Jian-sheng Huang, Yong Guo, Ping Yang et al.

Water Science and Technology • 2014

<jats:p>In order to study the performance and bacterial communities of an anaerobic fluidized bed microbial fuel cell (AFB-MFC) system, the 16S rDNA gene sequencing was applied, and high-strength synthetic wastewater was treated by the AFB-MFC system. The high-strength synthetic wastewater, in which the concentrations of chemical oxygen demand (COD), nitrite nitrogen, and nitrate nitrogen were above 19,000, 2,516–3,871 and 927–1,427 mg/L, was treated by the AFB-MFC system. The removal efficiency of COD, nitrite nitrogen, and nitrate nitrogen reached 70–89, 98 and 98%, while the maximum voltage was 394 mV. The bacteria analysis revealed the presence of Alistipes putredinis, Carnobacterium sp., Victivallis vadensis, Klebsiella pneumoniae, Thauera sp., Parabacteroides merdae, Parvimonas micra, Parabacteroides sp., and Desulfomicrobium baculatum in the anode chamber. In addition, the Klebsiella pneumoniae was observed to have the capability of organic degradation and electricity generation, while the Thauera sp. has the capability of denitrification.</jats:p>

Tolera G. Degefa, Marek Łukasz Płaczek, Grzegorz Kokot

Applied Sciences • 0

<jats:p>MFC (Microfiber composite) piezoelectric transducers are one of the smart composite materials used among others in alternative energy sources and autonomous wireless sensors which exploit vibrational energy. This work presents the theoretical and experimental investigations of the integration of MFC piezoelectric transducers on epoxy glass fiber composite material and explores the capacity of power generation based on a variety of ambient temperatures and frequencies. The study examined the use of ambient vibrational energy to power small electronic devices of wireless sensor networks which eliminates the need for external power, periodic battery replacement costs, and chemical waste from conventional batteries. The test was conducted using a laboratory stand equipped with a thermal chamber and an Instron ElectroPulse waveform generator which induces a concentric cyclic load to the laminated beam. Laminated MFC was loaded with a low–frequency range, controlled displacement under different moderate temperatures. The test was conducted at temperatures ranging from 25 to 60 degrees Celsius and at frequencies ranging from 5 to 25 Hz. The results show that the voltage generated by the transducer is highly affected by both temperature and frequency of excitation.</jats:p>

C. Turick, S. Shimpalee, P. Satjaritanun et al.

Applied Microbiology and Biotechnology • 2019

Real-time electrochemical monitoring in bioprocesses is an improvement over existing systems because it is versatile and provides more information to the user than periodic measurements of cell density or metabolic activity. Real-time electrochemical monitoring provides the ability to monitor the physiological status of actively growing cells related to electron transfer activity and potential changes in the proton gradient of the cells. Voltammetric and amperometric techniques offer opportunities to monitor electron transfer reactions when electrogenic microbes are used in microbial fuel cells or bioelectrochemical synthesis. Impedance techniques provide the ability to monitor the physiological status of a wide range of microorganisms in conventional bioprocesses. Impedance techniques involve scanning a range of frequencies to define physiological activity in terms of equivalent electrical circuits, thereby enabling the use of computer modeling to evaluate specific growth parameters. Electrochemical monitoring of microbial activity has applications throughout the biotechnology industry for generating real-time data and offers the potential for automated process controls for specific bioprocesses.

Azwar Muhammad Yahya, M. Hussain, Ahmad Khairi Abdul Wahab

International Journal of Energy Research • 2015

An integrated modeling, optimization, and control approach for the design of a microbial electrolysis cell (MEC) was studied in this paper. Initially, this study describes the improvement of the mathematical MEC model for hydrogen production from wastewater in a fed‐batch reactor. The model, which was modified from an already existing model, is based on material balance with the integration of bioelectrochemical reactions describing the steady‐state behavior of biomass growth, consumption of substrates, hydrogen production, and the effect of applied voltage on the performance of the MEC fed‐batch reactor. Another goal of this work is to implement a suitable control strategy to optimize the production of biohydrogen gas by selecting the optimal current and applied voltage to the MEC. Various simulation tests involving multiple set‐point changes, disturbance rejection, and noise effects were performed to evaluate the performance where the proposed proportional–integral–derivative control system was tuned with an adaptive gain technique and compared with the Ziegler–Nichols method. The simulation results show that optimal tuning can provide better control effect on the MEC system, where optimal H2 gas production for the system was achieved. Copyright © 2014 John Wiley & Sons, Ltd.

Xuee Wu, F. Zhao, N. Rahunen et al.

Angewandte Chemie International Edition • 2011

Herein we have demonstrated a DET mechanism used by D. desulfuricans; where the periplasmic cytochromes and hydrogenases play an important role, and Pd nanoparticles bound to the microbes may participate in the electron transfer process. The present work is of importance not only for the fundamental studies of electron transfer processes in microbial physiology and ecology, but also for increased understanding and improvement of the performance of bioelectrochemical techniques e.g. precious metals are extensively used and important catalysts, and therefore present in many industry processing wastewaters. Bio-nanoparticles can oxidize in situ metabolites e.g. H2, formate and ethanol in the anode chambers, while also acting as cathodic catalysts for the oxygen reduction reaction[23]. In addition, this study indicates the feasibility of using bioelectrochemical systems for metal immobilization, recovery or detoxification

Pengyi Yuan, Younggy Kim

Biotechnology for Biofuels • 2017

BackgroundMicrobial electrolysis cells (MECs) use bioelectrochemical reactions to remove organic contaminants at the bioanode and produce hydrogen gas at the cathode. High local pH conditions near the cathode can also be utilized to produce struvite from nutrient-rich wastewater. This beneficial aspect was investigated using lab-scale MECs fed with dewatering centrate collected at a local wastewater treatment plant. The main objective was to improve phosphorus recovery by examining various cathode configurations and electric current conditions.ResultsThe stainless steel mesh (SSM) cathode was relatively inefficient to achieve complete phosphorus recovery because struvite crystals were smaller (a few to tens of micrometers) than the open space between mesh wires (80 µm). As a result, the use of multiple pieces of SSM also showed a limited improvement in the phosphorus recovery up to only 68% with 5 SSM pieces. Readily available organic substrates were not sufficient in the dewatering centrate, resulting in relatively low electric current density (mostly below 0.2 A/m2). The slow electrode reaction did not provide sufficiently high pH conditions near the cathode for complete recovery of phosphorus as struvite. Based on these findings, additional experiments were conducted using stainless steel foil (SSF) as the cathode and acetate (12 mM) as an additional organic substrate for exoelectrogens at the bioanode. With the high electric current (>2 A/m2), a thick layer of struvite crystals was formed on the SSF cathode. The phosphorus recovery increased to 96% with the increasing MEC operation time from 1 to 7 days. With the high phosphorus recovery, estimated energy requirement was relatively low at 13.8 kWh (with acetate) and 0.30 kWh (without acetate) to produce 1 kg struvite from dewatering centrate.ConclusionsFor efficient phosphorus recovery from real wastewater, a foil-type cathode is recommended to avoid potential losses of small struvite crystals. Also, presence of readily available organic substrates is important to maintain high electric current and establish high local pH conditions near the cathode. Struvite precipitation was relatively slow, requiring 7 days for nearly complete removal (92%) and recovery (96%). Future studies need to focus on shortening the time requirement.

