Commercial Solid Oxide Fuel Cells Research Articles

A comprehensive survey of artificial intelligence-based techniques for performance enhancement of solid oxide fuel cells: Test cases with debates

Since installing solid oxide fuel cells (SOFCs)-based systems suffers from high expenses, accurate and reliable modeling is heavily demanded to detect any design issue prior to the system establishment. However, such mathematical models comprise certain unknowns that should be properly estimated to effectively describe the actual operation of SOFCs. Accordingly, due to their recent promising achievements, a tremendous number of metaheuristic optimizers (MHOs) have been utilized to handle this task. Hence, this effort targets providing a novel thorough review of the most recent MHOs applied to define the ungiven parameters of SOFCs stacks. Specifically, among over 300 attempts, only 175 articles are reported, where thirty up-to-date MHOs from the last five years are comprehensively illustrated. Particularly, the discussed MHOs are classified according to their behavior into; evolutionary-based, physics-based, swarm-based, and nature-based algorithms. Each is touched with a brief of their inspiration, features, merits, and demerits, along with their results in SOFC parameters determination. Furthermore, an overall platform is constructed where the reader can easily investigate each algorithm individually in terms of its governing factors, besides, the simulation circumstances related to the studied SOFC test cases. Over and above, numerical simulations are also introduced for commercial SOFCs’ stacks to evaluate the proposed MHOs-based methodology. Moreover, the mathematical formulation of various assessment criteria is systematically presented. After all, some perspectives and observations are provided in the conclusion to pave the way for further analyses and innovations.

Hydrothermal synthesis of zirconia doped with naturally mixed rare earths oxides and their electrochemical properties for possible applications in solid oxide fuel cells

Solid oxide fuel cells (SOFC) are electrochemical conversion devices that produces electricity directly from oxidizing a fuel and their development became of high importance to drastically reduce the greenhouse emission. Rare earth elements (REEs) are widely used as materials and dopants in controlling the ionic conductivity of solid electrolytes for SOFCs. Their criticality and high costs for separation to individual REEs lead to first studies aiming to search possible use of mixed REEs with natural occurrence as extracted from concentrates. This paper focused on obtaining sintered pellets based on zirconia doped with natural mixture of REEs extracted from monazite and study their microstructure, impedance spectra and dielectric properties vs. operating temperatures to assess their potential applications as solid electrolyte. ZrO2 doped powders with 8% natural mixture of REEs (8ZrMZ) were synthesized by hydrothermal process. ZrO2 doped with 4% Y2O3 (4ZrY) and 8%Y2O3 (8ZrY) were also obtained by the same route and used as standard materials already used in commercial SOFCs. All powders were uniaxially pressed and sintered in air, with highest densities obtained for 1400 °C. The Niquist diagrams for 8ZrMZ samples show significantly lower ionic conductivity compared to standards 4ZrY and 8 ZrY. This may be attributed to the presence of detrimental Fe and Si impurities following the mixed REE after Th and U removal from monazite concentrates and the ratio of REEs in the dopant composition affecting the ionic conductivity due to possible association of structural defects. Research works are further needed to improve the receipt for using naturally mixed REEs and asses their possible use as a competitive dopant for solid electrolytes.

The Performance of Solid Oxide Fuel Cells Based on Methanol Solution

The availability of hydrocarbon fuel is a unique advantage of solid oxide fuel cells (SOFCs). Methanol is one of the good choices for SOFC fuel because of its wide source, large output and easy storage and transportation. Methanol generally needs the steam reforming process before being used in SOFCs. In this paper, methanol reforming products under different steam-to-carbon ratio and temperature were tested on a commercial reforming equipment. Composition was compared with thermodynamic calculation results. The results show that when the temperature is below 700℃, a large deviation between components and thermodynamic calculation exists, indicating that methanol conversion is incomplete. When the temperature is above 700℃, methanol conversion is generally complete, and the temperature has little effect on the composition under this situation, while the steam-to-carbon ratio becomes the main influence factor. The hydrogen proportion in the products increases with the decrease of the steam-to-carbon ratio. A group of reforming products components were selected and tested on a commercial SOFC, and good performance was obtained, indicating the effectiveness of the optimization, which provides a research basis for the future application of methanol in SOFCs.

