Investigation of Ni-coated-steel-meshes as alternative anode contact material to nickel in an SOFC stack

Solid oxide fuel cell is a promising technology to convert renewable energy sources to electricity electrochemically at high efficiencies, thus an important applied research topic worldwide. The in-house developed so-called F-stack-design aims at stationary applications and can achieve a very long lifetime. However, since production costs should be reduced, one research focus lies on finding suitable less expensive materials. Therefore, alternatives for the benchmark Ni-mesh as anode contacting element in the stack were studied. Several types of Ni-coated-steels were tested in a stack. After 3000 h of operation the different anode contact materials are compared with the Ni-mesh in terms of microstructure as well as chemical composition. A discussion of the results is given.     

3D multiphysics modeling aided APU development for vehicle applications: A thermo-structural investigation

Solid oxide fuel cells (SOFC) are suitable for on-board electricity generation as Auxiliary Power Unit (APU) to support the electric power supply in heavy-duty vehicles. In order to satisfy the requirements of a lightweight fuel cell stack for mobile applications, thin-walled components must be used for the stack structure. This necessity is associated with material, process and design difficulties that must be solved in order to achieve a successful utilization. In this work a novel lightweight SOFC stack design with metal-supported cell was studied both numerically and experimentally. The metallic components are made from the Intermediate Temperature Metal (ITM), a high performance, high chromium ferritic stainless steels alloy. The multiphysics modeling approach (fluid dynamics, heat transfer, structural mechanics) was utilized in this work to predict the temperature distribution and the thermo-structural behavior of the new developed design. Geometric details of the fuel cell stack components as well as appropriate nonlinear, temperature and time-dependent constitutive models were developed to describe the material behavior. Experimental data were used to determine the material model parameters and validated the simulation results. The three-dimensional stress and deformation distributions in the individual stack components were evaluated and their maximum values for elements at risk were identified. Thus, the developed model enables the investigation of sustainability and serviceability of the structural elements to ensure a reliable operation of the stack. The developed computational model can be used as a design tool for parametric studies and optimization analysis to investigate the effects of process boundary conditions, material properties as well as geometrical design parameters and their variation on the induced thermal stresses.     

Analysis of air conditioning system impact on a fuel cell vehicle performance based on a realistic model under actual urban conditions

In this study, a practical fuel cell vehicle considering the Heating, Ventilation, and Air conditioning system is considered to analyze hydrogen consumption under different working conditions. As a prevalent hydrogen-fueled vehicle, Toyota Mirai has been meticulously modeled in Simecenter Amesim software. The simulated model covers all of the vehicle's components with a concentration on Heating, Ventilation, and Air conditioning system. Since the air temperature and ‘weather conditions can significantly impact the vehicle's overall performance, various environmental conditions, including temperature variations, humidity, and varied solar fluxes, are taken into account. Furthermore, New York City is chosen as a densely populated megacity to simulate the dynamic behavior of the fuel cell vehicle under actual driving circumstances. The results illustrate that the Heating, Ventilation, and Air conditioning system can notably alter hydrogen consumption under real driving conditions. In this regard, turning on the Heating, Ventilation, and Air Conditioning system results in a 19% increase in fuel consumption. Moreover, the degradation phenomenon, which is a typical result of using fuel cell vehicles under urban driving conditions, impacts the vehicle's mileage and hydrogen consumption. The simulation results indicate that a fresh fuel cell stack consumes 80 g of hydrogen, while for 2500 and 5500 working hours fuel cells, the stack consumes 89.6 and 107 g of hydrogen, respectively. Based on the obtained results, a 33.75% increase in fuel consumption occurs by implementing a degraded fuel cell stack under real driving conditions.     