Faiz Miran, M. Mumtaz, H. Mukhtar et al.

Frontiers in Bioengineering and Biotechnology • 2021

The microbial fuel cell (MFC) is emerging as a potential technology for extracting energy from wastes/wastewater while they are treated. The major hindrance in MFC commercialization is lower power generation due to the sluggish transfer of electrons from the biocatalyst (bacteria) to the anode surface and inefficient microbial consortia for treating real complex wastewater. To overcome these concerns, a traditional carbon felt (CF) electrode modification was carried out by iron oxide (Fe3O4) nanoparticles via facile dip-and-dry methods, and mixed sulfate-reducing bacteria (SRBs) were utilized as efficient microbial consortia. In the modified CF electrode with SRBs, a considerable improvement in the bioelectrochemical operation was observed, where the power density (309 ± 13 mW/m2) was 1.86 times higher than bare CF with SRBs (166 ± 11 mW/m2), suggesting better bioelectrochemical performance of an SRB-enriched Fe3O4@CF anode in the MFC. This superior activity can be assigned to the lower charge transfer resistance, higher conductance, and increased number of catalytic sites of the Fe3O4@CF electrode. The SRB-enriched Fe3O4@CF anode also assists in enhancing MFC performance in terms of COD removal (>75%), indicating efficient biodegradability of tannery wastewater and a higher electron transfer rate from SRBs to the conductive anode. These findings demonstrate that a combination of the favorable properties of nanocomposites such as Fe3O4@CF anodes and efficient microbes for treating complex wastes can encourage new directions for renewable energy–related applications.

R. Mateos, A. Sotres, Raúl M. Alonso et al.

Energies • 2019

Bioelectrochemical systems (BESs) is a term that encompasses a group of novel technologies able to interconvert electrical energy and chemical energy by means of a bioelectroactive biofilm. Microbial electrosynthesis (MES) systems, which branch off from BESs, are able to convert CO2 into valuable organic chemicals and fuels. This study demonstrates that CO2 reduction in MES systems can be enhanced by enriching the inoculum and improving CO2 availability to the biofilm. The proposed system is proven to be a repetitive, efficient, and selective way of consuming CO2 for the production of acetic acid, showing cathodic efficiencies of over 55% and CO2 conversions of over 80%. Continuous recirculation of the gas headspace through the catholyte allowed for a 44% improvement in performance, achieving CO2 fixation rates of 171 mL CO2 L−1·d−1, a maximum daily acetate production rate of 261 mg HAc·L−1·d−1, and a maximum acetate titer of 1957 mg·L−1. High-throughput sequencing revealed that CO2 reduction was mainly driven by a mixed-culture biocathode, in which Sporomusa and Clostridium, both bioelectrochemical acetogenic bacteria, were identified together with other species such as Desulfovibrio, Pseudomonas, Arcobacter, Acinetobacter or Sulfurospirillum, which are usually found in cathodic biofilms. Moreover, results suggest that these communities are responsible of maintaining a stable reactor performance.

Leifeng Chen, Leifeng Chen, Pier-Luc Tremblay et al.

Journal of Materials Chemistry A • 2016

Microbes can reduce CO2 into multicarbon chemicals with electrons acquired from the cathode of a bioelectrochemical reactor. This bioprocess is termed microbial electrosynthesis (MES). One of the main challenges for the development of highly productive MES reactors is achieving efficient electron transfer from the cathode to microbes. Here, carbon cloth cathodes modified with reduced graphene oxide functionalized with tetraethylene pentamine (rGO-TEPA) were readily self-assembled in the cathodic chamber of a MES reactor. Electroactive biofilms with unique spatial arrangement were subsequently formed with Sporomusa ovata at the surface of rGO-TEPA-modified electrodes resulting in a more performant MES process. The acetate production rate from CO2 was increased 3.6 fold with the formation of dense biofilms when wild type S. ovata was combined with rGO-TEPA. An improvement of 11.8 fold was observed with a highly structured biofilm including multiple spherical structures possibly consisting of bioinorganic networks of rGO-TEPA and bacterial cells from a novel strain of S. ovata adapted to reduce CO2 faster. The three dimensional biofilms observed in this study enabled highly effective electric interactions between S. ovata and the cathode, demonstrating that the development of dense cathode biofilms is an effective approach to improve MES productivity.

Xiaofang Yan, Danyang Liu, Johannes B. M. Klok et al.

Environmental Science &amp; Technology • 2023

Bioelectrochemical systems (BESs) are considered to be energy-efficient to convert ammonium, which is present in wastewater. The application of BESs as a technology to treat wastewater on an industrial scale is hindered by the slow removal rate and lack of understanding of the underlying ammonium conversion pathways. This study shows ammonium oxidation rates up to 228 ± 0.4 g-N m–3 d–1 under microoxic conditions (dissolved oxygen at 0.02–0.2 mg-O2/L), which is a significant improvement compared to anoxic conditions (120 ± 21 g-N m–3 d–1). We found that this enhancement was related to the formation of hydroxylamine (NH2OH), which is rate limiting in ammonium oxidation by ammonia-oxidizing microorganisms. NH2OH was intermediate in both the absence and presence of oxygen. The dominant end-product of ammonium oxidation was dinitrogen gas, with about 75% conversion efficiency in the presence of a microoxic level of dissolved oxygen and 100% conversion efficiency in the absence of oxygen. This work elucidates the dominant pathways under microoxic and anoxic conditions which is a step toward the application of BESs for ammonium removal in wastewater treatment.

Putty Ekadewi, M. Hardhi, Putri Anggun Puspitarini et al.

E3S Web of Conferences • 2018

Denitrification is the conversion process of nitrate to gaseous nitrogen forms carried out by bacteria commonly referred to as denitrifiers. Microbial Electrolysis Cell (MEC) is a type of bioelectrochemical system (BES) that is connected to external power source to aid the reactions. This research investigates the effect of applied voltage value on denitrification by nitrate removal efficiency of two model denitrifying species from the genus Pseudomonas in single-chambered MEC. Pseudomonas aeruginosa and Pseudomonas nitroreducens exhibited native removal efficiency at 70.62% and 68.20%, respectively. These values respectively reached up to 89.67% and 88.58% at 1.20 V, the upper limit of this study. Pseudomonas aeruginosa displayed better performance in MEC based off its produced current stability (mA) across the 0.35-1.20 V range. The effect of applied voltage on nitrate removal efficiency and setup performance was more prominent on known exoelectrogenic species of Pseudomonas such as Pseudomonas aeruginosa compared to Pseudomonas nitroreducens. Operating applied voltages of 0.35 V and 0.70 V was recommended for the application of the system based on technical and economical considerations. Further studies are needed to determine the response of the bacteria on wider range of applied voltages in MEC as well as elucidating these effects on autotrophic systems.

