An improved mechanism for capacity payment based on system dynamics modeling for investment planning in competitive electricity environment

Many countries have experienced restructuring in their electric utilities. This restructuring has presented the power industries with new challenges, the most important of which is long-term investment planning under uncertain conditions. This paper presents an improved mechanism for capacity payment. The mechanism has been investigated based on system dynamic modeling. In our proposed mechanism, generators will recover a part of their investment through capacity payment. While the payment for any plant remains constant during the operation period, it depends on the investment needed to build it. The main factors affecting long-term planning have been considered in our model. The approach can be used to investigate the effects of fixed as well as variable capacity payment in market investment. We used the probability density function of load as a new concept to calculate average market price. Delays in unit constructions, estimation of demand, and market capacity growth during construction periods have been included in the proposed algorithm as parameters, which affect the regulator's decision for changing capacity payment. The model can be used by regulators to investigate strategies that may affect the fluctuations in the market.     

Iterative step‐by‐step procedure for optimal placement and design of viscoelastic dampers to improve damping ratio

In this study, an iterative step‐by‐step procedure is proposed for optimal placement and design of viscoelastic dampers in order to achieve a target damping ratio based on simple equations and quick estimation. Through the procedure, the dampers are placed one by one in stories with maximum interstory drift at each sequence. Effect of lateral stiffness of added dampers and consequent changes in frequency of the structure as well as changes in damping characteristic of the structure after adding each damper are also considered at each sequence. In order to achieve an economical design, dampers are designed according to the lateral stiffness at each story of the main structure instead of using identical dampers in all stories. During the whole procedure, a time‐history analysis is performed at each sequence. Two numerical examples, including an 8‐story and a 15‐story building, are presented. The results indicate that optimal arrangement of dampers has a considerable influence on reduction of roof displacement up to 25% compared to uniformly distributed arrangement of dampers. In addition, with optimal arrangement, the number of dampers needed to achieve a specific interstory drift is significantly reduced, and the structural damping ratio is improved to a target value, reflecting global optimality of the proposed method.     

Sustainability in highrise building design and construction

This paper presents a review of the recent literature on sustainability in construction and design with a focus on highrise buildings. The paper is divided into the following main sections: energy consumption, environmental effects and green practices for highrise buildings. A number of concepts in sustainable design are reviewed including passive solar design, renewable energy resources, cogeneration and tri‐generations, embodied energy reduction, net zero energy building, carbon emission reduction, envelope environment quality, green materials, efficient mechanical design and innovative structural systems. Their applications in a dozen signature and iconic structures are described. In order to achieve net zero energy in a new highrise building, first, multiple green solutions need to be evaluated using two categorical solutions: passive solar and envelop environment design and renewable energy resources along with efficient energy generators. Next, a robust optimization algorithm should be used to select the optimum set of solutions. This is worth pursuing in future sustainable design of highrise buildings because they are massive and complex structures with many components. Copyright © 2016 John Wiley & Sons, Ltd.     

A Complete Experimental Investigation on The Rheological Behavior of Silver Oil Based Nanofluid

In this study, thermo‐physical properties including thermal conductivity, viscosity, density and specific heat capacity of an oil based nanofluid including silver as to be nanoparticles have been experimentally studied. The results indicate an enhancement in thermal conductivity which was depended on bulk temperature and volume fraction of utilized nanofluids. Viscosity data show a significant increment through volume fraction increasing. In addition, the specific heat capacity and density of nanofluids were studied experimentally and it was found that, all measured rheological properties of these nanofluids, were not in agreement to published correlations.     

A comparative study for synthesis methods of nano-structured (9Ni–2Mg–Y) alloy catalysts and effect of the produced alloy on hydrogen desorption properties of MgH2

9Ni–2Mg–Y alloy powders were prepared by arc melting, induction melting, mechanical alloying, solid state reaction and subsequent ball milling processes. The results showed that melting processes are not suitable for preparation of 9Ni–2Mg–Y alloy due to high losses of Mg and Y. Therefore, 9Ni–2Mg–Y alloy powder was prepared by three methods including: 1) mechanical alloying, 2) mechanical alloying + solid state reaction + ball milling, and 3) mixing + solid state reaction + ball milling. The prepared 9Ni–2Mg–Y alloy powders were compared for their catalytic effects on hydrogen desorption of MgH₂. It is found that 9Ni–2Mg–Y alloy powder prepared by mechanical alloying + solid state reaction + ball milling method has a smaller particle size (1–5 μm) and higher surface area (1.7 m² g⁻¹) than that of other methods. H₂ desorption tests revealed that addition of 9Ni–2Mg–Y alloy prepared by mechanical alloying + solid state reaction + ball milling to MgH₂ decreases the hydrogen desorption temperature of MgH₂ from 425 to 210 °C and improves the hydrogen desorption capacity from 0 to 3.5 wt.% at 350 °C during 8 min.     