Numerical study of cold start performance of proton exchange membrane fuel cell with coolant circulation

It has been well recognized that cold start is one of the key issues of proton exchange membrane fuel cell (PEMFC) used as the engine of vehicles. Coolant circulation is usually launched synchronously with the fuel cell during cold start to avoid sudden large temperature variation, which greatly increases the cell thermal mass, lowers the heating rate, and worsens the cell performance. Considering the flow and heat transfer of coolant circulation, a three-dimensional, transient, multi-disciplinary model for cold start is built up. The numerical results agree reasonably well with experimental data, indicating that the model can be used for the investigation of PEMFC cold start processes. The analysis of circulation parameter effects shows that increasing the coolant flow rate or coolant tank capacity has little influence on the cell voltage, but will increase the non-uniformity of temperature distribution along flow direction. At lower start-up temperature, this non-uniformity is more obvious. With higher coolant flow rate, although the distribution of current density becomes more evenly, the ice formation amount increases and its distribution and location are greatly affected.     

On the economics of a hydrogen bus fleet powered by a wind park – A case study for Austria

This paper investigates the economics of a fuel cell bus fleet powered by hydrogen produced from electricity generated by a wind park in Austria. The main research question is to simultaneously identify the most economical hydrogen generation business model for the electric utility owning wind power plants and to evaluate the economics of operating a fuel cell bus fleet, with the core objective to minimize the total costs of the overall fuel supply (hydrogen production) and use (bus and operation) system. For that, three possible operation modes of the electrolyzer have been identified and the resulting hydrogen production costs calculated. Furthermore, an in-depth economic analysis of the fuel cell buses as well as the electrolyzer technology has been conducted. Results show that investment costs are the largest cost factor for both technologies. Thus, continuous hydrogen production with the smallest possible electrolyzer is the economically most favorable option. In such an operation mode (power grid), the costs of production per kg/H₂ were the lowest. However, this means that the electrolyzer cannot be solely operated with electricity from the wind park, but is also dependent on the electricity mix from the grid. For fuel cell buses, the future cost development will depend very much on the respective policies and funding programs for the market uptake, as to date, the total cost of use for the fuel cell bus is more than two times higher than the diesel bus. The major final conclusion of this paper is that to make fuel cell electric busses competitive in the next years today severe policy interferences, such as subsidies for these busses as well as electrolyzers and bans for fossil energy, along with investments in the setup of a hydrogen infrastructure, are necessary.     

Biomass gasification coupled with producer gas cleaning,bottling and HTS catalyst treatment for H2-rich gas production

The aim of the present study is to demonstrate the production of hydrogen-rich fuel gas from J. curcas residue cake. A comprehensive experimental study for the production of hydrogen rich fuel gas from J. curcas residue cake via downdraft gasification followed by high temperature water gas shift catalytic treatment has been carried out. The gasification experiments are performed at different equivalence ratios and performance of the process is reported in terms of producer gas composition & its calorific value, gas production rate and cold gas efficiency. The producer gas is cleaned of tar and particulate matters by passing it through venturi scrubber followed by sand bed filter. The clean producer gas is then compressed at 0.6 MPa and bottled into a gas cylinder. The bottled producer gas and a simulated mixture of producer gas are then subjected to high temperature shift (HTS) catalytic treatment for hydrogen enriched gas production. The effect of three different operating parameters GHSV, steam to CO ratio and reactor temperature on the product gas composition and CO conversion is reported. From the experimental study it is found that, the presence of oxygen in the bottled producer gas has affected the catalyst activity. Moreover, higher concentration of oxygen concentration in the bottled producer gas leads to the instantaneous deactivation of the HTS catalyst.     

Review: Influence of alloy addition and spinel coatings on Cr-based metallic interconnects of solid oxide fuel cells

Solid oxide fuel cell (SOFC) is the modern eco-friendly technology of fuel cell power generation system. It generates electricity from a redox chemical reaction without producing hazardous gases. It consists of anode, cathode and electrolyte. It is operated in the form of stack connected by interconnects to boost-up power output. The recent development of low-temperature (600 °C–800 °C) brings an opportunity to use metallic interconnects over ceramics. Cr-based metallic interconnects are one of the prominent metallic interconnects. They offer chemical inertness, thermal stability, compatible coefficient of thermal expansion and highly dense structure. However, the Cr-migration towards the cathode side is the major problem in them which adversely affect the SOFCs performance. Therefore a good oxidation resistance without sacrificing electrical conductivity is required. To resolve this issue, several alloying elements and spinel coatings have experimented. These spinel coatings are the thin solid films of Mn, Co, Cu and rare earth metals. This review concluded that the Mn–Co based spinal coating showed excellent performance in reducing the Cr-migration in specially designed expensive Crofer 22 APU interconnect. However, the emerging low-cost ferritic interconnects also show their best results with Cu–Fe based spinel coating. Among them, the SUS-430 interconnect shows the equivalent performance of Crofer 22 APU interconnect after surface treatment and appropriate Cu–Fe based spinel coating. Therefore, it can replace the Crofer 22 APU interconnect on a cost basis.     

