Fast Start-up Research Articles

Metal-Supported Solid Oxide Cells for Energy Conversion, Electrolysis, and Chemical Synthesis

This talk will provide an overview and update of performance, durability, and applications of metal-supported solid oxide fuel cell (MS-SOFC) and electrolysis cell (MS-SOEC) technology developed at Lawrence Berkeley National Laboratory (LBNL). The unique LBNL symmetric cell architecture design, with thin zirconia ceramic backbones and electrolyte sandwiched between porous metal supports, offers a number of advantages over conventional all-ceramic cells, including low-cost structural materials (e.g. stainless steel), mechanical ruggedness, excellent tolerance to redox cycling, and extremely fast start-up capability. These features enable a wide variety of applications including vehicle range extenders, electrolysis for intermittent renewables, personal power generators, and distributed generation.With infiltrated catalysts, the catalyst compositions can be easily tailored to a variety of reactions, without re-optimizing the entire cell. Recent efforts have developed catalysts for internal reforming of natural gas and ethanol, steam electrolysis to produce hydrogen, oxidative coupling of methane to synthesize ethylene, and oxygen generation from air. A recent focus is 1000+ hour continuous operation with detailed post-mortem analysis. Progress on cell performance and durability for each of these applications will be discussed.Infiltrated catalysts, however, present a tradeoff between initial performance and long-term stability. Extremely high surface area promotes high electrochemical reaction rates, but also provides high surface energy leading to coarsening and facilitates Cr deposition. Recent approaches to mitigating catalyst coarsening and Cr deposition within the cathode include coatings to prevent Cr evaporation from the stainless steel components, and optimization of infiltrated catalyst processing to stabilize the microstructure during operation. The metal support structure has also been optimized for improved mass transport.

Fast sensorless startup method for ultra-high-speed PMSMs with air bearings

Fast sensorless startup method for ultra-high-speed PMSMs with air bearings

Facile Synthesis of Nitrogen Doped Porous Carbon Supported Platinum Catalyst and Improvement of Electrocatalytic Ethanol Performance

Direct ethanol fuel cells (DEFCs) have become an alternative to traditional fossil fuels because of their low emissions, fast start-up and high energy density. Platinum (Pt)-based catalysts are the most effective catalysts for DEFCs, but their high cost and poor electrocatalytic performance hinder their practical application. Therefore, there is an urgent need to design Pt-based catalysts with low platinum content, high electrochemical activity and stability. Herein, nitrogen-doped porous carbon-loaded Pt catalysts (Pt@Co-CN) were prepared by in situ polymerization and high-temperature calcination using the metal-organic framework materials (MOFs) ZIF-8@ZIF-67 as the carriers. The effects of the addition of pyrrole monomer on the morphology and electrocatalytic properties of the samples were investigated. The sample with the complete coating layer and uniformly dispersed Pt nanoparticles (Pt@Co-CN) could be obtained by adding an appropriate amount of pyrrole monomer. The results of the electrochemical tests showed that the electrochemical activity of Pt@Co-CN catalytic ethanol is superior to that of commercial catalysts and samples with insufficient or excessive addition of pyrrole monomers. The content of this study provides a new method for the electrocatalyst of DEFCs.