An efficient multi-point impedance method for real-time monitoring the working state of solid oxide fuel cells

During the practical operation of commercial solid oxide fuel cells (SOFCs), it is significant and urgent to implement a non-destructive and timely diagnosis of performance degradation. However, the method, which can completely fulfill the above requirements, is still not available. This study presents a novel approach, the multi-point impedance (MPI) method, which enables in-situ and real-time monitoring of the operating state of commercial SOFCs. The method involves two critical steps: the determination of characteristic frequencies using the distribution of relaxation time (DRT) and the selection of reference frequencies for calculating impedances. The reliability of the MPI method is evaluated both theoretically and experimentally. The results of theoretical investigation reveal that the MPI method can accurately estimate the resistances of resistance-capacitance (RC) components. Subsequently, the MPI method is employed to monitor the working state of commercial microtubular SOFCs (MT-SOFCs) during the stability test. The experimental results show that by using the MPI method, the impact of different electrochemical processes on the durability of MT-SOFCs can be clearly clarified. Combining the theoretical and experimental studies, it demonstrates that the MPI method can serve as an efficient and simple diagnostic approach for real-time monitoring SOFCs.

The Performance of Solid Oxide Fuel Cells Based on Methanol Solution

Methanol generally needs a steam reforming process before being used in solid oxide fuel cells (SOFCs). This paper calculated and tested the composition of methanol reforming gas under different steam-to-carbon ratio (S/C ratio) and temperature. Results show that when the temperature is between 720°C and 820°C, experiment results are almost consistent with calculation results. When the temperature is around 620°C, a significant deviation exists between the experiment and calculation results, indicating that methanol conversion is incomplete. When the S/C ratio needs to be higher than 1.2 due to the equipment's limit, the appropriate reaction condition is 725°C and S/C ratio of 1.2. Methanol reforming gas under this condition was tested on a commercial SOFC. The peak power is 39.31W under 750°C and 46.97W under 800°C. The highest electrical efficiency reaches 52.4% when fuel utilization is 80%. These results provide a research basis for the future application of methanol in SOFCs.

Numerical and experimental assessment of a novel SOFC-based system for micro-power generation

In this work, a novel micro-scale system based on solid oxide fuel cells (SOFCs) is studied for operation at low temperature, assessing the expected performance numerically and the actual cell operation experimentally. The potential application is powering gas-connected but off-electric-grid remote electronic devices with nominal capacity of tens of watts, such as those necessary to monitor and operate the gas grid, using methane as feed. Since water is generally not available in such distributed uses, feed pre-treating is critical and poses technical challenges for the high and stable performance of the SOFC. Several promising design configurations for the system are defined. The use of commercial YSZ-based SOFCs is envisioned, and recirculation is needed to avoid carbon deposition, which is predicted by the calculation of carbon activity and confirmed by the experimental observations. A higher anodic recirculation is required at low (≤50%) fuel utilization in order to decrease the estimated carbon activity, due to a lower content of oxygen atoms in the anode outlet stream. The anode inlet composition was numerically estimated assuming a fuel utilization factor of 70% with 60% anodic recirculation, then was experimentally tested, achieving a stable power generation without carbon deposition.

Optimization of a 30 kW SOFC combined heat and power system with different cycles and hydrocarbon fuels

Solid oxide fuel cells (SOFCs) could generate power cleanly and efficiently by using a wide range of fuels. Through the recovery and utilization of the energy in the SOFC tail gas, SOFC combined heat and power (CHP) systems achieve efficient cascade utilization of fuels. In this article, an efficient 30 kW SOFC CHP system with multiple cycles is designed based on a commercial kw-level SOFC device. The energy and substances could be recycled at multiple levels in this system, which makes the system do not need external water supply anymore during working. Meanwhile, the performance, fuel applicability, flexibility and reliability of the system are investigated. Finally, an optimized operating condition is confirmed, in which the electrical efficiency is 54.0%, and the thermoelectric efficiency could reach 88.8% by using methanol as fuel.

