Solid Oxide Fuel Cell Technology Research Articles

Enriching Nano-Heterointerfaces in Proton Conducting TiO2-SrTiO3@TiO2 Yolk-Shell Electrolyte for Low-Temperature Solid Oxide Fuel Cells.

A challenging task in solid oxide fuel cells (SOFCs) is seeking for an alternative electrolyte, enabling high ionic conduction at relatively low operating temperatures, i.e., 300-600°C. Proton-conducting candidates, in particular, hold a significant promise due to their low transport activation energy to deliver protons. Here, a unique hierarchical TiO2-SrTiO3@TiO2 structure is developed inside an intercalated TiO2-SrTiO3 core as "yolk" decorating densely packed flake TiO2 as shell, creating plentiful nano-heterointerfaces with a continuous TiO2 and SrTiO3 "in-house" interfaces, as well the interfaces between TiO2-SrTiO3 yolk and TiO2 shell. It exhibits a reduced activation energy, down to 0.225eV, and an unexpectedly high proton conductivity at low temperature, e.g., 0.084 S cm-1 at 550°C, confirmed by experimentally H/D isotope method and proton-filtrating membrane measurement. Raman mapping technique identifies the presence of hydrogenated HO─Sr bonds, providing further evidence for proton conduction. And its interfacial conduction is comparatively analyzed with a directly-mixing TiO2-SrTiO3 composite electrolyte. Consequently, a single fuel cell based on the TiO2-SrTiO3@TiO2 heterogeneous electrolyte delivers a good peak power density of 799.7mW cm-2 at 550°C. These findings highlight a dexterous nano-heterointerface design strategy of highly proton-conductive electrolytes at reduced operating temperatures for SOFC technology.

State of art of hydrogen utilization for building sector and set-up with preliminary experimental results of 1 kWel solid oxide fuel cell installed in a nearly zero energy house

The diffusion on large scale of the hydrogen-fueled technologies could be a strategy for boosting the expected decarbonisation of the civil sector. However, there are still a lot of unanswered questions about the real feasibility and the problems of the integration in a pre-existing building-plants system. Despite some conflicting opinions, the research about the application of the hydrogen system in the building sector must continue to make the technology more attractive and easily available at low cost. Therefore, first of all, the paper analyses advantages and issues through a broad overview. The main limits of the available studies regard both the approach and the technology integration. Indeed, there are few data about in-field performance analysis since the simulative/numerical investigations are usually based on in-lab prototypes. The most diffused systems referred to integrated energy solutions with proton exchange membrane fuel cell technology and in any case the integration in very low energy buildings such as the nearly zero energy (nZEB) ones is not discussed. Then basing on the discussed research gap, the paper focuses on the set-up of a new installation of micro-combined cooling, heating and power unit based on solid oxide fuel cell technology fueled by green hydrogen. The complexity in the design of the integration with other innovative plant configurations is discussed considering as real case study a nZEB in Mediterranean climate. Preliminarily experimental results show that the combination of fuel cell and photovoltaic system could bring to positive energy with surplus energy, during autumn season, of about 23.8 kWh. Moreover, it is also proposed the validation of a dynamic numerical model developed by means of TRNSYS (Transient System Simulation Tool) that will be used for further sensitivity analysis.

Internal dry reforming of methane in solid oxide fuel cells

In the context of global efforts to reduce greenhouse gas emissions and combat extreme global warming, the direct dry reforming of methane reaction in solid oxide fuel cells presents a promising avenue for clean energy production. This study delves into the influence of temperature, gas composition, and current density on the kinetics of dry methane reforming in solid oxide fuel cells. Power Law and Langmuir-Hinshelwood kinetic models were proposed to highlight the impact of operating conditions on dry methane reforming reactions. Results revealed that the feed gas composition strongly affects methane conversion, with higher methane contents resulting in lower conversions. Increasing the CH4/CO2 ratio increases reaction rates, and the effect decreases at a ratio of 1.25. The changes in methane concentration on dry methane reforming reaction rate are more significant than those for carbon dioxide. However, increasing carbon dioxide concentration enhances methane conversion. The exothermic nature of CO2 adsorption suggests that the adsorption process is thermodynamically favourable in dry reforming, and the elevated temperatures generally improve reaction rates and methane conversion by removing carbon deposits and providing the energy needed to break down the chemical bonds in methane which facilitating its transformation. A higher current density significantly enhances the CO2 adsorption equilibrium constant and further increases methane conversion, highlighting the positive role of electrochemical reactions on dry methane reforming. This study aims to fill the knowledge gap regarding the influence of electrochemical reactions on dry methane reforming behaviours in solid oxide fuel cells, offering critical insights for advancing anode design, thus contributing to the development of solid oxide fuel cell technologies to address global warming and reduce greenhouse gas emissions.