The Story of AWS Glue

AWS Glue is Amazon's serverless data integration cloud service that makes it simple and cost effective to extract, clean, enrich, load, and organize data. Originally launched in August 2017, AWS Glue began as an extract-transform-load (ETL) service designed to relieve developers and data engineers of the undifferentiated heavy lifting needed to load databases, data warehouses, and build data lakes on Amazon S3. Since then, it has evolved to serve a larger audience including ETL specialists and data scientists, and includes a broader suite of data integration capabilities. Today, hundreds of thousands of customers use AWS Glue every month. In this paper, we describe the use cases and challenges cloud customers face in preparing data for analytics and the tenets we chose to drive Glue's design. We chose early on to focus on ease-of-use, scale, and extensibility. At its core, Glue offers serverless Apache Spark and Python engines backed by a purpose-built resource manager for fast startup and auto-scaling. In Spark, it offers a new data structure --- DynamicFrames --- for manipulating messy schema-free semi-structured data such as event logs, a variety of transformations and tooling to simplify data preparation, and a new shuffle plugin to offload to cloud storage. It also includes a Hivemetastore compatible Data Catalog with Glue crawlers to build and manage metadata, e.g. for data lakes on Amazon S3. Finally, Glue Studio is its visual interface for authoring Spark and Python-based ETL jobs. We describe the innovations that differentiate AWS Glue and drive its popularity and how it has evolved over the years.

Fast Transient State Trajectory Control for Switched-Capacitor-Based Resonant Converter

This paper presents a state trajectory control scheme for switched-capacitor-based resonant converter consisting of two half-bridge circuits with four switches. The proposed technique can not only bring improved dynamic response of output voltage regulation, but ensure that the converter benefits from soft-switching operation. The analysis in the two state planes provides insight into the switching modes of the converter and creates an accurate behavior framework in the geometrical domain. As a result, a finite state-machine controller is designed based on the planning of the state trajectories. The switching conditions are exploited to obtain fast start-up and step-load transient responses. The proposed control method is verified with experimental results of a 14.5V, 5.8A converter prototype.

An Energy Efficient Coherent IR-UWB Receiver With Non-Coherent-Assisted Synchronization

This paper presents a non-coherent assisted synchronization mechanism for low data rate coherent () receivers. A two-step coarse and fine acquisition mechanism is utilized to simplify the coherent synchronization and minimize the total required packet length. This hybrid scheme reduces the total power consumption of the receiver. The reception of a UWB packet begins with an energy efficient non-coherent synchronization portion in () modulation non-coherent acquisition. This reduces the search space for the coherent reception by first finding the best integration window that has the most energy of the received signal. Afterwards, the receiver searches coherently in () modulation within only the pre-selected integration window instead of the whole symbol time. Self-mixing and template-based correlation are utilized for the non-coherent and coherent reception, respectively. Most of the front-end blocks are shared between the coherent and non-coherent modes, including the LNA, mixer, and the baseband circuitry that follows to minimize the total power consumption of the receiver. A differential architecture including a (), a mixer, a fast start-up template generator, an integrator, and a differential comparator are utilized for the receiver front-end. A prototype of the proposed receiver operating from 3.5 to 5 GHz over four bands, each spaced by 500 MHz, is implemented in 65-nm CMOS technology. The proposed receiver architecture achieves a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 68 dBm, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 70.5 dBm, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$-$</tex-math> </inline-formula> 70.8 dBm sensitivity at a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{-3}$</tex-math> </inline-formula> BER at 50 MHz () in the non-coherent, coherent, and proposed hybrid synchronization modes, respectively. The receiver consumes 6.8 mW and 8.8 mW in the non-coherent and coherent mode, respectively, when continuously ON. Using its novel synchronization mechanism, the receiver can reduce the ON time of the receiver by 68% and 34% in order to coherently synchronize and receive a 100-bit and 1024-bit payload, respectively. As a result, the () of the receiver is reduced by a factor of 2.9 from 1.24 nJ/b to 422 pJ/b for 100-bit payloads, and by a factor of 1.5 from 309 pJ/b to 204 pJ/b for 1024-bit payloads, increasing energy efficiency while maintaining the sensitivity benefits of coherent detection.

