Procedure for determining maximum sustainable power generated by microbial fuel cells

Power generated by microbial fuel cells is computed as a product of current passing through an external resistor and voltage drop across this resistor. If the applied resistance is very low, then high instantaneous power generated by the cell is measured, which is not sustainable; the cell cannot deliver that much power for long periods of time. Since using small electrical resistors leads to erroneous assessment of the capabilities of microbial fuel cells, a question arises: what resistor should be used in such measurements? To address this question, we have defined the sustainable power as the steady state of power delivery by a microbial fuel cell under a given set of conditions and the maximum sustainable power as the highest sustainable power that a microbial fuel cell can deliver under a given set of conditions. Selecting the external resistance that is associated with the maximum sustainable power in a microbial fuel cell (MFC) is difficult because the operator has limited influence on the main factors that control power generation: the rate of charge transfer at the current-limiting electrode and the potential established across the fuel cell. The internal electrical resistance of microbial fuel cells varies, and it depends on the operational conditions of the fuel cell. We have designed an empirical procedure to predict the maximum sustainable power that can be generated by a microbial fuel cell operated under a given set of conditions. Following the procedure, we change the external resistors incrementally, in steps of 500 omega every 10, 60, or 180 s and measure the anode potential, the cathode potential, and the cell current. Power generated in the microbial fuel cell that we were using was limited by the anodic current. The anodic potential was used to determine the condition where the maximum sustainable power is obtained. The procedure is simple, microbial fuel cells can be characterized within an hour, and the results of the measurements can serve many purposes, such as: (1) estimating power generation in various MFCs, (2) comparing power generation in MFCs using different electroactive reactants, (3) quantifying the effects of the operational regime on the power generation in MFCs, and finally, (4) the purpose for which the procedure was designed, optimizing the performance of existing MFCs.     

Benthic microbial fuel cell as direct power source for an acoustic modem and seawater oxygen/temperature sensor system

Supported by the natural potential difference between anoxic sediment and oxic seawater, benthic microbial fuel cells (BMFCs) promise to be ideal power sources for certain low-power marine sensors and communication devices. In this study a chambered BMFC with a 0.25 m(2) footprint was used to power an acoustic modem interfaced with an oceanographic sensor that measures dissolved oxygen and temperature. The experiment was conducted in Yaquina Bay, Oregon over 50 days. Several improvements were made in the BMFC design and power management system based on lessons learned from earlier prototypes. The energy was harvested by a dynamic gain charge pump circuit that maintains a desired point on the BMFC's power curve and stores the energy in a 200 F supercapacitor. The system also used an ultralow power microcontroller and quartz clock to read the oxygen/temperature sensor hourly, store data with a time stamp, and perform daily polarizations. Data records were transmitted to the surface by the acoustic modem every 1-5 days after receiving an acoustic prompt from a surface hydrophone. After jump-starting energy production with supplemental macroalgae placed in the BMFC's anode chamber, the average power density of the BMFC adjusted to 44 mW/m(2) of seafloor area which is better than past demonstrations at this site. The highest power density was 158 mW/m(2), and the useful energy produced and stored was ≥ 1.7 times the energy required to operate the system.     

Electricity generation from synthetic acid-mine drainage (AMD) water using fuel cell technologies

Acid-mine drainage (AMD) is difficult and costly to treat. We investigated a new approach to AMD treatment using fuel cell technologies to generate electricity while removing iron from the water. Utilizing a recently developed microbial fuel cell architecture, we developed an acid-mine drainage fuel cell (AMD-FC) capable of abiotic electricity generation. The AMD-FC operated in fed-batch mode generated a maximum power density of 290 mW/m2 at a Coulombic efficiency greater than 97%. Ferrous iron was completely removed through oxidation to insoluble Fe(III), forming a precipitate in the bottom of the anode chamber and on the anode electrode. Several factors were examined to determine their effect on operation, including pH, ferrous iron concentration, and solution chemistry. Optimum conditions were a pH of 6.3 and a ferrous iron concentration above approximately 0.0036 M. These results suggest that fuel cell technologies can be used not only for treating AMD through removal of metals from solution, but also for producing useful products such as electricity and recoverable metals. Advances being made in wastewater fuel cells will enable more efficient power generation and systems suitable for scale-up.     

