|It can't go on like this ...|
The predominantly used fossil energy sources will come to an end one day. Even now, the pretty one-sided dependency on crude oil is being felt. Perhaps it is more advisable from a political point of view, than because of the dwindling supplies, to to find our way out of this dead-end situation. What is going to happen to those who do not yet have our our standard of comfort and mobility?
|Please, avoid carbon dioxide emission at all costs ...|
In the long term, we need vehicles which are not powered by customary energy and above all, we need engines which don't emit carbon dioxide. Customary technology distinctly reduces the pollutants, but has made no appreciable progress in the elimination of carbon dioxide emission.
|Hydrogen engine is roughly the same as a petrol engine|
The above picture shows a possibility which is fairly simple to realise. Here we have a combustion engine which has been adapted to use hydrogen as an energy source. Hydrogen has, in contrast to todays fuels, an unlimited availability and has roughly the same octane rating as regular petrol. It belongs in the catagory of renewable energy sources. Because electricity, also a renewable energy source, cannot be stored at will, nor can it be transported over long distances, the advantage of hydrogen is becoming more obvious.
|Hydrogen is difficult to transport|
Nonetheless, the disadvantages of this project, are, the storage and the transport. While hydrogen can be stored under pressure in stationary tanks, the energy density is not sufficient for vehicles. A certain travelling range could be achieved, e.g., with very high pressure. Due to the fact that, in the case of accidents, high explosive hydrogen may, under no circumstances, be set free, this means, the tanks must be very stable, (figure 2) secure and thus, also very heavy.
|Space problems, but perhaps there are other solutions ...|
A further possibility is the liquefaction of the hydrogen, then however, the temperature must be kept permanently below -250°C. This can be done, for a period of three days, using insulating material, e.g., that developed for space travel, after this period the energy begins to escape or, it must also be used for cooling purposes. The third figure shows the amount of space lost through the installation of this type of tank.
|Is it more simple in city-busses?|
Hydrogen propulsion is also being installed for test purposes, in urban public transport, where a fairly large range can be achieved, However, the amount of space needed is far higher (see figure 2) than it is when using Diesel fuel. One promising method, is the storage of hydrogen in metal-hydrides or even in liquid substances, e.g., Borax. In this case however, two tanks would be necessary and at the filling station, one would not only 'fill-up', but also deposit a 'used' tank.
|Who pays for the filling station network?|
Filling stations, this is the next important key-word. Getting started in the hydrogen-energy market requires the investment of thousands of millions. The currently available BMW 745H, from which the above engine comes, fills up for approx. €8,- per kg. 03/09