We are post-doctoral researchers in the field of high temperature Solid Oxide Fuel Cells (SOFCs). SOFC stack construction was the subject of Blesznowski’s PhD whereas Skrzypkiewicz’s PhD was dedicated to Direct Carbon SOFCs (DC-SOFC). Institute of Power Engineering cooperates also with TU Graz within the BIO-CCHP: “Advanced biomass CCHP based on gasification, SOFC and cooling machines” project funded in ERA-NET BIOENERGY 11th call. The aim of BRISK2 project was to strengthen this collaboration.
Together with our hosts, we preliminarily shaped an experimental campaign merging scientific interests of both sides. The main objective of the stay was to enable the possibility to demonstrate the technological readiness and potential of fuelling solid oxide fuel cells (SOFC) manufactured in a cost-effective way with a producer gas generated in biomass gasification.
For the testing campaign, three Anode Supported SOFCs with external dimensions of 100 mm x 100 mm (Figure 1) were delivered by the Institute of Power Engineering (IEn). The fuel cell no. 1 was sent before the campaign. The test rig was assembled at TU Graz and the heating procedure was beforehand remotely discussed, so that on the first day of the stay the test rig TUG3 was ready to perform measurements. The experiment was performed with a reference fuel (mixture of hydrogen and nitrogen). Unfortunately, the test could not be continued due to the observed leakage. The disassembly revealed that the SOFC cell was not fully compatible with the standard testing procedure and test rig at TU Graz. During the first week together with our hosts we adjusted the start-up procedure and modified the test stand for investigating the IEn’s cells with reference fuel mixtures as well as in alternative modes of operation. The first introduced changes did not completely eliminate the problem and therefore the second fuel cell broke as well (Figure 2).
In the last attempt with SOFC cell no 3 additional procedure modifications solved the problem and enabled conducting a stable experiment. The modifications included an increase of pneumatic force, extending the duration of glass softening process in the critical temperature range (800°C -> 850°C -> 800°C), and an early start of the reduction process of the SOFC anode. The previous difficulties lead to the extension of the visit from 7 to 8 working days.
Within the 3rd experiment, characterisation of the cell has been performed with fuels with a heating value similar to a producer gases from biomass gasifiers. The gas was composed of 17% H2 and 83% N2. The cell operation was very stable and open circuit voltage equalled 976 mV. The U-I curve was recorded for voltages 976 ÷ 700 mV (Figure 3). Within this range, the cell produced ca. 9 W of total power which is considered as a good result for the particular SOFC, especially taking into account the new test environment.
To perform a thoroughly verification of the testing setup, measurements of four different modus operandi of the Solid Oxide Cell have been experimentally verified: fuel cell, electrolyser, nitrogen-assisted electrolyser and fuel-assisted electrolyser.
This work was an important basis for the future demonstration of the use of cost-effective SOFCs, produced with the high-pressure injection molding (HPIM) technique, fuelled with a simulated gas from biomass gasification. Moreover, the acquired results will be used to prepare a common journal publication and the visit allowed to establish a closer cooperation between the IEn and TU Graz. We would like to thank our hosts Andrés Anca-Couce, Vanja Subotič and Gernot Pongratz (Figure 4) for the warm welcome, help and openness for modifications of testing procedure and test stand in order to achieve very promising research results.