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The operating parameters of proton exchange membrane fuel cell (PEMFC) are critical to its performance and working life. This study presents a data-driven modeling approach combining a surrogate model with the particle swarm optimization algorithm to optimize operating parameters for PEMFC and obtain the maximum power density. The results show that the operating parameters significantly influence power density under high current densities, with inlet temperature having the most significant effect. Lower inlet temperature, relative humidity in the cathode and anode, along with higher operating pressure yield improved output performance. The Genetic Algorithm-Backpropagation Neural Network based surrogate model exhibits excellent predictive performance with correlation coefficients of 0.99896 and 0.99815 for the training and test sets, respectively. Optimized conditions achieve a 3.3% increase in power density compared to initial settings, with only a 0.15% error in simulation calculations. This data-driven approach provides valuable insights for maximizing PEMFC efficiency and performance. • An approach combining surrogate model with PSO algorithm to predict PEMFC performance is proposed. • The GA-BP-based surrogate model exhibits excellent predictive performance. • Maximum power density and corresponding operating parameters are achieved. [ABSTRACT FROM AUTHOR]

Ambarella is one of the most popular tropical fruits in Southeast Asia. Since it has a high concentration of organic acids, the fruit has the potential to be employed as an electrolyte in biobatteries. In this work, Zn-Cu biobattery electrolytes are derived from the flesh and peel of ambarella fruit. The Open- and Closed-Circuit Voltage, Maximum Power Density, and Battery Capacity of Zn-Cu Biobatteries were investigated. The OCV of the fruit's flesh was 455 mV, while the OCV of its peel was 530 mV. Given the average CCV created by ambarella peel was 471.3 mV and the average CCV generated by ambarella flesh was 342.1 mV. The highest power of Zn-Cu biobatteries was 0.27 mW when fruit flesh was used as the electrolyte and 0.22 mW when fruit peel was used as the electrolyte, Indicating a difference of 18.5%. The peel of an ambarella fruit has a battery capacity of 540 mAh, while the flesh has a capacity of 328 mAh for the Zn-Cu biobattery. This indicates that Zn-Cu with an Ambarella peel has a greater capacity but less power, urging that it be investigated prior to any prospective use. [ABSTRACT FROM AUTHOR]

An important part of a photo-bioelectrochemical cell (PBEC) is the photo-biocatalyst substrate taken as anode. This study aims to explain the effect of CNT/TiO2/chlorophyll photocatalyst coated on the cellulose nanopaper (CNP) substrate on the PBEC performance and to compare the results with those obtained for the commercial indium tin oxide (ITO) glass and flexible ITO as substrates. The results showed high sheet resistance of CNP, which is 61182 Ω sq-1, which is reduced by 80 % in the presence of CNT/TiO2/Chl biocatalyst. The highest output voltage of 0.95 to 1 V was produced by coating CNT/TiO2/Chl on the flexible ITO. The maximum current density (Jmax) of 3726 mA m-2 and the highest maximum power density value of around 574 mW m-2 were obtained for illuminated CNT/TiO2/Chl on the rigid ITO anode. In dark conditions, the highest power density was observed for CNP as the supporting substrate. The photo-bioelectrochemical cell adopting CNT/TiO2/Chl and CNP as the supporting substrate material has great potential for a variety of applications, such as wearable electronics, environmental monitoring, remote or off-grid energy supply, and renewable energy systems, thereby contributing to the advancement of sustainable energy technologies.

Considering the increasing interest in the realization of carbon-neutral and RE100 systems, and the expansion of the supply of renewable energy through large-scale floating photovoltaic systems (FPVs), this study designed large-scale bifacial FPVs for maximum power density. Moreover, the estimated power generation was compared and analyzed according to the installation methods of the conventional monofacial PV module facing south (Mono-S), bifacial PV module facing south (Bi-S), and bifacial PV module facing east and west (Bi-EW). Using the proposed design method, the power generation per unit area for FPVs was 17.87% to 36.08% higher than that of the conventional installation method. In addition, this method can contribute to gird stability by decreasing the peak power around noon and increasing power generation during low irradiation and can be applicable to marine photovoltaics(MPVs).

