Energy management of fuel cell/solar cell/supercapacitor hybrid power source

This study presents an original control algorithm for a hybrid energy system with a renewable energy source, namely, a polymer electrolyte membrane fuel cell (PEMFC) and a photovoltaic (PV) array. A single storage device, i.e., a supercapacitor (ultracapacitor) module, is in the proposed structure. The main weak point of fuel cells (FCs) is slow dynamics because the power slope is limited to prevent fuel starvation problems, improve performance and increase lifetime. The very fast power response and high specific power of a supercapacitor complements the slower power output of the main source to produce the compatibility and performance characteristics needed in a load. The energy in the system is balanced by d.c.-bus energy regulation (or indirect voltage regulation). A supercapacitor module functions by supplying energy to regulate the d.c.-bus energy. The fuel cell, as a slow dynamic source in this system, supplies energy to the supercapacitor module in order to keep it charged. The photovoltaic array assists the fuel cell during daytime. To verify the proposed principle, a hardware system is realized with analog circuits for the fuel cell, solar cell and supercapacitor current control loops, and with numerical calculation (dSPACE) for the energy control loops. Experimental results with small-scale devices, namely, a PEMFC (1200 W, 46 A) manufactured by the Ballard Power System Company, a photovoltaic array (800 W, 31 A) manufactured by the Ekarat Solar Company and a supercapacitor module (100 F, 32 V) manufactured by the Maxwell Technologies Company, illustrate the excellent energy-management scheme during load cycles.     

The benefits of hybridization

This article presents the impact of the performance of an FC and control strategies on the benefits of hybridization of fuel cell/supercapacitor hybrid sources for vehicle applications. Then, the storage device can complement the main source to produce the compatibility and performance characteristics needed in a load. The studies of two hybrid power systems for vehicle applications, FC/battery and FC/supercapacitor hybrid power sources, are explained. Experimental results with small-scale devices (a PEMFC of 500 W, 40 A, and 13 V; a lead-xicid battery module of 33 Ah and 48 V; and a supercapacitor module of 292 F, 500 A, and 30 V) in laboratory will illustrate the performance of the system during motor-drive cycles.     

Optimal Operation of Distributed Generations Considering Demand Response in a Microgrid Using GWO Algorithm

The widespread penetration of distributed energy sources and the use of load response programs, especially in a microgrid, have caused many power system issues, such as control and operation of these networks, to be affected. The control and operation of many small-distributed generation units with different performance characteristics create another challenge for the safe and efficient operation of the microgrid. In this paper, the optimum operation of distributed generation resources and heat and power storage in a microgrid, was performed based on real-time pricing through the proposed gray wolf optimization (GWO) algorithm to reduce the energy supply cost with the microgrid. Distributed generation resources such as solar panels, diesel generators with battery storage, and boiler thermal resources with thermal storage were used in the studied microgrid. Also, a combined heat and power (CHP) unit was used to produce thermal and electrical energy simultaneously. In the simulations, in addition to the gray wolf algorithm, some optimization algorithms have also been used. Then the results of 20 runs for each algorithm confirmed the high accuracy of the proposed GWO algorithm. The results of the simulations indicated that the CHP energy resources must be managed to have a minimum cost of energy supply in the microgrid, considering the demand response program.     

Fuel cell high-power applications

Energy consumption plays an important role in our modern civilization and daily life, which is heavily dependent on burning fossil fuels. The increasing threat of the fast depletion of resources such as petroleum, coal, and natural gas forces people to seek regenerative energy sources, such as solar, wind, geothermal, and hydroelectric energies. Another way of saving valuable natural resources and solving the environmental problem is to develop cleaner and more efficient energy conversion devices. In recent years, fuel cell (FC) research and development have received much attention for their higher energy conversion efficiency and lower or nongreenhousegas emissions than thermal engines in the processes of converting fuel into usable energies [1]-[3]. The power and energy efficiency of an FC is highly dependent on thermodynamics, electrode kinetics, and reactant mass transfer, as well as materials and components for assembling the FC. These factors have been addressed throughout the FC history and are now still the major challenges for FC research and development [4]-[6].     

