Stationary Power Research Articles

Effect of side dilution jets on the velocity field and mixing in swirl and bluff-body stabilised annular confined flows

Stationary and mobile power generation systems, as well as those for aero propulsion, continue to rely heavily on gas turbines. Operational envelopes which critically depends on (flame) jet stabilisation mechanisms, such as swirl, are also affected by considerations for emissions control. In this context, the evolving swirling flow domains feature injection of side (peripheral) dilution air. Despite this, the role of side dilution jets on modifying the flow, turbulence, and mixing fields of turbulent bluff-body (BB) stabilised (swirling) annular flows has not been investigated. This study uses three-dimensional simulations, supported with experimental data to establish boundary conditions, to investigate the interaction of side dilution jets (Red = 18,000) with both non-swirling (S = 0) and swirling (S = 0.3) turbulent BB stabilised annular flows (Res = 35,500). Constant Temperature Anemometry (CTA) measurements are conducted to resolve inlet boundary conditions. The Reynolds Stress Model (RSM) and species transport model (isothermal) are used with validations against benchmark datasets. Results show that the introduction of side dilution jets into a confined domain, whether swirling or not, induces (asymmetrical) Peripheral Recirculation Zones (PRZ). However, the strength, length, and location of PRZ varies with swirl and the downstream positioning of side dilution jets (H = 2.6D, 6.6D). Additionally, side dilution jets increase centreline velocity decay for both, non-swirling and swirling BB flows. In terms of turbulence characteristics, addition of side dilution jets leads to significant gains in shear layer turbulence with an increase of 72% and 35% in turbulent kinetic energy for non-swirling and swirling BB flows, respectively. Analysis of the mixing characteristics shows negligible impact of side dilution jets in the upstream region, however, from x/D > 3 considerable improvement in central jet (fuel) mixing is observed.

Research on Optimization of Horizontal Omnidirectional Misalignment Tolerance of WPT Based on Double D Coupler

DD (Double D) coils have been researched and utilized due to their excellent misalignment tolerance. Here, a compound DD coupler sets for stationary wireless power chargers, which has significantly better anti-misalignment performance than single DD coupler in all directions, is proposed. The transmitting coils are composed of two parts of DD coils wound in opposite directions. Moreover, to obtain the low-level variation of mutual inductance between compound transmitting coils and receiving coils when offset occurs, a parameter optimization strategy of compensation coils is also proposed. With the properly designed parameters, the mutual inductance between transmitting and receiving coils could remain basically constant when misalignment occurs, which means that the efficiency and power remain relatively constant when offset occurs. Finally, both single DD coils and compound DD coils experimental prototypes are built to compare anti-misalignment ability performance. The results show that the proposed system is basically more stable and has a higher output power and more stable efficiency than that of unoptimized coupler during migration. In particular, with the employment of the antiparallel winding, the efficiency fluctuates from 85.5% to 85% when the 0.1-m offset in the X-axis and Y-axis occurs simultaneously. Moreover, the higher and basically more stable output power is also achieved.

Advanced aqueous batteries: Status and challenges

The electricity grids with high stability and reliability require a desired balance of energy supply and demand. As the typical sustainable energy, the intermittent solar and wind would result in electricity grid instability. Aqueous batteries have been considered to be appealing stationary power sources for sustainable energy. Advanced aqueous batteries can address the safety concern derived from the employment of highly toxic and flammable organic solvents in lithium-ion batteries together with the poor cycle life presented in commercialized aqueous rechargeable batteries. This review will introduce several kinds of newly developed aqueous batteries, including aqueous Li (Na)-ion batteries, zinc anode-based batteries (Zn-metal oxide, Zn-air, Zn–Br2, and Zn–Ni(OH)2 batteries), and Ni(OH)2 cathode-based batteries (Ni(OH)2–MH and Ni(OH)2-organic composite batteries). The materials, mechanisms, and battery techniques for the above aqueous batteries will be introduced in detail. The status and challenges for the application of aqueous batteries will also be discussed. The status for advanced aqueous batteries are summarized in detail. The challenges for the application of aqueous batteries are discussed.

(Invited, Digital Presentation) The Discovery and Development of Rechargeable Zn/CuO Batteries