Performance improvement of fuel cell and photovoltaic system

This article considers and studies a hybrid energy storage system as a potential replacement for a utility grid. It also examines its organisational structure. The hybrid energy storage technology is used to ensure a constant supply of convenient grid electricity that is sufficient to handle changing power spikes. Batteries are used to stabilise the surges with measurable variation, whereas a massive capacitor is utilised to stabilise the surges with fast variation. In isolated areas where connecting to the main utility grid is impractical, standalone renewable generation may provide the advantage of a reduced operational cost as well as a reduction in protection fees. In order to encourage non-conventional power production in the overall renewable energy system, advancements in solid oxide fuel-cell technology and solar photovoltaic (PV) technology have also been made. Grid-coupled solar PV energy producing systems are being extensively used worldwide, and solar PV modules are increasingly being used in residential applications linked to the electrical grid.

Recent advancement of solid oxide fuel cells towards semiconductor membrane fuel cells

In the last few decades, there has been remarkable progress in the development of solid oxide fuel cells (SOFCs) based on both traditional solid electrolyte materials and novel semiconductor membranes. However, limited attention has been given to the transition of SOFCs from oxide ion-based electrolyte membranes to semiconductor membrane devices, considering the overall perspective of materials, technology, and scientific principles. Traditional knowledge strictly dictates that semiconductors should not be used as the membrane unless these materials possess negligible electronic conduction. This is because semiconductor membrane materials typically exhibit significantly higher electrical conductivity, surpassing the inherent ionic conductivity. Interestingly, by using semiconductors as the membrane, numerous novel materials have been demonstrated in the literature, which seems difficult to understand from traditional SOFC knowledge. Therefore, there is an emerging need to summarize and explore new understanding and knowledge of materials, technology, and science of SOFCs and Semiconductor Membrane Fuel Cells and their transition. In this review, we attempted to summarize the gap between the current state of SOFCs and the advancements in new materials, technologies, scientific principles, and mechanisms driving the development of such devices.

Toward solid-state Limetal-air batteries; an SOFC perspective of solid 3D architectures, heterogeneous interfaces, and oxygen exchange kinetics.

The full electrification of transportation will require batteries with both 3-5× higher energy densities and a lower cost than what is available in the market today. Energy densities of >1000 W h kg-1 will enable electrification of air transport and are among the very few technologies capable of achieving this energy density. Limetal-O2 or Limetal-air are theoretically able to achieve this energy density and are also capable of reducing the cost of batteries by replacing expensive supply chain constrained cathode materials with "free" air. However, the utilization of liquid electrolytes in the Limetal-O2/Limetal-air battery has presented many obstacles to the optimum performance of this battery including oxidation of the liquid electrolyte and the Limetal anode. In this paper a path towards the development of a Limetal-air battery using a cubic garnet Li7La3Zr2O12 (LLZ) solid-state ceramic electrolyte in a 3D architecture is described including initial cycling results of a Limetal-O2 battery using a recently developed mixed ionic and electronic (MIEC) LLZ in that 3D architecture. This 3D architecture with porous MIEC structures for the O2/air cathode is essentially the same as a solid oxide fuel cell (SOFC) indicating the importance of leveraging SOFC technology in the development of solid-state Limetal-O2/air batteries.

Study on the composite structure of cobalt-free oxides as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs)

Summary: Solid Oxide Fuel Cells (SOFCs) represent a promising technology for efficient and clean energy conversion. This study focuses on the design and development of a novel cathode material for SOFCs, specifically exploring the use of a free-cobalt cathode within a composite structure. Investigating the structure of cobalt-free composites of Ba0.5Sr0.5FeO3-δ (BSF) and Ba0.5Sr0.5Fe0.8B0.2O3-δ (B=Cu, Zn) (BSFB) have been prepared and evaluated as cathodes for IT-SOFCs. The solid-state reaction was employed for generating and modifying the composite structure of the model system. The decomposition reaction and the formation of perovskite structure have been observed using thermal gravimetric analysis and X-ray diffraction. The study encompasses experimental procedures, data processing using GSAS software, and the application of the Rietveld method to achieve precise analysis results. Rietveld analysis outcomes offer intricate details about the crystal structure, encompassing crystal unit parameters, and scale factors. The solid-state reaction led to the reduction in the weight of the composite during the heating process. The decomposition reaction of oxides was generated between 650 to 950 oC. The average of total weight loss during the period treatment was achieved up to 18 % and the perovskite phase formed in the composite structure. A single-phase perovskite from a cubic structure with space group Pm-3m was demonstrated by all composite’s models. The lattice parameter and a unit cell volume were obtained from the model system of BSF, BSFC and BSFZ, respectively. This study explores the potential development of SOFCs technology with the hope of making a positive contribution to advancing clean and sustainable energy solutions in the future

Advancements in Perovskite-Based Cathode Materials for Solid Oxide Fuel Cells: A Comprehensive Review.