Microbial fuel cells generating electricity from rhizodeposits of rice plants

Living plants transport substantial amounts of organic material into the soil. This process, called rhizodeposition, provides the substrate for the rhizospheric microbial community. In this study, a laboratory-scale sediment microbial fuel cell, of which the anode is positioned in the rhizosphere of the rice plants, is used to microbially oxidize the plant-derived organics. An electrical current was generated through the in situ oxidation of rhizodeposits from living rice plants. The electrical power output of a sediment microbial fuel cell was found to be a factor 7 higher in the presence of actively growing plants. This process offers the potential of light-driven power generation from living plants in a nondestructive way. Sustainable power productions up to 330 W ha(-1) could be attributed to the oxidation of the plant-derived compounds.     

Harvesting energy from the marine sediment--water interface

Pairs of platinum mesh or graphite fiber-based electrodes, one embedded in marine sediment (anode), the other in proximal seawater (cathode), have been used to harvest low-level power from natural, microbe established, voltage gradients at marine sediment-seawater interfaces in laboratory aquaria. The sustained power harvested thus far has been on the order of 0.01 W/m2 of electrode geometric area but is dependent on electrode design, sediment composition, and temperature. It is proposed that the sediment/anode-seawater/cathode configuration constitutes a microbial fuel cell in which power results from the net oxidation of sediment organic matter by dissolved seawater oxygen. Considering typical sediment organic carbon contents, typical fluxes of additional reduced carbon by sedimentation to sea floors < 1,000 m deep, and the proven viability of dissolved seawater oxygen as an oxidant for power generation by seawater batteries, it is calculated that optimized power supplies based on the phenomenon demonstrated here could power oceanographic instruments deployed for routine long-term monitoring operations in the coastal ocean.     

一种用于冷链物流肉类品质在线检测的电子鼻系统

为确保冷链物流的肉类品质,设计一种用于在线检测的电子鼻系统。系统根据肉类分解气体选择特定传感器组建阵列,在专门搭建的气室中执行检测。检测结果通过GPRS/SIM模块自动上传至远程数据中心进一步分析处理,远程数据中心也可发送检测指令进行动态控制。结果表明,用于冷链物流肉类品质在线检测的电子鼻系统测量精度高、通信能力强,能够满足冷链物流需求。     

智能运动文胸电子监测系统设计方案与实施

随着人们对运动和健康的需求与日俱增,市场对运动服装的舒适性与智能化要求不断提升,智能运动文胸研发应需而生。为采集人体在运动过程中的各项生理参数和运动信息,在集成各类微小的传感器和低功耗控制芯片基础上,提出了智能运动文胸的电子监测系统方案和工作流程。围绕此方案,优化传统运动文胸设计,开发了一款基本的智能运动文胸,可采集穿用者的位置、运动状态、体温、心率和排汗参数等信息。通过无线方式上传数据到终端,分析穿用者当前的生理和运动状态,判断健康状况,并通过智能终端向用户展示信息和预警。     

Diversifying biological fuel cell designs by use of nanoporous filters

The use of proton exchange membranes (PEMs) in biological fuel cells limits the diversity of novel designs for increasing output power or enabling autonomous function in unique environments. Here we show that selected nanoporous polymer filters (nylon, cellulose, or polycarbonate) can be used effectively in place of PEMs in a miniature microbial fuel cell (mini-MFC, device cross-section 2 cm2), generating a power density of 16 W/m3 with an uncoated graphite felt oxygen reduction reaction (ORR) cathode. The incorporation of polycarbonate or nylon membranes into biological fuel cell designs produced comparable power and durability to Nafion-117 membranes. Also, high power densities for novel larger (5 cm3 anode volume, 0.6 W/m3) and smaller (0.025 cm3 projected geometric volume, average power density 10 W/m3) chamberless and pumpless microbial fuel cells were observed. As an additional benefit, the nanoporous membranes isolated the anode from invading natural bacteria, increasing the potential applications for MFCs beyond aquatic sediment environments. This work is a practical solution for decreasing the cost of biological fuel cells while incorporating new features for powering long-term autonomous devices.     

