Novel SrO-Containing Glass-Ceramic Sealants for Solid Oxide Electrolysis Cells (SOEC): Their Design and Characterization under Relevant Conditions.

This study presents results on the development of strontium oxide (SrO) containing glass sealants used to join Crofer22APU to yttria-stabilized zirconia (3YSZ), in which the main glass components, that is, silicon oxide (SiO2), strontium oxide (SrO), calcium oxide (CaO) and aluminum oxide (Al2O3), have been varied appropriately. Certain properties, such as the crystallization behavior, the coefficient of thermal expansion, adhesion, and reactivity of the sealants in contact with Crofer22APU, have been reviewed and discussed. The optimized glass composition (with CTE in the 9.8-10.3 × 10-6 K-1 range) results in a good joining behavior by hindering the formation of undesirable strontium chromate (SrCrO4) on contact with the Crofer22APU steel after 1000 h. at 850 °C. High specific resistivity values of about 106 Ohm.cm have been obtained, thus demonstrating good insulating properties at 850 °C under an applied voltage of 1.6 V. A negligible degradation in the electrical resistivity trend was measured during the test up to 1000 h, thus excluding the presence of detrimental reactions of the glass-ceramic sealant in contact with Crofer22APU under a dual atmosphere, as confirmed using SEM-EDS post-mortem analyses.

Modeling Analysis of a Polygeneration Plant Using a CeO2/Ce2O3 Chemical Looping.

In the current context of complexity between climate change, environmental sustainability, resource scarcity, and geopolitical aspects of energy resources, a polygenerative system with a circular approach is considered to generate energy (thermal, electrical, and fuel), contributing to the control of CO2 emissions. A plant for the multiple productions of electrical energy, thermal heat, DME, syngas, and methanol is discussed and analyzed, integrating a chemical cycle for CO2/H2O splitting driven using concentrated solar energy and biomethane. Two-stage chemical looping is the central part of the plant, operating with the CeO2/Ce2O3 redox couple and operating at 1.2 bar and 900 °C. The system is coupled to biomethane reforming. The chemical loop generates fuel for the plant's secondary units: a DME synthesis and distillation unit and a solid oxide fuel cell (SOFC). The DME synthesis and distillation unit are integrated with a biomethane reforming reactor powered by concentrated solar energy to produce syngas at 800 °C. The technical feasibility in terms of performance is presented in this paper, both with and without solar irradiation, with the following results, respectively: overall efficiencies of 62.56% and 59.08%, electricity production of 6.17 MWe and 28.96 MWe, and heat production of 111.97 MWt and 35.82 MWt. The fuel production, which occurs only at high irradiance, is 0.71 kg/s methanol, 6.18 kg/s DME, and 19.68 kg/s for the syngas. The increase in plant productivity is studied by decoupling the operation of the chemical looping with a biomethane reformer from intermittent solar energy using the heat from the SOFC unit.

A bottom-up appraisal of the technically installable capacity of biogas-based solid oxide fuel cells for self power generation in wastewater treatment plants.

This paper proposes a bottom-up method to estimate the technical capacity of solid oxide fuel cells to be installed in wastewater treatment plants and valorise the biogas obtained from the sludge through an efficient conversion into electricity and heat. The methodology uses stochastic optimisation on 200 biogas profile scenarios generated from industrial data and envisages a Pareto approach for an a posteriori assessment of the optimal number of generation unit for the most representative plant configuration sizes. The method ensures that the dominant role of biogas fluctuation is included in the market potential and guarantees that the utilization factor of the modules remains higher than 70% to justify the investment costs. Results show that the market potential for solid oxide fuel cells across Europe would lead up to 1,300 MW of installed electric capacity in the niche market of wastewater treatment and could initiate a capital and fixed costs reduction which could make the technology comparable with alternative combined heat and power solutions.

In Situ Formation of Er0.4Bi1.6O3 Protective Layer at Cobaltite Cathode/Y2O3-ZrO2 Electrolyte Interface under Solid Oxide Fuel Cell Operation Conditions.

