An efficient approach for the siting and sizing problem of distributed generation

This paper deals with the subject of finding the site and size of distributed generation in distribution systems. This problem corresponds to a mixed-integer nonlinear problem which is difficult and hard to solve with classical optimization techniques. Many approaches and with different objective functions have been applied to solve it. In this paper, the problem to solve comprises multiple distributed generation sources and the objective of minimizing power losses and generation costs, both for the distributed and conventional generators. Since it is highly combinatorial, a search space reduction is needed. So, an approximate model is used to reduce the search space of the possible buses where the distributed generation has to be located. Then, for each combination of the reduced space search, a nonlinear equations system is solved by a numerical method to get the size of the distributed generation, checking the voltage limits and the lines’ capacities. To test the method, a comparison between the proposed algorithm and a force brute algorithm is performed on a 69 and 118 bus test systems. The obtained results indicate that this method find the optimal or near optimal solution in a reasonable computation time.     

A novel quasi-oppositional harmony search algorithm and fuzzy logic controller for frequency stabilization of an isolated hybrid power system

The intermittent wind power in isolated hybrid distributed generation (IHDG) may cause serious problems associated with frequency (f) and power (P) fluctuation. Energy storage devices such as battery, super capacitor, and superconducting magnetic energy storage (SMES) may be used to reduce these fluctuations associated with f and P. This paper presents a study of IHDG power system for improving both f and P deviation profiles with the help of SMES. The studied IHDG power system is consisted of wind turbine generator and diesel engine generator. Both f and P control problems of the studied power system model are addressed in presence or absence of SMES. Fuzzy logic based proportional–integral–derivative (PID) controller with SMES is used for the purpose of minimization of f and P deviations. The different tunable parameters of the PID controller and those of the SMES are tuned by a novel quasi-oppositional harmony search algorithm. Performance study of the IHDG power system model is carried out under different perturbation conditions. The results demonstrate minimum f and P deviations may be achieved by using the proposed fuzzy logic based PID controller along with SMES.     

Compensation of droop control using common load condition in DC microgrids to improve voltage regulation and load sharing

DC microgrid is one feasible and effective solution to integrate renewable energy resources, as well as to supply reliable electricity. The control objective of DC microgrids is to obtain system stability, low voltage regulation and equal load sharing in per unit. The droop control is an effectively method adopted to implement the control of microgrids with multiple distributed energy units. However in the application of low-voltage DC microgrids, the nominal reference mismatch and unequal cable resistances require a trade-off to be made between voltage regulation and load sharing. In this paper, a unified compensation framework is proposed using the common load condition in local controller, to compensate the voltage drop and load sharing errors. The voltage deviation is compensated with a P controller while the load sharing is compensated through a PI controller. An additional low bandwidth communication is introduced to share the output current information, and the average output current in per unit is generated to represent the common load condition. The performance of the proposed method is analyzed and compared with basic droop control and hierarchical structure method. The large signal stability is analyzed to define the margin of compensation coefficients. Simulations and experiments are carried out to verify the performance of the proposed method.     

Experimental study on the heat transfer and flow characteristics of nanorefrigerants inside a corrugated tube

The heat transfer and flow characteristics of MWCNT-R141b nanorefrigerant with different mass fractions have been studied through experiments. Experimental results were compared with existing correlations. A two-step method was used to prepare the nanorefrigerants. Span-80 was used as surfactant with an average particle diameter of 20 nm. Transmittance method was used to evaluate the stability of nanorefrigerants. Results showed that the stability of MWCNT-R141b nanorefrigerant, which is the added dispersant, was good during the experiments. The 0.3 wt% MWCNT-R141b nanorefrigerants had optimal heat transfer enhancement effects compared with pure refrigerants. The maximum Nusselt number increased by 40%. The specific pressure drop of nanorefrigerant increased as the Reynolds number (Re) increased, and the specific pressure drop of the pure refrigerant was minimum, which is similar to R141b.     

Numerical study of entropy generation in Darcy-Forchheimer (D-F) Bödewadt flow of CNTs

Three-dimensional Bödewadt flow (fluid rotates at a large enough distance from the stationary plate) of carbon nanomaterial is examined. Single walled and multi walled CNTs are dissolved in water and gasoline oil baseliquids. Darcy-Forchheimer porous medium is considered. Stationary disk is further stretched linearly in radial direction. Heat transfer effect is examined in presence of radiation and convection. Effect of viscous dissipation is accounted. Entropy generation rate is studied. By using adequate transformation (von Kármán relations), the flow field equations (PDEs) are transmitted into ODEs. Solutions to these ODEs are constructed via implementation of shooting method (bvp4c). In addition to Entropy generation rate, Bejan number, heat transfer rate (Nusselt number), skin friction and temperature of fluid are examined through involved physical parameters. Axial component of velocity intensifies with increment in nanoparticles volume fraction and ratio of stretching rate to angular velocity parameter while it decays with higher porosity parameter. Higher nanoparticles volume fraction and porosity parameter lead to decay in radial as well as tangential component of velocity. However it enhances with higher ratio of stretching rate to angular velocity parameter. Temperature of fluid directly varies with higher ratio of stretching rate to angular velocity parameter, radiation parameter, Eckert number, Biot number and nanoparticles volume fraction. Rate of Entropy generation is reduced with higher estimations of porosity parameter, nanoparticles volume fraction and radiation parameter. Skin friction coefficient decays with higher porosity parameter and ratio of stretching rate to angular velocity parameter. Intensification in porosity parameter, nanoparticles volume fraction and Biot number leads to higher Nusselt number. Prominent impact is shown by multiple-walled CNTs with gasoline oil basefluid than single-walled CNTs with water basefluid.     