The high-temperature solid oxide fuel cells (SOFCs) are the most efficient and green conversion technology for electricity generation from hydrogen-based fuel as compared to conventional thermal power plants. Many efforts have been made to reduce the high operating temperature (>800 °C) to intermediate/low operating temperature (400 °C<T<800 °C) in SOFCs in order to extend their life span, thermal compatibility, cost-effectiveness, and ease of fabrication. However, the major challenges in developing cathode materials for low/intermediate temperature SOFCs include structural stability, catalytic activity for oxygen adsorption and reduction, and tolerance against contaminants such as chromium, boron, and sulfur. This research aims to provide an updated review of the perovskite-based state-of-the-art cathode materials LaSrMnO3 (LSM) and LaSrCOFeO3 (LSCF), as well as the recent trending Ruddlesden-Popper phase (RP) and double perovskite-structured materials SOFCs technology. Our review highlights various strategies such as surface modification, codoping, infiltration/impregnation, and composites with fluorite phases to address the challenges related to LSM/LSCF-based electrode materials and improve their electrocatalytic activity. Moreover, this study also offers insight into the electrochemical performance of the double perovskite oxides and Ruddlesden-Popper phase materials as cathodes for SOFCs.

Crossflow flat solid oxide fuel cell (SOFC) semi-empirical modeling and the multi-fuel property based on a commercial 700 W stack

Solid Oxide Fuel Cell (SOFC) technology has attracted vast attention for combined heat and power (CHP) application on low or zero carbon emissions because of its high efficiency and multi-fuel selectivity. Due to the high operation temperature, a commercial SOFC system requires a complex system thermal balance and stack self-heating ability which are dramatically influenced by the inlet temperature, reaction heat and thermal radiation of the stack. Multi-fuel selectivity is a further distinct advantage when considering the future variety of renewable fuel sources, such as ammonia (from animal farming), bio-methane (from agriculture), and the other hydrocarbons using carbon capture as an effective H2 carrier. However, the alternating between different fuel types may result in reduced power and the internal heat balance to change, which may further lead to the stack cooling down or over heated. An appropriate model with fast calculation processing capability is necessary to assess the internal changes before switching the fuel source and to inform further decision making to enable the control system to adapt to the change. In this paper, a cross-channel, flat SOFC semi-empirical model is proposed and validated by a commercial 700 W stack using real testing data to assess the accuracy of the simulation results. The SOFC model has multi-fuel ability which presents different properties and internal understanding for H2, NH3, and reformed CH4 through relevant charts (for feed, velocity, temperature, reaction rate, current, power, heat, efficiency). The power outputs for the different fuel sources, H2, NH3, and reformed CH4, are 721.0 W, 628.9 W and 679.7 W respectively when calculated at an air inlet temperature of 893 K. The modeling work was completed using Aspen Plus for SOFC system thermal balance simulations which determined the power output property for 813.3 W (H2), 744.5 W (direct NH3) and 740.7 W (reformed CH4) at the 2.0 times stoichiometric ratio of air feed, and CHP rate of 0.903 (H2), 0.787 (direct NH3) and 0.311 (reformed CH4). This work has the potential to contribute to the United Nation Sustainable Development Goal for Affordable and Clean Energy, Goal 7.

Thin film Si solar cell and solid oxide fuel cell technologies for a low cost, environmentally friendly and sustainable source of energy

Thin-film solar cell technology based on hydrogenated amorphous silicon has matured over the last two decades and is capable to deliver commercial modules with almost 10 % stabilized efficiency. Moreover attention on hydrogen fuel cells is increasing as the range of potential commercial applications expands, with more than 3800 fuel cell systems being installed and operated worldwide. These systems attain high theoretical efficiencies in the range of 43.7-70.4 %, with an additional 20% as heat recovery, and operating at carbon-free conditions between 50 °C and 900 °C. In this paper the status of thin-film silicon solar cell technology is reviewed by comparing it to other major solar cell technologies. A discussion is also made upon the benefits obtained from the few potential applications, as long-term potential actions for sustainable development, and the future of Solid Oxide Fuel Cells (SOFCs). Applications of thin-film silicon modules and SOFCs are presented. EPIA (European Photovoltaic Industry Association) estimates that half of the growth in the next two years will come from thin-film technology.

Evaluation of the environmental sustainability of SOFC-based cogeneration systems in commercial buildings

In order to achieve the European Union (EU)’s climate targets, efficient and sustainable solutions must be developed. In this context, the building sector has a key role to play in the transition to a decarbonized society. Cogeneration is considered an efficient solution that enables better use of fuel energy to supply buildings with heat and electricity. In particular, fuel cell-based cogeneration systems have shown promising performance, thus attracting considerable attention in recent years. The main goal of this study is to analyze the environmental impact of Solid Oxide Fuel Cell (SOFC) cogeneration systems, focusing on commercial buildings. The analysis was performed in the framework of the H2020 Comsos project, whose aim is to investigate the techno-economic and environmental feasibility of SOFC-based systems in non-residential buildings. An MILP-based optimization framework was developed to address the optimal design and operation of energy systems with the inclusion of SOFC-based cogeneration solutions. Electrical and thermal efficiency curves, derived from real SOFC operation, were used to improve the accuracy of the SOFC performance simulation. A sensitivity analysis on the carbon intensity of electricity was carried out to explore the role of the SOFC technology under different levels of electrical grid decarbonization. It was found that natural gas-fed SOFC systems become environmentally advantageous (in terms of CO2 emissions) when the carbon intensity of electricity is higher than ∼ 300 gCO2/kWh.