Bismuth-based oxides exhibit outstanding oxygen ionic conductivity and fast oxygen surface kinetics and have shown great potential as a highly active component for electrode materials in solid oxide fuel cells (SOFCs). Herein, a Nb-doped La0.6Sr0.4Co0.2Fe0.7Nb0.1O3-δ (LSCFNb) electrode with 40% Er0.4Bi1.6O3 (ESB) composite electrode was successfully fabricated by decoration method and directly assembled on barrier-layer-free yttrium-stabilized zirconia (YSZ) electrolyte cells, achieving a peak power density of 1.32 W cm-2 and excellent stability at 750 °C and 250 mA cm-2 for 100 h. ESB decoration also significantly reduces the activation energy from 214 kJ mol-1 for the O2 reduction on pristine LSCFNb electrode to 98 kJ mol-1. Further microstructural analysis reveals that there is a redistribution and migration of the ESB phase in the ESB-LSCFNb composite toward the YSZ electrolyte under the influence of cathodic polarization, forming a thin ESB layer at the cathode/YSZ electrolyte interface. The in situ formed ESB layer not only prevents the direct contact and subsequent reaction between segregated SrO and YSZ electrolytes, but also remarkably promotes the oxygen migration/diffusion at the interface for O2 reduction reaction, resulting in a remarkable increase in power output and a decrease in activation energy. The present study clearly demonstrated the in situ formation of a highly functional and active ESB protective layer at LSCFNb cobaltite cathode and YSZ electrolyte interface via ESB-decorated LSCFNb composite cathode under SOFC operation conditions.

Biogas from the organic fraction of municipal solid waste: dealing with contaminants for a solid oxide fuel cell energy generator.

The present work investigates electricity production using a high efficiency electrochemical generator that employs as fuel a biogas from the dry anaerobic digestion of the organic fraction of municipal solid waste (OFMSW). The as-produced biogas contains several contaminants (sulfur, halogen, organic silicon and aromatic compounds) that can be harmful for the fuel cell: these were monitored via an innovative mass spectrometry technique that enables for in-line and real-time quantification. A cleaning trap with activated carbons for the removal of sulfur and other VOCs contained in the biogas was also tested and monitored by observing the different breakthrough times of studied contaminants. The electrochemical generator was a commercial Ni anode-supported planar Solid Oxide Fuel Cell (SOFC), tested for more than 300 h with a simulated biogas mixture (CH4 60 vol.%, CO2 40 vol.%), directly fed to the anode electrode. Air was added to promote the direct internal conversion of CH4 to H2 and CO via partial oxidation (POx). The initial breakthrough of H2S from the cleaning section was also simulated and tested by adding ∼1 ppm(v) of sulfur in the anode feed; a full recovery of the fuel cell performance after 24h of sulfur exposure (∼1 ppm(v)) was observed upon its removal, indicating the reliable time of anode exposure to sulfur in case of exhausted guard bed.

Monitoring of volatile compound emissions during dry anaerobic digestion of the Organic Fraction of Municipal Solid Waste by Proton Transfer Reaction Time-of-Flight Mass Spectrometry.

Volatile Organic Compounds (VOCs) formed during anaerobic digestion of aerobically pre-treated Organic Fraction of Municipal Solid Waste (OFMSW), have been monitored over a 30 day period by a direct injection mass spectrometric technique: Proton Transfer Reaction Time-of-Flight Mass Spectrometry (PTR-ToF-MS). Most of the tentatively identified compounds exhibited a double-peaked emission pattern which is probably the combined result from the volatilization or oxidation of the biomass-inherited organic compounds and the microbial degradation of organic substrates. Of the sulfur compounds, hydrogen sulfide had the highest accumulative production. Alkylthiols were the predominant sulfur organic compounds, reaching their maximum levels during the last stage of the process. H(2)S formation seems to be influenced by the metabolic reactions that the sulfur organic compounds undergo, such as a methanogenesis induced mechanism i.e. an amino acid degradation/sulfate reduction. Comparison of different batches indicates that PTR-ToF-MS is a suitable tool providing information for rapid in situ bioprocess monitoring.