In addition to simultaneously supplying heat and electricity, CCHP systems also provide the cooling demand of the buildings. The input energy of this system can be supplied from renewable energy sources such as solar energy, geothermal energy and so on. Compared to conventional power generation systems, cogeneration systems have higher energy efficiency, lower pollutant production, and higher reliability. In this paper, a solar-powered CCHP system equipped with a PEM electrolyzer and fuel cell is simulated and optimized. The combination of the PEM electrolyzer and the fuel cell is used in order to provide sustainable heat and electricity. For this purpose, the electrical power produced in the cycle is converted to hydrogen by the electrolyzer as the demand for electricity is low and converted to electricity by the fuel cell when needed. The results of system optimization showed that energy efficiency and exergy efficiency increased by 22. 32% and 8. 61% in the first scenario, respectively. Moreover, the total cost rate of the system is reduced by 6. 65% in the second scenario.

In recent years the energy shortage and environmental impact from consuming fossil fuels have led to the development of renewable energy source systems. Since these sources are not reliable and are usually time dependent, an energy storing system likehydrogen production is required. In this regard, a PEM electrolyzer can be efficiently used to decompose liquid water into hydrogen and oxygen. Because of the dynamic nature of renewable sources, a dynamic model of a PEM electrolyzer is a necessity for investigating its performance. In this paper, a new one-dimensional dynamic model PEM electrolyzer which solves electrochemical and two phase fluid flow equations at each time step is proposed. The finite volume method with an upwind scheme is used to solve a set of nonlinear partial differential equations of fluid flowfor discretization. The obtained algebraic set of equations is implicitly solved to ensure good stability at large time steps as well as low mesh nodes which provide the capability of system level simulation. Storing gas produced by the electrolysis process continuously increases vessels pressure and leads to dynamic behavior of the electrolyzer. This phenomenon is investigated in this research using the proposed model. Results show that although the concentration of produced gas was raised by increasing vessel pressure, the hydrogen concentration was essentially constant along the electrolyzer on the cathode side. It was also observed that increasing vessel pressure results in high power consumption. However, when the pressure on the anode side reaches the moderate level the water mass flow rate can be reduced, which causes a reduction in pump energy consumption.

Hydrogen production using PEM electrolysers is an effective method to produce a renewable energy resource. Also، the hydrogen and oxygen generated by electrlyzer can be used in a fuel cell of drones. Thermodynamic analysis of PEM electrolyzer is essential to identify key losses and to optimize the performance of the electrolyzer. In this article، the process of water electrolysis in a PEM electrolyser integrated with concentrating solar plant to produce power and hydrogen is studied and the effect of solar intensity، current density and other operating parameters on the rate of the hydrogen production is investigated. The results indicate that increase of current density and consequently the rate of the hydrogen production leads to increase of voltage and decrease of energy and exergy efficiency of the electrolyser. Also، increase of temperature، decrease of pressure and thickness of nafion membrane lead to decrease of voltage and improve the performance of electrolyser. Increase of solar intensity by 145 percent leads to increase of the rate of hydrogen production by 110 percent and decrease the exergy and energy efficiency of electrolyser by 13. 8 percent.

Today, for enhancing the trend of energy demand in the world, the use of energy by the approach of maximizing the efficiency of energy systems is inevitable. On the other hand, the high growth rate of unmanned aerial vehicles (UAV), governments investment to develop the necessary infrastructures for the progress of this technology, the variety of applications, and the advantages, indicate its special role in the future. In the present study, an integrated system consisting of PEM electrolyzer, PEM fuel cell, photovoltaic panel, and hydrogen and oxygen storage tanks is developed as a UAV propulsion system so that it can provide the required power. The power required by the UAV was supplied by the PEM fuel cell of the system. The intended hydrogen and oxygen are provided through a hydrogen and oxygen storage tank. In this condition, the capacity of the tanks is known as the limiting factor during the UAV flight time. For more flight continuity, part of the consumable hydrogen and oxygen during the flight is regenerated by installing a photovoltaic panel, using solar renewable energy and also PEM electrolyzer. The hydrogen and oxygen generated by the electrolyzer is 49.04% of the PEM fuel cell consumption, indicating that the UAV flight continuity using the integrated structure of the present study can be increased up to approximately 1.5 times. Then, by performing a parametric study and changing the main parameters of the system, including current densities of PEM electrolyzer and PEM fuel cell, as well as temperature and solar radiation level, the integrated system is evaluated in different conditions and the results are reported. Finally, by examining various aspects of the present plan, including the weight conditions, the efficiency of the integrated system developed in the present study as a new propulsion system for UAVs with various purposes has been specified.

