SOFC Power Generation Research Articles

LaMnO3-Type Perovskite Nanofibers as Effective Catalysts for On-Cell CH4 Reforming via Solid Oxide Fuel Cells.

CH4 has become the most attractive fuel for solid oxide fuel cells due to its wide availability, narrow explosion limit range, low price, and easy storage. Thus, we present the concept of on-cell reforming via SOFC power generation, in which CH4 and CO2 can be converted into H2 and the formed H2 is electrochemically oxidized on a Ni-BZCYYb anode. We modified the porosity and specific surface area of a perovskite reforming catalyst via an optimized electrostatic spinning method, and the prepared LCMN nanofibers, which displayed an ideal LaMnO3-type perovskite structure with a high specific surface area, were imposed on a conventional Ni-BZCYYb anode for on-cell CH4 reforming. Compared to LCMN nanoparticles used as on-cell reforming catalysts, the NF-SOFC showed lower ohmic and polarization resistances, indicating that the porous nanofibers could reduce the resistances of fuel gas transport and charge transport in the anode. Accordingly, the NF-SOFC displayed a maximum power density (MPD) of 781 mW cm-2 and a stable discharge voltage of around 0.62 V for 72 h without coking in the Ni-BZCYYb anode. The present LCMN NF materials and on-cell reforming system demonstrated stability and potential for highly efficient power generation with hydrocarbon fuels.

Experimental and modeling study of full- condition combustion characteristics of exhaust gas burners for solid oxide fuel cells

SOFC exhaust gas burner is an essential component of the SOFC thermal management system. The burner in the whole operating conditions of safe and stable combustion and smooth transition in the switching operating conditions is of great significance to the long-term and efficient operation of the SOFC power generation system. This paper builds an experimental test platform for the SOFC exhaust gas burner, tests the combustion performance of the burner in full operating conditions and operating conditions switching process, and establishes a prediction model for the combustion performance of SOFC exhaust gas burner by machine learning algorithm. The results show that the SOFC exhaust gas burner can meet the requirements of safe and stable combustion in all operating conditions and smooth transition between operating conditions; reliable combustion is achieved at the stable power generation condition with excess air factor of 7 ∼ 26, and the average cathode and anode pressure drop in the stable power generation condition is 142 Pa and 185 Pa, respectively; BP neural networks, support vector machines and random forests are used to establish a prediction model for the performance of the SOFC exhaust gas burner, and the random forests achieve the best prediction effect.

Energy, exergy and exergo-economic analysis of a novel SOFC based CHP system integrated with organic Rankine cycle and biomass co-gasification

This paper proposes a novel SOFC based cogeneration system, consisting of biomass co-gasification, SOFC power generation and ORC waste heat recovery, to achieve the efficient and clean utilization of poultry litter. Based on the conceptual design, the energy, exergy and exergo-economic analysis are conducted, including sensitivity analysis, uncertainty analysis and multi-objective optimization. Results show that when using straw as the co-gasification biomass with poultry litter, the highest energy utilization efficiency of 44.70 % is obtained with the electricity and heat production of 162.02 kW and 52.41 kW, respectively. The biomass gasifier and the SOFC stack have the highest exergy destruction, accounting for 24.43 % and 19.99 % of the total. Sensitivity analysis presents complex results concerning mass fraction of poultry litter, water content, equivalent air ratio and water-carbon ratio, etc. The optimal solution for the current optimization problem is obtained. When poultry litter mass fraction is fixed at 25 %, TSOFC = 852 °C and uf = 0.73, the exergy efficiency is obtained as 41.95 % and the overall exergy cost per unit is obtained as 42.35 $/GJ. This paper investigates a novel cogeneration system relying on the biomass co-gasification of poultry litter, providing a new solution for poultry litter treatment and sustainable development of agriculture, forestry and husbandry.