Experimental study of a passive thermal management system using vapor chamber for proton exchange membrane fuel cell stack

To mitigate the parasitic power consumption caused by conventional air and water cooling, this study proposes a novel passive cooling scheme that integrates vapor chambers into proton exchange membrane fuel cell stack for thermal management. A 1.32 mm thick vapor chamber is designed and fabricated, and its heat transfer performance is verified through tests conducted at different powers using a heating pad. After confirming that vapor chambers can meet the heat dissipation requirements, the output characteristics of the stack coupled with vapor chambers, are experimentally evaluated during both fast start-up and steady-state operation. Results demonstrate that the vapor chamber efficiently operates at a heat flux density of only 0.052 W/cm2 at evaporation section, while maintaining a maximum in-plane temperature difference of 2.6 °C at 48 W. During fast start-up loading of the stack from 0 A to 40 A, the vapor chamber exhibits rapid thermal response and excellent temperature uniformity, preventing stack performance degradation due to improper operating temperatures. Compared to a general air-cooled stack, the stack coupled with vapor chambers exhibits a significant 21.7% improvement in stack voltage. These results systematically demonstrate the feasibility of vapor chambers for the thermal management of air-cooled proton exchange membrane fuel cell stacks.

Uncertainty analysis of the China experimental fast reactor start-up tests based on refined calculation results

In this paper, the numerical calculations of China Experimental Fast Reactor (CEFR) start-up tests were performed by using SARAX code with the improved core model. The results of criticality, control rod worth, and reactivity effect were compared against the experimental data. The numerical results showed the SARAX code could be reliably used for CEFR. Moreover, the sensitivity of the keff value due to the change of input parameters was analyzed. At the same time, the uncertainty quantification of calculated keff value and control rod worth and detailed contribution to the total uncertainty were analyzed. For the reactor loaded with highly enriched UO2 fuel, the uncertainty of keff value could reach more than 2%. Besides, the capture reaction of 235U contributed the most with a value of 1.91%. The uncertainty analysis of the control rod worth showed that the total uncertainty depended on the control rod layout rather than the composition.

Electrochromic performance and potential stability of sputtered V2O5 film for a complementary inorganic all-solid-state electrochromic device

Vanadium Pentoxide (V2O5) has good ion storage capacity and weak anodic electrochromism. Since the V2O5 and Tungsten Trioxide(WO3) films were used as the auxiliary and major color-changing layers, respectively, then they were combined with heat-cured gel (LiClO4 + PC) + PMMA electrolyte as an complementary all-solid-state electrochromic device (ECD). Also, the V2O5 films were prepared at different oxygen flows and annealing temperatures. These results exhibited that oxygen flow of 4 sccm and annealing temperature of 400 °C can enable the optimal optical contrast (ΔT) to reach 38.7%@550 nm. The response time of the coloring(tc) and the bleaching(tb) were 5 and 4 s, respectively. Raman spectrum showed the stable phase of V5+ and specific element ratio of 2.52 and X-ray photoelectron spectroscopy (XPS) had the red shift phenomenon. However, the performance of ITO/V2O5/gel-electrolyte/WO3/ITO device, the best working voltage was measured as ±2.5 V, the optical contrast was ΔT = 42% and the response time of tc and tb were 6.5 and 5.5 s, respectively. These results demonstrate that ECD has the advantages of fast response time and low voltage stable startup.

Composite Sliding Mode Speed Control for Sinusoidal Doubly Salient Electromagnetic Machine Drives Using Fast Reaching Law and Disturbance Compensation

The proportional-integral speed controller is widely used in field-oriented control due to its simplicity in implementation; however, parameter variations and load disturbance easily lead to the deterioration of its dynamic performance. To address the above problem, a composite sliding mode speed control (CSMSC) is proposed in this article, which is composed of a sliding mode controller based on a new fast reaching law (FRL-SMC) and an extended state observer (ESO). The FRL-SMC can effectively solve the contradiction between response time and chattering amplitude, which is superior to the traditional SMC approaches; the lumped disturbance is estimated online by the ESO, and then the estimated value used as feedforward compensation is introduced into the FRL-SMC to enhance the disturbance reject ability. The sinusoidal doubly salient electromagnetic machine (SDSEM) speed regulation system applying the proposed CSMSC obtains a fast startup response and load step response, an excellent anti-disturbance performance, and a small <i>q</i>-axis current steady chattering. Finally, the effectiveness of the proposed method is verified by experimental results for a SDSEM test platform.

