Maximum Average Power Density Research Articles

Nano-Fe3O4/polymerize aniline/carbon cathode based microbial fuel cell for efficient power generation and uranium separation

Microbial fuel cells (MFCs) have gained increasing attention in the field of uranium-containing wastewater (UCW) treatment as a self-powered bioelectrochemical system (BES) due to its advantages of recovering uranium resources and generating electricity. However, the lack of catalytic active sites on the carbon fiber cathode significantly hinders the reaction performance of surface electrons with uranium ions in solution, thereby limiting the application of MFC. In this study, we propose a carbon brush (CB) cathode modification process that utilizes cyclic voltammetry synthesis technique (CVS) to polymerize aniline (PA) on the surface of carbon fibers and uniformly load nano-Fe3O4 particles (nFe3O4). The loading of PA/nFe3O4 not only significantly improve the catalytic active sites but also enhance the synergistic effect of adsorption and conductivity of CB cathode. Consequently, the nFe3O4/PA/CB-MFC showed excellent ability to continuous power generation and uranium separation. Over eight cycles of uranium separation, the nFe3O4/PA/CB-MFC exhibited an average maximum power density of 15.17 mW/m2 and a uranium separation efficiency of 95.52 %, showcasing substantial enhancements by 2.10-fold and 1.44-fold compared to the CB-MFC, respectively. Our study presents an efficient approach to enhance the efficiency of uranium separation and boost power density of MFC by increase catalytic active sites on carbon-based cathode.

Non-uniform design of proton exchange membrane fuel cell and its matching with operations

Improving the uniformity of internal multiphysics is a critical issue for proton exchange membrane fuel cells (PEMFC). To overcome the non-uniformity of the pressure, reactant, and water in PEMFC operation and improve the performance, a non-uniform structural design is proposed for PEMFC. The gradient distribution of channel width and the porosity in porous electrode components (gas diffusion layer, microporous layer, and catalyst layer) are studied in the present research. Among them, the integrated decreasing design of the cathode with 0.3 mm channel width gradient and 0.1 porous electrode porosity gradient contributes 2.77% to the performance improvement. A joint operation model integrated with the particle swarm optimization algorithm was constructed to implement the matching of operating parameters with the non-uniform structure design. The maximum average power density could be realized with operation pressure 250000Pa, operation temperature 333K, anode relative humidity 85.60%, cathode relative humidity 50%, anode stoichiometric ratio 1.92, and cathode stoichiometric ratio 3.

Performance analysis and structure optimization for concentrated photovoltaic-phase change material-thermoelectric system in space conditions

High-efficient thermal management is urgently needed for concentrated photovoltaic-thermoelectric hybrid system due to the high heat flux. In present paper, a three-dimensional model for the hybrid system in outer space conditions was established by coupling phase change temperature control and radiation heat sink technologies to find the propriate thermal management scheme. Firstly, the three shortcomings in the typical hybrid system were proposed and their adverse effects on efficiency were elucidated. Then, a heat transfer pillar for temperature control unit and a newly designed circular fins for heat sink were designed. The effects of structure parameters on power generation performance were investigated, and the interaction between temperature control unit and heat sink were discussed. The results show that the hybrid systems with the newly designed heat transfer pillar and circular fins have higher efficiency. After that, a united structure optimization by artificial neural network-multi-objective genetic algorithm was performed to solve the interaction and to balance the electrical efficiency and power density of hybrid system. The comprehensive power generation performance of hybrid system can be further improved after the optimization. The system with PCM thickness dPCM = 6.33 mm, heat transfer pillar width a = 18.19 mm, fin length L = 49.99 mm and fin radius R = 50 mm, has the maximum average total efficiency (31.83%, 2.98% higher than the typical system); the system with dPCM = 3.02 mm, a = 10.05 mm, L = 47.03 mm and R = 25.86 mm, has the maximum average power density (36.97 W/kg, 15.78% higher than the typical system).