Results of Continuous 200kW SOFC Power Generation Using Biomethane Gas from a Brewery's Wastewater Treatment Process

Based on the Paris Agreement compiled at COP21, many nations are now obligated to have penalties for CO2 emission reductions.As a result, many companies are working to reduce CO2 emissions to ensure their survival.We in the liquor, soft drinks, and food industries are no exception, and all members are working to reduce CO2 emissions, but it is believed that existing technologies alone will not allow them to achieve zero CO2 emissions while continuing their operations.Asahi Quality and Innovations, Ltd. , where I work, is an independent research subsidiary of Asahi Group Holdings, Ltd. and is currently working on a number of technological developments to create a new model for medium- to long-term CO2 emissions reduction at the 212 companies and 70 plants that manufacture and sell Asahi Group beer, liquor, soft drinks and food products sold around the world.This time, we report on one of those technological development items, the successful development of a technology for acquiring carbon-neutral electricity using SOFC, and its contents and results.Asahi Breweries, Ltd. and Asahi Soft Drinks, Ltd. under the Asahi Group began introducing anaerobic wastewater treatment processes in their factories from 1988, and all of their factories in Japan are now operating stably on a daily basis.The anaerobic wastewater treatment process uses methane fermentation as the main reaction, which produces methane gas as a byproduct. This methane gas is defined as carbon-neutral methane gas because they are from beer or beverage production derived from agricultural crops. This methane gas has been combusted in boilers and recovered as thermal energy.However, it was confirmed that converting methane gas into electricity using fuel cells, rather than burning it to convert it into thermal energy, has significant cost advantages and reduces CO2 emissions. Therefore, we decided to change the use of methane gas from boiler fuel to fuel for electricity power generation, and to implement power generation using SOFC.However, although many challenges to fuel cell power generation using biomethane gas had been implemented, there were no reports of successful power generation exceeding 10,000 hours. The most significant reason for this was thought to be the presence of poisoned substances in the methane gas.The poisoned substances present in the fuel will constantly attack the electrodes during power generation and the electrodes become inactive and eventually lose their ability to generate power as a fuel cell.Since highly purified fuel is the key to long-term power generation, the goal of this R&D was to improve the purification accuracy to below the detection limit for all poisoned substances.Based on the results of these studies, we aimed to develop a technology that would enable stable long-term continuous SOFC power generation for more than 10,000 hours by highly purifying biomethane gas, a byproduct of the anaerobic wastewater treatment process.Development goals:1. Remove poisoned substances to below than the detection limit (less than 10 ppb).2. Fuel cell degradation rate of less than 1% after start of power generation(challenge target: less than 0.5%)We analyzed the biomethane gas comprehensively and identified hydrogen sulfide and sulfur compounds as the poisoned substances to be dealt with, aiming to reduce them to below the detection limit.The research was conducted by transporting gas purified in a small bench-scale purification system installed in our brewery to the Kyushu University Next-Generation Fuel Cell Research Center for power generation tests. (manufactured by Mitsubishi Heavy Industries, Ltd.).As a result, continuous power generation for 10,000 hours was successfully achieved. The power generation time was 10,650 hours. Degradation throughout the period was 0.3%, an extremely low result.Based on these results, a hybrid SOFC demonstration power plant that combines an in-house designed biomethane refining facility and a 200kW stationary SOFC power generator, backed up by biomethane gas with city gas, was constructed in our brewery with supported from the Japanese Ministry of the Environment. The plant started its automatic continuous power generation in the fall of 2021. As a result, the total operating hours reached 10,676 hours, and 3,408 hours for biomethane gas alone (end of October,2022). Degradation during this period was less than 0.5%/1,000 hours, and automatic operation is still ongoing.This paper reports the results of this 200 kW biomethane gas SOFC demonstration power plant operation and the key points of the design for practical use. Figure 1

Simulation Assisted Development of SOFC Power Generation

SOFC Power Generation systems are getting more and more popular in the stationary and marine sector, to move away from traditional internal combustion engines, not only to reduce emissions, but also for higher system efficiency. In this presentation AVL shows how system simulation was initially used for definition of appropriate system architecture, following by correct component selection to fulfill contract efficiency and performance targets. To get the most reliable results at any point of V process development, simulation tool has to be predictive enough in concept phase and it should also offer simple parameterization of components where more data is available, either from component supplier or actual measurements. The complete workflow will be shown to have an idea how AVL is utilizing the software at any point of the V process for SOFC system development.