Batteries are easy to use, remotely monitorable, not fuel dependent, easily permitted and installed, and start automatically and reliably during an electrical outage. This makes them optimal for stationary storage and power assurance applications. Within battery-based grid storage, as of mid-2017, lithium-ion, sodium-ion, and lead-acid systems are the leaders, comprising 59% (~1.1 GW), 8% (0.15 GW), and 3% (0.06 GW) of global operational electrochemical storage, respectively.1 However, these batteries suffer from low energy density, high cost, poor safety, environmental concerns, and/or cycle life. Existing battery options on the market also do not meet the required market needs for long-duration backup power. For example, lead-acid batteries require too much space, are heavy, and contain toxic materials. Lithium-ion batteries, while compact and capable of excellent cycle life, are too expensive to serve long outages and have notable flammability and environmental risks.Alkaline zinc-based batteries are a strong candidate for electrical grid storage applications due to zinc’s high capacity (820 mAh/g), established materials supply chain and low cost.1 Alkaline-based cells are generally considered safe and do not have the temperature limitations of Li-ion or Pb-acid batteries, thereby removing the need for complicated thermal management control strategies and providing for simpler systems with lower integration costs. To realize the highest energy density batteries, Zn needs to be coupled with a similarly low cost, abundant and high-capacity cathode. Historically Zn has been paired with MnO2 (616 mAh/g), CuO (674 mAh/g) and S (1675 mAh/g) cathodes to produce energy dense primary batteries. If reversibility can be proven for these conversion cathodes, they would be enticing candidates for grid storage systems.In this presentation, we will report on the development of electrochemically reversible conversion cathodes for alkaline Zn-batteries. Specifically, we will focus on copper oxide-based cathodes and their use in alkaline Zn/CuO batteries with application for large scale grid storage.2 Sandia has recently developed rechargeable alkaline Zn/CuO batteries with very high areal capacities of ~ 40 mAh/cm2 and energy densities of > 200 Wh/L. This is among the highest ever energy density reported for a laboratory scale alkaline Zn–based battery using a conversion cathode. In this example, the rechargeability is enabled by the addition of a bismuth (Bi2O3) additive that facilitates the electrochemical reversibility of Cu2O and Cu(OH)2 species. Data collected from a variety of techniques, including cyclic voltammetry (CV), rotating ring-disk electrode (RRDE) voltammetry, electrochemical impedance spectroscopy (EIS), electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and operando energy-dispersive X-ray diffraction measurements will be presented to elucidate the role of the additive in enabling reversibility in Zn/CuO batteries. In addition, the general challenges of achieving high-capacity Zn anodes and the pairing of two high-capacity conversion electrodes to form the battery, each which cycles through the formation of soluble “-ate” complexes [i.e., cuprate, Cu(OH)4 2- and zincate, Zn(OH)4 2-] will also be covered.The goal is to demonstrate a Zn/CuO battery with long lifetime, at appreciable energy densities (> 200 Wh/L), with excellent safety, lower toxicity and sufficiently low cost to be manufactured and installed on the grid. While these laboratory scale Zn/CuO battery builds have very promising characteristics to date they have not been optimized or adapted for consumer or market-based needs in terms of power performance, energy density, cycle life or stability in terms of shelf life and the ability to tolerate partial state of charge. Progress towards these goals may also be discussed.This work was supported by the U.S. Department of Energy, Office of Electricity, and the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Evaluation of Porous Media Gas Diffusion Models for PEMFC Applications

. Polymer electrolyte membrane fuel cells (PEMFCs) are considered as zero emission power sources for transportation and stationary power purposes. The membrane electrode assembly (MEA) is the core of PEMFC and is composed of a gas diffusion layer (GDL), catalyst layer (CL) and proton exchange membrane (PEM). GDL is a carbon-based, fibrous porous medium that simultaneously provides a path for heat, mass and electron transport, as well as providing a mechanically robust support for the CL. The gas diffusion in the GDL can be estimated by Fick’s law where the effective diffusion coefficient of gaseous species is used.There are many models in the literature based on correlations defining the effective diffusion coefficients through GDLs. Some of these models were originally derived to estimate the transport properties of a porous media composed of spherical particles, e.g. Bruggeman approximation and effective medium approximation. Inherently, such models tend to result to more inaccurate outcomes compared to the models which assume the GDL structure as cylindrical carbon fibers, i.e. the diffusion model based on percolation theory. The percolation theory model considers GDL as a medium composed of freely overlapping fibers oriented in different directions. However, there are several models available in the literature with less simplifying assumptions in GDL structure. The pore network model (PNM) reconstruct the porous media using topology and size information extracted from high resolution tomographic patterns. Also CFD based models can even investigate the actual GDL structure and reconstruct the 3D stochastic porous medium microstructure. These models combine pore-scale model with CFD approaches, e.g. lattice Boltzmann method (LBM) or direct numerical simulation (DNS). This study compares the available models for dry gas diffusion in GDL with experimental data acquired from symmetrical modified Loschmidt cell (SMLC). The SMLC is employed to measure the effective diffusion coefficient of oxygen passing through GDL samples, i.e. SGL SIGRACET 24BA, 24 BC, 25BA, 25BC and TGP-H-060. The SMLC result for effective diffusion coefficient in TGP-H-060 has less than 2% difference with the available data in the literature for this type of GDL. In order to evaluate the accuracy of effective medium models and percolation theory model, the experimental data for the above-mentioned GDLs is compared with the predictions of these models. The porosity of GDL samples are in the valid range of diffusion models. The diffusion models based on the effective medium approximation have the greater difference with SMLC data in compare with the percolation theory model. The model’s predictions are the worst for the GDLs with microporous layer (MPL), i.e. SIGRACET 24 BC and 25BC. Since the MPL imposes an extra resistance to gas diffusion which is not considered in any GDL diffusion models. The least error in model’s outcome is 30% which associates to the effective diffusion coefficient predicted by percolation theory model for SIGRACET 25BA.