Deep Treatment of Tailwater by Aerobic Denitrifying Bacteria Enhanced Biofilter

The high concentration of total nitrogen in the tailwater discharged from some wastewater treatment plants is relatively high, which is easy to cause eutrophication in the receiving water bodies. In this study, the aerobic denitrifying bacteria were combined with denitrifying biofilter through bioreinforcement technology. The aerobic denitrifying bacteria strains W30 and Z66 isolated from activated sludge were used to construct a complex bacterial agent to strengthen the denitrifying biofilter, and the enhanced nitrogen removal effect of the complex bacterial agent was investigated, and the microbial community structure in the system after bioreinforcement was analyzed by high-throughput sequencing technology. The results showed that strain W30 was identified as Pannonibacter and strain Z66 as Pseudomonas by 16S rDNA sequencing analysis. The bioreinforced denitrification biofilter had a fast start-up rate of membrane hanging, and the removal rate of total nitrogen (TN) increased by 9. 36% under natural oxygenation compared with that under aeration; the single-factor test of carbon/nitrogen ratio (C/N) and hydraulic retention time (HRT) determined C/N=4. 27 and HRT=1. 0 h as the optimal working conditions of the filter cell; the highthroughput sequencing results further showed that the percentages of Pannonibacter and Pseudomonas in the denitrifying biofilter decreased from 0. 49% and 2. 56% at the beginning of operation to 0. 073% and 0. 18% after 130 days of operation. A stable denitrification system was formed with Thauera, Dechlorobacter, Exiguobacterium and other genera.

Culturing partial-denitrification (PD) granules in continuous flow reactor with waste sludge as inoculum: performance, granular sludge characteristics and microbial community

ABSTRACT Partial denitrification granular sludge (PDGS) can provide long-term stable nitrite for anaerobic ammonia oxidation (anammox). The cultivation of ordinary activated sludge from wastewater treatment plants into PDGS can further promote the application of PD in practical engineering. In this study, the feasibility of fast start-up of PDGS was explored by inoculating waste sludge in up-flow anaerobic sludge blanket (UASB) reactor with synergistic control of nitrogen load rate (NLR, 0.05–0.65 kg N/m3/d) and electron donor starvation (EDS) (240–168 mg L−1), and system performance, particle characteristics and microbial structure were studied. The results showed that PD-UASB started successfully within 48 days, the average nitrite accumulation rate (NTR) and nitrate removal ratio (NRR) reached 79.6% and 82.5% after successful initiation, accompanied by high abundance of PD bacteria (Thauera, Pseudomonas, unclassflied commamonadaceae and Limnobacter) (25.3%). The increase of PD activity, and the difference between nitrate reductase (NAR) and nitrite reductase (NIR) contributed to nitrite production. Besides, the sludge shifted from flocculated (≤0.5 mm, 95.37%) to granulated state (0.5–2 mm, 64.74%), which could be due to the increase of extracellular polymers (EPS) (especially T-EPS) and metabolism of specific microorganisms (Bacteroidota and Chloroflexi, 19.92%). Good sludge granulation promoted the settleability of PD (the SVI5 was 47.248 mL/ g. ss after successful start-up). In summary, good PD sludge granulation process could be achieved in a short time by synergistically controlling NLR and EDS.