Self-powered smart agriculture sensing using triboelectric nanogenerators based on living plant leaves

Environmental pressure has a negative effect on plant health and productivity, so accurate monitoring of environmental pressure is of great significance for improving food production and smart agriculture. Here, composite films with good stability and humidity sensitivity are made via solution-casting process of multilayer graphene oxide (GO), spherical polyvinylsilsesquioxane (PVSQ), and polyvinyl alcohol (PVA). Subsequently, a living plant leaf-based triboelectric nanogenerator (LPL-TENG) consisting of the GO-PVSQ/PVA composite films and the living leaves is proposed. With a maximum average power density of 90.67 mW/m-2, the LPL-TENG can drive miniature commercial electronic equipment. The LPL-TENG is able to respond linearly to plant leaf humidity with a sensitivity of about − 3.0 V/% RH without affecting plant growth. In addition, the feature of alarming at high wind speed can also be exhibited by the LPL-TENG to realize remote control. This work has broad application prospects in building smart agriculture.

Livestock’s Urine-Based Plant Microbial Fuel Cells Improve Plant Growth and Power Generation

Plant microbial fuel cells (P-MFCs) are sustainable and eco-friendly technologies, which use plant root exudates to directly nourish the electrochemically active bacteria (EABs) to generate sustainable electricity. However, their use in evaluating plant growth has been insufficiently studied. In this study, interconnection between plant growth and the production of bioelectricity was evaluated by using P-MFCs inoculated with 642.865 mL ≅ 643 mL of livestock’s urine such as cow urine, goat urine, and sheep urine. The greatest mean stem diameter of 0.52 ± 0.01 cm was found in P-MFC-3 inoculated with goat urine, while the P-MFC-2 treated with cow urine reached a higher average number of roots with a value of 86 ± 2.50 (95% improvement) (p < 0.05). Besides, P-MFC-4 presented greater height of 50.08 ± 0.67 cm. For polarization curve experiment a higher maximum power density of 132 ± 11.6 mW m−2 (931 mA m−2) was reached with cow urine; in turn, with regard to the long-term operation, the same reactor indicated a higher maximum average power density of 43.68 ± 3.05 mW m−2. The study’s findings indicated that Stevia P-MFC inoculated with urine was a good option to increase the biomass amount for the agricultural plants along with power generation. Further, this study opens the way for more investigation of evaluating the impact of P-MFC on plant growth.

Adaptable and Wearable Thermocell Based on Stretchable Hydrogel for Body Heat Harvesting

AbstractThe application of traditional inorganic thermoelectric materials to wearable energy harvesters has been hindered by the rigid bulkiness, while flexible organic conductive polymers have been long troubled by their intrinsic low thermopower. An ideal solution that possesses the merits of the two thermoelectric materials is desperately needed for practical application. Here it is demonstrated that a polyacrylamide (PAAm)‐based ultra‐stretchable hydrogel can be selected as a superior candidate matrix for flexible and stretchable thermocells to adapt to the curved surface of the human body and deformation of the ankle. Fe(ClO4)3/Fe(ClO4)2 is selected as n‐type ion pair for their comparable thermoelectric performance to K3[Fe(CN)6]/K4[Fe(CN)6]. The p‐n pair hydrogel electrolytes show a voltage output of 29 mV and current output of 8.5 Am−2 with an average maximum power density of 0.66 mW K−2 m−2 for each p‐n cell (ΔT = 10 K). By integrating with the graphite paper electrode, a body‐conformal and portable thermocell device, employing the hydrogel electrolytes, is fabricated and reached a voltage output of 0.16 V with 14 pairs of p‐n cells (ΔT = 4.1 K). This commercially‐effective blueprint demonstrates the bright future of hydrogel‐based ionic thermocell in daily wearable scenarios.

Biological/metal oxide composite transport layers cast from green solvents for boosting light harvesting response of organic photovoltaic cells indoors

