Sharif Digital Repository

Photovoltaic-electrolyzer systems are one of the most promising alternatives for obtaining hydrogen from a renewable energy source. Determining size and the operational conditions are always a key issue while coupling directly renewable electricity sources to PEM electrolyzer. In this research, the multi objective optimization approach based on an imperialist competitive algorithm (ICA), which is employed to optimize the size and the operating conditions of a directly coupled photovoltaic (PV)-PEM electrolyzer. This allows the optimization of the system by considering two different objectives, including, minimization of energy transfer loss and maximization of hydrogen generation. Multi... 

Hydrogen is an important storage medium and can be produced by the water electrolysis. In this research, energy transfer loss between a photovoltaic (PV) unit and electrolyzer is minimized by optimizing the size and operating condition of an electrolyzer directly connected to a PV module. In directly coupled photovoltaic-electrolyzer (PV/EL) systems, there is a mismatch between output PV's maximum power point characteristic and input PEM electrolyzer's characteristic. With proper sizing optimization methods, it is possible to directly couple photovoltaic-electrolyzer systems. The evolutionary optimization algorithms like genetic algorithm (GA), particle swarm optimization (PSO) and... 

Hydrogen is considered to be the fuel of the future. It is a cleaner alternative to the fossil fuels we consume every day. Of all the different hydrogen production pathways that exist, producing the gas by utilizing the power generated by renewable energy sources has been a topic of interest for many researchers across the world. The following work focuses on minimizing the energy loss by optimizing the size and the operating conditions of an electrolyzer directly connected to a photovoltaic (PV) module at different irradiance. The hydrogen, in the proposed system, is produced using a proton exchange membrane (PEM) electrolyzer. A nonlinear method is considered, because of the complexity of... 

In the natural gas transmission network, from supply points to demand nods there are various technological options that include processing, transportation, conversion and gas distribution. Comprehensive analysis of natural gas network requires evaluation of different chains of gas flow through various levels based on economical and environmental criteria subject to technical and operational constraints such as feasibility, operability and reliability of different alternatives. To aid decision-making process in the sector of natural gas, a generic optimization-based model has been developed for assessing long term energy issues related to planning and design of natural gas supply systems. The... 

Hydrogen is a flexible energy carrier and storage medium and can be generated by electrolysis of water. In this research, hydrogen generation is maximized by optimizing the optimal sizing and operating condition of an electrolyzer directly connected to a PV module. The method presented here is based on Particle swarm optimization algorithm (PSO). The hydrogen, in this study, was produced using a proton exchange membrane (PEM) electrolyzer. The required power was supplied by a photovoltaic module rated at 80 watt. In order to optimize Hydrogen generation, the cell number of the electrolyser and its activity must be 9 and 3, respectively. As a result, it is possible to closely match the... 

In this study, hybrid renewable energy system based on wind/electrolyzer/PEM fuel cell are conceptually modeled, and also, exergy and energy analysis are performed. The energy and exergy flows are investigated by the proposed model for Khaf region-Iran with high average wind speed and monsoon. Exergy and energy analysis framework is made based on thermodynamic, electro-chemical and mechanical model of the different component of hybrid system. Also, the effects of various operating parameters in exergy efficiency are calculated. The results show an optimum wind speed where the exergy efficiency and power coefficient is at maximum level, and also, when the ambient temperature start to be... 

The present study investigated the biological treatment of produced water in a microbial electrochemical cell (MXC). The main objectives were to develop a novel spiral microbial electrochemical cell (SMXC) and test its performance for produced water treatment under highly saline conditions (salinity > 200000 ppm). The bioelectrochemical performance of the system was also evaluated in terms of power and hydrogen production over time. The comparatively inexpensive material and ease of application increased the feasibility of the SMXC configuration for produced water treatment. Optimal SMXC performance as a microbial fuel cell was achieved at a maximum open circuit potential of 330 mV, maximum... 

The objective of this study was to construct a novel model to be applied in a general manner to simulate microbial electrochemical cells (MXCs); for both microbial fuel cell (MFC) and microbial electrolysis cell (MEC). The liquid bulk was modeled based on the organic matters degradation to acetate via the anaerobic digestion process. Biofilm simulation was established based upon one-dimensional distribution and the dynamical electron transfer was completed by means of the conduction-based mechanism. We, for the first time, introduced biofilm local potential modeling for MEC simulation with general and simplified linear boundary conditions. The MFC-related part of the model was evaluated... 

Solar energy exists extensively in all parts of the world. However the intermittency of solar energy presents critical challenges to PV system. The intermittency can be covered by storing solar energy in chemical bonds such as hydrogen. This process can be performed by photovoltaic powered electrolysis of water. The energy transfer efficiency between PV and electrolyzer is subject to the distance between maximum power points (MPP) of PV module and operating points. The operating points can be adjusted by optimizing the design parameters of the electrolyzer but the maximum power points are function of PV module characteristics, solar radiation and ambient temperature. Therefore the weather... 

Microbial electrolysis cells (MECs) are bioelectrochemical reactors in which chemical energy stored in organic compounds are converted to hydrogen through biocatalytic oxidation by microorganisms. The performance of MECs is highly affected by microbial communities that are impartible parts of this technology. A better understanding of microbial interactions and competitions mechanisms, has aided the comprehension of ideas and guidelines for cost effective commercial scales design. In this study, a comprehensive review of current knowledge in the microbial characterization, enrichment, and evaluation of effective parameters of microbial community in microbial electrolysis cells for typical... 