Proton-exchange membrane fuel cell ionomer hydration model using finite volume method

In this paper a dynamic membrane electrode assembly water transport model, based on the Finite Volume Method, is presented. The purpose of this paper is to provide an accessible and reproductible model capable of real time simulation. To this aim, a detailed explanation is provided regarding the equations and methods used to compute the physical-based fuel cell model. Additionally, the model is purposely developed using basic code (on Matlab?), to not be limited to a single programming language. Two phase water transport through multi-gaseous porous media (electrodes), interfacial transport, as well as diffusion, convection, and electro-osmosis within the polymer are considered. The main novelty relies in the restructuring of all equations into a single implicit system, which can iteratively be resolved through LU decomposition. This computationally efficient method allows the model to be capable of real-time simulation, by displaying the membrane water content profile evolution on a 3D figure. For nominal PEMFC operating conditions, a dry membrane reaches 35% of its final water concentration value after 2 s, and fully converges after 20 s. The final water content profile displays an 18% gradient (9 and 11 molecules per sulfonic acid sites on the anode and cathode sides, respectively). To calibrate and validate this model, mass transfer (flowmeter) and electrical (ohmmeter) methods have been applied.     

Improving inter-plant integration of syngas production technologies by the recycling of CO2 and by-product of the Fischer-Tropsch process

This paper deals with the emission reduction in synthesis-gas production by better integration and increasing the energy efficiency of a high-temperature co-electrolysis unit combined with the Fischer-Tropsch process. The investigated process utilises the by-product of Fischer-Tropsch, as an energy source and carbon dioxide as a feedstock for synthesis gas production. The proposed approach is based on adjusting process streams temperatures with the further synthesis of a new heat exchangers network and optimisation of the utility system. The potential of secondary energy resources was determined using plus/minus principles and simulation of a high-temperature co-electrolysis unit. The proposed technique maximises the economic and environmental benefits of inter-unit integration. Two scenarios were considered for sharing the high-temperature co-electrolysis and the Fischer-Tropsch process. In the first scenario, by-products from the Fischer-Tropsch process were used as fuel for a high-temperature co-electrolysis. Optimisation of secondary energy sources and the synthesis of a new heat exchanger network reduce fuel consumption by 47% and electricity by 11%. An additional environmental benefit is reflected in emission reduction by 25,145 tCO₂/y. The second scenario uses fossil fuel as a primary energy source. The new exchanger network for the high-temperature co-electrolysis was built for different energy sources. The use of natural gas resulted in total annual costs of the heat exchanger network to 1,388,034 USD/y, which is 1%, 14%, 116% less than for coal, fuel oil and LPG, respectively. The use of natural gas as a fuel has the lowest carbon footprint of 7288 tCO₂/y. On the other hand, coal as an energy source has commensurable economic indicators that produce 2 times more CO₂, which can be used as a feedstock for a high-temperature co-electrolysis. This work shows how in-depth preliminary analysis can optimise the use of primary and secondary energy resources during inter-plant integration.     

Cold-start icing characteristics of proton-exchange membrane fuel cells

Understanding the icing characteristics of proton-exchange membrane fuel cells (PEMFCs) is essential for optimizing their cold-start performance. This study examined the effects of start-up temperature, current density, and microporous layer (MPL) hydrophobicity on the cold-start performance and icing characteristics of PEMFCs. Further, the cold-start icing characteristics of PEMFCs were studied by testing the PEMFC output voltage, impedance, and temperature changes at different positions of the cathode gas diffusion layer. Observation of the MPL surface after cold-start failure allowed determination of the distribution of ice formation at the catalytic layer/MPL interface. At fuel cell temperatures below 0 °C, supercooled water in the cell was more likely to undergo concentrated instantaneous freezing at higher temperatures (−4 and −5 °C), whereas the cathode tended to freeze in sequence at lower temperatures (−8 °C). In addition, a more hydrophobic MPL resulted in two successive instantaneous icing phenomena in the fuel cell and improved the cold-start performance.     