This paper is devoted to the determination of the value of the maximum specific power of capacitive electrostatic micromotors based on nanometer working gaps. The motors under consideration were developed earlier. They have the following structure: a metal—thin crystalline ferroelectric layer with a high dielectric constant—a nanometer working gap—a movable electrode. The mechanism limiting the magnitude of the maximum field in the gap have also been determined in previous works. The mechanism is the stripping of atoms from the surface of the movable electrode under the action of electrostatic forces. It was shown that the maximum energy density in the working gap can be as high as 1.6 × 109 J/m3. In the presented paper, a maximum frequency of electromechanical energy conversion as high as 10 MHz is estimated for these motors, with a maximum specific power of 5 × 108 W/kg. The application of the proposed motors for micromachines is discussed.

This paper describes the use of a commercial Fumasep® FAA3-50 membrane as an anion exchange membrane (AEM) in alkaline direct methanol fuel cells (ADMFCs). The membrane, supplied in bromide form, is first exchanged in chloride and successively in the hydroxide form. Anionic conductivity measurements are carried out in both a KOH aqueous solution and in a KOH/methanol mixture. AEM-DMFC tests are performed by feeding 1 M methanol, with or without 1 M KOH as a supporting electrolyte. A maximum power density of 5.2 mW cm−2 at 60 °C and 33.2 mW cm−2 at 80 °C is reached in KOH-free feeding and in the alkaline mixture, respectively. These values are in good agreement with some results in the literature obtained with similar experimental conditions but with different anion exchange membranes (AEMs). Finally, methanol crossover is investigated and corresponds to a maximum value of 1.45 × 10−8 mol s−1 cm−2 at 50 °C in a 1 M KOH methanol solution, thus indicating that the Fumasep® FAA3-50 membrane in OH form is a good candidate for ADMFC application. [ABSTRACT FROM AUTHOR]

This paper is devoted to the determination of the value of the maximum specific power of capacitive electrostatic micromotors based on nanometer working gaps. The motors under consideration were developed earlier. They have the following structure: a metal—thin crystalline ferroelectric layer with a high dielectric constant—a nanometer working gap—a movable electrode. The mechanism limiting the magnitude of the maximum field in the gap have also been determined in previous works. The mechanism is the stripping of atoms from the surface of the movable electrode under the action of electrostatic forces. It was shown that the maximum energy density in the working gap can be as high as 1.6 × 109 J/m3. In the presented paper, a maximum frequency of electromechanical energy conversion as high as 10 MHz is estimated for these motors, with a maximum specific power of 5 × 108 W/kg. The application of the proposed motors for micromachines is discussed. [ABSTRACT FROM AUTHOR]

Electricity access is an essential factor for any nation's fast-growing economic and technological development. Therefore, to meet the fast-growing world population, the adoption of a mix of energy sources, including renewable energy, is one of the ways to address the paucity supply of energy worldwide. In this paper, the performance yields of five solar photovoltaic (PV) modules, named PV1, PV2, PV3, PV4, and PV5, from different manufacturers were analyzed and compared to their respective cost benefits for profitable customer's choice. The study on the panels was conducted at the geographical locations of 25.7535° S latitude and 28.2079° E longitude, with an average perimeter of 525.6 m in Pretoria, South Africa. The panels were installed without shading under the same condition of solar irradiation. The power output of each module was collected three times a day for six months. The analysis showed that the power outputs or performances of the respective modules are majorly affected by their surface temperatures as indicated by the values of multiple regression correlation of 92.9%, 96.9%, 99.1%, 97.2%, and 77.5% between the respective modules' power outputs and temperature. The study also showed a techno-economic evaluation method that helps to economically alleviate the cost of solar PVs and balance the choice of the PV panels according to their short-term performances. [ABSTRACT FROM AUTHOR]

In this review, recent achievements in the application of high-entropy alloys (HEAs) and high-entropy oxides (HEOs) in the technology of solid oxide fuel cells (SOFC) are discussed for the first time. The mechanisms of the stabilization of a high-entropy state in such materials, as well as the effect of structural and charge factors on the stability of the resulting homogeneous solid solution are performed. An introduction to the synthesis methods for HEAs and HEOs is given. The review highlights such advantages of high-entropy materials as high strength and the sluggish diffusion of components, which are promising for the use at the elevated temperatures, which are characteristic of SOFCs. Application of the medium- and high-entropy materials in the hydrocarbon-fueled SOFCs as protective layers for interconnectors and as anode components, caused by their high stability, are covered. High-entropy solid electrolytes are discussed in comparison with traditional electrolyte materials in terms of conductivity. High-entropy oxides are considered as prospective cathodes for SOFCs due to their superior electrochemical activity and long-term stability compared with the conventional perovskites. The present review also determines the prioritizing directions in the future development of high-entropy materials as electrolytes and electrodes for SOFCs operating in the intermediate and low temperature ranges. [ABSTRACT FROM AUTHOR]