Energy Agility for Space Vehicle Applications Enabled by Bipropellant Consuming Solid Oxide Fuel Cells

The difficulty and cost of deploying space assets coupled with the variety of operations a space vehicle may be tasked to perform, the range of challenges a space vehicle may face, and the extended duration a space vehicle is often expected to operate without servicing make it desirable to create robust space vehicles that are capable of adapting to evolving circumstances or mission requirements. To help realize this vision, a research effort was begun to develop low profile Solid Oxide Fuel Cells (SOFCs) that can be used to generate electricity, on demand, by consuming fuel and oxidizer used in bipropellant thrusters for on-orbit maneuvering and station keeping. Developing a fuel cell to pair with a bipropellant thruster is of interest as such a combination can allow satellite operators to utilize the fuel and oxidizer stowed onboard a spacecraft equipped with a bipropellant thruster to generate electricity if the need arises. Moreover, creating such a fuel cell using solid oxide technology is of interest as the high operating temperature of SOFCs make them less susceptible to poisoning by contaminants which can be found in reactant flows, the nature of SOFCs make them easily customizable to meet specific electrical needs, and the large amount of energy which can be stowed in chemical storage tanks that can be subsequently converted into electricity by SOFCs can enable a spacecraft loaded with bipropellant chemicals to operate without tapping any other sources of energy for extended periods of time. Results from this work indicate that fuel cells assembled using commercial SOFC components designed to run on hydrogen (H2) and oxygen (O2) are often also effective at generating electricity by consuming fuels and oxidizers under consideration as green alternatives to the hazardous hydrazine (N2H4) fuel and nitrogen tetroxide (N2O4) oxidizer pair commonly used in on-orbit bipropellant thrusters. In this presentation, how fuel cells made with commercial components performed when fed different fuel and oxidizer combinations, each suitable for use in bipropellant thrusters, and the implications of these performances on efforts to create space deployable bipropellant driven SOFCs will be detailed.

Optimizing Solid Oxide Fuel Cell Performance to Re-evaluate Its Role in the Mobility Sector.

A sustainable, interconnected, and smart energy network in which hydrogen plays a major role cannot be dismissed as a utopia anymore. There are vast international and industrial ambitions to reach the envisioned system transformation, and the decarbonization of the mobility sector is a central pillar comprising a huge economic share. Solid oxide fuel cells (SOFCs) are one of the most promising technologies in the brigade of clean energy devices and have potentially wide applicability for transportation, due to their high efficiencies and impurity tolerance. To uncover future pathways to boost the cell's performance, we propose a detailed multiscale modeling methodology to evaluate the direct impact of cell materials and morphologies on commercial-scale system performance. After acquiring intrinsic electrokinetics decoupled from mass and charge transport of different anode and cathode materials via a half-cell model, a full cell model is employed to identify the most promising electrode combination. Subsequently, a scale-up to the system level is performed by coupling a 3-D kW-stack model to the balance of plant components while focusing on morphological optimization of the membrane electrode assembly (MEA). On optimally tailoring the MEA, model results demonstrate that an advanced cell design comprising a Ni fiber-CGO matrix structured anode and a LSCF-infiltrated CGO cathode could reach a stack power density of 1.85 kW L-1 and a net system efficiency of 52.2% for operation at <700 °C, with manageable stack temperature gradients of <14 K cm-1. The model-optimized power density is substantially higher than those of commercial stacks and surpasses industrial targets for SOFC-based range extenders. Thus, with further cell and stack development targeting the performance limiting processes elucidated in the paper, commercial SOFCs could, alongside range extenders, also act as prime movers in larger scale transport applications such as trucks, trains, and ships.