Surfactant-Assisted Electrodeposition of Stable Porous Platinum Structures for the Oxygen Reduction Reaction

The demands on the alternative energy sector necessitates high quality research and development to produce economical, reliable and environment friendly energy sources. Proton exchange fuel cells (PEFCs) offer a versatile and dependable alternative to conventional energies both in the transportation and stationary power sectors. Their widespread use is, however, still restricted due to their high cost and the limited availability of platinum (Pt) resources. The high cost of PEFCs is attributed in part to the higher loading of Pt based catalyst at the cathode. The reduction of Pt loadings at the cathode is generally accompanied by significant performance losses due to sluggish oxygen reduction reaction (ORR) kinetics. This issue can be resolved by maximizing the Pt utilization without sacrificing the performance. Hence, on-going research and development work is seeking to better utilize Pt with lower loadings along with optimized performance. Compared to their solid or bulk counterparts, porous structures exhibit a high electrochemical active surface area (A ecsa) and, thus, can enhance the Pt utilization. These porous nanostructures can restructure during fuel cell cycling, and structural collapse can lead to an eventual decrease in Pt utilization.1 Stabilizing agents such as surfactants are usually employed during the Pt nanoparticle (NP) synthesis to prevent NP aggregation. These surfactants can also assist in the formation of the mesoporous structure.2 This study describes the electrochemical deposition of a stable porous Pt structure in the presence of surfactants.A site-directed electrodeposition offers advantages to the wet chemical synthesis of Pt nanocatalysts as it ensures that the Pt is deposited onto specific regions of a support that have a sufficient ionic and electrical conductivity. In this study, we demonstrated the use of anionic, cationic, and non-ionic surfactants to produce porous Pt using electrodeposition and the influence of these surfactants in stabilizing the porous structure during the ORR in acidic medium. The conditions for electrodeposition, such as concentration of surfactants and potential for the nucleation and growth stages were each optimized through a series of experiments. These surfactants included cetyl trimethylammonium bromide (CTAB), sodium dodecylsulfate (SDS), and polyethylene glycol octadecyl ether (Brij 78). We utilized scanning electron microscopy techniques to evaluate the porosity of the deposited NPs and their surface coverage. In these experiments, an initial applied pulse was used to induce nucleation of the Pt followed by the growth of these materials with further electrodeposition at a lower potential. These parameters were evaluated for their influence on the final product, such as the porosity, A ecsa, and the surface coverage these materials.The porosity, composition, and crystallinity of these mesoporous particles were confirmed using transmission electron microscopy (TEM) and selected area electron diffraction techniques. These surfactant systems each resulted in the formation of porous Pt. The porous Pt was also subjected to durability testing by cycling the applied potential over a range of oxidizing potentials. Further analysis of these materials by TEM indicated that the mesoporous structure was maintained after the durability tests with a negligible change in their half-wave potential towards the ORR. The durability testing conducted after the removal of surfactants using Soxhlet extractor confirmed the role of the surfactants in helping to stabilize the porous Pt structure.

(Digital Presentation) Facile Fabrication of Graphene Quantum Dot- Doped Polyaniline Embedded Cu Metal-Organic Frameworks Composite Electrode As Improved Anode Electrocatalyst for Methanol Oxidation