Low-grade waste heat released from alkaline fuel cells (AFCs) contains enormous useful energy, which can be recycled for energy cascade utilization. However, the traditional heat energy harvesting techniques are limited by low power generation and conversion efficiency. In this work, an alkaline fuel cell/thermoradiative device hybrid system is proposed to address this challenge, where the thermoradiative device (TRD) recycles the waste heat from an AFC, thereby providing additional electrical power. A comprehensive mathematical model of the hybrid system is developed to investigate its general performance characteristics and optimal parameter designs. The hybrid system possesses better output performance than other previously proposed AFC-based hybrid systems, which indicates that the TRD can more efficiently harvest the waste heat produced from AFC than other conventional cogeneration devices. The maximum power density of the hybrid system can be as much as 1.75 times that of the single AFC, and hence, the hybrid system can offer a significant performance boost. Additionally, the optimal operating regime and the critical parameter designs are determined, offering theoretical guidance for improving system performance. The presented work shall pave new routes and provide essential guidelines for designing high-performance waste heat recycling devices. • An AFC-TRD hybrid system for efficient waste heat recovery is proposed. • Overall performance is greatly improved compared with a single AFC. • The optimally operating regions and parameter choice criteria are given. • Optimal output performance is superior to other AFC-based hybrid systems. • This work provides new insights for design and optimization of hybrid devices. [ABSTRACT FROM AUTHOR]

Summary: Microbial fuel cell (MFC) is a promising technology since two important processes: wastewater treatment and electrical energy, can be obtained simultaneously. The performance of the MFC (maximum power density (MPD) and COD removal) depends mainly on substrate concentration, pH time, and initial COD. Therefore, the main target of this work is to simultaneously increase the MPD and COD removal by determining the optimal controlling parameters. The proposed methodology integrates fuzzy modelling and Harris Hawks optimization (HHO). Firstly, based on the experimental data set, an accurate fuzzy model is created to simulate the performance of MFC in terms of four controlling parameters. To prove the superiority of fuzzy model, the results are compared with response surface methodology (RSM) in terms of RMSE and coefficient of determination (R2). Secondly, using HHO, the optimal values of substrate concentration, co‐culture composition, pH, and time are determined. These four controlling parameters are used as decision variables during the optimization process, whereas the objective function is the simultaneous maximization of the MPD and COD removal. The obtained results proved that the optimal substrate concentration, pH, time, and initial COD values are 58.2%, 7, 14.4 days, and 32 × 10−3 (mg/L) respectively. Under this condition, the integration between fuzzy and HHO, the overall performance of MFC has been improved by 10.37% and 19.13%, respectively, compared with the experimental and RSM. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe-based materials significantly improve the efficiency of microbial fuel cells. • Fe catalysts at cathode enhance ORR, favor 4e- pathway and reduce H 2 O 2 formation. • Regulating Fe and N dispersion enhances ORR activity and increases active sites. • Fe-N-C and FePc/CS catalysts outperformed commercial Pt/C in MPDs. • AI holds potential to improve Fe-MFCs by parameter and catalyst optimization. Microbial fuel cells (MFCs) face substantial challenges, including electrode cost, biofouling, and slow kinetics of the oxygen reduction reaction (ORR) at the cathode. This review examines iron-based (Fe-based) materials as electrodes and catalysts, emphasizing their efficacy in pollutant degradation and electricity generation. As anode modifiers, Fe-based materials enhance electrical energy production by improving electron transport, increasing anode voltage, and promoting microbial adhesion. At the cathode, they facilitate a more efficient 4-electron transfer process for the ORR, reducing undesirable hydrogen peroxide formation. This review discusses the impact of Fe and N dispersion, surface, and active site optimization on ORR activity and stability, highlighting the advantages of Fe-based materials in terms of stability, reproducibility, and biocompatibility through multi-element doping and nanoscale interface engineering. These modifications enable Fe-based materials to outperform traditional Pt/C catalysts in power density. The role of microbial communities, including Geobacter and Pseudomonas , in electron transfer and wastewater treatment in Fe-based MFCs is also addressed. Additionally, the potential of artificial intelligence (AI) to optimize operational and catalyst performance in enhancing Fe-based MFC efficiency is explored. This review concludes with a comprehensive assessment of Fe-based materials in MFCs, focusing on their contributions to sustainable energy and water purification by examining bioelectricity generation, fabrication costs, and power output, thereby providing a holistic overview of the advancement of Fe-based materials for environmentally sustainable applications. [ABSTRACT FROM AUTHOR]