阳电极面积对微生物燃料电池产电性能的影响

微生物燃料电池（MFC）最具应用前景之一是处理废水的同时能够产生电能。以糖蜜废水作为阳极基质,以金属离子的电镀废水做阴极溶液,研究了双室微生物燃料电池不同电极面积对产电性能和COD的影响。结果发现,当外电阻为300Q时,大反应器微生物燃料电池A．（阳极面积为78．15cm^2）及小反应器微生物燃料电池～（阳极面积为76．8cm^2）最大功率密度分别为0．28mW／cm^2和0．22mW／cm^2。在前200个小时内,A：电池在第60个小时时产生最大电压71．1mV和最大电流189．5μA,A,在第190个小时时产生最大电压81．1mV和最大电流228．1μA。同时,当Zn^2＋作阴极溶液时,小反应器微生物燃料电池阳极溶液的COD去除率在1．5％到7．02％之间,大反应器微生物燃料电池阳极溶液的COD去除率在0到14．96％之间。阴极中Zn^2＋去除率A1中为28．6％,A2为21．2％。     

Influence of artificial mediators on yeast-based fuel cell performance

Soluble artificial mediators are often applied to enhance the electron transfer from living cells to an anode in microbial fuel cells. Recently, we have demonstrated that the Candida melibiosica 2491 yeast strain possesses electrogenic properties and can be used as a biocatalyst in yeast-based fuel cells even in the absence of artificial mediators. To enhance the generated electrical power, the potential application of several organic compounds as mediators in a C. melibiosica-based fuel cell was examined in this study. The choice of compounds was based upon observed cyclic voltammetry reversible electrochemical behavior at potentials appropriate for mediated electron transfer. Among the studied mediators, methylene blue, methyl orange, methyl red and neutral red significantly increased the current and power outputs in comparison with those obtained with a mediatorless yeast-based fuel cell.     

Affinity of microbial fuel cell biofilm for the anodic potential

In analogy to the well established dependency of microbial reactions on the redox potential of the terminal electron acceptor, the dependency of the microbial activity in a highly active microbial fuel cell on the potential of the electron-accepting electrode (anode) in a microbial fuel cell (MFC) is investigated. An acetate-fed, pH-controlled MFC was operated for over 200 days to establish a highly active MFC anodic biofilm using ferricyanide as the catholyte and granular graphite as electrode material. From the Coulombic efficiency of 83% of the MFC the microbial activity could be recorded by online monitoring of the current. Our results suggest that (1) in analogy to the Michaelis-Menten kinetics a half-saturation anodic potential (here termed k(AP) value) could be established at which the microbial metabolic rate reached half its maximum rate. This k(AP) value was about -455 mV (vs Ag/AgCl) for our acetate-driven MFC and independent of the oxidation capacity of the cathodic half-cell; (2) a critical AP (here termed AP(crit)) of about -420 mV (vs Ag/AgCl) was established that characterizes the bacterial saturation by the electron-accepting system. This critical potential appeared to characterize the maximum power output of the MFC. This information would be useful for modeling and optimization of microbial fuel cells and the relative comparison of different microbial consortia at the anode.     

低成本电子系统印刷电子技术的开发与应用现状

近年来,印刷电子技术作为一种可实现低成本、大面积电子系统的技术,已获得了可观的收益.印刷允许进行充分有效的处理,从而降低了过程的复杂性,减少了材料的使用种类.加上使用如塑料、金属箔等低成本基板,预计印刷电子技术能实现更多领域电子系统的简单开发,包括显示器,传感器和RFID标签等.回顾印刷电子技术开发及应用工作,通过合成无机纳米粒子和有机材料的结合,可以制成一系列的印刷电子"油墨",并用于印刷无源元件、多层互联结构、二极管、晶体管、存储器、电池、不同类型的气体和生物传感器.通过拓展印刷能力,进一步降低将多种功能材料集成在相同基板上的成本.因此,开发出具有该优势的印刷系统是有可能的.     