Nonrenewable energy sources accounted for roughly 80% of total energy consumption [1]. Solar energy, wind energy, geothermal energy, hydropower, and fuel cells (FCs) have all recently been described as renewable energy sources. In commercial uses, renewable energy has experienced meteorological and logistical obstacles. Because of advantages such as simple fabrication/operation conditions, eco-friendly, high energy conversion efficiency, and long-term durability, FCs technologies are considered one of the most important renewable energy sources for many applications such as portable devices, cars, and electricity plants [2–5]. Methanol can be utilized in direct methanol fuel cells (DMFC) to produce clean energy that can be used in smart electronic gadgets or small automobiles in this regard [6]. However, before DMFC can be used commercially, the slow oxidation kinetics and catalyst toxicity [7] must be resolved. Therefore, the development of direct methanol fuel cells (DMFCs) is one of the most promising technologies for the applications of these devices in stationary power supplies and electric vehicles [8]. Apart from the future of mobile devices such as mobile chargers, phones, computers, and many other applications, this energy is environmentally benign because no gases are emitted and the waste is simply clean water. The biggest issue that this technique may encounter is its high cost due to the usage of noble metal catalysts (platinum (Pt) and ruthenium (Ru)) [9]. Methanol is oxidized via a multi-electron process and several products and/or intermediates can be formed, depending on the electrolyte and the nature of the electrode. Electrode materials are important parameters in the electrochemical oxidation of methanol, where high efficient electrocatalysts are needed. Several metal oxides such as Fe2O3, CeO2, MoOx, Co3O4, NiO, and CuO has been used in various applications, such as catalysis, water splitting photocatalysis, solar cells and gas sensing, besides their uses to enhance the electrocatalytic activity for methanol oxidation [10-11].This paper describes the preparation of graphene quantum dot-doped polyaniline embedded copper metal-organic frameworks composite catalysts for investigating methanol oxidation in alkaline solutions. The electrode surface was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and electrochemical impedance spectroscopy (EIS). After physicochemical characterizations of graphene quantum dot-doped polyaniline embedded copper metal-organic frameworks composite modified carbon ceramic electrode (Cu- MOF/GQDs-PAN/CCE), its electrocatalytic and stability characterizations toward methanol oxidation in alkaline media were investigated in detail by cyclic voltammetry and chronoamperometry. Results showed that, the electrocatalytic activity of the Cu- MOF/GQDs-PAN/CCE electrode is much higher than those of unmodified electrode under similar experimental conditions, showing the possibility of attaining good electrocatalytic anodes for fuel cells. Kinetic parameters such as the electron transfer coefficient (α) and the number of electrons involved in the rate determining step (nα) for the oxidation of methanol were determined utilizing cyclic voltammetry (CV). Keywords: Graphene quantum dot, Polyaniline, Metal-organic frameworks, electrocatalyst, MethanolReferences[1] S.K. Kamarudin, F. Ahmad, W.R.W. Daud, Overview on application of direct methanol fuel cell (DMFC) for portable electronic devices, Int. J. Hydrog. Energy 34 (2009) 6902–6916.[2] L. Carrette, K.A. Friedrich, U. Stimming, Fuel cells: principles, types, fuels and applications, ChemPhysChem 1 (2000) 162–193.[3] A.B. Stambouli, Fuel cells: The expectations for an environmental-friendly and sustainable source of energy, Renew. Sustain. Energy Rev. 15 (9) (2011) 4507– 4520.[4] P. Joghee, J.N. Malik, S. Pylypenko, R. O’Hayre, A review on direct methanol fuel cells – In the perspective of energy and sustainability, MRS Energy Sustain. 2 (2015), https://doi.org/10.1557/mre.2015.4.[5] D. Hassen, M.A. Shenashen, S.A. El-Safty, M.M. Selim, H. Isago, A. Elmarakbi, H. Yamaguchi, Nitrogen-doped carbon-embedded TiO2 nanofibers as promising oxygen reduction reaction electrocatalysts, J. Power Sources 330 (2016) 292– 303.[6] M. Mansor, S.N. Timmiati, K.L. Lim, W.Y. Wong, S.K. Kamarudin, N.H. Nazirah Kamarudin, Recent progress of anode catalysts and their support materials for methanol electrooxidation reaction, Int. J. Hydrogen Energy 44 (29) (2019) 14744–14769, https://doi.org/10.1016/j.ijhydene.2019.04.100.[7] Z. Mousavi, A. Benvidi, S. Jahanbani, M. Mazloum-Ardakani, R. Vafazadeh, H. R. Zare, Investigation of electrochemical oxidation of methanol at a carbon paste electrode modified with Ni(II)-BS complex and reduced graphene oxide nano sheets, Electroanalysis 28 (12) (2016) 2985–2992, https://doi.org/10.1002/ elan.201501183.[8] S. Wasmus, A. Küver, Methanol oxidation and direct methanol fuel cells: a selective review, J. Electroanal. Chem. 461 (1-2) (1999) 14–31.[9] M. Liu, R. Zhang, W. Chen, Graphene-Supported Nanoelectrocatalysts for Fuel Cells: Synthesis, Properties, and Applications, Chem. Rev. 114 (2014) 5117– 5160.[10] N. Spinner, W.E. Mustain, Electrochim. Acta 56 (2011) 5656.[11] M.S. Risbud, S. Baxter, M. Skyllas-Kazacos, Open Fuels Energy Sci. J. 5 (2012) 9.