In this paper, a standalone solar based Hydrogen production in Tehran, the capital of Iran, is simulated and the cost of produced hydrogen is evaluated. Local solar power profile is obtained using TRNSYS software for a typical parking station in Tehran. The generated electricity is used to supply power to a Proton Exchange Membrane (PEM) electrolyzer for Hydrogen production. Dynamic nature of solar power and necessity of reasonable accuracy for estimating the amount of produced Hydrogen, leads to propose a new 1D dynamic fluid flow model for PEM electrolyzer cell simulation. The Hydrogen price in this system is estimated using Equivalent Annual Worth (EAW) analysis. Although it is convenient to select a yearly useful lifetime for electrolyzer as well as solar cells, in this paper, an hourly lifetime which allows finding the Hydrogen cost based on electrolyzer operating time, is considered. Also, electrolyzer sizing is done by selecting various numbers of cells for each stack and alternatives are compared from performance and economic point of view. In this regard, 4 cases consisting of 2, 3, 4, and 5 electrolyzer cells are compared. Hydrogen price at each case is evaluated and sensitivity analysis is performed. Results represent that the larger the electrolyzer sizes, the higher would be the system efficiency and consequently higher Hydrogen production would be obtained. However, the system with higher efficiency is not always an economical choice. As an alternative, turning the electrolyzer off in some conditions is also investigated for possibility of extending lifetime and reducing the Hydrogen price. It shows reduction in the efficiency for all cases though in this situation the efficiency does not necessarily increase with the electrolyzer size. It is also found that turning off the electrolyzer under specified minimum current density (2000 A/m2) in all cases, reduces the final price of the produced Hydrogen.

In the current work different organic rankine cycles (base and modified) coupled with proton exchange membrane presented to produce hydrogen and power. Organic rankine cycles used in this work are basic Organic Rankine Cycles (ORC), ORC incorporating regenerator, ORC incorporating feed fluid heater and ORC incorporating both the regenerator and feed fluid heater. ORC energy demand supplied by geothermal energy. A thermodynamic model (energy and exergy) of systems done. EES software used to model the systems. Also, a parametric study done to investigate the effects of the performance parameters (energetic and exergetic) of considered systems. The results showed that ORC incorporating both regenerator and feed fluid heater with PEM electrolyzer had the maximum energy (3.514%) and exergy (68.93%) efficiency in comparison with other systems. Also, it can be observed that evaporator and electrolyzer had the highest portion of exergy destruction of the system. Energy efficiency, exergy efficiency, hydrogen production and net power increased by pressure growth in all systems. The amount of exergy efficiency, energy efficiency, hydrogen production and net power increased by the evaporator temperature addition in ORC incorporating regenerator with PEM electrolyzer and ORC incorporating both regenerator and feed fluid heater with PEM electrolyzer, but their amount marginally decreased by the evaporator temperature addition in basic ORC incorporating with PEM electrolyzer and ORC incorporating feed fluid heater with PEM electrolyzer.