Open air biocathode enables effective electricity generation with microbial fuel cells

The reduction of oxygen at the cathode is one of the major bottlenecks of microbial fuel cells (MFCs). While research so far has mainly focused on chemical catalysis of this oxygen reduction, here we present a continuously wetted cathode with microorganisms that act as biocatalysts for oxygen reduction. We combined the anode of an acetate oxidizing tubular microbial fuel cell with an open air biocathode for electricity production. The maximum power production was 83 +/- 11 W m(-3) MFC (0.183 L MFC) for batch-fed systems (20-40% Coulombic yield) and 65 +/- 5 W m(-3) MFC for a continuous system with an acetate loading rate of 1.5 kg COD m(-3) day(-1) (90 +/- 3% Coulombic yield). Electrochemical precipitation of manganese oxides on the cathodic graphite felt decreased the start-up period with approximately 30% versus a non-treated graphite felt. After the start-up period, the cell performance was similar for the pretreated and non-treated cathodic electrodes. Several reactor designs were tested, and it was found that enlargement of the 0.183 L MFC reactor by a factor 2.9-3.8 reduced the volumetric power output by 60-67%. Biocathodes alleviate the need to use noble or non-noble catalysts for the reduction of oxygen, which increases substantially the viability and sustainability of MFCs.     

Microbial electrodialysis cell for simultaneous water desalination and hydrogen gas production

A new approach to water desalination is to use exoelectrogenic bacteria to generate electrical power from the biodegradation of organic matter, moving charged ions from a middle chamber between two membranes in a type of microbial fuel cell called a microbial desalination cell. Desalination efficiency using this approach is limited by the voltage produced by the bacteria. Here we examine an alternative strategy based on boosting the voltage produced by the bacteria to achieve hydrogen gas evolution from the cathode using a three-chambered system we refer to as a microbial electrodialysis cell (MEDC). We examined the use of the MEDC process using two different initial NaCl concentrations of 5 g/L and 20 g/L. Conductivity in the desalination chamber was reduced by up to 68 ± 3% in a single fed-batch cycle, with electrical energy efficiencies reaching 231 ± 59%, and maximum hydrogen production rates of 0.16 ± 0.05 m(3) H(2)/m(3) d obtained at an applied voltage of 0.55 V. The advantage of this system compared to a microbial fuel cell approach is that the potentials between the electrodes can be better controlled, and the hydrogen gas that is produced can be used to recover energy to make the desalination process self-sustaining with respect to electrical power requirements.     

微生物燃料电池降解木素磺酸盐并同步产电

以厌氧活性污泥为接种体构建铁氰化钾阴极微生物燃料电池（Microbial fuel cell,MFC）,对木素磺酸盐的降解及产电效果进行了研究。结果表明：经过3个周期连续添加葡萄糖后MFC成功启动,并产生了446mV的电压。以木素磺酸盐为单一底物的MFC经过50h运行,最大功率密度达到177．9mW／m^2,阳极液CODCr和木素磺酸盐去除率分别为;35．5％和46．7％。MFC可以降解木素磺酸盐并同步产电,这为解决造纸废水中生物质能的开发和利用提供了新途径。     

Radiotelemetry system for continuously monitoring temperature in cows

Deep body temperature is an important index of the physiological status of an animal. A radiotelemetry system was developed to monitor continuously udder and body temperatures in cows under normal housing conditions. Radiotransmitters were crystal controlled blocking oscillators operating in the 27 MHz band. Functionally, the transmitters turned on and off in a pulsatile fashion with temperature encoded as the time interval between two pulses (nominally .5 s at 38 degrees C). Transmitters were powered by lithium batteries (6-mo lifespan) and were encapsulated in paraffin/Elvax (cylinder 6 cm X 3 cm diameter). Signals were detected using a radio receiver in the AM mode. Reception frequency was selected by computer. Each audio pulse was electronically converted to a digital pulse. A PDP 11/23 computer converted intervals between digital pulses to temperature values. As finally configured, the computer collected data from 12 transmitters every 1.4 min (1024 readings/transmitter/d). Temperatures were graphed continuously and stored on magnetic media for future analyses.     