Metal-Supported Solid Oxide Fuel Cells: A Review of Recent Developments and Problems

The design of metal-supported solid oxide fuel cells (MS-SOFCs) has again aroused interest in recent years due to their low cost of materials, strength, and resistance to thermal cycling, as well as the advantages of manufacturability. MS-SOFCs are promising electrochemical devices for hydrogen energy. Compared to SOFCs, where ceramic electrodes or electrolytes are used as a carrier base, they are of great interest due to their fast start-up capability, greater reliability, mechanical stability, and resistance to the thermal cycle. MS-SOFCs have many advantages over conventional ceramic-based SOFCs, with the selection of metal-based electrode materials (anode, cathode) and their degradation processes being some of the biggest challenges facing researchers. Therefore, this review reports on the state of the latest research on MS-SOFCs with various structures, discusses the corresponding electrode materials and their existing problems, and puts forward topical issues that need to be addressed in MS-SOFCs.

Application of Machine Learning in Fuel Cell Research

A fuel cell is an energy conversion device that utilizes hydrogen energy through an electrochemical reaction. Despite their many advantages, such as high efficiency, zero emissions, and fast startup, fuel cells have not yet been fully commercialized due to deficiencies in service life, cost, and performance. Efficient evaluation methods for performance and service life are critical for the design and optimization of fuel cells. The purpose of this paper was to review the application of common machine learning algorithms in fuel cells. The significance and status of machine learning applications in fuel cells are briefly described. Common machine learning algorithms, such as artificial neural networks, support vector machines, and random forests are introduced, and their applications in fuel cell performance prediction and optimization are comprehensively elaborated. The review revealed that machine learning algorithms can be successfully used for performance prediction, service life prediction, and fault diagnosis in fuel cells, with good accuracy in solving nonlinear problems. Combined with optimization algorithms, machine learning models can further carry out the optimization of design and operating parameters to achieve multiple optimization goals with good accuracy and efficiency. It is expected that this review paper could help the reader comprehend the state of the art of machine learning applications in fuel fuels and shed light on further development directions in fuel cell research.

Failure Mechanism and Optimization of Metal-Supported Solid Oxide Fuel Cells.

A solid oxide fuel cell (SOFC) is a clean, efficient energy conversion device with wide fuel applicability. Metal-supported solid oxide fuel cells (MS-SOFCs) exhibit better thermal shock resistance, better machinability, and faster startup than traditional SOFCs, making them more suitable for commercial applications, especially in mobile transportation. However, many challenges remain that hinder the development and application of MS-SOFCs. High temperature may accelerate these challenges. In this paper, the existing problems in MS-SOFCs, including high-temperature oxidation, cationic interdiffusion, thermal matching, and electrolyte defects, as well as lower temperature preparation technologies, including the infiltration method, spraying method, and sintering aids method, are summarized from different perspectives, and the improvement strategy of existing material structure optimization and technology integration is put forward.

Metal-Supported Solid Oxide Cells for Energy Conversion, Electrolysis, and Chemical Synthesis

The LBNL metal-supported solid oxide cell architecture contains zirconia electrolyte and porous backbones co-sintered between porous stainless steel supports. Advantages of this design include low-cost structural materials, mechanical ruggedness, excellent tolerance to redox cycling, and extremely fast start-up capability. These features enable a wide variety of applications including electrolysis for intermittent renewables, distributed power generation, and synthesis of valuable chemicals. Highlights from efforts in these areas are presented.

Design of High Specific Power Solid Oxide Fuel Cells

Fuel-Cell Electric-Vehicle demonstrated by PCI was fueled with military-spec F-24/JP-8 and does not require on-board hydrogen storage. An onboard fuel reformer with integrated sulfur trap was used for processing these fuels. The 10-kW electric generator included a SOFC and balance of plant components. It was hybridized with a rechargeable battery for startup, peak loads, and load following. The power produced was sufficient for vehicle propulsion and export power. Both 28-32 VDC and 110 VAC for charging batteries and supporting external load demands were available onboard. Initial off-road demonstrations were successfully conducted at PCI and customer sites. This prototype unit showed the feasibility of utilizing hydrocarbon fuels with on-board reforming and SOFC stack to generate power suitable for mobile applications while the system weight and start-up time still need to be improved. To reduce the system weight and start-up time, we are separately investigating advanced SOFC’s that show potential to address the known limitations of the state-of-the-art technology. These advanced SOFC’s demonstrated potential for fast start-up and high-power density on the cell level at 750-800°C of operating temperatures. By optimizing the configuration and design, the system performance is expected to be further improved.

