HT-SOFC

For all-ceramic HT/SOFCs the rate of preheating will be slow compared with IT/SOFCs with flexible metallic structural parts between the MEAs. In future SOFCs capable of direct oxidation of hydrocarbons (Section 4.1.11) and without a reformer, the preheating manoeuvres will be simplified by the absence of the reformer. An exception is the small-tube SOFC (Sections 4.11 and 4.12), which can be preheated rapidly. 

In all ceramic high-temperature (HT) SOFC systems, LaCr(Mg)O3 and La(Ca)CrO3 are the interconnect materials used. The disadvantages of this include an expensive manufacturing route and a poor ability to withstand rapid temperature changes. Ferritic stainless steel can be used in IT SOFCs (see Figure 12.9). 

Fifl-3 The typical nricroalnictam / apadtlcatkm of INER-HT-SOFC-MEA... 

Start up company HT-Ceramics, which has developed a specific (anode supported thin layer electrolyte) SOFC system. The PEM research is carried out by the Paul Scherrer Institute in collaboration with the Federal Institute of Technology Zurich and the University of applied science in Biel. The Paul Scherrer Institute is also researching DMFC systems, while the Federal Institute of Technology Lausanne is involved in research activities for HTcceramics. 

Feed H20 Ht 90 10 3,OOe-6 molfsec-channel 10% of SOFC Air 4,2e-6 moFsec-channel... 

On recent years these proton-conducting ceramics have attracted increasing interest, not only as SOFC materials but also for HT electrolysis, for sensors, and for electrochemical processes. However, their widespread application depends on a number of factors, such as material stability, electrochemical and energetic efficiency and, of course, their cost. 

The situation is different for HT-PEMFC and LT-PEMFC. The adsorption of carbon monoxide on electro catalyst is driven by the temperature. The CO adsorption is promoted at lower temperatures. A high amount of absorb carbon monoxide on the electro catalysts decreases the performance of the fuel cell dramatically. So low temperature fuel cell requires a hydrogen-rich gas with a very low content of CO in the range of a few ppm. High temperature PEMFC can tolerate a few percent of CO in the hydrogen rich gas and SOFC can use CO directly due to the high operation temperatures. 

In comparison with the PEFC, the HT-PEFC requires a description of the electrochemistry with modification to higher tolerance against carbon monoxide (CO) and a simpler approach to fluid flow because of the absence of liquid water. The CO tolerance requires special submodels that account for the reversible decrease in catalyst activity if the fuel is reformate gas. Compared with the SOFC, the HT-PEFC requires different electrochemical parameters because of the very different catalysts and operating temperatures and the use of H+ instead of 0 as charge carrier. Thermomechanical stress is less important because of the much more moderate operating temperature. 

Evaluation criteria SOFC HT-PEFC HT-PEFC PEFC... 

With regard to the application of desulfurization in fuel-cell systems, there are still challenges. It seems that SOFCs and HT-PEFCs offer some advantages over MCFCs and PEFCs. Further research is required on the long-term effects and the reasons for the sudden death of materials. 

Costs of desulphurization, reformer materials and catalytic converters Reformers for biogas, LPG and fuel oil Costs of stack materials, reduce platinum load LT and HT PEM increase power output SOFC cyclability, redox resistance Establish production capacities on an industrial scale... 

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