Organic solar cells with biological/metal–oxide electron transport layers (ETLs), consisting of a ZnO compact layer covered by a thin DNA layer, both of which deposited with green solvents (water or water/alcohols mixtures) are presented for application under low intensity indoor lighting. Under white LED lamp (200, 400 lx), photovoltaic cells with P3HT:PC70BM polymer semiconductor blends delivered an average maximum power density (MPD) of 8.7 μW cm−2, corresponding to a power conversion efficiency, PCE, of = 8.56% (PCE of best cell was 8.74%). The ZnO/DNA bilayer boosted efficiency by 68% and 13% in relative terms compared to cells made with DNA-only and ZnO-only ETLs at 400 lx. Photovoltaic cells with ZnO/DNA composite ETLs based on PTB7:PC70BM blends, that absorb a broader range of the indoor lighting spectrum, delivered MPDs of 16.2 μW cm−2 with an estimated average PCE of 14.3% (best cell efficiency of 15.8%) at 400 lx. The best efficiencies for cells fabricated on flexible plastic substrates were 11.9% at 400 lx. This is the first report in which polymer photovoltaics incorporating biological materials have shown to increment performance at these low light levels and work very efficiently under indoor artificial light illumination. The finding can be useful for the production of more bio-compatible photovoltaics as well as bio-sensing devices based on organic semiconductors.

The use of marine microalgae in microbial fuel cells, photosynthetic microbial fuel cells and biophotovoltaic platforms for bioelectricity generation.

Algal green energy has emerged as an alternative to conventional energy production using fossil fuels. Microbial fuel cells (MFCs), photosynthetic microbial fuel cells (PMFCs) and biophotovoltaic (BPV) platforms have been developed to utilize microalgae for bioelectricity generation, wastewater treatment and biomass production. There remains a lack of research on marine microalgae in these systems, so to the best of our knowledge, all information on their integration in these systems have been gathered in this review, and are used to compare with the interesting studies on freshwater microalgae. The performance of the systems is extremely reliant on the microalgae species and/or microbial community used, the size of the bio-electrochemical cell, and electrode material and distance used. The mean was calculated for each system, PMFC has the highest average maximum power density of 344 mW/m2, followed by MFC (179 mW/m2) and BPV (58.9 mW/m2). In addition, the advantages and disadvantages of each system are highlighted. Although all three systems face the issue of low power outputs, the integration of a suitable energy harvester could potentially increase power efficiency and make them applicable for lower power applications.

Membrane electrode assembly hybridized anaerobic digester for co-generation of methane enriched biogas and electricity

The endeavor for utilization of various kinds of organic wastes into a valuable energy source through the process of anaerobic digestion is gaining ground amongst the researchers worldwide. In this context, a single chamber, above the ground, portable anaerobic digester (AD) was developed which was hybridized with a membrane electrode assembly (MEA) to facilitate the generation of enriched biogas and electricity as a byproduct. The analysis showed enrichment of CH4 in the biogas, while the AD was hybridized with the MEA. The highest concentration of CH4 in control was 56.3 ± 1.5% whereas in AD-MEA, the concentration of CH4 increased to 73.7 ± 3.9%. Thus, the incorporation of conductive surface in the anaerobic chamber of the AD-MEA system could promote the enrichment of methane. The presence of the non-biological conductive surface in the anaerobic chamber stimulated syntrophic interactions among exoelectrogens and hydrogenotrophic methanogens for conversion of CO2 directly to CH4. Moreover, the hybridized AD-MEA system could produce a maximum of 496 ± 7 mV OCV, with a maximum average power density of 2.87 mW/m2 and 70 mA/m2 current density.

Diurnal variation of RF power density with distance from selected mobile phone base transceiver stations in Offa metropolis, Kwara State Nigeria

Diumal variation of radiofrequency power density with distance from some 20 twenty (20) selected mobile phone base transceiver stations of four (4) major mobile phone network providers (MTN, GLO, 9Mobile, and Airtel) in the Offa metropolis Kwara State Nigeria were studied. A digital Radio-frequency (RF) meter (HF-B8G High Frequency10 Mhz - 8 GHz RF EMF Meter) is used to measure RF field strength first at foot at the base station and subsequently at every interval of 25 m up to 250 m in radial routes. Concurrently, the distance, geographical coordinates, and altitude of each point were measured using a Global Positioning System (GPS). The average maximum power density obtained ranged from 0.294 Wm−2 and 0.057 Wm−2 at a radial distance of 150 m and 0 m away from the base transceiver station respectively. The result of the study shows that the degree of power density variation with distance during the morning, afternoon, and night hours of the day was found to be highly different. The maximum level of exposure to RF electromagnetic radiation was experienced at night, followed by noon, and the minimum in the morning hours of the day in the majority of the base transceiver stations. For the different time of the day considered in this study, the results show that the power density obtained constitute no RF exposure hazard to the dwellers of Offa metropolis when compared with the RF exposure limit prescribed by the International Commission on Non-Ionizing Radiation Protection (ICNIRP).