A novel multi-generation energy harvesting system integrating photovoltaic and solid oxide fuel cell technologies

This paper designs a new multi-generation system based on solar tower power supply, integrating a solid oxide fuel cell-gas turbine system, a supercritical recompressed carbon dioxide cycle, a Rankine cycle, an organic Rankine cycle, a compressed air energy storage system and a liquefied natural gas system. The aim is to overcome the intermittent and unstable nature of the solar power supply and ensure continuous power generation throughout the day, as well as improving the energy efficiency of the solar power system and minimising exhaust emissions from the integrated system. The system is modelled and evaluated in terms of energy, exergy, environment and economy. The results show the solar system energy efficiency of 10.09%, the total system energy efficiency of 19.28%, a round-trip efficiency of 58.66% and an exergetic round-trip efficiency of 52.06%, preventing the emission of 2090 tons of CO2 (a total of $50175 in environmental fines) per year. Finally, the proposed system was applied to a case study in the Xixiangtang district of Nanning, China, where the system, combined with real data, produced 24.8 MWh of electricity on the day with the highest direct of normal irradiance. In addition, the results of the economic analysis show the dynamic payback period is 6.9 years.

Solid Oxide Cell Technology for Power Generation, Hydrogen Production and Energy Storage

The progress in maturation of solid oxide cell technology has led to development of new applications that would explode its presence in many areas, far beyond power generation. The solid oxide cell technology has the potential to have a formidable presence in production of hydrogen and, eventually, long duration storage of electric power.Following the successful operation of a 200 kW SOFC system under a project supported by Department Energy/NETL, FuelCell Energy (FCE) is pursing the development of SOC based plant configurations from subMW to electrolysis, and further, to energy storage.Multi-faceted evolution of the technology has been underway since the earlier demonstration of SOFC power plant. FCE has developed state-of-the-art lightweight Compact SOFC Architecture (CSA) stacks that are packaged in compact modules with adaptability for use in a variety of configurations and capacities. The CSA stacks can operate directly on a variety of fuels - natural gas, biogas, and hydrogen- without any modification. FCE’s existing fuel cell pilot manufacturing line for CSA cells and stacks includes robotics and automation such as cell screen printing, interconnect subassembly, seal application, QC, as well as stack assembly and conditioning. Via a design for manufacturing approach, as well as focus on minimization of raw material, recent detailed cost studies show a path to low factory stack production cost (<100/kW) at high volumes (1,000 MW/year). The large market existing for power generation equipment, in the range of 200-300kW, is a significant driver for development of high efficiency SOFC products that would easily cater to early-adopters prior to wide-spread acceptance. The accelerated interest in hydrogen as the fuel source will widen the market for SOFC deployment even more. Under a project supported by DOE, FCE is working on design of MW-class SOFC power plants as future extension of the subMW SOFC plant products.FCE is developing a first-of-a-kind 250kW Solid Oxide Electrolyzer Cell (SOEC) system with the hydrogen production capacity of 150kg/day. The overarching goal of the project is to verify that the integration of Solid Oxide Electrolysis Cell (SOEC) systems within nuclear plants will maximize the plants’ efficiency and flexibility and will increase their revenue by switching between electric power generation and hydrogen production. Hybrid nuclear-hydrogen production operations are expected to help the present and future nuclear plants diversify and increase profitability.The 250kW SOEC system is planned to be demonstrated and operated at Idaho National Laboratory (INL). The project will culminate in verification and validation testing and solidify SOEC technology as a low cost and efficient means for hydrogen production integrated within the nuclear power plant environment. The SOEC system will be interfaced with a High-Level front-end Controller (HLC) simulating communications from a nuclear plant and the electric grid. The HLC will determine an optimized hydrogen production schedule to meet all contractual obligations, while maximizing revenue from the integrated operations.FCE is also developing energy storage systems based on the Company’s Solid Oxide Fuel Cell (SOFC) technology. Reversible Solid Oxide Fuel Cell (RSOFC) technology is suitable for medium to long-duration energy storage achieving high round trip electric efficiencies near 70% (electricity-in to electricity-out) at an expected levelized cycle cost of ≤ $0.05 / kWh-cycle.FCE is currently conducting operational tests of an RSOFC prototype system to accomplish the of validation and verification of engineering/pilot-scale RSOFC technology in a relevant environment. A bread-board pilot demonstration system is being utilized to verify cell materials and stack design improvements as well as to validate power electronics and system control strategies that will be utilized for optimization of efficiency, transient response, and lifetime characteristics.

