Fuel cell system Introduction

The PEMFC is technically in quite an advanced status. Fuel cell systems for both transport as well as stationary applications exist in a wide variety and are being operated in demonstration programs under practical conditions [57]. For large-scale market introduction, cost has to be reduced significantly, and durability must be improved. Both items cannot be solved by clever engineering only -new materials are also required. 

United States Plug Power is developing a 7 kWe fuel cell system for residential applications. They have tested their system on hydrogen and are planning market introduction of several models which could use hydrogen, propane, or natural gas. 

Initial introduction of fuel cell vehicles may be in applications where the range requirements are modest, such as fixed route buses, delivery vehicles and trucks. Also the markets for fuel cell trains and ships seem more interesting that current activities indicate. The auxiliary system components should not be neglected, because as mentioned the cost of filling stations and transport/transmission systems for of delivering hydrogen to these (or producing it on-site) can substantially influence the overall attractiveness of the fuel cell system. 

The second option is to use pressure storage cartridges which are state of the art for laboratory use and have been developed for up to 700 bars with an internal pressure reducer. Such hydrogen canisters undergo at present necessary certification processes and will afterwards be available to customers. This would be one important prerequisite for market introduction of portable hydrogen operated fuel-cell systems. 

SOFC and PEFC are competing in several stationary markets, with advantages to SOFC technology when reformed hydrocarbon or alcohol fuels are used. PEFC systems however have some distinct advantages in applications where frequent start-stop-cycles and extended periods of standstill are required such as in residential CHP applications. Therefore, more PEFC than SOFC units are ciurently in the field in Japan where market introduction of residential fuel cell systems has already taken place. SOFC systems are in the early phase of deployment. 

Yoon, S, Bae, J. A diesel fuel processor for stable operation of solid oxide fuel cell system I. Introduction to post-reforming for the diesel fuel processor. Catal. Today 2010 156 49-57. 

Aalborg University, Department of Energy Technology (2012) Introduction on Fuel Cell and Battery Systems, http //www.et.aau.dk/research-prog rammes/fuel-cell-systems/ (last accessed 25 January 2012). 

This means that at the time of mass-market introduction, their expected lifetime needs to be 5,000 h, with an end of life performance, which is at least 90% of the performance at the beginning of life. No external conditions, except for severe crashes, might lead to severe deterioration of the fuel cell performance. In practice, this means that the fuel cell system needs to operate between 40°C and +50°C ambient temperature, under aU relative humidities. 

Contamination of the membrane is mainly through the introduction of cationic species, either through contaminated air and fuel streams, or from the leaching of metal materials within the fuel cell system. Metal contamination may be present in the stack or cell component materials, such as in the carbon catalyst support or gas diffusion layer. Seal and gasketing materials may contain silicone, which can decompose and contaminate the membrane. The key effect of cationic contaminants... 

The system we have considered is very simple, yet we have been able to build a model against which to quantitatively judge the issue of the optimum pressure. However, this is only an introduction to the topic of fuel cell system modelling. There are other issues that must be considered, other factors that might make higher operational pressures more or less attractive. These we consider in the next section. 

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