51 Introduction

In the last chapter we outlined the operation of fuel cells, and explained the main engineering problems with proton exchange membrane (PEM) fuel cells. However, perhaps the most difficult problem was not addressed: how to obtain the hydrogen fuel. It should be said at this point that the question of how to supply hydrogen does not only concern fuel cell vehicles. In the last chapter we alluded to the possibility (and indeed the practice) of running internal combustion (IC) engines on hydrogen. A hydrogen powered IC engine in a hybrid electric system could also provide a system with very low pollution.

There is already a considerable infrastructure for the manufacture and supply of hydrogen. It is used in large quantities as a chemical reagent, especially for oil refining and petroleum processing. It is also produced in huge quantities for the manufacture of ammonia in the fertiliser industry. The great majority of this hydrogen is produced by steam reforming of natural gas, which is outlined below in Section 5.2.

However, when it comes to providing hydrogen on a smaller scale, to mobile systems like a vehicle, then many problems occur, to which no really satisfactory solutions have yet been found. There are many ways in which the problem could be solved, and it is as yet far from clear which will emerge as the winners. The different possibilities are shown in Figure 5.1.

In terms of infrastructure changes, the simplest method would be to adapt the current large scale hydrogen production methods to a very small scale, and have 'reformers' on board vehicles that produce hydrogen from currently standard fuels such as gasoline. This approach is also explained in Section 5.2.

One solution is to use the present production methods, and have the hydrogen produced in large central plants, or by electrolysers, and stored and transported for fuel cell use as hydrogen. If such bulk hydrogen were produced by electrolysers running off electricity produced from renewable sources, or by chemical means from biomass fuels, then this would represent a system that was 'carbon dioxide neutral', and is the future as seen by the more optimistic.1

1 However, it has to be said that at the moment the great majority of hydrogen production involves the creation of carbon dioxide.

Electric Vehicle Technology Explained James Larminie and John Lowry © 2003 John Wiley & Sons, Ltd ISBN: 0-470-85163-5

Electricity generated by renewable energy -solar, wind, wave, hydro etc.

Electricity generated by renewable energy -solar, wind, wave, hydro etc.

Large chemical plants reforming fuels to hydrogen Sect. 5.2
Biological hydrogen generation systems

Power station,

grid

connected

Mobile fuel cell using hydrogen

Figure 5.1 The supply of hydrogen to fuel cell powered vehicles can be achieved in many different ways

In this scenario the bulk hydrogen would be stored at local filling stations, and vehicles would 'fill up' with hydrogen, much as they do now with diesel or gasoline. Already a very few such filling stations exist, and one is shown in Figure 5.2. However, the storage of hydrogen in such stations, and even more so onboard the vehicle, is far from simple. The reasons for this are explained in Section 5.3. The problem is made more complex because

Figure 5.2 A hydrogen filling station. The bus in the picture is not electric, but uses a hydrogen fuelled IC engine (picture kindly supplied by MAN Nutzfahtzeuge A.G.)

some of the ways of storing hydrogen are so radically different. However, two distinct groups of methods can be identified. In one the hydrogen is stored simply as hydrogen, either compressed, or liquefied, or held in some kind of 'absorber'. The possible methods of doing this are explained in Section 5.3. This section also addresses the important issue of hydrogen safety.

In the second group of hydrogen storage methods the hydrogen is produced in large chemical plants, and is then used to produce hydrogen-rich chemicals or man-made fuels. Among these are ammonia and methanol. These 'hydrogen carrier' compounds can be made to give up their hydrogen much more easily than fossil fuels, and can be used in mobile systems. The most important of these compounds, and the ways they could be used, are explained in Section 5.4.

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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