Al2O3–Water nanofluid heat transfer and entropy generation in a ribbed channel with wavy wall in the presence of magnetic field

In this article, a parametric study is conducted to evaluate heat transfer enhancement in a ribbed channel containing Al₂O₃–Water nanofluid with wavy wall. The physical domain is under the influence of the magnetic field that creates a negative force against the working fluid to move. Nanofluid with higher temperature enters the cool ribbed duct and heat is exchanged along the walls of channel. The effects of the dominant parameters including number of the blocks, solid volume fractions of nanofluid, Hartmann number, Reynolds number, and different states of amplitude sine waves are numerically tested on the local and average Nusselt number, skin friction, and total entropy generation. Excellent agreement between present study and previous literature is observed. It is found that, an augmentation in magnetic field will result in higher values of both local and average Nusselt number accompanying with bigger values of skin friction and entropy generation. Computations illustrate that, increasing the solid volume fraction of the Al₂O₃ nanoparticles will raise the Nusselt number and total entropy generation rate but its effect on the skin friction is negligible. Also, numerical results imply that increasing amplitude sine waves of the geometry has incremental effect on the Nusselt number and skin friction but its effect on the total entropy generation rate is not so clear. Moreover, by adding number of the used blocks in the presence of magnetic field, the local Nusselt number experiences more jumps but it does not increase the average Nusselt number, necessarily. In addition, using more blocks increases skin friction but it has a reverse effect on the total entropy generation rate.     

Evaluation of hydrogen permeation through standalone thermally sprayed coatings of AISI 316L stainless steel

This research evaluates hydrogen permeation and its diffusion characteristics through standalone thermally sprayed coatings of AISI 316L stainless steel. The effects of various charging currents and other parameters on hydrogen diffusion coefficient were scrutinized using electrochemical hydrogen permeation tests. Hydrogen permeation through the thermally sprayed coatings displayed anomalous behavior such that a maximum pinnacle was observed in the permeation curves, attributed to heavily trapped hydrogen atoms in the delayed surface cracks. Therefore, new diffusion parameters were defined for modeling of the anomalous permeation curves. The fitted diffusion parameters were consistently identified, and hence, the model perfectly explained experimental data. The results showed that the increase in charging current caused fast activation and development of surface cracks. The measured diffusion coefficient of hydrogen in the stainless steel thermally sprayed coating was relatively high because the microstructure of the coating contained some ferritic phases and dense dendritic structure, which configure fast diffusion paths.     

Static and dynamic wind turbine simulator using a converter controlled dc motor

This paper describes a new wind turbine simulator for dynamic conditions. The authors have developed an experimental platform to simulate the static and dynamic characteristics of real wind energy conversion system. This system consists of a 3 kW dc motor, which drives a synchronous generator. The converter is a 3 kW single-phase half-controlled converter. MATLAB/Simulink real time control software interfaced to I/O board and a converter controlled dc motor are used instead of a real wind turbine. A MATLAB/Simulink model is developed that obtains wind profiles and, by applying real wind turbine characteristics in dynamics and rotational speed of dc motor, calculates the command shaft torque of a real wind turbine. Based on the comparison between calculated torques with command one, the shaft torque of dc motor is regulated accordingly by controlling armature current demand of a single-phase half-controlled ac–dc converter. Simulation and experimental results confirm the effectiveness of proposed wind turbine simulator in emulating and therefore evaluating various turbines under a wide variety of wind conditions.     

Catalytic oxidative desulfurization of dibenzothiophene utilizing molybdenum and vanadium oxides supported on MCM-41

As a series of bimetallic nanocatalysts, molybdenum/vanadium oxides supported on the silica (MoO₃/V₂O₅/MCM-41) were prepared by the impregnation. Their catalytic activity in the oxidation of dibenzothiophene was investigated using H₂O₂ as an oxidant. Textures and surface properties of the prepared catalysts were characterized using FT-IR, XRD, FESEM-EDX and N₂ adsorption/desorption techniques. The effects of main process variables including H₂O₂/DBT molar ratio, catalyst dosage, reaction temperature and reaction time were analyzed by employing the response surface methodology (RSM). The effect of the MoO₃/V₂O₅ loading on the catalytic performance of the catalysts was also investigated. The results indicated that the catalytic activity of the catalyst was increased by enhancing the MoO₃/V₂O₅ content. Thus, the catalyst with high MoO₃/V₂O₅ loading (20%MoO₃/20%V₂O₅/60%MCM-41) indicated the highest catalytic activity and could convert 99.06% of dibenzothiophene under the optimum conditions. Mass and FT-IR analysis demonstrated that the major product of dibenzothiophene oxidation was its corresponding sulfone. The catalyst could be recycled five times without any considerable reduction in its catalytic activity. The kinetics of the reaction fitted the pseudo-first-order equation pretty well. Eventually, a reaction mechanism for the catalytic oxidation of DBT in the presence of MoO₃/V₂O₅/MCM-41 was proposed.