DIFFERENTIAL ANALYSIS OF SOFC CURRENT-VOLTAGE CHARACTERISTCS Zdravko Stoynov 1 , Daria Vladikova 1 ,*, , Blagoy Burdin 1 , Jerome Laurencin 2 , Dario Montinaro 3 , Gergana Raikova 1 , Günter Schiller 4 , Patric Szabo 4 1 Institute of Electrochemistry and Energy systems - BAS, 10 Acad. G. Bonchev St., 1113 Sofia, Bulgaria 2 Univ. Grenoble Alpes – CEA/LITEN, 17 rue des Martyrs, 38054 Grenoble, France 3 SOLIDpower S.p.A, Viale Trento 117, 38017 Mezzolombardo, Italy 4 German Aerospace Center (DLR), Linder Höhe, 51147 Cologne, Germany ABSTRACT Solid Oxide Fuel Cells (SOFC) are regarded as a promising technology for economic power generation due to their high efficiency and large fuel flexibility. Durability is a severe hurdle towards their deployment. The near future targets in respect to Degradation Rate (DR) are about 0.1%.kh-1, which needs improved monitoring and diagnostics. This work aims at introducing new approach based on Differential Analysis of the i-V curves, named DiVA. It operates with the Differential Resistance (DR) Rd and its evolution during long term testing. Since derivatives are more sensitive to small deviations, the Differential Resistance Analysis (DRA) ensures increased sensitivity and information capability in respect to degradation monitoring and diagnostics, which is demonstrated on a small stack during thermal cycling conditions – before and after the first thermal cycle, on button cells tested up to 9000 hours, as well as on button cells operating in fuel cell and in electrolysis mode. The results show that DRA is several times more sensitive in comparison with the classical DR evaluation based on registration of the voltage decrease at constant current. Key word: current-voltage characteristics; degradation rate, differential resistance analysis, durability