In this study, a DEFC with an anion-exchange membrane is investigated to evaluate fuel utilization both theoretically and experimentally. The effects of variations in the input fuel temperature and fuel concentration on fuel utilization and power density were analyzed through sensitivity analysis. To this end, for different test conditions containing initial conditions, increasing the input fuel temperature and oxygen blowing to the cathode with fuel circulation, ethanol utilization factor and maximum power density were calculated. The findings revealed increasing the fuel temperature and oxygen blowing led to an increase in the ethanol utilization factor from 66.92% to 85.15% and 73.54%. Moreover, maximum power density was increased from 16.2 to 17.5 and 22.5 mWcm−2 for increasing the fuel temperature and oxygen blowing states. According to the results, it was proved that increasing the input fuel temperature and oxygen-blowing conditions had a contradictory impact on the performance analysis. As a solution, a new parameter named δ is introduced to conduct a more accurate performance analysis of DEFC. This parameter indicates the amount of produced power per unit of fuel consumption. The results demonstrated that parameter δ was increased from 0.14 to 0.21 and 0.31 mWcm−2 for increasing the fuel temperature and oxygen blowing states. [Display omitted] [ABSTRACT FROM AUTHOR]

During the operation of alkaline fuel cells (AFCs), a significant amount of waste heat is generated, which has negative impacts on energy utilization and the environment. To improve energy efficiency, cost savings, environmental sustainability, and industrial practices, an effective approach is proposed to employ thermogalvanic cells (TGCs) for electric power generation by harvesting low-grade exhaust heat produced in AFCs. A mathematical model of the AFC-TGC hybrid system is established, taking into account the three overpotential losses in AFCs and the irreversible heat losses in TGCs. Based on this thermal-electric coupled model, we investigate the hybrid system's output performance characteristics and optimal parameter design. The calculated results indicate that the hybrid system achieves a considerable increase of 19.72% in maximum power density from 247.07 W m−2 to 295.80 W m−2 and 5.71% in conversion efficiency from 10.16% to 10.74% compared to a single AFC, respectively. In addition, the output performance of the hybrid system can be further improved by adjusting system parameters such as the AFC's operating temperature, the length of each TGC cell, the heat sink temperature, and the thermal convection coefficient. More importantly, a comparative study of the maximum power density of AFC-based cogeneration systems reveals that the TGC demonstrates a remarkable ability to economically recover waste heat from the AFC, surpassing previously reported thermal energy utilization devices. This study provides important theoretical guidance for the optimal design and parametric analysis of AFC-TGC hybrid systems, thereby facilitating the development of high-performance energy cascade utilization systems based on AFC devices. • An AFC-TGC hybrid system is proposed for waste heat recovery and cogeneration. • The total power density and overall efficiency are increased by 19.72% and 5.71%. • Parametric selection criteria for achieving better output performance are determined. • Potential advantages of the output electrical performance and cost are demonstrated. [ABSTRACT FROM AUTHOR]

Ibuprofen degradation and energy generation in a single-chamber Microbial Fuel Cell (MFC) were evaluated using a bioanode fabricated from devil fish bone char (BCA) synthesized by calcination in air atmosphere. Its performance was compared with conventional carbon felt (CF). Bone char textural properties were determined by nitrogen adsorption. Before and after, the bacterial colonization on the materials was analyzed by environmental scanning electron microscopy. Energy generation was evaluated by electrochemical techniques as open-circuit potential, linear sweep voltammetry, and electrochemical impedance spectroscopy. Ibuprofen degradation was analyzed by High-Performance Liquid Chromatography-Ultraviolet, and the chemical oxygen demand (COD) removal was measured. Results showed a specific area of 136m²/g for BCA, having enough space to immobilize microorganisms. The micrographs confirmed the biofilm formation on the electrode materials. Over the 14 days, MFC with BCA reached a maximum power density of 4.26mW/m², 175% higher than CF, and an electron transfer resistance 2.1 times lower than it. This coincides with the COD removal and ibuprofen degradation efficiencies, which were 43.6% and 34% for BCA and 31.8% and 27% for CF. Hence, these findings confirmed that BCA in MFC could provide an alternative electrode material for ibuprofen degradation and energy generation. [ABSTRACT FROM AUTHOR]

