Current Issue : July - September Volume : 2012 Issue Number : 3 Articles : 6 Articles
The purpose of this study is to introduce and demonstrate a fully automated process for optimizing the airfoil cross-section of a\r\nvertical-axis wind turbine (VAWT). The objective is to maximize the torque while enforcing typical wind turbine design constraints\r\nsuch as tip speed ratio, solidity, and blade profile. By fixing the tip speed ratio of the wind turbine, there exists an airfoil crosssection\r\nand solidity for which the torque can be maximized, requiring the development of an iterative design system. The design\r\nsystem required to maximize torque incorporates rapid geometry generation and automated hybrid mesh generation tools with\r\nviscous, unsteady computational fluid dynamics (CFD) simulation software. The flexibility and automation of the modular design\r\nand simulation system allows for it to easily be coupled with a parallel differential evolution algorithm used to obtain an optimized\r\nblade design that maximizes the efficiency of the wind turbine....
Growing concern for the environmental degradation has led to the world’s interest in renewable energy resources. But due to the beneficiary policy and large potential of wind for generation the wind generation is gradually increased in Gujarat. Wind. generation is variable source, it generates less electricity when the consumption is higher in the season and it generates more electricity in off season of consumption. This variable generation create unbalancing in the grid systems when it is connected with transmission network. For ease of reference and facilitate understanding, this literature categories to control the wind generation as load demand and according to that voltage profile controlled with use of real time management and its different methodology....
We review the construction of families of projective varieties, in particular Calabi-Yau threefolds,\r\nas quasilinear sections in weighted flag varieties. We also describe a construction of tautological\r\norbibundles on these varieties, which may be of interest in heterotic model building....
China has achieved notable success in developing its economy with approximate\r\n10 percent average annual GDP growth over the last two decades. At the same time, energy\r\nconsumption and CO2 emissions almost doubled every five years, which led China to be\r\nthe world top emitter in 2007. In response, Chinaââ?¬â?¢s government has put forward a carbon\r\nmitigation target of 40%ââ?¬â??45% reduction of CO2 emission intensity by 2020. To better\r\nunderstand the potential for success or failure of such a policy, it is essential to assess\r\ndifferent driving forces such as population, lifestyle and technology and their associated\r\nCO2 emissions. This study confirms that increase of affluence has been the main driving\r\nforce for Chinaââ?¬â?¢s CO2 emissions since the late 1970s, which outweighs reductions achieved\r\nthrough technical progress. Meanwhile, the contribution of population growth to CO2\r\nemissions was relatively small. We also found a huge disparity between urban and rural\r\nhouseholds in terms of changes of lifestyle and consumption patterns. Lifestyles in urban\r\nChina are beginning to resemble Western lifestyles, and approaching their level of CO2\r\nemissions. Therefore, in addition to the apparent inefficiencies in terms of production\r\ntechnologies there is also a lot of room for improvement on the consumption side especially\r\nin interaction of current infrastructure investments and future consumption....
We analyze the properties of electroweak chiral effective Lagrangian with an extended SU2R\r\ngauge group. Right-handed SU2R gauge bosons affect electroweak observables by mixing with\r\nelectroweak gauge bosons WL,�µ and B�µ. We discuss all possible mass mixing terms and calculate\r\nthe exact physical mass eigenvalues by diagonalization of mixing matrix without any approximate\r\nassumptions. The contributions to oblique radiative corrections parameters STU from SU2R\r\nfields are also presented....
Modeling of an alkaline electrolyzer and a proton exchange membrane fuel cell (PEMFC) is presented. Also, a parametric study\r\nis performed for both components in order to determine the effect of variable operating conditions on their performance. The\r\naim of this study is to determine the optimum operating conditions when the electrolyzer and the PEMFC are coupled together\r\nas part of a residential solar powered stand-alone power system comprising photovoltaic (PV) arrays, an alkaline electrolyzer,\r\nstorage tanks, a secondary battery, and a PEMFC. The optimum conditions are determined based on an economic study which\r\nis performed to determine the cost of electricity (COE) produced from this system so as to determine the lowest possible COE.\r\nAll of the calculations are performed using a computer code developed by using MATLAB. The code is designed so that any user\r\ncan easily change the data concerning the location of the system or the working parameters of any of the system�s components to\r\nestimate the performance of a modified system. Cairo city in Egypt was used as the place at which the output of the system will be\r\ndetermined. It was found that the optimum operating temperature of the electrolyzer is 25?C. Also, the optimum coupling pressure\r\nof the electrolyzer and the PEMFC is 4 bars. The operating temperature of the PEMFC had a slight effect on its performance while\r\nan optimum current density of 400 mA/cm2 was detected. By operating the fuel cell at optimum conditions, its efficiency was\r\nfound to be 64.66% with a need of 0.5168Nm3 (Nm3 is a m3 measured at temperature of 0?C and pressure of 1 bar) of hydrogen\r\nto produce 1kWh of electricity while its cogeneration efficiency was found to be 84.34%. The COE of the system was found to be\r\n49 cents/kWh, at an overall efficiency of 9.87%, for an operational life of 20 years....
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