Cathodic Pd1-XNiX Nanocatalyst Development for Alkaline Fuel Cell Applications

Alkaline fuel cells are a versatile, low-emission alternative energy source for use in transportation, as well as for portable and stationary power applications. These systems use chemical energy from the electrochemical conversion of hydrogen and oxygen gas to produce electrical energy, with only water and heat as by-products. They operate through two interdependent redox reactions within the cell consisting of oxidation of hydrogen fuel at the anode and reduction of oxygen at the cathode. One of the most significant barriers that fuel cells face is the sluggish nature of the oxygen reduction reaction (ORR) and its dependence on platinum (Pt), a rare and costly metal, as a catalyst for the reaction. Through the development and optimization of the structures and materials, the amount of precious metal catalyst can be decreased without sacrificing performance and enabling an increase in the commercial viability of the device.An alternative cathode material is palladium (Pd), which possesses similar chemical properties to Pt but is more stable in alkaline media and available in a greater abundance. Additionally, the catalytic ability of Pd is comparable to that of Pt, but due to the electronic structure of Pd, it bonds oxygen to a stronger extent, leading to a reduced activity. Theoretical analyses of the Pd electronic structure have shown that tuning the metal d-band decreases the oxygen-metal adsorption strength and increases the catalytic ability.1 Tuning of the metal d-band can be achieved experimentally through the addition of ancillary metals, thus altering the electronic structure of the catalyst. Furthermore, volcano trends of metal alloys in acidic media have shown a significant increase in activity when plotted against the oxygen adsorption strength.2 The increase in activity is particularly evident when Pt, for example, is alloyed with ancillary nickel (Ni). Due to the decreased stability of Pt in alkaline media, this study aims to assess the variations in activity of Pd through the addition of varying amounts of Ni. The incorporation of Ni increases the Pd utilization and incorporates a more cost-effective and abundant transition metal, enabling a decrease in the amount of precious metal required for the catalyst. Furthermore, the use of nanoparticles as the basis for the cathode catalyst creates a high surface area on which the ORR can occur. Nanoparticles allow for a more efficient use of the catalyst materials and, consequently, decrease the amount of metal required and the overall cost of the catalyst.This study assesses the viability of palladium-nickel nanocatalysts synthesized using a water-in-oil microemulsion3 method. The synthetic method was optimized to produce small, well-dispersed nanoparticles with a narrow size distribution ideal for the ORR. Furthermore, the synthesis was tuned to produce the desired ratios of Pd to Ni to determine an optimal composition for increased catalytic performance. The analysis of these nanocatalysts includes assessing the relationship between their composition, structure, and function using a combination of electrochemical and microscopy techniques. The results demonstrate a promising catalytic activity, indicating a comparable performance for all compositions. The consistent performance allows for a significant decrease in the precious metal content through the replacement with a more abundant and cost-effective metal. Further studies are being carried out to better understand the stability of these materials in alkaline media under a range of operating conditions relevant to the ORR. These studies aim to enhance the durability and to increase the overall viability of the catalyst. B. Hammer, J.K. Nørskov, Theoretical surface science and catalysis - calculations and concepts, Adv. Catal. 45 (2000) 71-129.A. Holewinski, H. Xin, E. Nikolla, S. Linic, Identifying optimal active sites for heterogeneous catalysis by metal alloys based on molecular descriptors and electronic structure engineering, Curr. Opin. Chem. Eng. 2 (2013) 312-319.S. Lankiang, M. Chiwata, S. Baranton, H. Uchida, C. Coutanceau, Oxygen Reduction Reaction at Binary and Ternary Nanocatalysts Based on Pt, Pd and Au. Electrochim. Acta. 182 (2015) 131–142.

A Critical Review on Artificial Intelligence for Fuel Cell Diagnosis

In recent years, fuel cell (FC) technology has seen a promising increase in its proportion in stationary power production. Several pilot projects are in operation across the world, with the number of running hours steadily rising, either as stand-alone units or as part of integrated gas turbine–electric energy plants. FCs are a potential energy source with great efficiency and zero emissions. To ensure the best performance, they normally function within a confined temperature and humidity range; nevertheless, this makes the system difficult to regulate, resulting in defects and hastened deterioration. For diagnosis, there are two primary approaches: restricted input information, which gives an unobtrusive, rapid yet restricted examination, and advanced characterization, which provides a more accurate diagnosis but frequently necessitates invasive or delayed tests. Artificial Intelligence (AI) algorithms have shown considerable promise in providing accurate diagnoses with quick data collecting. This work focuses on software models that allow the user to evaluate many different possibilities in the shortest amount of time and is a vital method for proper and dynamic analysis of such entities. The artificial neural network, genetic algorithm, particle swarm optimization, random forest, support vector machine, and extreme learning machine are common AI approaches discussed in this review. This article examines the modern practice and provides recommendations for future machine learning methodologies in fuel cell diagnostic applications. In this study, these six AI tools are specifically explained with results for a better understanding of the fuel cell diagnosis. The conclusion suggests that these approaches are not only a popular and beneficial tool for simulating the nature of an FC system, but they are also appropriate for optimizing the operational parameters necessary for an ideal FC device. Finally, observations and ideas for future research, enhancements, and investigations are offered.

Ultrafast and Long-Cycle Stable Aluminum Polyphenylene Batteries.

Rechargeable aluminum-ion batteries (RAIBs) are highly sought after due to the extremely high resource reserves and theoretical capacity (2980 mA h/g) of metal aluminum. However, the lack of ideal cathode materials restricts its practical advancement. Here, we report a conductive polymer, polyphenylene, which is produced by the polymerization of molecular benzene as a cathode material for RAIBs with an excellent electrochemical performance. In electrochemical redox, polyphenylene is oxidized and loses electrons to form radical cations and intercalates with [AlCl4]- anion to achieve electrical neutrality and realize electrochemical energy storage. The stable structure of polyphenylene makes its discharge specific capacity reach 92 mA h/g at 100 mA/g; the discharge plateau is about 1.4 V and exhibits an excellent rate performance and long cycle stability. Under the super high current density of 10 A/g (∼85 C), the charging can be completed in 25 s, and the capacities have almost no decay after 30,000 cycles. Aluminum polyphenylene batteries have the potential to be used as low-cost, easy-to-process, lightweight, and high-capacity superfast rechargeable batteries for large-scale stationary power storage.

Wide-range robust wireless power transfer using heterogeneously coupled and flippable neutrals in parity-time symmetry.