• Performance of SMFCs at different distances in open channels was studied. • Higher maximum power densities were produced by SMFCs with a larger distance. • LOI removal was improved by sufficient increase in distance between SMFCs. • Sediment storage lowered initial LOI of sediment and LOI removal in the SMFCs. • Low LOI removal of stored-sediment SMFCs was associated with their low power density. In this study, influence of distance between two sediment microbial fuel cells (SMFCs) and storage of sediment for several months in an open channel were investigated in different configurations. Results indicated that SMFCs with the largest distance outperformed the neighboring SMFCs in terms of voltage and power output in different configurations. In addition, it was shown that long-term sediment storage weakened SMFC performance. Maximum power densities of 39 and 50 mW m−2 were achieved for the two SMFCs with the largest distance, while 30 and 26 mW m−2 were obtained for the two adjacent SMFCs operating with fresh sediment. Furthermore, loss on ignition (LOI) removal was enhanced with a sufficient increase in SMFC distances, so that LOI removal of 49.8 % and 21.4 % in the SMFCs with the largest distance was considerably higher than the neighboring SMFCs (18.2 % and 12.9 %). On the other hand, employing the stored sediment, SMFCs with the largest distance produced the highest maximum power densities of 35 and 32 mW m−2 whereas 23 and 22 mW m−2 were obtained by the neighboring SMFCs. Power density of the SMFCs with the largest distances was higher than the neighboring cells in both series and parallel connections as well. [ABSTRACT FROM AUTHOR]

The power density of a direct methanol fuel cell (DMFC) stack as a function of temperature, methanol concentration, oxygen flow rate, and methanol flow rate was studied using a response surface methodology (RSM) to maximize the power density. The operating variables investigated experimentally include temperature (50-75 °C), methanol concentration (0.5-2 M), methanol flow rate (15-30 ml min-1), and oxygen flow rate (900-1800 ml min-1). A new design of the central composite design (CCD) for a wide range of operating variables that optimize the power density was obtained using a quadratic model. The optimum conditions that yield the highest maximum power density of 86.45 mW cm-2 were provided using 3-cell stack at a fuel cell temperature of 75 °C with a methanol flow rate of 30 ml min-1, a methanol concentration of 0.5 M, and an oxygen flow rate of 1800 ml min-1. Results showed that the power density of DMFC increased with an increase in the temperature and methanol flow rate. The experimental data were in good agreement with the model predictions, demonstrating that the regression model was useful in optimizing maximum power density from the independent operating variables of the fuel cell stack.

In order improve the fuel cell performance of a free-standing graphene oxide (GO) membrane, the impacts of both the additional oxidation of GO and the modification with vinilsulfonic acid were investigated. The modification with vinilsulfonic acid was conducted with and without adding potassium persulfate, K 2 S 2 O 8 , which is a radical initiator for the polymerization of vinylsulfonate. A total of six types of free-standing GO membranes with and without the oxidation and/or the modification were prepared. The oxidation and the modification additively increased the proton conductivity, and the oxidation significantly improved the durability of the fuel cell performance at 30 °C. The membrane of GOhvsi, of which GO was oxidized and modified with the initiator, showed very high in-plane proton conductivities at 30 °C, i.e., 0.54 S cm−1 at RH 100%. The H 2 –O 2 fuel cell using GOhvsi showed maximum power densities as high as 136 mW cm−2 and 184 mW cm−2 at 30 °C and 50 °C, respectively. The performance at 30 °C was stable for more than 20 h. The improved durability by the oxidation was attributed to the increased defects of carbon based on an XPS analysis. The TPD-MS analysis suggested that the oxygenated functional groups at the defects would increase the binding strength. • The oxidation of GO significantly improved the fuel cell performance and durability. • The modification of GO with vinilsulfonic acid increased the membrane conductivity. • A 158 mW cm−2 power density was achieved by the free-standing GO membrane. • Stable operation at 30 °C continued for over 20 h by the free-standing GO membrane. • The oxidation and modification additively improved the fuel cell performance. [ABSTRACT FROM AUTHOR]

