the last decades hydrogen, (H2) has gained more and more
attention as an environmentally friendly fuel and storage medium. Combustion
of pure hydrogen produces only water as exhaust. Hydrocarbon and carbon
oxide emissions can only come from motor oil in the combustion chamber.
Nitrous oxide emissions result from the nitrogen content in the air and
increase exponentially with the combustion temperature. By using H2
in fuel cells, practically no pollution occurs. In this respect, hydrogen
offers emission levels that are much lower than existing and future
Hydrogen has been an important raw material in the chemical
industry for over 100 years. It is a key component in the manufacture of
chemicals like ammonia, methanol and fertilisers and large amounts are used
in petrol refineries. Other, perhaps unexpected, products where hydrogen is
used include glass, refined metals, vitamins, cosmetics, semiconductor
circuits, soaps, margarine and peanut butter.
NASA space rocket carrying the space
Molecular hydrogen, H2.
is the most common of all elements in the universe. It is estimated that as
much as 90% of the atoms and 75% of the total mass is H2.
Unfortunately, the amount of available free hydrogen on the earth is small,
and it therefore has to be produced from other sources. Thus, hydrogen is
not an energy source but rather an energy carrier.
is the smallest and lightest of all elements. Based on mass, the energy
density of hydrogen is more than twice that of natural gas and almost three
times higher than petrol. In applications where mass rather than volume is
important, as in space rockets, hydrogen has been utilised as a fuel for
years. About 1 % of the annual global consumption of more than 500 bn m³ is
used in space activities.
table below shows the energy density, both volumetric and gravimetric, of
hydrogen and some other common fuels.
gas (300 bar)
gas (300 bar)
gas, liquid (-160°C)
contrast to the high gravimetric energy density for hydrogen mentioned above,
the volumetric density is correspondingly low. It is important to mention
that in order to correctly compare different fuels, one also has to consider
complete systems, including the mass and volume of all components and of
course the efficiency of the energy converter. In addition, overall costs
and maintenance of the system also influence the rating.
desire for a long-term transition to a hydrogen society is mainly based on
the need to reduce polluting and climate-affecting emissions and the concern
about depletion of fossil fuel resources. Today about 90 % of the world's
energy consumption is covered by fossil fuels, and most of this comes from a
limited number of regions in the world. Even if hydrogen will be used on a
large scale in the future, there is still a need for an energy source to
produce it. Renewable energy technology such as hydro electricity, wind,
wave and solar power are in principle available, but are not yet mature for
mass production and/or fully developed.
production and storage of hydrogen are not the only important issues for the
future energy supply. Just as critical is the distribution from the
production site to the consumers. Since hydrogen already is utilised in the
industry, the transportation technology is available. Large amounts of
liquid and gaseous hydrogen are transported by sea and land, and
approximately 1100 km of hydrogen pipeline exist in the U.S., Germany and
England. This is small compared to the natural gas system, but it is
important to note that there are hydrogen pipelines in operation today that
deliver gas to the user successfully. The main challenge will be to expand
the capacity and network to meet the demand.