Improving fuel cell batteries
9/22/09

What makes possible the capture of heat lost is an important characteristic of fuel cell batteries: the yield is independent of the size of the battery. This is not the case with traditional power stations (thermal or nuclear) hence their gigantic sizes. But in this case, we don’t know how to make the most of the heat because there is not enough demand at a local level and the heat is transportable over long distances. Conversely, a fuel cell battery of a size large enough to power a building with electricity has a size almost the same as the building, and, moreover, makes it possible to supply the building with electricity. «This is what we have been able to demonstrate experimentally at Sart Tilman some years ago, the battery had a power of 250 kilowatt with a yield of 50%: we were thus producing250 kW of heat which allowed us to heat the swimming pool of Sart Tilman», recalls Professor Germain. This characteristic allows therefore for the decentralisation of power where it is necessary. In this way the distribution of electrical energy is greatly reduced. It is therefore a new system in relation to what we already know. In a car, there will no doubt not be one battery, but one for each wheel, one for the air conditioning, one for lighting etc. A complete rethinking of our conception of the distribution of electrical energy is probable.

Micrograph Pt catalyst carbon xerogel

Can we imagine even higher temperatures? The electrolyte, which facilitates the transport of ions, has variable properties depending on the temperature. In the water ions are channelled easily by the classic electrolyte. In the case of solids this is not so easy. As we have seen, polymers that can conduct ions exist, but only in circumstances where low temperatures apply. If we want to go to higher temperatures (800 tom 900 degrees), we need to have recourse to ceramic conductors. At such temperatures, reactions take place easily. There is no need for a catalyst, no need for platinum: the electrodes are generally made of nickel. It is, however necessary to find the suitable electrolyte. It is possible today to imagine ceramics that can conduct ions, but they are only effective conductors at temperatures in excess of 800 degrees centigrade. These are systems that must be maintained constantly at these temperatures to avoid thermal shocks. Batteries of this type are not suitable therefore for certain applications which necessitate a continuous production of energy, for example to supply a whole quarter of a city, or for «nomadic» applications such as cars for example. Another characteristic of these batteries is that the fuel does not necessarily have to be hydrogen, but could be perhaps, for example, natural gas.

 

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