Microbial fuel cell using anaerobic respiration as an anodic reaction and biomineralized manganese as a cathodic reactant

We have operated a microbial fuel cell in which glucose was oxidized by Klebsiella pneumoniae in the anodic compartment, and biomineralized manganese oxides, deposited by Leptothrix discophora, were electrochemically reduced in the cathodic compartment. In the anodic compartment, to facilitate the electron transfer from glucose to the graphite electrode, we added a redox mediator, 2-hydroxy-1,4-naphthoquinone. We did not add any redox mediator to the cathodic compartment because the biomineralized manganese oxides were deposited on the surface of a graphite electrode and were reduced directly by electrons from the electrode. We have demonstrated that biomineralized manganese oxides are superiorto oxygen when used as cathodic reactants in microbial fuel cells. The current density delivered by using biomineralized manganese oxides as the cathodic reactant was almost 2 orders of magnitude higher than that delivered using oxygen. Several fuel cells were operated for 500 h, reaching anodic potentials of -441.5 +/- 31 mVscE and cathodic potentials of +384.5 +/- 64 mVscE. When the electrodes were connected by a 50 Ohms resistor, the fuel cell delivered the peak power density of 126.7 +/- 31.5 mW/m2.     

微生物燃料电池处理CTMP制浆废水的研究

以化学热磨机械浆(CTMP)制浆废水为底物,采用铁氰化钾阴极微生物燃料电池(MFC),对MFC处理CTMP制浆废水的可行性和废水CODCr浓度对MFC产电性能的影响进行研究.结果表明,MFC最大功率密度随废水CODCr浓度的增大而升高,最高为233 mW/m2,CODCr去除率达到54.3％～ 62.4％;当CODCr增大至5200 mg/L以上时,过高的CODCr浓度抑制微生物活性,电池最大功率密度和CODCr去除率分别降低至34.2 mW/m2和32.8％.CTMP制浆废水可以作为MFC底物,在产电的同时实现有效降解,这为废水资源化利用提供了新途径.     

基于物联网的木门门扇四边锯故障智能诊断系统研究

针对数控门扇四边锯出现的故障特征,利用振动、噪声和温度传感器实时采集四边锯工作状态信息,并利用无线网络将采集的信息传送至上位机和设备技术服务中心,借助python编程语言开发数据处理程序,利用C#编程语言开发人机交互界面与数据库,建立一套基于物联网的数控门扇四边锯故障智能诊断系统,实现现场故障的预警和诊断分析,给出相应...     

Microbial reverse electrodialysis cells for synergistically enhanced power production

A new type of bioelectrochemical system for producing electrical power, called a microbial reverse-electrodialysis cell (MRC), was developed to increase voltages and power densities compared to those generated individually by microbial fuel cells (MFCs) or reverse electrodialysis (RED) systems. In RED systems, electrode overpotentials create significant energy losses due to thermodynamically unfavorable electrode reactions, and therefore a large number of stacked cells must be used to have significant energy recovery. This results in high capital costs for the large number of membranes, and increases energy losses from pumping water through a large number of cells. In an MRC, high overpotentials are avoided through oxidation of organic matter by exoelectrogenic bacteria on the anode and oxygen reduction on the cathode. An MRC containing only five pairs of RED cells, fed solutions typical of seawater (600 mM NaCl) and river water (12 mM NaCl) at 0.85 mL/min, produced up to 3.6 W/m(2) (cathode surface area) and 1.2-1.3 V with acetate as a substrate. Pumping accounted for <2% of the produced power. A higher flow rate (1.55 mL/min) increased power densities up to 4.3 W/m(2). COD removal was 98% with a Coulombic efficiency of 64%. Power production by the individual components was substantially lower with 0.7 W/m(2) without salinity driven energy, and <0.015 W/m(2) with reduced exoelectrogenic activity due to substrate depletion. These results show that the combination of an MFC and a RED stack synergistically increases performance relative to the individual systems, producing a new type of system that can be used to more efficiently capture salinity driven energy from seawater and river water.