Recently, stationary wireless power transfer (WPT) has been widely adopted in commercial devices. However, the current WPT configuration is limited in its operational area and susceptible to operating condition changes, impeding its applications for dynamic environments. To overcome the limitations, we propose a WPT system with laterally aligned neutral elements in parity-time (PT) symmetry, which can widen the operational area with the number of neutrals N. Compared to the conventional multiple-input–single-output WPT, the dimension of system complexity is substantially reduced from R × CN to RN+1 because the neutral amplitudes are simply controlled by coupling capacitors. The operational frequency is automatically adjusted to a real eigenvalue of the PT-symmetric system to achieve high voltage gain and efficiency, making the system robust. The performance of the system calculated by the coupled-mode theory was experimentally verified with rigid and flexible types of receivers, confirming its potential in both industrial and biomedical electronics.

Optimizing The Hot-Press Procedure Of High-Temperature Proton Exchange Membrane Fuel Cells For Adhesion Strength And Conductivity

High-temperature proton exchange membrane (HT-PEM) fuel cell systems are under active development for a variety of mobile and stationary power applications. Measurements of membrane-electrode assembly (MEA) thickness, impedance, and adhesion strength were obtained for samples fabricated over ranges of conditions to optimize for the most suitable processing parameters. Testing quantified the effects of hot-press time, temperature, and pressure, over ranges of 1-10 minutes, 140 – 200oC, and 7.72 – 92.67 MPa, respectively. After hot pressing, MEA samples were tested for resistance with a Solartron impedance analyzer, and for adhesion strength with a Scott internal bond tester. From these results, optimal hot-press parameters were established and four 25 cm2 MEAs were fabricated and tested. Post-pressing analysis of MEAs was conducted using scanning electron microscopy coupled with energy dispersive X-ray spectroscopy. Our results demonstrate that the optimal conditions for MEA hot-pressing for the HT-PEM system are around 170oC and 23.1 MPa for 5 minutes.

Dilution effects analysis on NOx emissions of opposed-jet H2/CO syngas diffusion flames

Syngas is a promising alternative fuel for stationary power generation due to cleaner combustion than convectional fossil fuels. During the gasification processes, the by-products of CO2, H2O, or N2 may be present in the syngas mixture to control the flame temperature and emissions. Several studies indicated that syngas with dilutions is capable of reducing pollutant emissions such as NOx emissions. This work applied a numerical model of opposed-jet diffusion fames to explore the dilution effects on NOx formation and differentiate the inert effect, thermal/diffusion effect, chemical effect, and radiation effect from CO2, H2O, or N2 dilutions. The numerical study was performed by a revised OPPDIF program coupling with narrowband radiation model and detail chemical mechanism. The dilution effects on NOx formation were analyzed by comparing the realistic and hypothetical cases. Regardless the diluent types, the inert effect is the main cause to reduce NO production, followed by chemical effect and radiation effect. The thermal/diffusion effect may promote NO formation because the preferential diffusion due to different diffusivities between diluents and syngas magnifies the reaction rate locally. CO2 dilution reduces NO by radiation effect at low strain rate, and contributes NO reduction by chemical effect at high strain rate. At the same dilution percentage, CO2 dilution reduces NO production the most, followed by H2O and N2. Besides the thermal/diffusion effect, the chemical effect of H2O enhances NO production through thermal route and reburn route.

Positional Accuracy of Portable GPS Devices during Different Ride Conditions

<div class="section abstract"><div class="htmlview paragraph">Rising electric scooter popularity has seen a surge in electric scooter crashes. Crash reconstructionists increasingly have access to global positioning system (GPS) data for micromobile vehicle trips, and GPS devices can produce a wealth of data about cyclists’, scooterists’, and other riders’ road paths and route usage. However, prior research has demonstrated that GPS positional accuracy is less reliable for more nuanced roadway positioning, such as which lane a vehicle occupies, as well as within-lane movements, such as acceleration and deceleration⁠. This limitation presents a challenge for crash reconstructionists that may have access to GPS data and require second-by-second positional accuracy to determine such nuanced maneuvers and vehicle positioning in their analysis. The purpose of this study was to explore the positional accuracy of five GPS units for a micromobile vehicle during three different ride conditions: acceleration, deceleration, and constant speed. The same devices were also tested for stationary accuracy and power cut-off scenarios. To obtain precise data from GPS units, tests were performed with an electric scooter ridden in rural landscapes with clear skies. Location data from the portable GPS devices were compared to reference data obtained from photogrammetry methods based on video recorded by DJI Mavic 2 drones. It was found that the overall average positional deviation from baseline across the devices and three ride conditions was 6.68 ft. The five devices also showed inconsistencies for which of the three ride stages had the greatest and least positional error. These findings can help investigators and crash reconstructionists quantify these devices’ GPS positional accuracy when using such data in their forensic analysis.</div></div>

Physics-based modeling of homogeneous charge compression ignition engines with exhaust throttling