K. So, S. Kawai, Y. Hamano et al.

Physical Chemistry Chemical Physics • 2014

The fructose/dioxygen biofuel cell, one of the direct electron transfer (DET)-type bioelectrochemical devices, utilizes fructose dehydrogenase (FDH) on the anode and multi-copper oxidase such as bilirubin oxidase (BOD) on the cathode as catalysts. The power density in the literature is limited by the biocathode performance. We show that the DET-type biocathode performance is greatly improved, when bilirubin or some related substances are adsorbed on electrodes before the BOD adsorption. Several data show that the substrate modification induces the appropriate orientation of BOD on the electrode surface for the DET. The substrate-modification method has successfully been applied to air-breathing gas-diffusion-type biocathodes. We have also optimized the conditions of the FDH adsorption on carbon cryogel electrodes. Finally, a one-compartment DET-type biofuel cell without separators has been constructed, and the maximum power density of 2.6 mW cm(-2) was achieved at 0.46 V of cell voltage under quiescent (passive) and air atmospheric conditions.

Q. Fu, Yoshihiro Kuramochi, N. Fukushima et al.

Environmental Science &amp; Technology • 2015

The use of thermophilic microorganisms as biocatalysts for electromethanogenesis was investigated. Single-chamber reactors inoculated with thermophiles and operated at 55 °C showed high CH4 production rates (max. 1103 mmol m(–2) day(–1) at an applied voltage of 0.8 V) with current-capture efficiencies >90%, indicating that thermophiles have high potential as biocatalysts. To improve the electromethanogenic activity, the developed biocathode was transferred to a two-chamber reactor and operated at a poised potential of −0.5 V vs SHE. The CH4 production rates of the biocathode were enhanced approximately 6-fold in 160 h of poised-potential incubation, indicating that the acclimation of the biocathode resulted in performance improvement. Compositional alteration of the cathodic microbiota suggested that a Methanothermobacter-related methanogen and synergistetes- and thermotogae-related bacteria were selected during the acclimation. Cyclic voltammetry of the “acclimated” biocathode showed an augmented cathodic catalytic wave with a midpoint potential at ca. −0.35 V vs SHE. Moreover, the biocathode was able to catalyze electromethanogenesis at −0.35 V vs SHE. These results suggested that the ability of the biocathode to catalyze electromethanogenesis via direct electron transfer was enhanced by the acclimation. This study provides new technological and fundamental information on electromethanogenic bioelectrochemical systems (BESs) that may be extended to other BESs.

Ke Chen, Chunling Ma, Xiaolei Cheng et al.

Bioresources and Bioprocessing • 0

<jats:title>Abstract</jats:title><jats:p>It is of great significance to utilize CO<jats:sub>2</jats:sub> as feedstock to synthesize biobased products, particularly single cell protein (SCP) as the alternative food and feed. Bioelectrochemical system (BES) driven by clean electric energy has been regarded as a promising way for <jats:italic>Cupriavidus necator</jats:italic> to produce SCP from CO<jats:sub>2</jats:sub> directly. At present, the key problem of culturing <jats:italic>C. necator</jats:italic> in BES is that reactive oxygen species (ROS) generated in cathode chamber are harmful to bacterial growth. Therefore, it is necessary to find a solution to mitigate the negative effect of ROS. In this study, we constructed a number of <jats:italic>C. necator</jats:italic> strains displayed with superoxide dismutase (SOD), which allowed the decomposition of superoxide anion radical. The effects of promoters and signal peptides on the cell surface displayed SOD were analyzed. The proteins displayed on the surface were further verified by the fluorescence experiment. Finally, the growth of <jats:italic>C. necator</jats:italic> CMS incorporating a pBAD-SOD-E-tag-IgAβ plasmid could achieve 4.9 ± 1.0 of OD<jats:sub>600</jats:sub> by 7 days, equivalent to 1.7 ± 0.3 g/L dry cell weight (DCW), and the production rate was 0.24 ± 0.04 g/L/d DCW, around 2.7-fold increase than the original <jats:italic>C. necator</jats:italic> CMS (1.8 ± 0.3 of OD<jats:sub>600</jats:sub>). This study can provide an effective and novel strategy of cultivating strains for the production of CO<jats:sub>2</jats:sub>-derived SCP or other chemicals in BES.</jats:p> <jats:p><jats:bold>Graphical Abstract</jats:bold></jats:p>

Li-hua Huang, Xiu-fen Li, Yueping Ren et al.

• 2017

Microbial fuel cell (MFC) technology has potential in recovering bioelectricity from different types of waste, which attracts more and more attention in the field of environment and energy. However, low power density, high cost and low substrate degradation rate, closely associated with anode performance, limit its practical application. In this study, proportional polyaniline (PANI) together with graphene was chosen to obtain the PANI dopped graphene composite. The as-received composite was modified onto the surface of glassy carbon electrode. The results of electrochemical analysis showed that the optimal mass ratio of graphene was 20% for cyclic voltammetry (CV) and linear sweep voltammetry (LSV) analysis. The anodes with 5% graphene produced a peak power density of (831±45) mW·m-2, which was 1.2, 1.3, 1.3, 1.5, 1.8 times of those with 20% graphene, 1% graphene, graphene, PANI and carbon cloth, respectively. Moreover, 5% graphene reactors showed the maximum values in output voltage, open-circuit voltage (OCV), chemical oxygen demand (COD) removal rate, coulombic efficiency (CE), and biomass density. The polarization resistance was only (24±2)Ω in 5% graphene reactors,which was 19.8% of that of carbon cloth. The results of electrochemical analysis were not consistent with those of bioelectrochemical analysis, demonstrating that the biocompatibility of electrode was one of the important factors affecting MFC performance. 5% graphene anode showed full advantages of graphene and PANI, which improved the performance of MFC.

Hoang Dung Nguyen, T. Dao, Nguyen Xuan Que Vo

IOP Conference Series: Earth and Environmental Science • 2024

Microbial fuel cells (MFCs) present promising technology for sustainable wastewater treatment and energy generation. In this study, we operated an algae-MFC system to investigate its performance in terms of electricity generation and wastewater treatment capacity. The MFC reactor, with the support of a separate algae vessel providing oxygen-rich water to the cathode chamber, was continuously operated with varying organic loading rates to the anode with the synthetic wastewater. Results showed that the algae-MFC achieved a stable electricity generation, reaching a maximum power density of 840 mW m−3 at the highest chemical oxygen demand (COD) loading rate (0.30 kg m−3 h−1). Furthermore, the system could remove 75% of COD at a short HRT of 4 h. Coulombic efficiency was unexpectedly low, from 0.35% to 0.70%, indicating the need of energy recovery improvement from wastewater. A challenge of internal resistance increase over time was identified and discussed. Future prospects were discussed including the algae integrating directly into the cathode chamber to enhance the nitrogen removal and to explore the co-cultivation possibility of microalgae and autotrophic bacteria for a simultaneous removal of organic substances and nutrients. Overall, this study demonstrated the application potential of algae-MFC systems for sustainable wastewater treatment and energy production.