Thin film flow of the water‐based carbon nanotubes hybrid nanofluid under the magnetic effects

In this article, the effects of magnetic field versus the thin liquid film water‐based ferrum oxide (Fe₃O₄) and carbon nanotubes (CNTs) nanofluids have been studied through stretching cylinder. The iron oxide and CNTs (single‐wall [SWCNTs] or multi‐wall [MWCNTs]) have been used as nanoparticles in carrier fluid water (H₂O). To the flow field, magnetic effects are applied vertically. The modeled system of partial differential equations are transformed to nonlinear ordinary differential equations by selecting variables. The analytic solution has been obtained through homotopy analysis method. The obtained results are further compared with the numerical ND‐solve method. The embedded constraints impacts are focused on pressure distribution, velocity profile, heat transfer, Nusselt number, and Skin friction through graphical illustration and tables. The dispersion of Fe₃O₄ and CNTs in base fluid significantly enhanced the mechanism of heat transfer. Moreover, from the results, it has been observed that the MWCNTs have a greater impact on heat transfer, velocity, and pressure profile.     

Drive friendly

Fuel cells are good energy sources to provide reliable power at steady state and supercapacitor energy storage devices can advance the load following characteristics of a fuel cell by providing a stronger power response to changes in system loading. During motor starts/stops or other considerable steps in load, the super-capacitors provide the balance of energy needed during the temporary load transition periods and also absorb excess energy from the generator source (motor braking). Adding supercapacitor energy storage to distributed power systems improves power quality and efficiency and reduces capital expenses by allowing the systems to be sized more closely to the steady-state power requirements rather than over-sizing the main generator to meet transient loading requirements.     

Magnetohydrodynamic mixed convective peristaltic slip transport of carbon nanotubes dispersed in water through an inclined channel with Joule heating

Carbon nanotubes are considered to be the latest nanotechnology innovation because of their remarkable physical and mechanical properties. Recently, researchers have shown great interest in the peristaltic transport of nanotube-based nanofluid as this process involves a wide range of uses in the bioengineering, biomechanics, and medical fields. In this investigation, influence of single-walled carbon nanotubes (SWCNTs) on magnetohydrodynamic mixed convective peristalsis through an inclined and asymmetric channel is analyzed. The additional physical mechanisms such as velocity slip, viscous dissipation, thermal slip, Joule heating, and heat consumption/injection are also encountered. The principal equations are formulated under the estimation of long wavelength and low Reynolds number. Perturbation method is operated to evaluate the solutions of subsequent nonlinear system of equations for small Brinkman number. To deeply analyze the characteristics of embedded parameters, graphs are presented and comprehensive interpretation is provided. Rate of heat transfer is augmented for higher proportion of SWCNTs in base fluid water. At the center of channel, increasing volume fraction of SWCNTs and strong Lorentz force retard the motion of fluid while flow is accelerated in more inclined channel. Volume fraction of SWCNTs, Grashof number, and inclination parameter encourage the pressure gradient at wider part of the channel. The size of bolus is contracted by strong Lorentz force and large volume fraction of SWCNTs. Three basic models named as Maxwell's, Hamilton-Crosser's, and Xue's model are utilized to forecast the thermal conductivity of nanofluid and succeeding numerical computations for heat transfer rate are presented through table. It is found that the Xue's model is most effective to anticipate the thermal conductivity of nanofluids. Moreover, the addition of a heat sink in the system significantly influences the heat transfer process and plays a supportive role to rapidly cool down the channel.     

Fuel starvation

The most important purpose of this work is to analyze the phenomenon of a fuel starvation of a PEM FC system. The incentive for automotive FC applications is quite different from that for stationary power generation or other applications. The dynamic characteristics of FC must be considered. Experimental results based on a PEMFC (500 W, 40 A) noticeably substantiate that, to employ an FC in dynamic applications, its current or power slope must be limited to improve an FC performance, including its voltage-current curve and lifetime. The use of other kinds of auxiliary power source(s) as depicted in the paper, such as batteries or supercapacitors to cooperate with FC main source, is mandatory for high dynamic applications, particularly for future FCVs.     

A novel algorithm for the computation of systems containing different types of integral and integro-differential equations

An easy and efficient technique is applied to get a reliable analytic approximate solution of linear and nonlinear integral and integro-differential equations arising in the phenomena of everyday life. The proposed technique consists of a series only in which the unknown constants are determined in the usual way. The obtained results by this technique are in good agreement with the exact solution and it is proved that this technique is effective and easy to apply. Some problems are solved to prove the above claims and also the results are compared with exact solutions as well as with the results obtained by already existing different techniques.