SOFC-VPSA System for Power Generation with CO2 Separation

Solid Oxide Fuel Cell (SOFC) has attracted huge scientific attentions lately, as it is a promising power production technology that can reduce user’s dependency on electricity-grid. SOFC system can generate electricity by using liquid or gaseous fuels. Small volume and external fuel storage make SOFC technology more compatible, and it can easily be adjusted for different industry power plant scales. Moreover, SOFC operates at high temperature (700 0C), and it cogenerates high-quality heat or steam, which can be used as a heat source within the system. As maximum fuel utilization for SOFC is around 85%, a burner is required for the combustion of unconverted fuels. The burner provides additional heat to the SOFC system, at the same time, it generates more CO2.In order to meet “net zero” emission target for greenhouse gases in the year 2050, it is essential to introduce Carbon Capture and Storage (CCS) technology that can retrieve most of the produced CO2 from emission intensive activities and store it permanently in nature (e.g, sequestration and mineralization), leading to an almost carbon neutral activity. The stored CO2 can also be used in methanation process, to convert it into green methane. By integrating an existing CCS technology with SOFC, and using biofuels as energy source, SOFC system can be considered as a carbon negative technology. The most common and widely used CCS technology is Chemical Absorption (CA). The CA process presents good retrofitting options. However, corrosion and degradation are major issues.The high efficiency of SOFC system is however penalised by the fact that the flue gases contain typically a mix of CO2 and N2, which makes it difficult and expensive to separate/capture the produced CO2. There is a possibility of directly injecting pure oxygen to the burner. For industrial scale, cryogenic distillation is commonly used air separation technology for producing O2. Cryogenic distillation is an energy intensive technology, and it is not suitable for small scale O2 production. In the recent times, other technologies such as Pressure Swing Adsorption (PSA) and membrane have evolved for O2 production from air. The non-cryogenic technologies for air separation are preferred to their lower operating cost and easier integration with other processes. PSA is usually suited for medium-range production capacity, and it can produce O2 with 94 % purity. However, it is still necessary to improve performance by reducing energy consumption. The energy consumption is 3.211 MJ/kg-O2 for PSA to produce oxygen. In the oxygen production process, energy consumption accounts for more than 90% of the operating cost.This study considers integration of a SOFC system with PSA, which consists of a SOFC stack, balance of plant components for SOFC system, PSA bed and auxiliary components for PSA. The PSA produces O2 from air, that is injected to the combustion chamber (or burner). In the integrated system, the energy needed for the PSA directly comes from SOFC system. The right amount of oxygen is used to complete the oxidation of the unconverted fuel from the anodic side of SOFC, and CO2 is separated automatically after water condensation. Figure 1 shows layout of integrated system. The performance of PSA is explored for different materials, different pressure ratio and temperature, to achieve minimum energy consumption. Moreover, heat integration has been studied for SOFC system, the integrated system has waste heat available, especially at the downstream of the burner. In order to valorize the waste heat of the system, a steam cycle has been integrated for producing extra amount of electricity, to improve the overall efficiency of the system. Finally, the performance of integrated system has been optimized for maximization of electrical efficiency and minimization of exergy distraction, via multi-objective optimization.In this study, the net electricity output from SOFC-PSA system is around 9 kW. The SOFC produces 9.8 kW electricity, and about 8% electricity is consumed by the PSA for producing O2 that is required for the combustion of unconverted fuel. The integrated system has an overall efficiency of more than 55%. A steam cycle has been integrated for producing extra amount of electricity, and it produces additional 2.5 kW of electricity. Hence, the overall efficiency of the integrated system reaches above 70% with automatic CO2 separation. Figure 1

Waste2Watts: Techno-Economic Feasibility of Biogas-Fed SOFC Power System Integrated with Biogas Cleaning Unit and Carbon Capture Technologies