Nanoscale Analysis of LSM/YSZ Interfaces within Composite Cathodes for Commercial Solid Oxide Fuel Cells

While performance degradation for solid oxide fuel cells (SOFCs) comes in many forms, one important contributor is cation transport during long-term operation. This transport alters the chemical composition at electrode/electrolyte interfaces. These interfaces are carefully engineered to provide the critical reaction sites for oxidation and reduction reactions that regulate SOFC electrical production. Therefore, fundamental understanding of the chemical evolution of these interfaces is critical. The current study coordinates scanning transmission electron microscopy (STEM) with atom probe tomography (APT) in order to probe composition at the nanoscale across cathode/electrolyte interfaces for anode-supported commercial SOFCs. These SOFCs contain a porous composite cathode layer, consisting of sintered (La0.8Sr0.2)0.95MnO3 cathode particles and yttria-stabilized zirconia (YSZ) electrolyte particles. SOFCs are operated up to 500 hours in duration at a current density of 0.75 A/cm2 (or at open circuit) and at an operation temperature of 800°C. Measured cell voltage increases over the first 100 hours of operation, followed by a steady and linear drop in cell voltage that translates to 5.35% performance loss per 1000 hours. STEM-based energy dispersive spectroscopy (EDS) indicates nanoscale Mn-oxide formation at LSM particle surfaces after 500 hours of operation. Compositional profiles acquired by APT across LSM/YSZ particle interfaces indicate as-sintered interfaces are chemically well-defined, but La and Mn penetrate up to 5 nm into YSZ particles over the course of 500 hours. Additionally, as-sintered LSM particles exhibit measurable Mn enrichment within 20 nm of an adjacent YSZ particle. After 100 hours of operation, A-site deficiency is restored for LSM particle surfaces adjacent to YSZ. Meanwhile, the YSZ composition adjacent to LSM exhibits depletion in Y content over the first 100 hours of operation. These results suggest that initial cell voltage increase within 100 hours of operation corresponds to both Mn and Y transport at LSM/YSZ interfaces. STEM-based electron energy loss spectroscopy (EELS) provides additional insight regarding local cation valence states in relation to measured composition variations for these LSM/YSZ interfaces.

Selection of Highlights of the European Project Next Generation Solid Oxide Fuel Cell and Electrolysis Technology – NewSOC

Solid oxide technologies (SOC: Solid oxide fuel cells SOFC & Solid oxide electrolysis SOE) are key enabling technologies for energy systems based on renewable sources and allow for a strong interlinking of sectors electricity, heat, and gas/fuels. SOC can emerge as key players in many concepts, such as fuel/gas to power and heat at small to large scale,energy storage through power to hydrogen/fuel,utilization and upgrading of biogas,balancing of intermittent electricity from renewable sources through load following and reversible operation, andcentral and decentral solutions for electricity and heat production. In a time, where first SOC systems enter demonstration and commercial markets, the NewSOC project focusses on next generations. It aims at significantly improving performance, durability, and cost competitiveness of solid oxide cells & stacks compared to state-of-the-art (SoA). In order to achieve these goals, NewSOC investigates twelve innovative concepts in the following areas: (i) structural optimization and innovative architectures based on SoA materials, (ii) alternative materials, which allow for overcoming inherent challenges of SoA, (iii) innovative manufacturing to reduce critical raw materials and reduction of environmental footprint at improved performance & lifetime. The NewSOC unifies competences of 16 strong research and industry players. First scientific highlights were achieved despite the challenging working conditions under the European wide covid-19 restrictions in the first year of the project. The presentation will provide a selection of these highlights.One focus area is the development of novel electrode materials, where high performance, impurity tolerance and stability are the primary targets. Nanostructured fuel electrodes based on doped SrTiO3 perovskites such as LaSrFeNiTiO3 are being developed as backbones. Subsequent, wet infiltration of Ni:GDC ensures high electro catalytic activity and ionic conductivity, while retaining the advantages of Ni-metal free fuel electrodes outlined above. Furthermore, a class of doped lanthanum chromites (La0.75Sr0.25CrxM1-xO3-δ, M=Fe, Mn, Ni) is developed as Ni-metal free fuel electrodes, to overcome the challenges faced by the SoA Ni-cermets. The perovskite structured electrodes, combined with highly conductive electrolytes have high performance, low ASR and flexibility in various operating modes (SOEC, rSOC). The most attractive feature of this class of electro catalysts is that they retain their properties (oxidative state, conductivity) in reducing and oxidizing environments at SOC operating temperatures, even in absence of a reducing agent, i.e. H2.Another approach is to modify SoA electrodes. Commercial (SoA) Ni/GDC was modified with iron by deposition – precipitation (D.P.), leading to enhanced performance as functional SOE fuel electrode. The promoting effect depends on the wt.% Fe content, where D.P. of quite a small amount of iron, through the formation of a Ni-Fe alloy, caused a 3-fold enhancement compared to Ni/GDC. Interestingly, the 0.5-Fe-Ni/GDC electrode performed similarly well like the noble-metal modified 3Au-0.3Mo-Ni/GDC.Materials compositions and structuring go hand in hand for tailoring cell properties. Under this focus, novel air electrode architectures for SOFC & SOE applications based on Co- and Ni-free materials with the (La, Ca, Sr)FeO3 perovskite class of materials are developed. The typically increased overpotential of Co- and Ni-free air electrodes is a challenge, which is tackled by introduction of a patterned porous barrier layer and addition of a composite layer at the electrode/electrolyte interface to enhance the triple phase boundary density between electrolyte and the Co-free air electrode. In another approach, the microstructure of SoA Ni/YSZ and LSCF/GDC electrodes was assessed to identify the best tradeoff between the cell performances, the durability and the robustness by a methodology coupling of manufacturing, characterization, and modeling. As a result, the performance of the LSCF/GDC composite electrode was improved, with different porosities, graded electrodes and composites. The role of the Ni/YSZ microstructure on the Ni migration during operation was investigated, with focus on finer and more homogeneous electrodes.Manufacturing and deposition methods contribute significantly to performance & lifetime, but also costs and environmental impact of SOC production. Thus, alternative approaches providing cells & stacks with required specifications are part of the NewSOC project. Progress on sputter deposited GDC buffer layers has been obtained in view of their implementation in the fabrication process of commercial Solid Oxide Fuel Cells.