M. Ghasemi, A. Nassef, M. Al-Dhaifallah et al.

International Journal of Energy Research • 2020

The current work introduces an enhancement in the performance of the microbial fuel cell through estimating the optimal set of controlling parameters. The maximization of both power density (PD) and the percentage of chemical oxygen demand (COD) removal were considered as the enhancement in the cell's performance. Three main parameters in terms of performance as well as commercialization are the system's inputs; the Pt which takes the range of 0.1‐0.5 mg/cm2, the degree of sulphonation in sulfonated‐poly‐ether‐ether‐ketone that changes in the range of 20‐80%, and the rate of aeration of cathode which varies between 10 and 150 mL/min. From the experimental dataset, two robust adaptive neuro‐fuzzy inference system models based on the fuzzy logic technique have been constructed. The comparisons between the models' outputs and the experimental data showed well‐fitting in both training and testing datasets. The mean squared errors of the PD model, for testing and whole datasets, were found 2.575 and 0.909 while for the COD model it showed 19.242 and 6.791, respectively. Then, based on the two fuzzy models, a Particle Swarm Optimization algorithm has been used to determine the best parameters that maximize both of the PD and the COD removal of the cell. The optimization process was utilized for single and multi‐object optimization processes. In the single optimization, the resulting maximums of the PD and the COD removal were found 62.844 (mW/m2) and 99.99 (%), respectively. Whereas, in the multi‐object optimization, the values of 61.787 (mW/m2) and 96.21 (%) were reached as the maximums for the PD and COD, respectively. This implies that, in both cases of optimization processes, the adopted methodology can efficiently enhance the microbial fuel cell performances than the previous work.

Siti Mariam Daud, Mimi Hani Abu Bakar, W. R. Wan Daud et al.

Energy Science &amp; Engineering • 2021

A proton exchange membrane (PEM) is one of the most critical and expensive components in a dual‐chamber microbial fuel cell (MFC) that separates the anode and cathode chambers. The novel macroporous kaolin earthenware coated with polybenzimidazole (NKE‐PBI) fabricated in this study could become an alternative to PEM membranes. Briefly, PBI powder was dissolved in dimethylacetamide. Thereafter, NKE was fabricated at different porosities (10%, 20%, and 30%) using different starch powder volumes, which acted as pore‐forming agents. The NKE‐PBI with 30 vol% starch powder content produced the highest power output of 2450 ± 25 mW m−2 (10.50 A m−2) and internal resistance of 71 ± 19 Ω under batch mode operation. The MFC–PEM reactor generated the lowest power output at the highest internal resistance of up to 1300 ± 15 mW m−2 (3.7 A m−2) and 313 ± 16 Ω, respectively. In this study, the nonselective porous NKE coated with PBI membranes improved proton conduction activity and displayed comparable power performance with that of Nafion 117 in a dual‐chambered MFC. Therefore, a porous earthenware membrane coated with a proton conductor could become a potential separator in a scaled‐up MFC system for commercialization.

M. S. Bhagat, A. K. Mungray, A. Mungray

Environmental Technology • 2023

ABSTRACT This study explored the effect of a solenoid magnetic field (SOMF) as a pre-treatment on anaerobic sewage sludge (ASS) before using it in an osmotic microbial fuel cell (OMFC) as an inoculant. The ASS efficiency in terms of colony-forming unit (CFU) was improved ten times by applying SOMF compared to the control conditions. The obtained highest power density, current density, and water flux in the OMFC were 32.70 ± 5 mW·m−2, 135.13 ± 15 mA·m−2, and 4.24 ± 0.11 L·m−2h−1 respectively, for 72 h at 1 mT magnetic field. The coulombic efficiency (CE) and chemical oxygen demand (COD) removal efficiency were increased to 40–45% and 4–5% respectively, compared to un-treated ASS. Also, the start-up time of the ASS-OMFC system was almost reduced to 1–2 days based on open circuit voltage data. On the other hand, increasing the pre-treatment intensity of SOMF with time, it decreased the performance of OMFC. Also, the low intensity with increased pre-treatment time up to a specific limit enhanced the performance of OMFC. GRAPHICAL ABSTRACT

Pankaj Kumar Dubey, Bindeshwar Singh, Varun Kumar

• 0

<jats:p id="p1">Fuel cells are used in many applications, from personal use to energy generation stations. The fuel cell 2 The entire system is efficient at maximum and half load, scales to a variety of sizes, is eco-friendly and has potentially comparable initial costs to conventional technologies. Portable electricity, mobility, cogeneration in buildings, and distributed electricity for utilities are promising applications for fuel cells. The vital barriers to the money orientation of fuel cells are pricing and longevity. We will talk about fuel cells, the classification of fuel cells, fuel cell problems, and how artificial intelligence can help improve the performance of fuel cells.</jats:p>

Qiuhong Jia, Caizhi Zhang, Bin Deng et al.

Journal of Fuel Cell Science and Technology • 2015

<jats:p>In a proton exchange membrane fuel cell (PEMFC), the hydrogen feed into the anode in a periodical pressure swing, so-called hydrogen pressure pulsation feed (HPPF), significantly affects the transport phenomena of hydrogen and water in the anode flow field. HPPF could adjust the distribution of the back diffusion water and the hydrogen partial pressure along the anode flow channels, improve hydrogen mass transfer in the anode flow field, and enhance the diffusion of hydrogen in the porous medium (anode diffusion layer). On the other hand, HPPF technique could mitigate the anode flooding issue caused by water back diffusion from the cathode, improve the fuel cell performance. In this work, the principle of HPPF technique was introduced and analyzed by a mathematic approach. Some of the important parameters used in HPPF technique, such as amplitude of pulsation pressure, pulsating frequency, etc., were experimentally investigated on dead-end mode PEMFC stack. The experimental results showed that the amplitude of pressure pulsation, pulsating frequency, and position applied for HPPF highly affected the performance of the PEMFC stack. It can be seen that higher the frequency and/or amplitude of pressure pulsation, the better the performance of PEMFC stack.</jats:p>

K. Rani, P. Sobha Rani, N. Chaitanya et al.

International Journal of Intelligent Engineering and Systems • 2022

Currently, modern electrical distribution networks (EDNs) are experiencing high demand with emerging electric vehicle loads and are being planned for specific load requirements such as agricultural loads. In this connection, characterization and optimization of their performance become essential in planning studies. In this paper, optimal reactive power compensation using a distribution-static synchronous compensator (D-STATCOM) is proposed with the aim of loss reduction, voltage profile improvement and voltage stability enhancement different types of loads including agricultural and electric vehicle loads. A recent efficient meta-heuristic approach, improved bald eagle search (IBES), is implemented for solving the proposed optimization problem considering different operational and planning constraints. The simulation results are performed on IEEE 33-bus for different types of load modelling. The computational efficiency of IBES is compared with basic BES and other literature works. From the results, IBES has shown superior computational characteristics than all compared works. On the other hand, the optimal location and size of D-STATCOM caused significant loss reduction, voltage profile improvement and voltage stability enhancement for kinds of loads as experiencing in the modern EDNs.