As a promising power generation technology, the solid oxide fuel cell (SOFC) system demonstrates high electrical efficiency and overall efficiency in cogeneration mode. Operating at high temperatures (> 680 ˚C), SOFCs cogenerate high-quality heat and can be integrated with different industry facilities. Furthermore, SOFC technology demonstrates high fuel tolerance, including hydrogen, natural gas, ammonia, LPG, etc. Unlike other fuel cell technologies, SOFC systems can also tolerate impurities in the fuel, e.g., CO2, N2 or even a small amount of O2. Besides, the compact system configuration makes SOFC system of great potential in the decentralized application.In the context of the Paris Agreement, more and more solutions to replace fossil fuels have been proposed, where biogas is considered as one promising alternative. Biogas generally contains several impurities, making its application limited in the fuel cell technology field. Removing all the impurities and making it compatible for all the fuel cell technologies would be expensive. Whereas, since SOFC has high tolerance in fuel impurities, keeping certain harmful impurities under safe thresholds with a biogas cleaning unit and injecting the purified biogas into the SOFC system will be less costly. In this case, a biogas-fed SOFC system integrated with a biogas cleaning unit can be considered as a promising renewable technology by avoiding fossil fuel use and converting biowaste into electricity and heat.Although biogas is produced from a renewable source, its use in SOFCs still generates CO2 emissions when it is fed with biogas. To realize carbon neutrality or even being carbon negative in a biogas-fed SOFC system, carbon capture (CC) technology is introduced to meet the net-zero carbon emission target in 2050. One conventional carbon capture storage (CCS) technology is the calcium looping system, which uses CaO/CaCO3 in a carbonation-calcination loop to separate and capture the CO2 from the exhaust gas. This type of technology is quite mature for large-scale applications and has been widely used in thermal power plants for the desulfurization and denitrification of exhaust. Novel technology based on sodium carbonate solution is capable of not only carbon capture, but also biogas cleaning. For the carbon capture utilization (CCU) technology, the Fischer-Tropsch (FT) synthesis can convert CO2 with hydrogen into syngas via electrochemical or thermochemical catalytically driven processes.Focusing on the decentralized power system, small-scale biogas-fed SOFC system integrated with a biogas cleaning unit and CC system should be considered with capacity ranging from 20 kW to 200 kW. As a cogeneration system, the integration should not be limited to mass exchange. The electricity consumed by the biogas cleaning unit and CC system can be fulfilled via the SOFC system. Based on the system temperature pattern, a bigger heat exchange network can be formulated between three parts, which can avoid extra heat input. In this case, the optimality of overall system efficiency and revenue can be achieved.In this study, one biogas-fed SOFC power system is proposed with capacity ranging from 20 kW to 200 kW. The techno-economic evaluation is carried out in two cases, with or without heat and electrical integration. Meanwhile, in different cases, the techno-economic analysis of different biogas cleaning technologies and CC technologies will be performed as well. Two operation modes of the SOFC system are considered: (1) hot recirculation mixed before the reformer, (2) cold recirculation mixed before the reformer. Without the biogas cleaning unit and the CC technology, the biogas-fed SOFC system's electrical efficiency can exceed 65% as is demonstrated in Figure 1. Furthermore, Detailed techno-economic analysis has been carried out by three indicators: capital expenditure (CAPEX), operating expenditure (OPEX) and levelized cost of electricity (LCOE). Integrated with biogas cleaning unit via only mass exchange, the LCOE of the biogas-fed system without CC technology ranges from around 0.11 EUR/kWh (20 kW) to 0.085 EUR/kWh (200 kW). The cost breakdown is shown in Figure 2(a). Based on the SOFC system techno-economic analysis, different CC technologies are added and compared. When the conventional CC technologies like Calcium looping (CaL) and Fischer-Tropsch (FT) synthesis are scaled down to 20-200 kW and applied, unaffordable LCOE prices (0.65 EUR/kWh for CaL and 5 EUR/kWh for FT) indicate that these large-scale conventional technologies are not feasible for our cases. However, a novel technology based on Sodium carbonate looping with 97% CC efficiency is rather promising and shows much lower cost. As is indicated in Figure 2(b), the LCOE cost of the whole system is only around 0.151 EUR/kWh at 200 kW system capacity, indicating that it is a techno-economically feasible solution for a carbon-neutral biogas-fed SOFC system. Figure 1

Contrasting Intermediate-Temperature La0.7Sr0.3VO3.86-⸹ (LSV) Porous Catalyst Elevated Sulfur Tolerance Using Gaseous and Liquid Fuel Explored through Experimental and Modeling Characterization Over Time