Solar energy will make a valuable contribution for power generation in the future. However the intermittency of solar energy has become an important issue in the utilization of PV system, especially small scale distributed solar energy conversion systems. The issue can be addressed through the management of production and storage of the energy in the form of hydrogen. The hydrogen can be produced by solar photovoltaic (PV) powered electrolysis of water. The amount of transferred energy to an electrolyzer from a PV module is a function of the distance between maximum power points (MPP) of PV module and the electrolyzer operating points. The distance can be minimized by optimizing the number... 

The present study deals with the feasibility of a microfluidic microbial electrolysis cell (MEC) as an efficient biohydrogen generator for medical usage for the first time. The evaluation of nickel in microfluidic MEC as an alternative for conventional electrodes indicates successful performance in the improvement of bioenergy production. The maximum biohydrogen production rate and produced power density of 2.2 μW cm−2 and 1.4 μl H2 μl substrate−1 day−1 were obtained, respectively. It is considered a promising technology for medical usage due to the following factors: significant biohydrogen generation, low consumption of expensive materials, simple construction, and utilization of human... 

It is well known that electro-hydrodynamical effects in freely suspended liquid films can force liquids to flow. Here, we report a purely electrically driven rotation in water and some other liquid suspended films with full control on the velocity and the chirality of the rotating vortices. The device, which is called "film motor", consists of a quasi two-dimensional electrolysis cell in an external in-plane electric field, crossing the mean electrolysis current density. If either the external field or the electrolysis voltage exceeds some threshold (while the other does not vanish), the liquid film begins to rotate. The device works perfectly with both DC and AC fields. © Springer-Verlag... 

We derive a new non-linear two dimensional model for melt flows and interface instability in aluminum reduction cells. This model is based on non-linear de St. Venant shallow water equations and contains the main features of an aluminum reduction cell. In this model we consider linear friction terms but in a new way that has not been considered in previous works. Our results are in good agreement with the results of simulation of viscous flow. This model is applicable both in determination of melt flows in molten aluminum and cryolite layers and also in finding the extreme limit for stability of interfacial waves in an aluminum reduction cell  

This research work presents a novel integrated structure for the cogeneration of electricity and renewable syngas. The base structure of the process is developed by solid oxide cells in which electricity is generated by the natural gas-fueled fuel cell unit, and renewable syngas is produced by the electrolyzer cell unit. Direct integration between fuel cell and electrolyzer cell units is established for optimal use of fuel cell off-gases. To improve system's sustainability, a solar power cycle, including solar collectors coupled with an organic Rankine cycle (ORC), is designed to provide renewable electricity for steam and CO2 co-electrolysis operation. 1D mathematical approaches are... 

As one of the cleanest energies, hydrogen has attracted much attention over the past decade. Hydrogen can be produced using water electrolysis in a Proton Exchange Membrane Electrolysis Cell (PEMEC). In the present study, the performance of the PEMEC, powered by the Photovoltaic-Thermal (PVT) system, is scrutinized. It is considered that the PVT system provides the required electrical power of the PEMEC and preheats the feedwater. A comprehensive numerical model of the coupled PVT-PEMEC system is developed. The model is used to investigate the effect of various operating parameters, including solar radiation intensity, inlet feedwater temperature, and feedwater mass flow rate, on the... 

Hydrogen technology through water electrolyzer systems has attracted a great attention to overcome the energy crisis. So, rationally designed non-noble metal based-electrocatalysts with high activity and durability can lead to high performance water electrolyzer systems and high purity hydrogen generation. Herein, a facile two-step method: hydrothermal and electrodeposition, respectively, are developed to decorate highly porous three-dimensional binder-free structure NiFeO/NiO nanosheets array on Ni foam (NiFeO/NiO/NF) with robust adhesion as a high-performance electrode for Hydrogen Evolution Reaction (HER). The electrodeposition process applied after the initial hydrothermal process... 

In this study, the performance of a Photovoltaic Thermal-Organic Rankine Cycle (PVT-ORC) system combined with a Proton Exchange Membrane Electrolysis Cell (PEMEC) is investigated. A combined numerical/theoretical model of the system is developed and used to evaluate the effect of various system design parameters. In addition, the effects of using water, ethylene glycol, and a mixture of water and ethylene glycol (50/50) as the working fluid of the PVT system and R134a, R410a, and R407c as the working fluid of the ORC cycle on the performance of the PVT-ORC-PEMEC system are studied. Based on the results, R134a and water demonstrated the best performance as the working fluid of the ORC and PVT... 

In current study, a meta-analysis approach was used to identify and evaluate the impact of various factors on the performance of integrated systems of anaerobic digestion with microbial electrolysis cell. In this study, related articles on the topic were systematically identified and collected according to the considered criteria, and the effect size that refers to the value of the difference between variables mean (total chemical oxygen demand (TCOD) removal rate and CH4 yield) was estimated. According to the meta-analysis, fed-batch operation mode, the range of 20< temperature ≤30 °C, metal cathodes, the range of 500< anode surface area ≤5000 cm2, HRT (hydraulic retention time) >20 days,... 

As one of the cleanest energies, hydrogen has attracted much attention over the past decade. Hydrogen can be produced using water electrolysis in a Proton Exchange Membrane Electrolysis Cell (PEMEC). In the present study, the performance of the PEMEC, powered by the Photovoltaic-Thermal (PVT) system, is scrutinized. It is considered that the PVT system provides the required electrical power of the PEMEC and preheats the feedwater. A comprehensive numerical model of the coupled PVT-PEMEC system is developed. The model is used to investigate the effect of various operating parameters, including solar radiation intensity, inlet feedwater temperature, and feedwater mass flow rate, on the...