H. Zou, L. Chu, Yan Wang

Archives of Environmental Protection • 2023

Azo dye wastewater treatment is urgent necessary nowadays. Electrochemical technologies commonly enable more effi cient degradation of recalcitrant organic contaminants than biological methods, but those rely greatly on the energy consumption. A novel process of biofi lm coupled with electrolysis, i.e., bioelectrochemical system (BES), for methyl orange (MO) dye wastewater treatment was proposed and optimization of main infl uence factors was performed in this study. The results showed that BES had a positive effect on enhancement of color removal of MO wastewater and 81.9% of color removal effi ciency was achieved at the optimum process parameters: applied voltage of 2.0 V, initial MO concentration of 20 mg/L, glucose loads of 0.5 g/L and pH of 8.0 when the hydraulic retention time (HRT) was maintained at 3 d, displaying an excellent color removal performance. Importantly, a wide range of effective pH, ranging from 6 to 9, was found, thus greatly favoring the practical application of BES described here. The absence of a peak at 463 nm showed that the azo bond of MO was almost completely cleaved after degradation in BES. From these results, the proposed method of biodegradation combined with electrochemical technique can be an effective technology for dye wastewater treatment and may hopefully be also applied for treatment of other recalcitrant compounds in water and wastewater. Azo dye wastewater treatment in a novel process of biofi lm coupled with electrolysis 39 wastewater by using BES in this study. In the BES designed here, a stainless steel column was used as the cathode, where an activated carbon fi ber (ACF) was attached to the surface of cathode to enrich microorganisms. The performance of BES was assessed in terms of color removal effi ciency of MO. The effect of applied voltage, MO concentration, carbon source content and pH on MO denitrifi cation rate was investigated to optimize the operation on BES. Moreover, to investigate the change of molecular and structural characteristics during the MO treatment, UV/Visible absorption spectra with reaction time was further analyzed. These results obtained from this study, BES linking biological with electrochemical process, may serve as a new suggestion for the treatment of dye wastewaters or non-biodegradable industrial wastewaters. Material and methods Experimental setup The BES was made from polyvinyl chloride with a single-chamber cylinder and Figure 1 shows the schematic diagram of BES adopted in this study. The BES had a total and working volume of 4.0 L and 3.0 L respectively with an internal diameter of 16 cm and 20 cm in height. The BES consisted of an ACF (Shanghai Zhaokuo, Co., Ltd, China) wrapped around the stainless steel column (6 cm internal diameter × 12 cm height × 0.15 cm wall thickness) as the cathode electrode and a high-purity graphite rod (2 cm diameter × 13 cm length) as the anode electrode. An adjustable direct current regulated power supply (PS-305DM; Dongguan Longwei Electronic Technology, Co., Ltd, China) was connected with anode and cathode to provide voltage. Besides, an automatic stirrer (OS20; Beijing Dragon Laboratory Instruments Limited, China) was installed at the top of the BES to provide well-mixed environment. Experimental design After construction, the experiments were carried out for 167 days. Activated sludge (1 L, 1 g/L of MLSS), i.e., seed sludge, was collected from an oxidation ditch confi guration (Fengyang Municipal Wastewater Treatment Plant, Anhui, China) and immediately washed three times using deionized water to remove soluble carbon sources. And then, it was inoculated in the BES reactor to accelerate the biofi lm development onto the surface of ACF cathode, including three stages: fi rstly, from day 0 to day 20, a single synthetic wastewater was fed to the BES to promote the rapid growth of microorganisms; secondly, after that, a 1:1 (vol/vol) mixture of synthetic wastewater and azo dyes wastewater containing 30 mg/L MO was fed for 15 days to gradually enrich the specifi c microorganisms; fi nally, from day 36, it was intensively enriched by feeding the only MO wastewater for 30 days. In order to investigate the effect of process parameters on MO color removal in BES, the applied voltage, MO concentration, carbon source content and pH were gradually increased respectively (see Table 1) after biofi lm formation. During the experimental period, the hydraulic retention time (HRT) was maintained at 3 d according to the preliminary test. The synthetic wastewater consisted of organic carbon, nutrients and buffer solution and its composition is as follows: 40 mg/L KH2PO4, 40 mg/L (NH4)2SO4, 3 mg/L CaCl2, 45 mg/L MgSO4∙7H2O and 1 mL/L of nutrient solution (1200 mg/L FeCl3∙6H2O, 130 mg/L H3BO3, 25 mg/L CuSO4∙5H2O, 160 mg/L KI, 100 mg/L MnCl2∙4H2O, 50 mg/L Na2MoO4∙2H2O, 110 mg/L ZnSO4∙7H2O, 130 mg/L CoCl2∙6H2O and 800 mg/L EDTA). In addition, glucose and MO were added into the synthetic wastewater according to the experimental arrangement, which was used as the carbon source. The other compositions acted as nutrient and buffer solution for microbial growth. Analytical methods Samples of effl uents were fi ltered through a 0.22 μm-pore-size syringe fi lter prior to analysis. MLSS analysis was performed according to the standard methods (APHA, 2005). pH was measured by a pH meter analyzer (S20, Mettler-Toledo, Switzerland). Absorbance was analyzed by measuring the adsorption at 463 nm using an UV-3600 (Shimadzu, Japan). Fig. 1. Schematic diagram of BES 40 H. Zou, L. Chu, Y. Wang Results and discussion Effect of applied voltage on color removal The performance of color removal in BES at different applied voltages (HRT: 3 d; applied voltage: 0, 0.6, 0.8, 1.0, 1.4, 1.8, 2.2, 2.5 and 3.0) are shown in Figure 2. MO concentration of infl uent was maintained at 20 mg/L. It is clearly observed from Figure 2 that color removal effi ciency increased with the increasing voltage applied from 0 V to 2.5 V, displaying the promoting effect of applied voltage on color removal. The BES is totally related to the current density and it was enhanced with the increasing voltage applied, providing suitable conditions for microorganism on the biofi lm and electrochemical reaction (Chen et al. 2015). The highest color removal effi ciency (80.5%) was observed in BES at an applied voltage of 2.5 V. The reason might be that the presence of current density was more conductive to the bacteria growth and electrochemical reaction. At 3.0 V, it was declined to 77.2%. This can be due to the fact that high concentrations of intermediate products would be formed in solution at an excessive applied voltage. There exists an inevitable comparison for electron between the further degradation of intermediate products and the rupture of –N=N– at the cathode’s surface (Liu et al. 2015), leading to the decline in current effi ciency. Notably, the color removal effi ciency was 68.9% at 1.8 V signifi cantly higher than that at 1.4 V (53.5%) in BES. This may be attributed to the oxidative electrolysis of water and reduction of protons (Thrash and Coates 2008), thus producing more oxygen at anode and hydrogen at cathode, which were utilized by microorganisms as electron acceptor and electron. Table 1. Experimental design used here Process parameters Set value Applied voltage 0, 0.6, 0.8, 1.0, 1.4, 1.8, 2.2, 2.5 and 3.0 V MO concentration 5, 10, 20, 40, 60, 80, 100 mg/L Carbon source content 0, 0.1, 0.3, 0.5, 0.7, and 1.0 g/L pH 3, 4, 5, 6, 7, 8, 9, 10, and 11 Fig. 2. Color removal effi ciency at different applied voltages in BES Fig. 3. Color removal effi ciency with different dye concentration of infl uent in BES As the BES was controlled under no electric fi led, i.e., applied voltage of 0 V, exhibiting only a typical biological reaction, the color removal effi ciency was rather low (21.2%). Dye wastewater is well known to be of low biodegradability, which was hard to be treated by using only a single biological treatment method. And then, it was sharply increased up to 36.8% at 0.6 V, suggesting that micro-current fl owing through the biofi lm on the cathodic surface had positive effect on the microbial metabolism due to the electric fi eld stimulation. Effect of dye concentration on color removal The effects of different MO concentration of infl uent (5, 10, 20, 40, 60, 80, 100 mg/L) on color removal performance are shown in Figure 3. During the treatment process, BES was operated at the same condition (HRT: 3 d; applied voltage: 2.0 V). Color removal effi ciency gradually decreased from 90.2% to 42.8% with the increase of initial MO concentration ranging from 5 mg/L to 100 mg/L, displaying a negative effect of initial dye loading on BES, which may be most likely due to the toxicity of the dye metabolites (such as aromatic amines) produced during dye reduction at high dye concentrations (Pearce et al. 2003). Similar results were also found in a report (Sponza and Işik 2005) that increase in Direct Black 38 concentration caused a decrease in color removal effi ciency in an anaerobic/aerobic sequential reactor responsible for dye wastewater treatment. These results suggested that the biomass inhibition effect could occur in BES when the dye concentration exceeded a proper range. Effect of carbon source content on color removal Figure 4 shows the effect of different carbon source content (0, 0.1, 0.3, 0.5, 0.7, and 1.0 g/L), glucose used here, on the color removal performance in BES. The other operation conditions were listed as follows: HRT=3 d, applied voltage=2.0 V, initial MO concentration=20 mg/L. It was observed that glucose displayed an obvious promotion on color removal effi ciency in BES. The color removal effi ciency was only 36.2% without addition of carbon source and it increased signifi cantly up to 59.5% with the addition of 0.1 mg/L of glucose. This result was consistent with other studies (Al-Amrani et al. 2013, Murali et al. 2013), where co-subs