Multilayer additive manufacturing of catalyst-coated membranes for polymer electrolyte membrane fuel cells by inkjet printing

Inkjet printing is a versatile, contactless and accurate material deposition technology. The present work is focused on developing innovative strategies for inkjet printing of Catalyst-Coated Membranes (CCM) by performing Additive Manufacturing (AM) applied to Polymer Electrolyte Membrane Fuel Cells (PEMFC), without resorting to intermediate substrates. Three different approaches for AM are presented and discussed: a) inkjet-printing of the membrane ionomer layer and the top catalyst layer; b) inkjet-printing of both catalyst layers onto a membrane; c) inkjet-printing of the ionomer layer as well as the catalyst layers onto the reinforcement layer of the membrane. The produced catalyst and membrane layers were characterized and proved uniform in terms of catalyst loading (0.2–0.4 and 0.08 mg_Pt cm^?2 for cathode and anode, respectively), ionomer distribution and thickness homogeneity (4 μm for catalyst layers). The fully inkjet-printed CCM outperformed conventionally made assemblies in electrochemical-performance testing, even reaching 15% higher power density.     

Graphite nanopowder functionalized 3-D acrylamide polymeric anode for enhanced performance of microbial fuel cell

3-D highly conductive polyvinyl formaldehyde sponges functionalized with acrylamide are fabricated using polyvinyl alcohol with varying concentrations of graphite nanopowder. The properties of the fabricated anodes are analyzed and its application in microbial fuel cells is evaluated. A comparative study with Graphite felt is also performed to evaluate its commercial viability. The presence of Hydroxyl and Amine functional groups enhanced the hydrophilic and biocompatible nature of the synthesized anodes. The phylogenetic analysis substantiated the biocompatible nature and mercury porosimetry showed macroporous nature of the fabricated anode. The highest power density of ~8 W/m² is recorded for C10 establishing solid biofilm formation. A ~94% COD removal revealed the versatility of the anode for MFC based wastewater treatment. The MFC performance was twice than that of control and was also highest among the most reported modified 3-D anodes. The durability study displayed the commercial opportunity of the anode for real-time MFC operation.     

Effect of manifold injection of hydrogen gas in producer gas and neem biodiesel fueled CRDI dual fuel engine

The high flammability of hydrogen gas gives it a steady flow without throttling in engines while operating. Such engines also include different induction/injection methods. Hydrogen fuels are encouraging fuel for applications of diesel engines in dual fuel mode operation. Engines operating with dual fuel can replace pilot injection of liquid fuel with gaseous fuels, significantly being eco-friendly. Lower particulate matter (PM) and nitrogen oxides (NO_x) emissions are the significant advantages of operating with dual fuel.Consequently, fuels used in the present work are renewable and can generate power for different applications. Hydrogen being gaseous fuel acts as an alternative and shows fascinating use along with diesel to operate the engines with lower emissions. Such engines can also be operated either by injection or induction on compression of gaseous fuels for combustion by initiating with the pilot amount of biodiesel. Present work highlights the experimental investigation conducted on dual fuel mode operation of diesel engine using Neem Oil Methyl Ester (NeOME) and producer gas with enriched hydrogen gas combination. Experiments were performed at four different manifold hydrogen gas injection timings of TDC, 5°aTDC, 10°aTDC and 15°aTDC and three injection durations of 30°CA, 60°CA, and 90°CA. Compared to baseline operation, improvement in engine performance was evaluated in combustion and its emission characteristics. Current experimental investigations revealed that the 10°aTDC hydrogen manifold injection with 60°CA injection duration showed better performance. The BTE of diesel + PG and NeOME + PG operation was found to be 28% and 23%, respectively, and the emissions level were reduced to 25.4%, 14.6%, 54.6%, and 26.8% for CO, HC, smoke, and NO_x, respectively.     