Results of Continuous 200kW SOFC Power Generation Using Biomethane Gas from a Brewery's Wastewater Treatment Process

Asahi Quality and Innovations, a research subsidiary of Asahi Group Holdings, is committed to innovative R&D for the future of our global liquor, soft drinks and food business. Therefore, with the aim of reducing CO2 emissions, we have developed a technology to utilize carbon-neutral biomethane gas, a byproduct of the wastewater treatment process at breweries, for SOFC power generation instead of conventional combustion. Although many attempts have been made to use biomethane gas for fuel cell power generation, there have been no reports of successful practical applications. We believed that this was due to the unstable purification of the poisoned substance. Therefore, we have succeeded in stabilizing the purification process by employing a gas-in-liquid dispersion method instead of a conventional scrubber for the purification operation. As a result, we have succeeded in long-term continuous power generation using a 200 kW SOFC. This paper reports on the technical details and results.

Operating economy analysis of SOFC power generation system with CO<sub>2</sub> utilization system

Operating economy analysis of SOFC power generation system with CO<sub>2</sub> utilization system

Field Test Result of Residential SOFC CHP System Over 10 Years, 89000 Hours

The maximum operating time, without stack replacement, residential SOFC power generation unit (manufactured by Kyocera in 2009), which was installed by Osaka Gas in a house in 2009, has exceeded over 10 years, 89,000 power generating hours. It may be the first data as a SOFC system to succeed in operating in the actual field for 10 years. We will report performance results for 10 years. In 2004, Osaka Gas and Kyocera started joint development of residential SOFC CHP system and from 2007, we conducted series of field test in the SOFC demonstration project operated by NEDO and NEF. At that time, various technical issues still remained, and after joint development with Aisin and Toyota Motor, it was mass-produced and commercialized in 2012. We also mention current status of residential SOFC (Manufactured by Aisin, Stack supplied by Kyocera), which have sold more than total 80,000 units at Osaka Gas.

Field Test Result of Residential SOFC CHP System Over 10 Years, 89000 Hours

The maxmum operating time without stack replacement, residential SOFC power generation unit (manufactured by Kyocera in 2009), which was installed by Osaka Gas in a house in 2009, has exceeded over 10 years, 89000 power generating hours. In 2004, Osaka Gas and Kyocera started joint development of residential SOFC CHP system and from 2007, we conducted series of field tests in the SOFC demonstration project operated by NEDO and NEF. At that time, various technical issues remained, and after joint development with Aisin and Toyota Motor, it was mass-produced and commercialized in 2012. We also mention the current status of residential SOFC (Manufactured by Aisin, SOFC stack supplied by Kyocera). Osaka Gas has sold more than a total of 88,000 residential SOFC CHP systems as of October 2020.

Concept for Temperature-Cascade Hydrogen Release from Organic Liquid Carriers Coupled with SOFC Power Generation

Summary For a sustainable hydrogen economy, large-scale transportation and storage of hydrogen becomes increasingly important. Typically, hydrogen is compressed or liquified, but both processes are energy intensive. Liquid organic hydrogen carriers (LOHCs) present a potential solution for mitigating these challenges while making use of the existing fossil fuel transportation infrastructure. Here, we present a process intensification strategy for improved LOHC dehydrogenation and an example of clean power generation using solid oxide fuel cells. Four LOHC candidates—ammonia, biphenyl-diphenylmethane eutectic mixture, N-phenylcarbazole, and N-ethylcarbazole—have been compared as stand-alone and integrated systems using comprehensive process simulation. “Temperature cascade” dehydrogenation was shown to increase the energy generated per unit mass (kWh/kg LOHC) by 1.3–2 times in an integrated system compared to stand-alone LOHC systems, thus providing a possibility for a positive impact on a LOHC-based hydrogen supply chain.

Preparation and Characterization of Alternative Ni-Based Anode Materials for SOFCs