Vijay Babu Pamshetti, Wei Zhang

2024 IEEE 4th International Conference on Sustainable Energy and Future Electric Transportation (SEFET) • 2024

The objective of this study is to assess the optimal design and operational strategy for multi-microgrids (MMGs) within an active distribution network, with the aim of enhancing supply security and reliability. In accordance with this perspective, the paper introduces a three-layer coordinated operational planning framework for MMG planning. This framework considers various elements, including distributed generation (DGs) such as wind, biomass, and solar production, distributed reactive power sources (DRSs), and battery energy storage (BES). The primary goal of the provided framework is to minimize power exchange between MMGs and the anticipated energy not served, ultimately leading to an enhancement in supply security and reliability. Furthermore, the study explores the impact of conservation voltage reduction (CVR). To address the unpredictability of load consumption and renewable energy generation, scenario modeling was implemented. A backward scenario reduction technique was then employed to strike a balance between model accuracy and computational efficiency. To validate the proposed framework, it was implemented on an IEEE 33 bus distribution system. Comparative analysis against conventional planning schemes revealed a significant improvement, with a 58.37% reduction in supply exchange between MMGs and a 63.91 % decrease in energy not served achieved by the proposed MMG formulation. These test results underscore the superior efficacy of the proposed framework in enhancing both supply security and reliability when compared to conventional planning approaches.

D. H. Wang, D. H. Wang, Do Youb Kim et al.

Angewandte Chemie International Edition • 2011

This research was supported by Future-based Technology Development Program (Nano Fields, 2010-0029321) and the WCU (World Class University) program (R32-2008-000-10142-0) through the NRF of Korea funded by the MEST. J. H. Park acknowledges the support from NRF of Korea funded by the MEST (NRF-2009- C1AAA001-2009-0094157, 2011-0006268). Research at UCSB was supported by the US Army General Technical Services (LLC/GTS-S- 09-1-196) and by the Department of Energy (BES-DOE- ER46535).

Yew Weng Kean, A. Ramasamy, S. Sukumar et al.

International Journal of Power Electronics and Drive Systems (IJPEDS) • 2018

This paper presents a stand-alone hybrid renewable energy system (SHRES) consisting of solar photovoltaic (PV), wind turbine (WT) and battery energy storage (BES) in an effort reduce the dependence on fossil fuels. The renewable energy sources have individual inverters and the PV inverter of the SHRES is operated using active and reactive power control. The PV inverter have two main control structures which are active power control and reactive power control and each contain a proportional integral (PI) controller. Accurate control of the PV inverter’s active power is essential for PV curtailment applications. Thus, this paper aims to enhance the performance of the SHRES in this work by optimizing the performance of the PV inverter’s active power PI controller parameters through the design of adaptive controllers. Therefore, an adaptive controller and an optimized adaptive controller are proposed in this paper. The performances of the proposed controllers are evaluated by minimizing the objective function which is the integral of the time weighted absolute error (ITAE) criterion and this performance is then compared with a controller that is tuned by the traditional trial and error method. Simulation results showed that the optimized adaptive controller is better as it recorded an error improvement of 42.59%. The dynamic optimized adaptive controller is more adept at handling the fast changes of the SHRES operation.

P. Kirmizakis, R. Doherty, C. Mendonça et al.

Environmental Science and Pollution Research • 2019

Here, we show the electrical response, bacterial community, and remediation of hydrocarbon-contaminated groundwater from a gasworks site using a graphite-chambered bio-electrochemical system (BES) that utilizes granular activated carbon (GAC) as both sorption agent and high surface area anode. Our innovative concept is the design of a graphite electrode chamber system rather than a classic non-conductive BES chamber coupled with GAC as part of the BES. The GAC BES is a good candidate as a sustainable remediation technology that provides improved degradation over GAC, and near real-time observation of associated electrical output. The BES chambers were effectively colonized by the bacterial communities from the contaminated groundwater. Principal coordinate analysis (PCoA) of UniFrac Observed Taxonomic Units shows distinct grouping of microbial types that are associated with the presence of GAC, and grouping of microbial types associated with electroactivity. Bacterial community analysis showed that β-proteobacteria (particularly the PAH-degrading Pseudomonadaceae) dominate all the samples. Rhodocyclaceae- and Comamonadaceae-related OTU were observed to increase in BES cells. The GAC BES (99% removal) outperformed the control graphite GAC chamber, as well as a graphite BES and a control chamber both filled with glass beads.

Jamal Faraji, M. Babaei, Navid Bayati et al.

Electronics • 2019

Extreme weather events lead to electrical network failures, damages, and long-lasting blackouts. Therefore, enhancement of the resiliency of electrical systems during emergency situations is essential. By using the concept of standby redundancy, this paper proposes two different energy systems for increasing load resiliency during a random blackout. The main contribution of this paper is the techno-economic and environmental comparison of two different resilient energy systems. The first energy system utilizes a typical traditional generator (TG) as a standby component for providing electricity during the blackouts and the second energy system is a grid-connected microgrid consisting of photovoltaic (PV) and battery energy storage (BES) as a standby component. Sensitivity analyses are conducted to investigate the survivability of both energy systems during the blackouts. The objective function minimizes total net present cost (NPC) and cost of energy (COE) by considering the defined constraints of the system for increasing the resiliency. Simulations are performed by HOMER, and results show that for having almost the same resilience enhancement in both systems, the second system, which is a grid-connected microgrid, indicates lower NPC and COE compared to the first system. More comparison details are shown in this paper to highlight the effectiveness and weakness of each resilient energy system.