Nanoscale Analysis of LSM/YSZ Interfaces within Composite Cathodes for Commercial Solid Oxide Fuel Cells

Atom probe tomography (APT) was utilized to probe composition at the nanoscale across cathode/electrolyte interfaces for anode-supported commercial SOFCs. These SOFCs contained a porous composite cathode layer, consisting of sintered (La0.8Sr0.2)0.95MnO3 (LSM) and yttria-stabilized zirconia (YSZ). SOFCs were operated up to a 500 h duration at a 0.75 A/cm2 current density and 800°C. The measured cell voltage increased over the first 100 hours of operation, followed by a steady and linear drop in cell voltage that translated to a 5.35% performance loss per 1000 h. Cation migration behavior was extrapolated through comparisons of compositional profiles acquired by APT across LSM/YSZ particle interfaces for as-sintered, operated, and thermally aged conditions. The results show that operation drives La/Sr away from the LSM nanoparticle surface and Y depletion at the YSZ nanoparticle surface. Energy dispersive spectroscopy (EDS) inside a scanning transmission electron microscope (STEM) provided additional insights regarding Mn aggregation behavior during operation.

Assessment of ammonia as energy carrier in the use with reversible solid oxide cells

Ammonia represents one of the most promising potential solutions as energy vector and hydrogen carrier, having a higher potential to transport energy than hydrogen itself in a pressurized form. Furthermore, solid oxide fuel cells (SOFCs) can directly be fed with ammonia, thus allowing for immediate electrical power and heat generation. This paper deals with the analysis of the dynamic behavior of commercial SOFCs when fueled with ammonia. Several measurements at different temperatures have been performed and performances are compared with hydrogen and a stoichiometrically equivalent mixture of H2 and N2 (3:1 M ratio). Higher temperature led to smaller drops in voltage for both fuels, thus providing higher efficiencies. Ammonia resulted slightly more performant (48% at 760 °C) than hydrogen (45% at 760 °C), in short stack tests. Moreover, different ammonia-to-air ratios have been investigated and the stack area-specific resistance has been studied in detail by comparing numerical modeling predictions and experimental values.