Membrane cleaning and performance insight of osmotic microbial fuel cell

Osmotic microbial fuel cell (OsMFC) integrating forward osmosis into microbial fuel cell (MFC) favors the merits of organic removal, bioenergy generation, and high-quality water extraction from wastewater. This study demonstrated an 18.7% power density enhancement over a conventional MFC due to the water-flux-facilitated proton advection and net positive charge (NPC)-flux-promoted countercurrent proton exchange. Among the three examined membrane cleaning methods, chemical cleaning using 0.2% NaClO was found to be especially effective in removing organic foulants composed of proteins and polysaccharides, resulting in a water flux recovery of up to 91.6% with minimal impact on average maximum power density and internal resistance. The effects of operating parameters including anode HRT and draw solution concentration were studied. Shortening HRT from 6.0 to 3.0 h increased power density by 78.0% due to a high organic loading rate and a slightly reduced polarization concentration. Increasing draw solution concentration from 0.2 to 1.0 M NaCl enhanced power density by approximately 2.7-fold due to enhanced proton advection. Water-flux-facilitated proton advection played a more important role in determining the electricity generation performance of OsMFC than the NPC-flux-promoted countercurrent proton exchange under varied operating conditions.

Performance analysis of two-stage pressure retarded osmosis

The performance of a two-stage pressure retarded osmosis (PRO) for power generation with a total membrane length of 1 meter was investigated and analyzed in this work. Two feed configurations of freshwater and seawater were studied: one with the freshwater entering at the first stage only and the other with freshwater entering at both stages. The effect of membrane length and flow ratio between freshwater and seawater on the PRO performance were also examined. The results revealed that the performances of both feed configurations were quite similar. The membrane with a shorter length offered a higher average power density than that of a longer length. It was also revealed that the flow ratio had a strong influence on the average power density produced. The maximum average power density of 10.15 W/m2 was obtained at the applied hydraulic pressure of 12 bar, the flow ratio of 5, and the membrane length of both stages of 0.5 meter. The best water utilization was achieved at 65%.

Biomimetic and porous nanofiber-based hybrid sensor for multifunctional pressure sensing and human gesture identification via deep learning method

Abstract Near-field electrospinning (NFES) is a site addressable microfabrication process and is utilized to deposit the micro/nano polyvinylidene fluoride (PVDF) fibers arrays on printed circuit board nanofiber-based based piezoelectric sensor architectures. In addition, a biomimetic and flexible hybrid self-powered sensors (BHSS) was created by hybridizing both Cu - biomimetic Polydimethylsiloxane triboelectric sensors to enhance the energy-harvesting characteristic. The optimized BHSS had open-circuit voltage (VOC) of 15 V and 115 nA of short-circuit current (ISC) and a maximum average power density is 675 μW m−2 with a load of 10 MΩ. Furthermore, an intelligent glove and the force sensor with are successively confirmed that the developed BHSS has promising applications in wearable self-power sensor technology. The machine learning algorithm of Long Short-Term Memory (LSTM) in the context of gesture recognition was used and effectively distinguish five human actions satisfactorily. LSTM based real-time electrical signals of five gestures dataset with varying duration and complexity can achieve an overall classification rate of 82.3%.

Dynamics of direct hydrocarbon polymer electrolyte membrane fuel cells

Hydrocarbons have 50-100 times higher energy per unit weight compared to commercially available batteries, thus harvesting only 10% of the energy from hydrocarbons could provide a far lighter energy source for portable electronic devices. With this motivation, the feasibility of using polymer electrolyte membrane fuel cells with propane fuel, operating at low temperatures (< 100˚C), was explored. It was interesting to note that there was a significant influence of the current history on the fuel cell performance. In particular, at higher current densities (>24 mA/cm2) the power output gradually decreases then rapidly “extinguishes” (i.e., produces no power). However, by employing an unconventional operating mode (load-interrupt) where the current is shut off for a short period of time and then reapplied, the average maximum power density increased to 11.6 mW/cm2. Furthermore, the extinction of the fuel cell can be further improved by seeding a small amount of unsaturated hydrocarbons (~2000ppm) into the fuel stream and can extend the lifetime of the fuel cell by more than 10 times.