Bhim Singh, Farheen Chishti, Shadab Murshid

2019 International Conference on Electrical, Electronics and Computer Engineering (UPCON) • 2019

This work proposes a solution for improving the voltage profile at point of common coupling (PCC) of an isolated microgrid using an improved filtered-X adaptive scheme. The power quality (PQ) is enhanced by filtering the component of load current so as to reduce the harmonic content. The enhanced PQ allows the application of voltage sensitive equipments and electronic loads together with nonlinear loads connected at PCC. The improved filtered X-control which is a variant of the least mean square (LMS) adaptive filter family, provides good convergence and low computational burden with good applicability in terms of noise reduction and harmonics filtering. Maximum power extraction scheme i.e. perturb and observe (P&O) is implemented to acquire the reference speed of synchronous generator (SG) generating wind power. The regulation of SG speed is acquired by implementing sensor-less field oriented control. The battery backs up the power, moreover, it promotes the overall performance of the microgrid. The test setup developed in the laboratory confirms the effective microgrid performance in the presence of load alterations and renewable intermittency.

Subhadip Chakraborty, Gaurav Modi, Bhim Singh

2022 IEEE 2nd International Conference on Sustainable Energy and Future Electric Transportation (SeFeT) • 2022

This paper presents a power management scheme to optimize the overall electrical energy consumption of a solar photovoltaic (SPV) array- battery energy storage (BES) based grid-connected microgrid (MG) for a water supply system (WSS). This paper utilizes the BES as an alternative to the diesel generator (DG) set to reduce the peak demand and energy consumption from the grid during peak hours and provide backup during the islanded condition. This paper also presents a cascaded non-identical frequency adaptive generalized integrator with a modified structure low pass filter type frequency locked loop (CNIFAGI-MSLPF-FLL) control algorithm during grid-connected mode (GCM) operation and a proportional multi resonant (PMR) controller with load current filter control during standalone mode (SAM) operation of the MG. The GCM and SAM controls along with the synchronization control, ensure seamless power transfer to the loads and improve the grid power quality (PQ) even in the presence of local nonlinear and single-phase loads. The power management with the load profile of WSS and the PQ performance of the system is analyzed in various conditions with developed Simulink model of MG.

Jamie P. Smith, Jonathan P. Metters, Osama I. G. Khreit et al.

Analytical Chemistry • 2014

The electrochemical sensing of new psychoactive substance(s) (NPSs), synthetic cathinone derivatives also termed "legal highs", are explored with the use of metallic modified screen-printed electrochemical sensors (SPES). It is found that no significant electrochemical enhancement is evident with the use of either in situ bismuth or mercury film modified SPES compared to the bare underlying electrode substrate. In fact, the direct electrochemical reduction of the cathinone derivatives mephedrone (4-methylmethcathinone; 4-MMC) and 4'-methyl-N-ethylcathinone (4-methylethcathinone; 4-MEC) is found to be possible for the first time, without heavy metal catalysis, giving rise to useful voltammetric electroanalytical signatures in model aqueous buffer solutions. This novel electroanalytical methodology is validated toward the determination of cathinone derivatives (4-MMC and 4-MEC) in three seized street samples that are independently analyzed with high-performance liquid chromatography (HPLC) wherein excellent agreement between the two analytical protocols is found. Such an approach provides a validated laboratory tool for the quantification of synthetic cathinone derivatives and holds potential for the basis of a portable analytical sensor for the determination of synthetic cathinone derivatives in seized street samples.

Jiahe Yan, Qin Lu, G. Giannakis

IEEE Transactions on Wireless Communications • 2022

Recent years have witnessed the emergence of mobile edge computing (MEC), on the premise of a cost-effective enhancement in the computational ability of hardware-constrained wireless devices (WDs) comprising the Internet of Things (IoT). In a general multi-server multi-user MEC system, each WD has a computational task to execute and has to select binary (off)loading decisions, along with the analog-amplitude resource allocation variables in an online manner, with the goal of minimizing the overall energy-delay cost (EDC) with dynamic system states. While past works typically rely on the explicit expression of the EDC function, the present contribution considers a practical setting, where in lieu of system state information, the EDC function is not available in analytical form, and instead only the function values at queried points are revealed. Towards tackling such a challenging online combinatorial problem with only bandit information, novel Bayesian optimization (BO) based approaches are put forth by leveraging the multi-armed bandit (MAB) framework. Per time slot, the discrete offloading decisions are first obtained via the MAB method, and the analog resource allocation variables are subsequently optimized using the BO selection rule. By exploiting both temporal and contextual information, two novel BO approaches, termed time-varying BO and contextual time-varying BO, are developed. Numerical tests validate the merits of the proposed BO approaches compared with contemporary benchmarks under different MEC network sizes.

Dinh C. Nguyen, Ming Ding, P. Pathirana et al.

IEEE Transactions on Mobile Computing • 2021

The convergence of mobile edge computing (MEC) and blockchain is transforming the current computing services in mobile networks, by offering task offloading solutions with security enhancement empowered by blockchain mining. Nevertheless, these important enabling technologies have been studied separately in most existing works. This article proposes a novel cooperative task offloading and block mining (TOBM) scheme for a blockchain-based MEC system where each edge device not only handles data tasks but also deals with block mining for improving the system utility. To address the latency issues caused by the blockchain operation in MEC, we develop a new Proof-of-Reputation consensus mechanism based on a lightweight block verification strategy. A multi-objective function is then formulated to maximize the system utility of the blockchain-based MEC system, by jointly optimizing offloading decision, channel selection, transmit power allocation, and computational resource allocation. We propose a novel distributed deep reinforcement learning-based approach by using a multi-agent deep deterministic policy gradient algorithm. We then develop a game-theoretic solution to model the offloading and mining competition among edge devices as a potential game, and prove the existence of a pure Nash equilibrium. Simulation results demonstrate the significant system utility improvements of our proposed scheme over baseline approaches.

Dan Luo, Chuyin Ma, Junfeng Hou et al.

Advanced Energy Materials • 2022

Sodium‐ion batteries (SIBs) have attracted much attention for their advantages of high operating voltage, environmental friendliness and cost‐effectiveness. However, the intrinsic defects of anode materials (such as poor electrical conductivity, sluggish kinetics, and large volume changes) hinder them from meeting the requirements for practical applications. Herein, a Nb2O5@carbon nanoreactor containing both a O–Nb–C heterointerface and oxygen vacancies (Nb2O5‐x@MEC) as an anode material is designed to drive SIBs toward extraordinary capacity and ultra‐long cycle life. The heterostructured nanoreactor both effectively immobilizes defective Nb2O5 by forming O‐Nb‐C heterointerface and offers homogeneous dispersion of Nb2O5 with desirable content to prevent their agglomeration. In addition, vast active interfaces, favored electrolyte infiltration, and a well‐structured ion–electron transportation channel are enabled by the framework, improving sodium ion storage and enhancing redox reaction kinetics. The enhancement brought by spatial confinement, defect implantation and heterointerface design give the composites a highly reversible sodiation–desodiation process and remarkable structural stability. By virtue of these superiorities, Nb2O5‐x@MEC delivers excellent performance, i.e., high areal capacity over 1.1 mAh cm‐2, admirable rate capability up to 20 A g‐1, and ultra‐long cycling performance over 5000 cycles, holding great promise for utilization in practically viable SIBs.