This study presents the energy, exergy, and economic evaluation of recovering energy from a modified Kalina power-cooling system to provide heating and hydrogen. An ORC is employed to use the waste heat of the Kalina cycle, and the generated power is transmitted to a PEM electrolyzer for hydrogen production. Furthermore, the waste heat of the separator outlet is recovered through a new heat exchanger to provide heating. The results show that the proposed system can produce 317 kW power, 714. 7 kW cooling, 50. 3 kW heating, and 4. 491 kg/h hydrogen. Moreover, the exergoeconomic analysis indicates that the PEM electrolyzer, the cascade heat exchanger, and the vapor generator have the highest cost rate among the system components. Additionally, a parametric study was performed on the system to investigate the variation of some key parameters, including the maximum operating pressure, separator II pressure, ammonia mass fraction in a basic solution, and pinch point temperature difference in the cascade heat exchanger for the thermodynamic and economic performance of the system.

This research aims to introduce an efficient power cycle that simultaneously produces power and hydrogen in PEM electrolyzer. This cycle is driven by geothermal energy. Comprehensive thermodynamic modeling (energy and exergy) has been performed to compare four different operating fluids' performance in the proposed system. EES software was used for modeling. A parametric study has also been applied to investigate the effect of important parameters on the system's energy and exergy performance. As a brief novelty statement, the unique model can be mentioned in which both power and chemicals can be produced, and hydrogen output can be used as a storage system that transforms energy into an energy carrier. The results showed that R245fa operating fluid with 3. 5% and %67. 6 of energy and exergy efficiency had the highest performance. The operating fluids R114, R600, and R236fa are also in the next ranks of performance characteristics. As the geothermal fluid temperature increases, the production of power and hydrogen increases, but the energy and exergy efficiency decrease. Also, it can be noted that the hydrogen unit significantly increases the exergy efficiency of the plant. As an example, in the R245fa case, it increases from 36% to 67. 6%.

One of the most important factors in decreasing the lifetime and inappropriate performance of PEM electrolyzers is the non-uniform current distribution on membrane surface. Since the smoothest distribution of species and water leads to optimal current distribution, in this research, a 1D-1D model has been developed that explores the distribution of species and water, and finally the current distribution in layers and determines the optimal performance conditions of the high PEM membrane electrolyzers. In this model, the pressure is assumed constant throughout the channel, the cell temperature is constant, and the membrane is fully hydrated. The length of the anode and cathode channels is divided into 20 equal parts. By simultaneously solving the equations along the channel and perpendicular to it in each section, the distribution of species and current are obtained. The result showed that by increasing the average flow density, the flow distribution is smoother along the channel and, with increasing water flow, the current distribution is smoothed, but it has little effect on the polarization curve. Fick’ s effect on the distribution of species at the interface between the membrane and the gas diffusion layer has been investigated. Finally, the effect of thickness on the polarization curve is determined. By increasing the thickness of the membrane and the electrodes, the function of the system decreases.

A multi-stage open cooling cycle of scramjet for electricity and hydrogen co-production is proposed in which the fuel of scramjet is used as a coolant of the cooling cycle. Thermodynamic and exergetic examinations of the advanced system have been conducted to appraise the performance of the cycle, electricity and hydrogen production. In this integral system, the waste heat of scramjet drives the power sub-cycle whilst the PEM electrolyzer input electricity is supplied by a portion of the net electricity output of the cycle. It is fi gured out that the multi-expansion process reveals more advantages in comparison to the single-expansion process in terms of more cooling capacity, electricity, and production. For the fuel mass fl ow rate of 0. 4 kg/s, the cooling capacity of the new proposed cycle is computed 9. 16 MW, the net electricity output is calculated about 3. 38 MW and the hydrogen production rate is attained 42. 16 kg/h. On the other hand, the exergetic analysis results have proved the fact that the PEM electrolyzer has the highest exergy destruction ratio by 48% among all components of the cycle. In this case, the energy and exergy effi ciencies of the overall set-up are acquired by 12. 95% and 22. 16%, correspondingly. The outcomes of parametric evaluation demonstrated that electricity and hydrogen productions are directly proportional to the backpressure of the pump accordingly, more electricity and hydrogen are generated by higher backpressure. But, increasing the mass fl ow rate of fuel does not have any tangible impact on energy and exergy effi ciency of the whole set-up thus both remain approximately constant.