Energy harvesting from a DE-based soft pendulum

This paper proposes a DE-based soft pendulum that is capable of converting the vibrational energy into electrical energy. A theoretical analysis model is developed to investigate the energy harvesting performance of the DE-based soft pendulum with diverse dimensional, electrical and dynamic parameters, which shows a good agreement with the experiment results. The research results show that there is an optimal resistance to maximize the average power density, and the optimal resistance can decrease with the increase in the initial voltage of the DE. When the natural frequency of the designed pendulum is equal to the excitation frequency, the maximum average power density can be achieved. In addition, the maximum average power density can be improved by enlarging the mass of the pendulum and the initial voltage of the DE, and reducing the initial length of the DE. The proposed model can serve as guidance for optimizing the energy harvesting system in future studies.

Electricity generation from wastewater using a floating air cathode microbial fuel cell

Recovering energy from wastewater is an important frontier of environmental engineering and science. Of the many proposed strategies, microbial fuel cells (MFCs) provide a direct path to electricity generation. Here, we report MFCs equipped with floating carbon-cloth air cathodes modified with manganese oxide (MnOx) or Platinum nanoparticle oxygen reduction catalysts. The performances of these MFCs were compared using domestic wastewater in a configuration suitable for electricity generation from primary settling tanks. The open-circuit voltages of the Mn-MFCs decreased gradually over time while those of the Pt-MFCs remained stable indicating that Mn leaching from the electrodes was occurring. Over 90% of the MnOx catalyst was solubilized from the cathode surface within the first twoweeks of operation. Initially, the Pt-MFCs did not generate as high of a current density as MnOx but after 55 days, Pt-MFCs had a higher average maximum power density during polarization than Mn-MFCs: 65.4 ± 4.6 and 48.4 ± 10.16 mW/m2 (based on anode geometric surface area), respectively. These results show the importance of evaluating promising alternative MFC cathode catalyst like MnOx in actual wastewater since it is difficult to predict how new catalysts designed to decrease cost yet increase the efficiency of the reduction of oxygen will respond in real-world wastewater applications.

A Stretchable Yarn Embedded Triboelectric Nanogenerator as Electronic Skin for Biomechanical Energy Harvesting and Multifunctional Pressure Sensing.

Flexible and stretchable physical sensors capable of both energy harvesting and self-powered sensing are vital to the rapid advancements in wearable electronics. Even so, there exist few studies that can integrate energy harvesting and self-powered sensing into a single electronic skin. Here, a stretchable and washable skin-inspired triboelectric nanogenerator (SI-TENG) is developed for both biomechanical energy harvesting and versatile pressure sensing. A planar and designable conductive yarn network constructed from a three-ply-twisted silver-coated nylon yarn is embedded into flexible elastomer, endowing the SI-TENG with desired stretchability, good sensitivity, high detection precision, fast responsivity, and excellent mechanical stability. With a maximum average power density of 230 mW m-2 , the SI-TENG is able to light up 170 light-emitting diodes, charge various capacitors, and drive miniature electronic products. As a self-powered multifunctional sensor, the SI-TENG is adopted to monitor human physiological signals, such as arterial pulse and voice vibrations. Furthermore, an intelligent prosthetic hand, a self-powered pedometer/speedometer, a flexible digital keyboard, and a proof-of-concept pressure-sensor array with 8 × 8 sensing pixels are successively demonstrated to further confirm its versatile application prospects. Based on these merits, the developed SI-TENG has promising applications in wearable powering technology, physiological monitoring, intelligent prostheses, and human-machine interfaces.