Homogeneous charge compression ignition (HCCI) engines create a more efficient power source for either stationary power generators or automotive applications. Due to the absence of direct actuation of ignition, HCCI based combustion control is quite challenging. For the purpose of control synthesis and design, a crank-angle based dynamic model of an HCCI engine with internal exhaust gas recirculation (EGR) is proposed in this paper. The HCCI autoignition timing is controlled by the amount of internal EGR induced by the cost effective exhaust throttling strategy. The zero dimensional single zone model is developed based on conservation of mass and energy and ideal gas law. The model is comprised of five subsystems: cylinder volume, intake, and exhaust runners along with combustion and heat-transfer models. Inputs to the model include engine speed, intake temperature, fueling rate, intake, and exhaust throttle positions. Outputs of the model contain the pressure, temperature, mass and burned gas fraction in the intake, exhaust and cylinder, air-to-fuel ratio (AFR), heat release rate, combustion phasing, and the indicated mean effective pressure (IMEP). The model is developed based on MATLAB/Simulink and validated against experimental data under steady-state and transient conditions at various intake temperatures, fueling levels, and exhaust throttle positions. Results demonstrate that by changing the exhaust throttle position, the pressure in the exhaust runner is regulated. As a result, the residual gas fraction is altered, leading to changes in mixture temperature and thus control of the HCCI combustion phasing. In the end, closed loop simulation is conducted with a linear quadratic Gaussian (LQG) controller applied to the crank-angle based model for regulation of combustion timing CA50 using exhaust throttle during load (fueling level) changes. In the future, this model can be utilized for control development and hardware in the loop (HIL) simulation.

Calculation of the Extra Capacity Required of Non-Fossil Fuel Power Generation Systems to Completely Phase Out Fossil Fuels

The task to phase out fossil fuels is now at hand. Most studies and publications to date focus on why fossil fuels should be phased out. This paper presents the physical requirements in terms of required non-fossil fuel industrial capacity, to completely phase out fossil fuels, and maintain the existing industrial ecosystem. The existing industrial ecosystem dependency on fossil fuels was mapped by fuel (oil, gas, and coal) and by industrial application. Data was collected globally for fossil fuel consumption, physical activity, and industrial actions for the year 2018. The number of vehicles in the global transport fleet was collected by class (passenger cars, buses, commercial vans, HCV Class 8 trucks, delivery trucks, etc.). The rail transport network, the international maritime shipping fleet, and the aviation transport fleet were mapped, in terms of activity and vehicle class. For each type of vehicle class, the distance travelled was estimated. Non-fossil fuel technology units that are commercially available on the market now were assembled to substitute fossil fuel supported technology. An example was selected to represent each vehicle class, for Electrical Vehicle and Hydrogen fuel cell systems. The requirements to substitute the ICE rail network and the maritime fleet with EV and hydrogen fuel cell systems were presented. The quantity of electrical power required to charge the batteries of a complete EV system was estimated. The quantity of electrical power to manufacture the required hydrogen for a complete H-cell system was estimated. An examination and comparison between EV and H-cell systems was conducted. Other fossil fuel industrial tasks like electrical power generation, building heating with gas and steel manufacture with coal were mapped and requirements for non-fossil fuel substitution were out estimated. The estimated sum total of extra annual capacity of non-fossil fuel power generation to phase out fossil fuels completely, and maintain the existing industrial ecosystem, at a global scale was 37670.6 TWh. If the same non-fossil fuel energy mix as that reported in 2018 is assumed, then this translates into an extra 221 594 new non-fossil fuel power plants will be needed to be constructed and commissioned. To mitigate intermittency of supply issues (from wind and solar) for just 4 weeks of production, global stationary power storage would require to be an estimated 574.3 TWh in capacity (or 74.6 million 100MW capacity stations).

Spark ignition timing effects on a converted diesel engine using natural gas: A numerical study

Since it is not expected to switch to fully electric and/or fuel cell vehicles in the near future, the search for alternative fuels for systems using internal combustion engines has accelerated. At the forefront of these studies is the use of natural gas instead of diesel fuel in on-road, off-road vehicles, or stationary power generation plants. Diesel engines with their special combustion chamber (i.e. bowl in-piston) can be converted to run entirely on natural gas by installing a natural gas fuel injector on the intake manifold and a spark plug instead of a diesel fuel injector. In this study, in-cylinder combustion characteristics, performance, and emission values for different Spark Ignition Time (SIT) of natural gas usage at 2300 rpm and full load in a tractor engine with a compression ratio of 17.5:1 were investigated numerically using ANSYS Forte three-dimensional analysis program. G-equation combustion model, RANS k-ε turbulence model, and methane chemical kinetic mechanism representing natural gas consisting of 29 species and 171 equations (a reduced mechanism) were used. First SIT was accepted as a 719.5 Crank Angle Degree (CAD) which is diesel injection start time. As a result, due to the special shape of the combustion chamber of diesel engines (re-entrant bowl in-piston), it was seen that the flame was faster and thicker in the bowl, while it was slower and thinner in the squish zone. With the advanced of SIT, the in-cylinder pressure ratio increased. By taking SIT too advanced (i.e. 690, 695, and 700 CAD SIT), more than one peak formation was observed in the heat release graph depending on the combustion characteristic. With the effect of both natural gas use and SIT, it was observed that HC and CO formations were almost not seen, while NOX formation remains above a certain level.