Natural aloe vera derived Pt supported N-doped porous carbon: A highly durable cathode catalyst of PEM fuel cell

Evolution of highly durable electrocatalyst for oxygen reduction reaction (ORR) is the most critical barrier in commercializing polymer electrolyte membrane fuel cell (PEMFC). In this work, Pt deposited N-doped mesoporous carbon derived from Aloe Vera is developed as an efficient and robust electro catalyst for ORR. Due to its high mesoporous nature, the aloe vera derived carbon (AVC) play a very vital role in supporting Pt nanoparticles (NPs) with N-doping. After doping N into AVC, more defects are created which facilitates uniform distribution of Pt NPs leading to more active sites towards ORR. Pt/N-AVC shows excellent ORR activity when compared with commercial Pt/C and showing a half wave potential (E_1/2–0.87 V Vs. RHE) and reduction potential (E_red ~ 0.72 V Vs. RHE) towards ORR. Even after 30,000 potential cycles, Pt/N-AVC shows in its E_1/2 only ~5 mV negative shift and lesser agglomeration of Pt NPs is seen in the catalyst. In membrane electrode assembly (MEA) fabrication, Pt/N-AVC as a cathode catalyst in a PEMFC fixture and performance were studied. The Pt/N-AVC shows good performance, which proves the potential application of this naturally available bio derived carbon, which serves as an excellent high durable support material in PEMFC. All these features show that the Pt/N-AVC is the most stable, efficient and suitable candidate for ORR catalyst.     

Economic valuation of green hydrogen charging compared to gray hydrogen charging: The case of South Korea

The South Korean government promotes hydrogen-powered vehicles to reduce greenhouse gas (GHG) emissions but these vehicles use gray hydrogen while charging, which causes GHG emissions. Therefore, converting this fuel into green hydrogen is necessary to help reduce GHG emissions, which will incur investment costs of approximately USD 20 billion over a decade. In this study, a contingent valuation method is applied in an analysis to examine the extent to which consumers are willing to pay for green hydrogen charging compared to gray hydrogen charging. The results indicate that the monthly mean of willingness to pay per driver is 51,674 KRW (USD 45.85), equivalent to 4302 KRW per kg (USD 3.82). Additionally, consumers accept a 28.5% increase in the monthly average fuel expenses when converting to green hydrogen. These findings can be used in the development of pricing and energy use plans to finance the expansion of green hydrogen infrastructure.     

Exergetic analysis of hydrogen utilisation pathways – Part 1: Energy supply in buildings

This article analyses exergy losses along hydrogen utilisation pathways recently discussed in Germany and other countries. As a renewable fuel hydrogen will be an important part of sustainable future economies. Hydrogen can be used in all sectors, especially in buildings, for mobility and in industry, e.g. in steel production or ammonia synthesis. However, hydrogen has to be produced in a sustainable way. The most promising production is via water electrolysis using renewable electricity. In the first part of this work, exergy analysis is made for the complete hydrogen pathways from production until final utilisation for energy supply in buildings. The second part will focus on pathways for mobility. In the third part, the results are compared with available alternatives to hydrogen such as direct use of electricity in building supply or mobility. The results for building energy supply show that firstly transportation in pipelines (mixture with natural gas and pure hydrogen) is very efficient. Secondly, major exergy losses are caused by the electrolyser. Thirdly, combustion of renewable hydrogen for room heating in common boilers cause the highest exergy losses, but the use of combined heat and power (CHP) units or fuel cells can improve the exergy efficiency substantially.     