Design, simulation, and experimental characterization of a heaving triboelectric-electromagnetic wave energy harvester

Hybridization of triboelectric (TENG) and electromagnetic (EMG) generators has recently shown to be an effective approach toward harvesting water wave energy. Therefore, it is critical to develop efficient hybrid TENG-EMG designs for this application. This paper presents a hybrid TENG-EMG energy harvester based on heaving wave-energy point absorber which can be potentially used for harvesting energy of waves. The design employs linear tubular EMG unit in conjunction with grating structured freestanding mode TENG. The mechanism of a heaving buoy is taken into the account to apply the energy of water waves into the harvester. The adopted EMG mechanism is a relatively simple and highly efficient configuration and the freestanding grating TENG is very effective due to the use of multiple segments and fixed electrodes. Initially, the working mechanism of the device is theoretically simulated to show the practicality of the design. Then, the output performance of the fabricated device is fully investigated under various dynamical experiments. The energy output capability of the proposed device is demonstrated considering different electrical loads. Accordingly, the phase 1, phase 2, and phase 3 of the EMG part obtains the maximum average power density of 170Wm−3,220Wm−3, and 130Wm−3, respectively. Also, the TENG unit achieves the maximum average power density of 120Wm−3. Finally, the practical application of the hybrid system for charging storage units, lighting light-emitting diodes, and powering a sensor is proved. In fact, the proposed device offers a very cost-effective, simple structure, and effective system which is potentially useful for the blue energy extraction.

Dynamics of Direct Hydrocarbon PEM Fuel Cells

Hydrocarbons have 50-100 times higher energy per unit weight compared to commercially available batteries, thus harvesting only 10% of the energy from hydrocarbons could provide a far lighter energy source for portable electronic devices. With this motivation, the feasibility of using Polymer Electrolyte Membrane (PEM) fuel cells with propane fuel, operating at low temperatures (< 100˚C), was explored. Nafion® membranes were used as electrolytes and platinum black was used as catalyst. At a catalyst loading of 15 mg/cm2 at anode and 8 mg/cm2 at cathode, a maximum steady-state power density of 7.5 mW/cm2 was observed. However, with hydrazine treatment of platinum black catalyst nearly doubled the power density of propane fuel and increased power by about 50% with hydrogen fuel. It was interesting to note that there was a significant influence of the current history on the fuel cell performance. In particular, at higher current densities (> 24 mA/cm2) the power output gradually decreases then rapidly “extinguishes” (i.e., produces no power). However, by employing an unconventional operating mode (“load-interrupt”) where the current is shut off for a short period of time and then reapplied, the maximum average power density increased to 11.6 mW/cm2. For dimethyl ether (DME) and hydrogen, no significant effect of current history was observed. It is proposed that the fuel cell “extinction” is associated with the formation of inactive intermediate species on the anode, blocking active sites. A simple model was developed in an effort to interpret “extinction” behavior. This model assumes all sites are in either an “active” or “inactive” state with heuristic kinetic relations to describe the rates of conversion of active to inactive sites and vice versa. This model was found to be in good qualitative agreement with the experiments when the rate of formation of inactive sites was proportional not only to the number of active sites but also the number of already-inactive sites, i.e. in a self-accelerating manner. Possible physical mechanisms for this heuristic model are discussed.

Effect of nitrate on electricity generation in single-chamber air cathode microbial fuel cells

Microbial fuel cells (MFCs) have the potential for simultaneous electricity generation and nitrogen removal in the treatment of wastewater that contains nitrate, but the denitrification of nitrate might affect electricity generation in single-chamber MFCs. In this study, the effect of nitrate on electricity generation in single-chamber air cathode MFCs was investigated. The chemical oxygen demand (COD) was removed faster by denitrification (0.977 ± 0.013 g COD g−1 NO3−) than by electricity generation in the MFCs. When the concentration of COD that excluded the COD removed by denitrification was more than 300 mg O2 L−1, denitrification only resulted in the decrease in the voltage of the MFCs at the denitrification stage, but did not affect the stable voltage and maximum power density (MPD) of the MFCs after the denitrification stage. The average MPDs during the 660-day batch operation ranged from 27.4 ± 0.9 to 28.4 ± 1.2 W m−3. At the same concentration of COD that excluded the COD removed by denitrification, the coulombic efficiency of the MFCs after the denitrification process increased with an increasing initial concentration of nitrate, which was probably attributed to the inhibition of the activity of certain non-exoelectrogenic bacteria by nitrate. A microbial community analysis showed that Thauera was the dominant genus of denitrifying bacteria and Geobacter was the dominant genus of exoelectrogenic bacteria at the anodes of the MFCs. With an increase in the initial concentration of nitrate, the proportion of denitrifying bacteria increased, whereas the proportion of exoelectrogenic bacteria decreased.