The U.S. Army is investigating Solid Oxide Fuel Cells (SOFCs), which can produce clean, secure, and sustainable energy to replace existing power sources. Today SOFCs are known to provide high density, high efficiency power with long term stability at low cost and environmental impact, utilizing a variety of naturally sourced fuels such as hydrogen, hydrocarbons, and alcohols. This fuel flexibility makes SOFCs attractive for use with multiple applications and helps bridge the gap between current hydrogen-fueled SOFC technologies and future hydrocarbon-fueled based use. Despite this potential, many technical hurdles remain, such as thermal stress cracking and coarsening, delamination, and catalyst contamination. Catalyst contamination is of particular concern for the U.S. Army, which operates on JP-8 kerosene-based fuel via AR-70 single fuel policy, as sulfur impurities commonly found in naturally sourced hydrocarbon-based fuels, can poison the catalyst, permanently degrading SOFC system performance, even at low concentrations. As the U.S. Army begins to investigate SOFCs to enable additional capabilities like silent watch, advanced radios, and exportable power in their fleet, catalyst poisoning from sulfur presents a concerning technology gap that must be addressed, especially since it is also possible that sulfur contaminated fuel, scavenged in theater, may be used, and could contain elevated levels (>300ppm) of sulfur.While lower temperature SOFC operation is also actively being pursued to help alleviate physical material degradation issues, with the introduction of hydrocarbon-based fuels, catalyst development to reduce sulfur poisoning degradation also needs further exploration. This study continues to experimentally and theoretically investigate the response of sulfur tolerant anode catalyst La0.7Sr0.3VO3.86-⸹ (LSV) at currently targeted SOFC intermediate operating temperatures (400-600°C). We have previously investigated low and moderate hydrogen sulfide (H2S) concentrations (30ppm, 300ppm) in balance hydrogen and methane gas environments for up to 100 hours. In this work, LSV showed significant sulfur tolerance in hydrogen and methane balance gases when compared to the industry standard Ni-YSZ anode, where sulfur adsorption rates were 278-287x lower in some cases. The lowest rates occurred between 600-700°C, which is attributed to the cubic structure the material presents in this temperature range. Higher adsorption rates were observed in the monoclinic/tetragonal structure the material presents at temperatures between 400-500°C. Average adsorption rates were overall higher in methane. When compared against Ni-YSZ, which is known to accumulate sulfur from hydrogen sulfide via two-step dissociative adsorption, LSV was observed to accumulate sulfur through weak chemisorption (H2S*, 0.43 eV max) of molecular hydrogen sulfide on oxygen deficient surfaces and one-step dissociative adsorption (H2S*, 0.34 eV, max, HS*+H*, 8.34 eV, max) on oxygen sufficient surfaces. The weak chemisorption behavior on oxygen deficient surfaces is attributed to the reduced oxygen stoichiometry of the material, in which only vanadium V2+/3+ couples exist. Overall, molecular adsorption/dissociation was observed to occur near strontium defects on LaO/SrO terminations. The propensity of H2S adsorption on LSV surfaces was observed to be significantly less for oxygen deficient LSV, and significantly higher for oxygen sufficient LSV, when compared to H2S adsorption calculations on Ni (100) surfaces, which follow a two-step dissociative adsorption reaction (H2S* → HS*+H* → H*+S*), resulting in a strongly adsorbed S* species (5.96 eV, max).Under the Army’s single fuel policy, it is more likely SOFCs would be fueled using hydrogen and/or methane, which are both gases, however SOFCs in the future could also be directly fueled using liquid alcohol fuels, or as scavenged from theater. Typical small alcohol molecules (methanol or ethanol) do not contain high concentrations of sulfur; however, alcohols can be contaminated with sulfur-containing hydrocarbons. This work will investigate sulfur adsorption using methanol contaminated with 300ppm thiophene using the same operating temperature and heating duration conditions with hydrogen and methane. These results will be contrasted against the 300ppm H2S hydrogen and methane results previously reported. Figure 1

Degradation Analysis of SOFC Performance for Long-Term Operation with High Fuel Utilization (2)

Solid oxide fuel cells (SOFCs) are a power generation technology with its high efficiency and low environmental impact, and the most important issue for SOFC for practical use is to improve reliability as well as high efficiency. A national project on SOFC development in Japan, “Development of advanced evaluation and analysis technologies for the durability of Solid Oxide Fuel Cells stacks (2020-),” has been initiated as a NEDO project in order to clarify their long-term durability and find dominant degradation factor for each SOFC stacks. Central Research Institute of Electric Power Industry (CRIEPI) has operated three kinds of different SOFC cell/stacks (flat-tubular and two kinds of planer) for durability under NEDO’s project, which have been developed by KYOCERA, MORIMURA SOFC Technology, and DENSO.Long-term durability tests of 20,000 hours have been conducted under high fuel utilization of 80% and 85%, which is close to the operating limit of each SOFC cell/stack for high efficiency, to evaluate the effects on the performance and degradation behavior of the cell/stack. In previous projects, we have developed an electrode polarization model that can accurately represent SOFC performance, including cell voltage and each overvoltage, under a variety of conditions. The degradation factors for durability of each SOFC cell/stack have been analyzed by using this model. The analysis revealed that the dominant degradation factors were increased cathode overvoltage and IR loss, similar to the SOFC cell/stacks that were modified from the previous project to improve their long-term durability. On the other hand, the degradation rate of cell voltage was higher at 85% than at 80% fuel utilization in one cell/stack, and the performance degradation factor analysis revealed that this difference was due to an increase in anode overvoltage at 85% than at 80% fuel utilization, where anode overvoltage was not the primary degradation factor.This work has been carried out under the projects (JPNP13001 and JPNP20003) of the New Energy and Industrial Technology Development Organization (NEDO), Japan as contract research. We would like to express our gratitude to NEDO, many SOFC developers, as well as to university partners and National Institute of Advanced Industrial Science and Technology (AIST).