Development of a hydrogen impurity analyzer based on mobile-gas chromatography for online hydrogen fuel monitoring

Hydrogen is an excellent alternative energy source, particularly for vehicles. Despite the expansion of a considerable number of infrastructures, such as hydrogen refueling stations, there is a lack of efficient inspection methods for monitoring the hydrogen fuel quality. In this study, a hydrogen impurity analyzer (HIA) based on mobile gas chromatography with a thermal conductivity detector is developed and evaluated for the quality assurance of hydrogen fuel. Accordingly, O₂, N₂, and Ar which help in monitoring air leaks at hydrogen refueling stations, and CH₄, which can also be detected by HIA, are selected as target impurities. The HIA reached limits of detection of 2.93, 0.72, 0.84, and 1.54 μmol/mol for O₂, Ar, N₂, and CH₄, respectively. Moreover, the ISO 14687 requirements are satisfied with respective HIA expanded uncertainties of 2.6, 8.7, 8.2, and 9.4% (coverage factor k = 2). The developed system is ISO-compliant and offers enhanced mobility for online inspections.     

Performance evaluation of a solarized gas turbine system integrated to a high temperature electrolyzer for hydrogen production

In this paper, the performance of a solar gas turbine (SGT) system integrated to a high temperature electrolyzer (HTE) to generate hybrid electrical power and hydrogen fuel is analyzed. The idea behind this design is to mitigate the losses in the electrical power transmission and use the enthalpy of exhaust gases released from the gas turbine (GT) to make steam for the HTE. In this context, a GT system is coupled with a solar tower including heliostat solar field and central receiver to generate electrical power. To make steam for the HTE, a flameless boiler is integrated to the SGT system applying the SGT extremely high temperature exhaust gases as the oxidizer. The results indicate that by increasing the solar receiver outlet temperature from 800 K to 1300 K, the solar share increases from 22.1% to 42.38% and the overall fuel consumption of the plant reduces from 7 kg/s to 2.7 kg/s. Furthermore, flameless mode is achievable in the boiler while the turbine inlet temperature (TIT) is maintained at the temperatures higher than 1314 K. Using constant amounts of the SGT electrical power, the HTE voltage decreases by enhancing the HTE steam temperature which result in the augmentation of the overall hydrogen production. To increase the HTE steam temperature from 950 K to 1350 K, the rate of fuel consumption in the flameless boiler increases from 0.1 m/s to 0.8 m/s; however, since the HTE hydrogen production increases from 4.24 mol/s to 16 mol/s it can be interpreted that the higher steam temperatures would be affordable. The presented hybrid system in this paper can be employed to perform more thermochemical analyses to achieve insightful understanding of the hybrid electrical power-hydrogen production systems.     

The economic feasibility study of a 100-MW Power-to-Gas plant

Power-to-Gas (PtG) is a grid-scale energy storage technology by which electricity is converted into gas fuel as an energy carrier. PtG utilizes surplus renewable electricity to generate hydrogen from Solid-Oxide-Cell, and the hydrogen is then combined with CO₂ in the Sabatier process to produce the methane. The transportation of methane is mature and energy-efficient within the existing natural gas pipeline or town gas network. Additionally, it is ideal to make use of the reverse function of SOC, the Solid-Oxide-Fuel-Cell, to generate electricity when the grid is weak in power. This study estimated the cost of building a hypothetical 100-MW PtG power plant with energy storage and power generation capabilities. The emphasis is on the effects of SOC cost, fuel cost and capacity factor to the Levelized Cost of Energy of the PtG plant. The net present value of the plant is analyzed to estimate the lowest affordable contract price to secure a positive present value. Besides, the plant payback period and CO₂ emission are estimated.     

Opimal design and 4E evaluation of a CCHP system using an improved version of weighted mean of vectors algorithm

Using CCHP systems (combined cooling, heating, and power) as an environmentally friendly and economical procedure of energy generation has taken a step towards cost reduction and proper management of energy sources in the contemporary era, due to the fact that the air pollution, energy crisis as well as its expensive supply has become an overarching problem. In this study, a novel method for the design optimization of a CCHP system is represented. The gas turbine used as the study's primary engine is intended for a rural setting in Guilin, China. Energetic, exergetic, environmental, and economic characteristics are the four key metrics used to evaluate the method's success. For higher accuracy and convergence, a new improved version of Weighted mean of vectors algorithm (IINFO) is used. In order to demonstrate the method's increased efficiency, the accomplishments of the recommended IINFO-based methodology are compared with those of the genetic and modified owl optimizers.