Hydrogen as the Main Fuel of the Future
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Over 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 standards. 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. |
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| NASA space rocket carrying the space shuttle Atlantis. |
Molecular hydrogen, H2. |
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Hydrogen 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. Hydrogen 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. The table below shows the energy density, both volumetric and gravimetric, of hydrogen and some other common fuels.
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In 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. The 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.
Stuart/CKI's Hydrogen Economy Vision. Link to more detailed description here. . The 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.
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