The Role of Bi-Polar Plate Design and the Start-Up Protocol in the Spatiotemporal Dynamics during Solid Oxide Fuel Cell Anode Reduction

Start-up conditions largely dictate the performance longevity for solid oxide fuel cells (SOFCs). The SOFC anode is typically deposited as NiO-ceramic that is reduced to Ni-ceramic during start-up. Effective reduction is imperative to ensuring that the anode is electrochemically active and able to produce electronic and ionic current; the bi-polar plates (BPP) next to the anode allow the transport of current and gases, via land and channels, respectively. This study investigates a commercial SOFC stack that failed following a typical start-up procedure. The BPP design was found to substantially affect the spatiotemporal dynamics of the anode reduction; Raman spectroscopy detected electrochemically inactive NiO on the anode surface below the BPP land-contacts; X-ray computed tomography (CT) and scanning electron microscopy (SEM) identified associated contrasts in the electrode porosity, confirming the extension of heterogeneous features beyond the anode surface, towards the electrolyte-anode interface. Failure studies such as this are important for improving statistical confidence in commercial SOFCs and ultimately their competitiveness within the mass-market. Moreover, the spatiotemporal information presented here may aid in the development of novel BPP design and improved reduction protocol methods that minimize cell and stack strain, and thus maximize cell longevity.

Materials and nano-structural processes for use in solid oxide fuel cells: a review

Solid oxide fuel cells (SOFCs) are considered to be the focus of investigation for energy systems owing to their efficiency in converting chemical energy into electrical energy, low carbon footprint, and fuel flexibility. Despite their high performance and durability, SOFCs suffer from critical problems such as carbon coking, agglomeration, and poor redox stability. This review presents research on the development of nanostructures for use in commercial SOFC systems and highlights various aspects of research and applications across the globe. The materials utilized for anodes, electrolytes, and cathodes are discussed and compared, detailing how their respective properties can attain high catalytic activity, conductivity, and stability at low temperatures with the aim of direct application using diverse fuels such as hydrogen, hydrocarbons, and carbon fuels. This review also discusses and compares the various processes used for the synthesis of the electrodes and electrolytes used in SOFCs, such as physical vapor deposition (PVD), chemical vapor deposition (CVD), infiltration, and in situ exsolution, that have gained much attention with a view to increase the active areas, decrease the Ohmic resistance, and reduce the manufacturing price.

Enhancing Activity, Charge Transport, Power Production, and Stability of Commercial Solid Oxide Fuel Cells with Yttria-Stabilized Zirconia Nanoparticles

Interconnected networks of 10–30 nm yttria-stabilized zirconia (YSZ) nanoparticles dramatically enhance both the electrocatalytic activity and bulk charge transport of commercial lanthanum strontium manganite (LSM)-YSZ solid oxide fuel cell (SOFC) cathodes. The improvement in both electrode functions increases the maximum power density of the commercial SOFC by 90%. In comparison, modifying cathodes with lanthanum strontium cobalt ferrite (LSCF) and praseodymium barium cobaltite (PBC) nanoparticles, highly active catalysts with mixed ionic-electronic conductivity (MIEC), only enhances electrocatalytic activity. The combination of dual enhanced electrode functions with nanoYSZ results in a maximum power density that is 50% and 11% higher than LSCF and PBC, respectively. Finally, the performance stability over time is highest for nanoYSZ modified cells.

Applicability of the SOFC technology for coupling with biomass-gasifier systems: Short- and long-term experimental study on SOFC performance and degradation behaviour

Coupling biomass gasification with high temperature Solid Oxide Fuel Cells (SOFCs) is a promising solution to increase the share of renewables and reduce emissions. The quality of the producer gas used can, however, significantly impact the SOFC durability and reliability. The great challenge is to ensure undisturbed operation of such system and to find a trade-off between optimal SOFC operating temperature and system thermal integration, which may limit the overall efficiency. Thus, this study focuses on experimental investigation of commercial SOFC single cells of industrial size fueled with different representative producer gas compositions of industrial relevance at two relevant operating temperatures. The extensive experimental and numerical analyses performed showed that feeding SOFC with a producer gas from a downdraft gasifier, with hot gas cleaning, at an operating temperature of 750 °C represents the most favorable setting, considering system integration and the highest fuel utilization. Additionally, a 120 h long-term test was carried out, showing that a long-term operation is possible under stated operating conditions. Local degradation took place, which can be detected at an early stage using appropriate online-monitoring tools.