Modeling of Supercritical CO2 Shell-and-Tube Heat Exchangers Under Extreme Conditions. Part I: Correlation Development

Abstract High-temperature supercritical CO2 Brayton cycles are promising possibilities for future stationary power generation and hybrid electric propulsion applications. Heat exchangers are critical components in supercritical CO2 thermal cycles and require accurate correlations and comprehensive performance modeling under extreme temperatures and pressures. In this paper (Part I), new Colburn and friction factor correlations are developed to quantify shell-side heat transfer and friction characteristics of flow within heat exchangers in the shell-and-tube configuration. Using experimental and computational fluid dynamics (CFD) data sets from existing literature, multivariate regression analysis is conducted to achieve correlations that capture the effect of multiple critical geometric parameters. These correlations offer superior accuracy and versatility as compared to previous studies and predict the thermohydraulic performance of about 90% of the existing experimental and CFD data within ±15%. Supplementary thermohydraulic performance data are acquired from CFD simulations with supercritical CO2 as working fluid to validate the developed correlations and demonstrate its capability to be applied to supercrtical CO2 heat exchangers.

High-Efficiency Module Design of Solid-State Transformers for Railway Vehicles

The solid-state transformer (SST) can be a promising solution to replace the conventional 50- or 60-Hz main transformer (MTr) for railway vehicles. Unlike the existing SST technologies for stationary power applications, the SST applied to railway vehicles requires severe constraint of installation space and intensive management of heat dissipation. To optimally design the SST module applied to the railway vehicles, which is one of the major components in the whole SST system, the optimal magnetic component designs for high-efficiency and thermal stable operations in the confined installation space are proposed in this article. In order to meet the SST system requirements for ac 25-kV-to-dc 1.5-kV power conversion, an overall SST topology and its control schemes are established. Based on the proposed SST topology, considering the operating drive profile of the urban railway vehicles, the operating sequence of the proposed SST is introduced and verified by simulation. By virtue of the proposed magnetic component design, the optimal number of turns for the inductor and transformer in dual-active-bridge converters can be appropriately determined for 50-kV high-voltage insulation and high-efficiency operation when the installation space for the magnetic components is given. For targeting the 3.0-MW maximum power transfer capability of the proposed SST system, the 300-kW SST modules, operating at 500 Hz and 10 kHz for ac/dc converters and dc/dc converters, respectively, were fabricated and verified by experiment. By two experimental SST module sets, the static performance of the power converters in the SST module and the dynamic operating sequence has been successfully implemented. For the 300-kW full-load operation, 99.7% of power transfer efficiency for the proposed magnetic components and 97.2% of total power efficiency were obtained. As a result, the measured temperature characteristics for the proposed SST module, including the magnetic components, were managed below 125 °C under a severe experimental environment.

Experimental performance and emissions of additively manufactured high-temperature combustion chambers for micro-gas turbines

To date, 59 countries, representing 54% of global greenhouse gas emissions have made pledges for net-zero emissions targets within this century. This will require cleaner and more efficient sources of energy which is driving research into small-scale engines and auxiliary power units for hybrid vehicles and stationary power generation. A suitable candidate for such applications is the micro gas turbine due to its high-power density, reliability and low emissions. Further development of such engines is required though due to their increasing parasitic energy losses relative to net power output as size decreases. Additive manufacturing offers the design freedom to not only increase efficiencies but to also reduce emissions when applied to the various components of micro gas turbines. This article reports the effects of several additive manufacturing (AM) enabled design features for micro gas turbine combustion chambers via experimental testing of full-scale parts. The main objective of the additively manufactured features is the reduction of exhaust emissions by improving the air-fuel mixture distribution and consequently ignition and combustion. Using additive manufacturing a novel conical radial swirl-stabilized tubular combustor with internal vane fuel injection was created as a baseline for the laboratory testing. Several other features, including augmented backside liner cooling surfaces, in-vane lattice structures for fuel mixing and upstream liner fuel injection rings were also generated to further the investigations into additively manufactured features and their effects on fuel mixing. Using multiple combinations of all these features, 10 geometries were generated and tested at a variety of operating conditions. Three inlet temperatures were tested (500°C, 600°C and 700°C) with varying fuel flow rates to investigate their operating limits at a constant inlet pressure of 4 bar absolute. Test results for the full range of equivalence ratios and operating conditions showed that the upstream liner fuel injection designs generated NOx, CO and THC emissions on par with the baseline but showed a reduction in the maximum and minimum operating ranges. This design, however, demonstrated the distinct advantage of being able to ignite at full air mass flow; this is not possible with the baseline designs and is also an added benefit to its main use which is the reduction of liner temperature. Overall, the test results underscore that designing combustion chambers for additive manufacturing can provide a myriad of benefits not only for micro gas turbines but also for other applications requiring high efficiency combustion chambers.