Introduction Ni is widely used as the anode material of SOFCs as a cermet containing ionic conductor and electronic conductor. In the SOFC power generation, the oxygen partial pressure in the downstream region of the SOFC systems increases, the metallic Ni can be oxidized to NiO, and thus volume expansion occurs1. Aggregation of adjacent Ni particles can degrade the electrode structure, which makes it difficult to fully utilize the fuel supplied. We have succeeded in fabricating an SOFC anode which is resistant to redox cycling using oxide conductors, La-doped SrTiO3 (LST) and Gd-doped CeO2 (GDC). In this study, we aim to develop (i) a novel electrode in which a metallic Ni catalyst is dissolved from the electrode material and precipitated on the surface of the anode in a reducing atmosphere (Ni-LST-GDC anode), and (ii) a novel electrode using a Ni-based alloy in the electrode framework (Ni-alloy-GDC anode)2,3. Experimental Alternative anode materials were prepared via wet process2,3. The cells were prepared by screen-printing the anode and the cathode followed by each sintering process in air. A platinum mesh was used for the current collector, and a Pt-based reference electrode was deposited on the cathode side for overvoltage separation between the anode and the cathode. The electrochemical performance of the fuel cells was evaluated from the I-V characteristics at the operating temperature of 800°C, using 3%-humidified hydrogen fuel. In order to evaluate the electrode activity, the electrode overvoltage was measured. The current interruption method was applied for evaluating the electrode overvoltages. Results and discussion Figure 1 shows the I-V characteristics of the cells with the newly prepared Ni-LST-GDC anode, the Ni-impregnated anode, and the LST-GDC anode without adding Ni, at 800°C, in 3%-humidified hydrogen fuel. Regarding the anode voltage and the anodic overvoltage, the Ni-LST-GDC anode exhibited better performance than the anode composed only of LST and GDC. In comparison with the Ni-impregnated anode, however, the cell performance was still lower both in anode voltage, overvoltage, and IR loss. Figure 2 shows STEM micrographs indicating that the Ni catalyst particle precipitated could locate on the GDC. Anode materials design principles of alternative Ni-based anodes will be discussed. But most of Ni particles located on the electron-conductive LST. In contrast, the cell with Ni-alloy anode exhibited comparable performance compared to that with the Ni-SSZ cermet.

New Applications of SOFC-MGT Hybrid Power Generation System for Low-Carbon Society

SOFC and micro gas turbine (MGT) hybrid power generation system in Fig.1 (a) is expected as a solution for energy saving and less CO2 emission. High temperature pressure swing absorption (HT-PSA) in Fig.1 (b) is also expected as an efficient method for pure O2 production. Applying HT-PSA to the pressurized high-temperature cathode off-gas of SOFC-MGT hybrid system, we are able to obtain pure O2 more efficiently than the other conventional method. Using obtained O2 for anode off-gas oxidation, we can easily capture CO2, which leads to effective carbon-less or negative-carbon solution. Produced O2 are also useful for efficient gasification, which leads to CO2-capture IGFC system. In this study, we performed basic performance tests of SOFC-MGT and HT-PSA systems. Using these results, we also studied expecting performance and technical issues of proposed SOFC application systems. Acknowledgements This research is supported by The Japan Science and Technology Agency (JST) through its “Center of Innovation Science and Technology based Radical Innovation and Entrepreneurship Program (COI Program)" and Mitsubishi Hitachi Power Systems(MHPS) Co., Ltd. Figure 1

Chemical and Structural Stability of SrxNiyOz Chromium Getter for Application in SOFC Systems

Non-noble, non-strategic and cost effective SrxNiyOz based chromium getter is being developed for capturing gas phase chromium species in SOFC power generation systems. In this study, we report the chemical and structural stability of the SrxNiyOz powder under synthesis and operational conditions. Phase stability of SrxNiyOz in the temperature range of 850 °C to 1000 °C has been analyzed by high temperature in-situ X-ray diffraction (XRD) technique and SEM-EDS is used to study the surface morphology. XRD results indicate that the synthesized SrxNiyOz remains stable at 850 °C and 900 °C sintering temperature with no/negligible phase separation into SrO and NiO compounds, whereas exposure to temperatures 950 °C and 1000 °C lead to the dissociation of parent phase into the formation of SrO and NiO phases. Further, it was observed that the powder samples sintered at 950 °C and 1000 °C show volume expansion and pulverization when exposed to the humid air atmosphere for 24 h post sintering at 950 °C and 1000 °C. Samples sintered at 850 °C and 900 °C maintain structural stability and shape.

No.22 固体酸化物型燃料電池アノード発電能および微細焼結構造に対する石炭ガス化ガス中微量成分の影響調査(灰・微量元素(2))

No.22 固体酸化物型燃料電池アノード発電能および微細焼結構造に対する石炭ガス化ガス中微量成分の影響調査(灰・微量元素(2))

Mitigation of Chromium Assisted Degradation of LSM Cathode in SOFC

Chromium evaporation, from chromia forming ferritic alloys used in the interconnect (IC) and the low cost iron and nickel base alloys, is considered as one of the leading causes for the long term irreversible performance degradation of cathode in SOFC power generation systems. Although, surface coatings and alloy modifications have proved beneficial in providing short term solution for the mitigation of chromium poisoning, the surface coatings and alloy chemistries remain susceptible to structural degradation in long term. A novel approach for mitigating cathode degradation by capturing gas phase chromium vapor from the air stream has been developed. Results from chromium capture tests conducted under simulated SOFC systems operating conditions will be presented.

