Experimental validation of a dynamic modelling of a Reversible Solid Oxide Cells (rSOCs)

The integration of Hydrogen technologies in different end-uses such as transport, electric microgrids, residential and industrial applications, will increase exponentially soon. Hydrogen as energy carrier allows more favourable energy conversion than other conventional systems and is crucial in worldwide decarbonize end uses. The production of green hydrogen, using RES, is a key area for the evolution of this technology. In this context, SWITCH is a Horizon 2020 European Project that aims to design, build and test an in-situ fully integrated and continuous multisource hydrogen production system, based on solid oxide cell technology. Reversible Solid Oxide Cell (rSOCs) technologies allow to convert renewable energy as hydrogen in the power-to-gas application (P2G) and in reversible mode is able to produce electricity from hydrogen stored, power-to-power application (P2P). rSOCs are really interesting to stabilize the random nature of RES because a combined electrolysis and fuel cell system should be able to switch between the two modes as quickly as possible in order to optimize the integration and the use of RES. However, rSOCs need a complex BoP from the thermal point of view, able to guarantee high efficiency even at partial load mode as well as easy start-up and shutdown procedures. In this work, a Stack Box Module dynamic model was developed in Modelica environment as a dynamic tool for the definition and optimization of BoP requirements. Stack model was validated in SOFC (Solid Oxide Fuel Cell) and SOE (Solid Oxide Electrolyser). The results of the simulation provide verification of the technical/thermodynamic behaviour and flexibility of a stack box of 70 cells. Dynamic modelling allows to evaluate the effect of the reagent inlet temperatures on the operation and hydrogen production/consumption in terms of yield as well as the transients between the different operative modes. Model has been validated by experimental measurements performed in the laboratory. In particular, the kinetics of the reactions governing steam methane reforming (SMR) was considered from data found in the literature, while the ASR (Area Specific Resistance) value was calibrated according to experimental data. The results of the dynamic model show as model can be a useful design and optimization tool for the SOCs technology.

Solid Oxide Cell Electrode Nanocomposites Fabricated by Inkjet Printing Infiltration of Ceria Scaffolds

The enhancement of solid oxide cell (SOC) oxygen electrode performance through the generation of nanocomposite electrodes via infiltration using wet-chemistry processes has been widely studied in recent years. An efficient oxygen electrode consists of a porous backbone and an active catalyst, which should provide ionic conductivity, high catalytic activity and electronic conductivity. Inkjet printing is a versatile additive manufacturing technique, which can be used for reliable and homogeneous functionalization of SOC electrodes via infiltration for either small- or large-area devices. In this study, we implemented the utilization of an inkjet printer for the automatic functionalization of different gadolinium-doped ceria scaffolds, via infiltration with ethanol:water-based La1−xSrxCo1−yFeyO3−δ (LSCF) ink. Scaffolds based on commercial and mesoporous Gd-doped ceria (CGO) powders were used to demonstrate the versatility of inkjet printing as an infiltration technique. Using yttrium-stabilized zirconia (YSZ) commercial electrolytes, symmetrical LSCF/LSCF–CGO/YSZ/LSCF–CGO/LSCF cells were fabricated via infiltration and characterized by SEM-EDX, XRD and EIS. Microstructural analysis demonstrated the feasibility and reproducibility of the process. Electrochemical characterization lead to an ASR value of ≈1.2 Ω cm2 at 750 °C, in the case of nanosized rare earth-doped ceria scaffolds, with the electrode contributing ≈0.18 Ω cm2. These results demonstrate the feasibility of inkjet printing as an infiltration technique for SOC fabrication.

Fabrication and Characterization of Thin-Film SOFC Supported by Microchannel-Structured Zirconia Substrate for Direct Methane Operation

Ni-cermet anode demonstrates excellent catalytic activity and electrical conductivity but suffers from carbon deposition issue. To utilize Ni-cermet anode while preventing carbon deposition, a synergic strategy is employed to design anode electrode. In particular, Zr is incorporated into Ce0.8Sm0.2O2-δ lattice to tailor oxygen storage and catalytic properties of Ni-Ce0.8-xSm0.2ZrxO2-δ anode for improving electrochemical oxidizations of various fuel species. An inert thick YSZ microtubular substrate with radially well-aligned microchannels open at the inner surface is used to support multi thin functional layers of solid oxide cell, i.e., Ni current collector, Ni-Ce0.8-xSm0.2ZrxO2-δ anode, YSZ/SDC electrolyte, and LSCF cathode. The thick YSZ substrate is able to inhibit the ratio of fuel to product gases in the thin anode functional layer, which favors the prevention of carbon buildup in the thin anode layer when synergistically combined with Ni-Ce0.8-xSm0.2ZrxO2-δ anode material. The microchannels embedded in the YSZ substrate can also avoid too much dilutions of the fuel in the anode functional layer. The cell is fabricated and tested with both hydrogen and methane as the fuel. A short-term test is conducted with methane as fuel and good stability is obtained. The fundamental mechanisms for the prevention of carbon buildup in anode functional layer are also discussed.