Pengcheng Chen, Yuxuan Yang, Bin Lyu et al.

IEEE Internet of Things Journal • 2024

In this article, we propose a movable antenna (MA)-enhanced scheme for wireless-powered mobile-edge computing (WP-MEC) system, where the hybrid access point (HAP) equipped with multiple MAs first emits wireless energy to charge wireless devices (WDs), and then receives the offloaded tasks from the WDs for edge computing. The MAs deployed at the HAP enhance the spatial Degrees of Freedom (DoFs) by flexibly adjusting the positions of MAs within an available region, thereby improving the efficiency of both downlink wireless energy transfer (WPT) and uplink task offloading. To balance the performance enhancement against the implementation intricacy, we further propose three types of MA positioning configurations, i.e., dynamic MA positioning, semidynamic MA positioning, and static MA positioning. In addition, the nonlinear power conversion of energy harvesting (EH) circuits at the WDs and the finite computing capability at the edge server are taken into account. Our objective is to maximize the sum computational rate (SCR) by jointly optimizing the time allocation, positions of MAs, energy beamforming matrix, receive combing vectors, and offloading strategies of WDs. To solve the nonconvex problems, efficient alternating optimization (AO) frameworks are proposed. Moreover, we propose a hybrid algorithm of particle swarm optimization with variable local search (PSO-VLS) to solve the subproblem of MA positioning. Numerical results validate the superiority of exploiting MAs over the fixed-position antennas (FPAs) for enhancing the SCR performance of WP-MEC systems.

Yue Li, Zhiqiang Zhao, Yafei Yang et al.

Journal of Chemical Technology &amp; Biotechnology • 2018

BACKGROUND Microbial electrolysis cell (MEC) has been widely reported as an efficient strategy to enhance anaerobic digestion. However, the role of MEC during acidogenesis for treatment of sulfate-containing wastes remains unclear as so far. In this study a pair of electrodes was placed into an acidogennic reactor to form a MEC-based acidogenesis to investigate its performance in sulfate-containing wastewater treatment. RESULTS MEC obviously improved anaerobic acidogenesis to treat sulfate-containing wastewater. Higher COD removal and sulfate reduction were obtained in the MEC-based acidogenesis even under high sulfate loading conditions. MEC accelerated the conversion of substrate to acetate, indicationg the acidogenesis was enhanced. From Fluorescence in situ hybridization (FISH) analysis, exoelectrogenic bacteria were enriched in anodic biofilm. CONCLUSION The syntrophic metabolism between anodic exoelectrogenic bacteria and anaerobic fermentative bacteria enriched might accelerate the anodic decomposition of complex substrates as well as cathodic sulfate reduction, then providing a positive environment for sulfate reduction during acidogenesis.

Kai Hu, Shuo-qiu Jia, Cheng Yang et al.

Bioengineered • 2020

ABSTRACT The influence of freezing-thawing (F/T) pretreatment on the degradation of highly concentrated organic matters from dewatered sludge (DS) in microbial electrolysis cell (MEC) was investigated in this study. Extended freezing disintegrated the DS matrix and resulted in accelerated hydrolysis rate. The biogas production and stabilization were increased due to the pretreatment by 25–70% of H2 production rate and 17.8–33.8% of COD reduction rate, respectively. Fourier transform infrared spectroscopy analysis indicated that the pretreatment was unable to alter the bioelectrochemical reactions except for accelerating degradation rate. Excitation and emission matrix (EEM) spectra showed that aromatic protein and soluble microbial products (SMPs)-like materials in DS were increasingly solubilized by the pretreatment and significantly removed during electrogenesis. The F/T-pretreated DS favored the enrichment of exoelectrogens in MEC. Graphical Abstract

Jeong-A Lim, Yeongjin Kim

2022 19th Annual IEEE International Conference on Sensing, Communication, and Networking (SECON) • 2022

As deep learning technology advances, mobile vision applications such as augmented reality or autonomous vehicles are widespread. The quality of experience (QoE) of such applications highly depends on hardware specification of mobile device, dynamic service requests, stochastic network status and characteristics of DNN model. In this paper, we propose an algorithm called RT-DMP that jointly optimizes DNN model partitioning and process/network resources adapting to system dynamics by leveraging virtual queue-based Lyapunov optimization framework. The RT-DMP jointly makes decisions on (i) partition point between a mobile device and an MEC server, (ii) mobile GPU clock frequency, and (iii) transmission rate through the wireless network every time slot. We theoretically show that RT-DMP optimally strikes the balance among three QoE metrics that are energy consumption, throughput and end-to-end latency, which has not been addressed in existing studies. Finally, we demonstrate the performance and feasibility of RT-DMP via trace-driven simulations and real testbed based on Nvidia Jetson TX2 and a high-end MEC server.

Yu Xu, Tiankui Zhang, Dingcheng Yang et al.

2021 IEEE International Conference on Communications Workshops (ICC Workshops) • 2021

Unmanned aerial vehicle (UAV) has the potential to support the terminal devices (TDs) performing the mobile edge computing (MEC) in Internet of Things (IoT). This paper investigates a UAV-assisted relaying and MEC network, in which the UAV acts as a MEC server to assist computation for the computation-hungry TDs, and also as a relay to deliver the sub-tasks to a ground access point (AP) for execution. We aim to minimize the task completion time of the network by jointly optimizing the communication bandwidth, UAV transmit power, computation resource, task partition, and UAV’s three-dimensional (3D) location deployment. Although the formulated problem is complex and non-convex, it is decomposed into three low-complex subproblems, and then efficiently solved by the proposed successive convex approximation (SCA) based joint optimization algorithm. Finally, numerical results demonstrate that: 1) a superior convergence is achieved by the proposed algorithm; 2) the 3D deployment optimization extremely contributes to the performance enhancement; 3) the task completion time is dramatically reduced by applying the proposed algorithm, compared to the benchmark schemes.

Abudukeremu Kadier, Yibadatihan Simayi, Washington Logroño et al.

• 2015

The Microbial electrolysis cell (MEC) is one of the promising and cutting-edge technologies for generating hydrogen from wastewater through biodegradation of organic waste by exoelectrogenic microbes. In MECs the operational parameters, such as applied voltage (E ap ), anode surface area, anode-cathode distance, and N 2 /CO 2 volume ratio have a significant impact on hydrogen yield and production. In the present study, to enhance current and hydrogen production of MECs, the effects of key operational conditions on the MEC performance were extensively investigated. The optimal operating condition for hydrogen production in MECs was determined as: the optimum applied voltage of 1.1 V, an anode surface area of 94 (cm 2 ), an anode-cathode distance of 1.5 (cm), and a N 2 /CO 2 volume ratio of 4:1. With these optimum conditions, the maximum H 2 volume, current density and hydrogen production rate (HPR) of the MEC reached to 270.09 mL, 314.01 ± 2.81 A/m 3 , and 4.25 ± 0.55 m 3 H 2 /m 3 d, respectively. The results obtained in this study imply that a systematic investigation of the key operational variables is an effective strategy to maximize the hydrogen production in single-chamber MECs.