Mitigation of Chromium Assisted Degradation of LSM Cathode in SOFC

Chromium evaporation, from chromia forming ferritic alloys used in interconnect (IC) and the low cost iron and nickel base alloys used in balance of plant (BOP) during exposure to ambient air, and subsequent interactions of gaseous chromium species with the cathode is considered as one of the leading causes for the long term irreversible performance degradation in SOFC power generation systems. Although, surface coatings and alloy modifications have proved helpful in providing near term solution for the mitigation of chromium poisoning, the aforesaid remain susceptible to structural degradation in long term. A novel approach for mitigating cathode degradation by capturing gas phase chromium vapor from the air stream has been developed. Results from transpiration and symmetric electrochemical tests, conducted under simulated SOFC systems operating conditions, will be presented. Underlying thermodynamic and electrochemical processes associated with chromium evaporation and subsequent interactions with getters will be presented.

Smart Fuel Cell Demonstration Project: A Challenge to Realize SOFC-Powered Campus

This paper introduces a challenge to realize a fuel-cell-powered campus at Kyushu University where SOFC technology plays a major role. The Smart Fuel Cell Demonstration Project, supported by Cabinet Secretariat/Office of Japan, enables us to install one 250 kW SOFC power generation system, other SOFC units, and the world-first university-owned fuel cell vehicle to which renewable hydrogen gas is supplied from the hydrogen refueling station in this campus using electrolyzers. The experience in this demonstrative project is described along with related efforts to accelerate industry-academia collaborations and fundamental scientific studies using advanced analytical facilities.

Start‐Up Characteristics of Segmented‐In‐Series Tubular SOFC Power Modules Improved by Catalytic Combustion at Cathodes

AbstractFor large‐scale SOFC power generation systems, a shorter start‐up time of SOFC cell stacks with relatively large heat capacity is one of the most important technological issues to determine the flexibility in SOFC system operation. In this study, start‐up procedures have been examined to shorten the start‐up time period. The conventional heating procedure using pre‐heated hot air and self‐heating by SOFC operation at low temperatures had a difficulty to shorten the start‐up time period because of the limitation in power generation at lower temperatures. In this study, as an alternative start‐up procedure, catalytic combustion at the SOFC cathodes is, for the first time, demonstrated to be useful on the system level. The applicability of the catalytic combustion to shorten the start‐up time period has been verified numerically as well as experimentally by using a large‐scale cell stack cartridge. This unique start‐up procedure enables to operate SOFC‐based large‐scale power generation systems.

SOFC Power Generation System by Bio-gasification

Power generation using SOFCs, is one of the technologies that can reduce emissions, allow fuel flexibility and achieve high efficiencies. Combining gasifiers with SOFCs would make it possible to extract energy from biomass with lower environmental impact compared to conventional fuel based systems. The hybrid SOFC-gasifier system is best suited for application in standalone systems. The present study shows the performance of a hybrid SOFC for different types of biomass feed. The gasifier reactions are simulated using AspenPlus and a 1D mathematical fuel cell model is used for calculating the SOFC performance. Amongst different biomass fuels chosen in our study, sugarcane bagasse shows best performance in hybrid SOFC. The electrochemical performance of the biomass fed hybrid SOFC is found to be less compared to a hydrogen fuelled system. The advantage of the hybrid system is that since energy generation is dependent on biomass feed, energy sustainability can be attained with proper policy and management.

Durability Verification of Residential SOFC CHP System

Osaka Gas started joint development of the residential SOFC CHP system with Kyocera in FY2004, and Aisin Seiki Co., Ltd. and Toyota Motor Corporation also took part in out development. Development for commercialization was completed at the end of the 2011 fiscal year, and product commercialization was started. Most significant issue for commercialization was durability. Osaka Gas has conducted durability verification of a large number and long time test for stacks, material, and SOFC generation units in order to establish 10 years life time. As these results, we judged that durability SOFC power generation unit which uses latest stack, hot module design, and control reached durability target.