Enhanced hydrogen generation from Al-water reaction mediated by metal salts

Hydrogen generation by the reaction of micrometer-aluminum powder with water at room temperature is hard to proceed due to the inhibition of alumina layer. In this study, a novel strategy of metal salts mediated Al-water reaction was proposed for more efficient and practical hydrogen generation. The effects of metal salt composition and dosage, and water injection rate and volume on hydrogen generation were investigated. The hydrogen yield of 230.0 mL was achieved in the Al/Ni/Cu/H₂O system within 600 s under the following conditions: 0.24 g aluminum with the molar ratio of Al, Ni and Cu at 10:1:1 and 2 mL water at the injection rate of 2 mL/min, which was equivalent to 70.4% of the theoretical hydrogen yield. Based on the morphology, element composition, crystal structure and electrochemical test results of the obtained composites after reaction, the mechanism of hydrogen production by metal salts mediated Al-water reaction was proposed.     

Noble-metal-free Co@Co2P/N-doped carbon nanotube polyhedron as an efficient catalyst for hydrogen generation from ammonia borane

Developing an efficient catalyst for hydrogen (H₂) generation from hydrolysis of ammonia borane (AB) to significantly improve the activity for the hydrogen generation from AB is important for its practical application. Herein, we report a novel hybrid nanostructure composed of uniformly dispersed Co@Co₂P core-shell nanoparticles (NPs) embedded in N-doped carbon nanotube polyhedron (Co@Co₂P/N–CNP) through a carbonization-phosphidation strategy derived from ZIF-67. Benefiting from the electronic effect of P doping, high dispersibility and strong interfacial interaction between Co@Co₂P and N-CNTs, the Co@Co₂P/N–CNP catalyst exhibits excellent catalytic performance towards the hydrolysis of AB for hydrogen generation, affording a high TOF value of 18.4 mol H₂ mol metal^?1 min^?1 at the first cycle. This work provides a promising lead for the design of efficient heterogeneous catalysts towards convenient H₂ generation from hydrogen-rich substrates in the close future.     

Investigation of hydrogen generation from sodium borohydride using different cobalt catalysts

Effective Co/Cu, CoB/Cu, and CoBM (M = Mo,Zn,Fe)/Cu catalysts were prepared on the copper surface by a simple electroless deposition method using a morpholine borane as a reducing agent in the glycine solution. The activity of the deposited catalysts was investigated for hydrogen generation from an alkaline sodium borohydride solution. It was determined that these synthesized catalysts demonstrated the catalytic activity for the hydrolysis reaction of NaBH₄. The lowest obtained activation energy (E_A) of the hydrolysis reaction of NaBH₄was 27 kJ mol^?1 for the CoBMo/Cu catalyst. The hydrogen generation rate of 15.30 ml min^?1 was achieved using CoBMo/Cu catalysts at 313 K and it increased ~3.5 times with the increase of temperature to 343 K. The highest hydrogen generation rate obtained by CoBMo/Cu films may be related to the hierarchical cauliflower-shaped 3D structures and the high roughness surface area. Moreover, the CoBMo/Cu catalyst showed an excellent reusability.     

Analytical estimation of energy dissipations: Viscous,Joulian, and Darcy of viscoelastic fluid flow phenomena over a deformable surface

In this paper, analytical estimation of energy dissipations, such as viscous, Joulian, and Darcy dissipation of viscoelastic flow phenomena over a deformable surface has been presented. This supplement to the study of many transport processes, which occur in nature, and various experimental setups that are driven or modified by the composition of the various flow characteristics and material or phase constitution. These processes are very important and have received considerable attention in the literature. The estimation of dissipative energy in the process of transport energy is an important phenomenon to investigate. The present analysis is carried out on steady MHD viscoelastic liquid due to deformable domains. Moreover, the impact of internal heat sources and prescribed thermal conditions, such as surface temperature and heat flux, are carefully studied. Analytical solutions to governing equations are obtained with the help of Kummer's function. The solutions are presented graphically as well as in tables to estimate the energy losses and their effects on transport processes, which serve as the salient features of the current analysis. The outcomes serve as a guideline due to the process of transport properties as per the design requirements. Looking into the current scenario, dissipative heat energies have several applications in industries and technological processes, such as electric heaters, fuses, food processing, and several others.