say that hydrogen, like electricity, is an « energy carrier », not a « source of primary energy » like oil or natural gas. Nevertheless, there is a fundamental difference between hydrogen and electricity: the former can be stored in large quantities and transported without losses, whilst the latter can only be stored in small quantities in heavy and costly accumulators and its transport, by high tension lines, generates significant losses in the form of heat (the Joule effect).
Once produced, one of the main attractions of hydrogen is its capacity to generate energy without the emission of pollutants or of CO2.
In the conventional internal combustion engine, hydrogen produces mechanical energy, which is useful energy, together with heat ; the products of combustion are steam and small quantities of nitrous oxide.
In a fuel cell, the hydrogen produces electricity, which is useful energy, and heat; the only product of combustion is steam. (see animation and focus)
The fuel cell has a better yield than the internal combustion engine and has the additional advantage of having a low noise level. Nevertheless, this new device must still make progress in technical terms (durability, reliability, cost).
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