Atomic Layer Deposition to Design Internal Surface of Porous Electrode for Accelerating Charge and Mass Transfer in Fuel Cells

The inadequate catalytic activity and conductivity from the porous electrode hinder the power density of the ceramic fuel cells operated at high temperatures. For the first generation Solid Oxide Fuel Cells (SOFCs) with yttria stabilized zirconia (YSZ) electrolyte, the present work employs atomic layer deposition (ALD) and implanted nanoscale eletrocatalysts on the internal surface of the composite cathode consisting lanthanum strontium manganite and YSZ. Upon electrochemical operation, the ALD layer with optimized nanostructure develops into a nano-porous uniform and conformal heterostructured electrochemical active percolating network, provides additional charge and mass transfer pathways, and subsequently extends the electrochemical active area from the original localized triple phase boundaries (TPBs) to the entire internal surface of porous cathode. For the as-fabricated commercial SOFCs, such ALD coating of LSM/YSZ cathode resulted in a large reduction of cell polarization resistance by up to over 50 % and an enormous increase of cell peak power density by over 300 %, which is significantly outperforming that of the state-of-the-art SOFCs with mixed ionic and electronic conducting cathode.

Optimization of an integrated biomass gasifier-fuel cell system: An experimental study on the cell response to process variations

Coupling biomass gasification with high temperature Solid Oxide Fuel Cells (SOFCs) is a promising solution to increase the share of renewables and raise energy efficiency. Optimal system integration and high durability of its components are both required for this purpose. Moreover, system optimization may ask for a compromise between optimal SOFC operating temperature and system thermal integration. Nevertheless, the producer gas quality and operating temperature have a noticeable impact on SOFC performance, which has to be considered.In order to address the challenges mentioned, this study focuses on experimental investigation of commercial SOFC single cells of industrial size fuelled with different gas mixtures. Namely, typical producer gas compositions from downdraft fixed bed gasification with air (with and without drying) and fluidized bed gasification with steam are considered. In addition to that, the effect of temperature variation is analysed. The results show that, although a higher cell temperature (800°C) and a dry product gas composition lead to higher efficiencies, it is feasible to run the SOFC on wet producer gas at lower cell temperatures (750°C). Despite a decreased efficiency, this would optimize the gasifier-SOFC coupling. Moreover, the presence of water in the producer gas (when drying is not included) reduces the possibility of carbon deposition, thus increasing the cell durability. Therefore, cases with low cell temperatures and presence of water in the gas should be considered as viable alternatives for the system coupling and possible SOFC degradation in such cases is going to be extensively analysed.

Comparative environmental profile assessments of commercial and novel material structures for solid oxide fuel cells

Globally, the issue of climate change due to greenhouse gas (GHG) emissions is now broadly acknowledged as one of the major challenges facing humankind that requires urgent attention. Accordingly, considerable efforts on clean energy technologies and policy recommendations have been developed to address this challenge. Solid oxide fuel cells (SOFCs) have been touted to play a role in achieving a reduction in global GHG emissions, offering numerous advantages including higher efficiencies and reduced emissions, over other conventional methods of energy generation. The increasing recognition and emphasis on fuel cells as a representative power generation system of the future has raised concerns over their environmental profile. Extensive research regarding the environmental profile of current structures of SOFCs can be found in the literature, but none consider the use of new materials to achieve lower environmental impacts. This research fills the gap and presents a comparison of the environmental profile of three SOFC structures: a commercially available structure, and two intermediate temperature structures, one using erbia-stabilised bismuth oxide electrolytes and a proposed structure using strontium-doped sodium bismuth titanate electrolytes. Using a functional unit of kg/100 kW of power output for each of the SOFC structures (excluding the interconnects), within a hybrid life cycle analysis framework, the environmental hotspots across the supply chains of each SOFC type are identified, quantified and ranked. The results show the use of these novel material combinations leads to a reduction in embodied materials and toxicological impact but higher electrical energy consumption during fabrication, in comparison to commercial SOFCs. The findings support the move to reduce the operating temperatures of SOFCs using these novel material architectures, which leads to an overall reduction in environmental impact due to the lower operational energy requirement of the chosen material constituents.