Traditional biofuel cells (BFCs) are devices that use biological catalysts to catalyze the oxidation of organic materials and in the meantime convert chemical energy into electrical energy. In this work, a nonenzymatic catalyst that integrated copper oxide with multi-walled carbon nanotubes (CuO/MWCNTs) was synthesized by a simple solvothermal method, and the composites show an outstanding electrocatalytic activity for oxidation of phenol due to the synergistical contribution of CuO nanoparticles and MWCNTs. The effects of the pH, concentration of electrolyte and phenol and scan rate on the phenol oxidation are investigated. Benefitting from the excellent performance toward phenol oxidation, a H-type phenol fuel cell was fabricated with CuO/MWCNTs as anode material and electro-deposited platinum film as cathode material. The results show that the phenol fuel cell has an open-circuit potential (OCP) of 0.69 V and can produce a maximum power density of 0.25 mW cm − 2 at 0.44 V with 500 mg ⋅ L − 1 phenol and 0.1 mol ⋅ L − 1 PBS. The stability test revealed that the fuel cell could still deliver about 0.24 mW ⋅ cm − 2 after repeating the test for five times, indicating that the fuel cell has good stability. A nonenzymatic catalyst that integrated copper oxide with multi-walled carbon nanotubes was synthesized by a simple solvothermal method, and the composites show an outstanding electrocatalytic activity for oxidation of phenol. H-type phenol/O2 fuel cell was fabricated combining CuO/MWCNTs/GCE anode for directly oxidizing phenol and Pt/GCE cathode for reducing oxygen. Test results show that fuel cells have high power density and good stability. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) generate a large amount of exhaust heat during operation, leading to environmental pollution and the greenhouse effect. To recover the low-grade exhaust heat produced by PEMFCs, a technically feasible approach is proposed by integrating liquid-state thermocells (LTCs) with PEMFCs for the cogeneration of electric power and efficient waste heat recovery. Considering the three overpotential losses in the PEMFC and the irreversible heat losses in the LTC, a comprehensive mathematical model of a PEMFC-LTC hybrid system is developed to explore the energetic performance characteristics and optimal device design. The results show that the hybrid system's maximum power density and corresponding conversion efficiency are 0.3007 W cm−2 and 24.59%, which is increased by 6.22% and 19.41% compared to a single PEMFC, respectively. Furthermore, raising the PEMFC temperature, optimizing the length of the individual LTC cell, reducing the heat sink temperature, and lowering the thermal convection coefficient can significantly improve the optimal output performance of the hybrid system. Finally, the optimal performance comparisons between the PEMFC-based cogeneration systems reveal that LTCs can more efficiently recycle the waste heat released from the PEMFC than other previously reported devices. This work offers crucial theoretical guidance for the optimal design and parametric analysis of PEMFC-LTC hybrid systems, thus paving the way for developing high-performance energy cascade utilization systems based on PEMFCs. • A PEMFC-LTC hybrid system for efficient exhaust heat recovery and cogeneration is proposed. • The maximum electric power density of the hybrid system yields 0.30 W/cm2 at 353 K. • The overall power density and conversion efficiency are increased by 6.22% and 19.41%. • Optimal performance of this hybrid system is higher than previously reported PEMFC-based systems. • System parametric selection criteria for achieving better output performance are determined. [ABSTRACT FROM AUTHOR]

The electrochemical properties of bi-layered electrolytes GDC(Gd 0.1 Ce 0.9 O 1.95)/YSZ(Y 0.16 Zr 0.84 O 1.92), ESB(Er 0.4 Bi 1.6 O 3)/GDC and ESB/YSZ with different layer thickness fractions in the temperature range from 400 to 800 °C have been investigated by simulating calculations based on a charge transport continuity equation and the characteristic conductivity parameters of YSZ, GDC and ESB. It has been found that the model cells with ESB/GDC and ESB/YSZ bi-layered electrolytes can render a higher maximum power density that increases with the ESB layer thickness than those with GDC/YSZ bi-layered electrolytes in the studied temperature range. While the oxygen partial pressure at the interface of ESB/GDC is much lower than that of ESB/YSZ electrolyte with the same ESB thickness fraction, a higher interfacial oxygen partial pressure than the critical decomposition value of Bi 2 O 3 can be achieved in the ESB/YSZ electrolytes even with small YSZ thickness fractions. This result strongly suggests that the ESB/YSZ, instead of ESB/GDC, would be a thermodynamic stable bi-layered electrolyte with high output power density for potential applications in the intermediate to low temperature SOFCs. • SOFC models with bi-layered electrolytes GDC/YSZ, ESB/GDC and ESB/YSZ are developed. • Reasonable characteristic conductivity parameters of YSZ, GDC and ESB are obtained. • Interfacial oxygen partial pressures of ESB/GDC and ESB/YSZ are figured out. • A best design of chemically stable bi-layered oxide electrolyte is given. [ABSTRACT FROM AUTHOR]