In Situ Enhanced Yields of Microbial Nanowires: The Key Role of Environmental Stress.

The conductive microbial nanowires of Geobacter sulfurreducens serve as a model for long-range extracellular electron transfer (EET), which is considered a revolutionary "green" nanomaterial in the fields of bioelectronics, renewable energy, and bioremediation. However, there is no efficient pathway to induce microorganisms to express a large amount of microbial nanowires. Here, several strategies have been used to successfully induce the expression of microbial nanowires. Microbial nanowire expression was closely related to the concentration of electron acceptors. The microbial nanowire was around 17.02 μm in length, more than 3 times compared to its own length. The graphite electrode was used as an alternative electron acceptor by G. sulfurreducens, which obtained a fast start-up time of 44 h in microbial fuel cells (MFCs). Meanwhile, Fe(III) citrate-coated sugarcane carbon and biochar were prepared to test the applicability of these strategies in the actual microbial community. The unsatisfied EET efficiency between c-type cytochrome and extracellular insoluble electron receptors promoted the expression of microbial nanowires. Hence, microbial nanowires were proposed to be an effective survival strategy for G. sulfurreducens to cope with various environmental stresses. Based on this top-down strategy of artificially constructed microbial environmental stress, this study is of great significance for exploring more efficient methods to induce microbial nanowires expression.

A Low Phase Noise Crystal Oscillator with a Fast Start-Up Bandgap Reference for WLAN Applications

This article presents the design and implementation of a 40 MHz crystal oscillator (XO) with low phase noise, based on the 55 nm CMOS process, for wireless transceiver systems, particularly those used in Wireless Local Area Network (WLAN). The proposed design employs a bandgap reference circuit that includes a start-up circuit and a low-voltage common-source common-gate current mirror, which ensures that the bandgap reference circuit is powered up effectively across all temperatures and process corners. A low-pass filter is also incorporated at the low dropout regulator (LDO) input to reduce the phase noise of the XO circuit. The experimental results demonstrate that the proposed design achieves a final phase noise of −164.36 dBc/Hz at 100 kHz offset frequency, with a power consumption of 0.444 mW. The test of start-up time is 0.718 ms and the compact chip area is 0.088 mm2. According to the simulation and test results, the final FOM value calculated in this paper is 209.93 dBc/Hz at 100 kHz offset.

Description of new single-chamber continuous-flow reactors of aerobic granular sludge: Technical and biological study

Aerobic granular sludge reactors usually operate in sequential batch mode, although this configuration limits the treatment of large volumes of wastewater, and they require a storage system. To implement this technology at full-scale, it would be necessary to design a simple and compact continuous-flow bioreactor able to treat larger volumes of wastewater. In this study, four aerobic granular sludge single-chamber continuous-flow reactors (R1, R2, R3 and R4) were designed and operated at the lab scale to evaluate and select a bioreactor configuration that achieves high organic matter removal performance while maintaining a stable granulation for long-term operation, promoting the washout of filamentous microorganisms. Results confirmed that the bioreactor including a lateral decanter (R1), was able to work in a steady state without loss of granular biomass and reached 95% of organic matter removal performance. Its granules had excellent compaction, with settling velocity values above 100 m·h−1. The R1 bioreactor also allowed rapid biomass adaptation and therefore a fast start-up (11 days). Results of this preliminary study at the lab scale suggested that the new and simple bioreactor design could be promising for its implementation at full scale. For that, future research is required to optimise the current model and to determine the most suitable operational parameters to treat domestic wastewater at full scale.