Obj 1: To implement an advanced Monitoring, Diagnostic and Lifetime Tool to prolong SOFC lifetime and increase availability.
The most critical faults have been defined: fuel starvation, carbon deposition and gas leakage, as well as a test protocol and the testing matrix. The test matrix has been completed with short stack testing campaigns. Finally, a 32-cell stackbox has been tested, with the fuel starvation protocol.
EIS was found to be an adequate technique to identify the fuel starvation and carbon deposition fault, at stack level. On the contrary, for gas leakage, it was found to be efficient at the RU scale. However, the signature of the defect was unfortunately lost through averaging at stack level. EIS diagrams extracted from PRBS excitation are well superimposed to those obtained from sine excitation, meaning that PRBS is a valuable technique in order to obtain faster EIS results that do not disturb too long the stack/system from its setpoint.
THDA method is sensitive to highlight high FU and to identify a weak component, the method is therefore a suitable indicator to enhance reliability.
Classical signals remain a useful tool to see a deviation of a stack/system from its standard operating conditions. It was particularly useful for the case of a leakage, in association with some specific deviation trials as compared to the nominal operating conditions.
An identification algorithm for EIS measurements metrics extraction based on Equivalent Circuit Model approach has been developed (UNISA patent) and validated.
Obj 2: To develop the hardware for the implementation of advanced Monitoring, Diagnostic and Lifetime (MDLT) algorithms on real SOFC system with low cost (less than 3% of system cost).
For the implementation of the diagnostic methods on board, the development of the firmware architecture and parameters configuration of the BitronBox device have been completed. Both BitronBox hardware and software have been completed. Each diagnostic method operates in two steps, the first one is devoted to the stimulation and data acquisition. The second one is dedicated to the data analysis for extracting the SOFC features. The functions for the data analysis have been developed for running on a high performance linux boards.
A 2nd version of the BitronBox embedding the MDLT tools has been released. 7 were produced.
In order to permit THD, EIS and PRBS measurements, the DC/DC converter integrated in SP commercial SOFC system has been modified and installed in the system used for the on-field test in WP6.
According to SP and BITRON data on system and board costs, the share of the MDLT tool is below 2% thus reaching the targets set.
Obj 3: To identify control actions able to mitigate the impact of both degradation mechanisms and faults on performance and durability of SOFC.
A diagnostic algorithm for Detection and Isolation of faults based on EIS was developed.
It is fast (<5 s). When one of the features is different for that expected under nominal conditions, an alarm is generated, and a detection and fault isolation process starts.
This method has been validated upon experimental data from WP2 but also during on-field tests.
In addition, fast models capable of predicting cell/stack degradation have been developed for different degradation phenomena. Several lifetime prediction algorithms were developed.