The optimal design of solid oxide and molten carbonate fuel cells integration with a CO2 recycling unit: An attempt to reach a clean transition process

High-temperature Solid Oxide Fuel Cell (SOFC) technology has great potential as a clean and effective energy source. However, several issues have prevented their widespread adoption, like high operating costs, difficulty integrating with other components, and being sensitive to fuel contamination. In order to address these challenges, the main novelties of the present work are carbon capture and utilization for clean energy production, using the flue gas condensation process as a cost-effective and energy-efficient strategy, and the combination of Molten Carbonate Fuel Cells (MCFC) for increased energy efficiency and most effective component integration. The proposed novel system is also equipped with a gasifier and vanadium chloride unit for syngas and clean hydrogen production. The system's practicality is evaluated by analyzing the key performance indicators from thermodynamic, exergo-economic, exergo-environmental, and sustainability viewpoints. Also, the Sankey diagram is presented to investigate each component's effectiveness from the exergy destruction facet. According to the findings, at the most optimum design condition, the acceptable energy and exergy efficiencies of 61.06% and 50.66%, respectively, are achieved, revealing the system's effectiveness. The suggested system is also financially attractive since it achieves a reasonable levelized power cost of 17.6 $/MWh at a total cost of 44.1 $/h. The findings show that carbon dioxide recovery is crucial in reducing the pollutants due to the low emission index of 5.01 kg/GWh. Finally, the exergo-environmental index, environmental damage effectiveness, and exergy stability factor have equivalent values of 0.012, 0.59, and 0.54.

The thermodynamic and life-cycle assessments of a novel charging station for electric vehicles in dynamic and steady-state conditions

The current study performs the thermodynamic and life-cycle assessments (LCA) of a novel charging station in two system designs. The goal is to design an efficient charging station for electric vehicles with high efficiencies and low environmental impacts using Solid Oxide Fuel Cell (SOFC) technology. SOFC is considered a sustainable and environmentally friendly technology to generate electricity compared to combustion engines. To ameliorate the performance, the exhaust heat of the SOFC stacks will be recovered for hydrogen production in an electrolyzer. The system uses four SOFCs to charge the electric vehicles while the output heat is recovered by an Organic Rankine Cycle (ORC) to generate further electricity for hydrogen production in an electrolyzer. In the first design, it is assumed that the SOFC stacks will work full-load during the 24 h of the day, while the second design considers full-load operation for 16 h and part-load (30%) operation for 8 h. The second design of the system analyzes the possibility of integrating a {mathrm{LiMn}}_{2}{mathrm{O}}_{4} lithium-ion battery stores the excessed electricity once the power load is low and acts as a backup in high power demands. Results of the thermodynamic analysis calculated the overall efficiencies of 60.84% and 60.67% for the energy and exergy, respectively, with the corresponding power and hydrogen production of 284.27 kWh and 0.17 g/s. It was observed that higher current density would increase the output of SOFC while reducing the overall energy and exergy efficiencies. In dynamic operation, the use of the batteries can well balance the change of the power loads and improve the dynamic response of the system to the simultaneous changes in the power demand. LCA results also showed that the 284.27kWh system leads to global warming (kg {mathrm{CO}}_{2} eq) of 5.17E+05, 4.47E+05, and 5.17E+05 using Solid Oxide Electrolyzer (SOE), Proton Exchange Membrane Electrolyzer (PEME), and Alkaline Electrolyzer (ALE), respectively. In this regard, the usage of PEME has the lowest impact on the environment in comparison to SOEC, and ALE. A comparison between the environmental impacts of different ORC’s working fluids also suggested against the usage of R227ea while R152a showed promising results to be used in the system. The size and weight study also revealed that the battery benefits from the lowest volume and weight in comparison to the other components. Among the considered components in this study, the SOFC unit and the PEME have by far the highest volume.

Model Based Comparative Analysis of GDC and YSZ Based Solid Oxide Fuel Cells

Although solid oxide fuel cells (SOFC) offer high fuel-to-electric energy conversion efficiencies, their relatively low power-to-weight ratios make it difficult to integrate them with aircraft propulsion systems. This paper explores the feasibility of designing high throughput SOFCs for hybridization with gas turbines in aircraft powerplants. This paper explores and compares two SOFC technologies for achieving high specific power (kW/kg) with different membrane electrode assembly architectures, one with thin-film yttria-stabilized zirconia (YSZ) electrolytes and the second with high-power density gadolinia doped-ceria (GDC) electrolytes. The studies explore the operation of the respective SOFC stacks with synthetic CH4 as a carbon-neutral aviation fuel. Down-the-channel SOFC models are calibrated to experimental measurements of YSZ- and GDC-electrolyte cells at Elcogen and at the University of Maryland respectively. The model results provide a basis for determining the flow inlet conditions that enable each cell type to achieve high specific powers. The results also indicate the requirement of high airflows and upstream fuel preprocessing to sustain the high specific powers with sustainable cell operating conditions.