A high-efficiency, stable, and flexible glucose/oxygen enzymatic biofuel cell is fabricated based on three-dimensional gold-coated nickel foam. The gold-coated layer makes the skeleton of nickel foam rougher, enhancing the relative apparent surface area of nickel foam and decreasing the electron transfer resistance. With the gold-coated nickel foam as substrate, the bioanode and biocathode exhibit good electrocatalysis activity and stability. By assembling the bioanode and biocathode with agarose gel electrolyte, cellulose acetate membrane, and silicone rubber layer-by-layer, the flexible biofuel cell is obtained. As per the results, the three-dimensional gold-coated nickel foam enlarges the enzymatic loading density to 5.68 × 10−7 mol cm−2, increasing the short circuit current density to 9.04 mA cm−2. The maximum power density of this flexible biofuel cell reaches 2.32 ± 0.07 mW cm−2 with excellent stability for retaining 84.6% of its performance after 60 days. Additionally, the flexible biofuel cell can be very stable in and after 1000 times of bending. [ABSTRACT FROM AUTHOR]

The exhaust heat released from SOFCs (solid oxide fuel cells) possesses tremendous energy that can be recovered for energy cascade utilization. Nevertheless, low conversion efficiency or power density limits the SOFC's high-grade waste heat recovery capabilities for the cogeneration of electric power. To address this challenge, a novel hybrid system coupling a SOFC with a GTEC (graphene-collector thermionic energy converter) is proposed, where the GTEC harvests the high-grade exhaust heat produced by the SOFC and generates extra electricity. It is found that the maximum power density of the hybrid system can reach 0.774 W/cm 2 at 1073 K, which is 1.20 times higher than that of the sole SOFC, indicating that the hybrid system offers a considerable improvement in output performance. Additionally, the optimal operating conditions and major parameter designs of the hybrid system are determined from the perspective of finite-time thermodynamics. Choosing the optimal area ratio, increasing the SOFC operating temperature, enhancing the heat transfer coefficient, decreasing the thermal emissivity, and fabricating the perfect optical reflector can further improve the optimal performance of the hybrid system. Compared with other SOFC-based hybrid systems, the SOFC-GTEC provides better output performance, proving that the GTEC can more efficiently utilize the exhaust heat produced by SOFC than other energy harvesting devices. This work provides crucial theoretical guidance on the optimal designs and parametric analysis of SOFC-GTEC hybrid systems, thus paving the way towards developing high-performance SOFC cogeneration systems. • A SOFC-GTEC hybrid system for cogeneration of electrical power is proposed. • The maximum power density of the hybrid system reaches 0.774 W/cm 2 at 1073 K. • The overall electrical power and conversion efficiency are increased by 20% and 40%. • Maximal power density (0.774 W/cm 2) and efficiency (38.8%) is higher than reported SOFC-based systems. • System parametric selection criteria for achieving higher power and efficiency are determined. [ABSTRACT FROM AUTHOR]

• A membrane-free battery was developed for low-grade waste heat recovery. • The M−TRB could remiss ammonia crossover and reduce the cost of power generation. • The effect of different operating parameters on power production was investigated. • The maximum power density of 220 W m−2 was obtained under optimum conditions. • The short version of the paper was presented at ICAE2022, Bochum, Germany, Aug 8–11, 2022. This paper is a substantial extension of the short version of the conference paper. The development of a low-cost and high-performance thermally regenerative battery is an extremely effective way for waste heat recovery. In this work, a membrane-free thermally regenerative battery (M−TRB) is designed for low-cost and high-performance low-grade thermal energy harvesting. It is exhibited that a M−TRB with a virtual membrane formed by the interface between electrolytes instead of the expensive anion exchange membrane (AEM) can achieve stable power generation successfully. And the maximum power density obtained in M−TRB is 118 W m−2 under the optimal operation condition. Moreover, a combination of M−TRB and hierarchical porous composite electrodes (PCEs) can further improve the maximum power density to 220 W m−2. The much lower cost caused by the simple structure without expensive AEM makes it more competitive in comparison to other TRBs. This indicated that the high-performance and low-cost M−TRB is a potential choice for the construction of systems in future applications. [ABSTRACT FROM AUTHOR]

Microbial fuel Cell (MFC) has gained a lot of attention in recent years due to its capability in simultaneously reducing organic component and generating electricity. Here multicultural rumen microbes (RM) were used to reduce organic component of slaughterhouse wastewater in a self-fabricated MFC. The objectives of this study were to determine the MFC configuration and to find out its maximum capability in organic degradation and electricity generation. The experiments were conducted by employing, different types of electrode materials, electrode size, and substrate-RM ratio. Configuration of MFC with graphite-copper electrode 31.4 cm2 in size, and substrate-RM ratio 1:10 shows the best result with current density of 318 mA m-2, potential 2.4 V, and achieve maximum power density up to 700 mW m-2. In addition, self-fabricated MFC also shows its ability in reducing organic component by measuring the chemical oxygen demand (COD) up to 67.9% followed by increasing pH from 5.9 to 7.5. MFC operating at ambient condition (29oC and pH 7.5), is emphasized as green-technology for slaughterhouse wastewater treatment. Article History: Received March 26, 2016; Received in revised form June 20, 2016; Accepted June 25, 2016; Available online How to Cite This Article: Prabowo, A.K., Tiarasukma, A.P., Christwardana, M. and Ariyanti, D. (2016) Microbial Fuel Cells for Simultaneous Electricity Generation and Organic Degradation from Slaughterhouse Wastewater. Int. Journal of Renewable Energy Development, 5(2), 107-112. http://dx.doi.org/10.14710/ijred.5.2.107-112

Microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) are promising bioelectrochemical systems (BESs) for simultaneous wastewater treatment and energy/resource recovery. Unlike conventional fuel cells that are based on stable chemical reactions, these BESs are sensitive to environmental and operating conditions, such as temperature, pH, external resistance, etc. Substrate type, electrode material, and reactor configuration are also important factors affecting power generation in MFCs and hydrogen production in MECs. In order to discuss the influence of these above factors on the performance of MFCs and MECs, this study analyzes published data via data synthesis and meta-analysis. The results revealed that domestic wastewater would be more suitable for treatment using MFCs or MECs, due to their lower toxicity for anode biofilms compared to swine wastewater and landfill leachate. The optimal temperature was 25-35 °C, optimal pH was 6-7, and optimal external resistance was 100-1000 W. Although systems using carbon cloth as the electrodes demonstrated better performance (due to carbon cloth's large surface area for microbial growth), the high prices of this material and other existing carbonaceous materials make it inappropriate for practical applications. To scale up and commercialize MFCs and MECs in the future, enhanced system performance and stability are needed, and could be possibly achieved with improved system designs. [ABSTRACT FROM AUTHOR]

We present new architectures in CH 3 NH 3 PbI 3 based planar perovskite solar cells incorporating solution processed SnO 2 /MgO composite electron transport layers that show the highest power outputs ever reported for photovoltaic cells under typical 200–400 lx indoor illumination conditions. When measured under white OSRAM LED lamp (200, 400 lx), the maximum power density values were 20.2 µW/cm 2 (estimated power conversion efficiency, PCE = 25.0%) at 200 lx and 41.6 µW/cm 2 (PCE = 26.9%) at 400 lx which correspond to a ∼ 20% increment compared to solar cells with a SnO 2 layer only (even at standard 1 sun illumination, where the maximum PCE was 19.0%). The thin MgO overlayer leads to more uniform films, reduces interfacial carrier recombination, and leads to better stability. All layers of the cells, except for the two electrodes, are solution processed at low temperatures for low cost processing. Furthermore, ambient indoor conditions represent a milder environment compared to stringent outdoor conditions for a technology that is still looking for a commercial outlet also due to stability concerns. The unparalleled performance here demonstrated, paves the way for perovskite solar cells to contribute strongly to the powering of the indoor electronics of the future (e.g. smart autonomous indoor wireless sensor networks, internet of things etc). [ABSTRACT FROM AUTHOR]

For practical implementation of MFC, increasing power generation is important because it is closely related with energy production rate and wastewater treatability. However, it is not known which relative arrangement of anode and cathode gives the best performance, and it is necessary to know electrochemical reference point of the brush anode for this. Five different brush-anode configurations were tested in a single-chambered cubic MFC. By merely changing a brush anode configuration, power and current densities were increased by 20% and 30%, respectively. The horizontally-positioned anode configuration (H1) with the closest anode-cathode distance produced the highest power and current. EIS showed that anode impedance and full-cell impedance were decreased by 60% and 49%, respectively. CE and EE were not significantly affected by the anode-cathode distance, but the horizontal type cells showed relatively higher CE, EE and COD removal rate and shorter batch time. The center of a titanium current collector and the center of carbon fibers of a brush-anode were found to be statistically-significant reference points for MFC electrochemistry. [ABSTRACT FROM AUTHOR]