Loading...
Search for:
wind-velocity
0.006 seconds
Total 27 records
Airflow in buildings with courtyards
, Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 29, Issue 2 , 2005 , Pages 187-206 ; 03601307 (ISSN) ; Bahadori, M. N ; Sharif University of Technology
2005
Abstract
The airflow rate through a two-story building with a courtyard, with and without trees, was estimated and compared with that of a building without a courtyard. The building and the courtyard were of square shapes, each 10 m to the side. The courtyard walls were 3m high and two separate trees of spherical, cylindrical and conical shapes were considered in the yard. The courtyard was directly south of the building and a wind angle of zero degree was considered when the wind was blowing directly from the south. It was found that when the wind angles were between 0 to ±90 degrees, the airflow rate through the building was reduced when compared with the building without a courtyard. The presence...
Novel sensorless fault-tolerant pitch control of a horizontal axis wind turbine with a new hybrid approach for effective wind velocity estimation
, Article Renewable Energy ; Volume 179 , December , 2021 , Pages 1291-1315 ; 09601481 (ISSN) ; Tse, K. T ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
In this research, the fault-tolerant pitch angle control of a horizontal axis wind turbine in region 3 (where the wind velocity is greater than rated wind speed) is investigated. The effective wind velocity (EWV) is one of the necessary information for each control system. Wind speed is measured by the anemometers on the top of the nacelle however, the measurement is not precise and is only applicable for one point in the rotor. To address this issue, we have developed a novel hybrid approach. The approach is based on a sliding mode observer to estimate the aerodynamic torque and an adaptive neuro-fuzzy inference system (ANFIS) is introduced for obtaining the EWV. The estimated aerodynamic...
Evaluating the performance of artificial neural network model in downscaling daily temperature, precipitation and wind speed parameters
, Article International Journal of Environmental Research ; Vol. 8, issue. 4 , 2014 , p. 1223-1230 ; Abbaspour, M ; Soltaniyeh, M ; Hosseinzadeh, F ; Abedi, Z ; Sharif University of Technology
Abstract
Numerous studies yet have been carried out on downscaling of the large-scale climate data using both dynamical and statistical methods to investigate the hydrological and meteorological impacts of climate change on different parts of the world. This study was also conducted to investigate the capability of feedforward neural network with error back-propagation algorithm to downscale the provincial segmentation of Iran (30 provinces) on a daily scale. This model was proposed for the downscaling daily temperature, precipitation and wind speed data, and it was calibrated and verified by using the daily outputs derived from the National Center for Environmental Prediction (NCEP) database...
Removal of airborne hexavalent chromium mist using chitosan gel beads as a new control approach
, Article International Journal of Environmental Science and Technology ; Volume 3, Issue 3 , 2006 , Pages 305-313 ; 17351472 (ISSN) ; Golbabaei, F ; Hamedi, J ; Nourijelyani, K ; Shahtaheri, S. J ; Moosavi, S. R ; Sharif University of Technology
CEERS
2006
Abstract
Airborne hexavalent chromium is a known human respiratory carcinogen and allergen. Many workers are exposed to hexavalent chromium in various processes which chromium electroplating plants are the most common. In this study, the feasibility of a new control approach to remove this pollutant using chitosan beads as a biosorbent was investigated. Hexavalent chromium sorption was studied relative to pH, pollution concentration, sorbent concentration, temperature, and air velocity using one factor at a time approach and Taguchi experimental design. Polluted air with different chromium mist concentrations (10-5000 μg/m3) was contacted to chitosan beads (3.3-20 g/L), floating in distilled water...
The study of air-cooled condenser in high wind velocity and environmental temperature conditions
, Article 52nd AIAA Aerospace Sciences Meeting - AIAA Science and Technology Forum and Exposition, SciTech 2014 ; 2014 ; ISBN: 9781624102561 ; Behrouzifar, A ; Salemkar, H ; Schneider, G. E ; Sharif University of Technology
Abstract
The use of air-cooled condenser (ACC) has become very popular in erecting thermal powerplants around the world since two or three decades ago. The advantages of forced convection heat cooling system, instead of the classical natural draught convection heat transfer cooling systems, promote the thermal powerplant designers and users to benefit more from such systems in their thermodynamics cycles. However, such forced convection heat transfer mechanisms, can lose their cooling efficiency in off-design ambient conditions, i.e., in high wind velocity and high ambient temperature conditions. There have already been some efforts to analyze the reduction of ACC System performance in some critical...
Details study of ambient wind effect on heat dissipation capacity of thermal-powerplant dry cooling-towers
, Article American Society of Mechanical Engineers, Fluids Engineering Division (Publication) FEDSM ; Volume 1A , August 3–7 , 2014 , pp. V01AT03A017 ; ISSN: 08888116 ; ISBN: 9780791846216 ; Behrouzifar, A ; Mirhashemi, A ; Salemkar, H ; Schneider, G. E ; Sharif University of Technology
Abstract
Thermal powerplants report a reduction in their dry cooling tower performances due to surrounding wind drafts. Therefore, it is very important to consider the influence of wind velocity in cooling tower design; especially in geographical points with high wind conditions. In this regard, we use the computational fluid dynamics (CFD) tool and simulate a dry cooling tower in different wind velocities of 0, 5 and 10 m/s. To extend our calculations; we also consider the temperature variation of circulating water through the tower heat exchanger or deltas one-by-one. We show that some heat exchangers around the tower cannot reduce the circulating water temperature sufficiently. This causes an...
Fuzzy modeling techniques and artificial neural networks to estimate annual energy output of a wind turbine
, Article Renewable Energy ; Volume 35, Issue 9 , September , 2010 , Pages 2008-2014 ; 09601481 (ISSN) ; Ranjbar, A. M ; Sharif University of Technology
2010
Abstract
The purpose of this article is to develop a new method to estimate annual energy output for a given wind turbine in any region which should be easy to use and has satisfactory accuracy. To do this, hourly wind speeds of 25 different stations in Netherlands, output power curve of S47 wind turbine and fuzzy modeling techniques and artificial neural networks were used and a model is developed to estimate annual energy output for S47 wind turbine in different regions. Since this model has three inputs (average wind speed, standard deviation of wind speed, and air density of that region), this model is easy to use. The accuracy of this method is compared with the accuracy of conventional methods...
Long-term prediction of solar and geomagnetic activity daily time series using singular spectrum analysis and fuzzy descriptor models
, Article Earth, Planets and Space ; Volume 61, Issue 9 , 2009 , Pages 1089-1101 ; 13438832 (ISSN) ; Kamaliha, E ; Shafiee, M ; Lucas, C ; Sharif University of Technology
Abstract
Of the various conditions that affect space weather, Sun-driven phenomena are the most dominant. Cyclic solar activity has a significant effect on the Earth, its climate, satellites, and space missions. In recent years, space weather hazards have become a major area of investigation, especially due to the advent of satellite technology. As such, the design of reliable alerting and warning systems is of utmost importance, and international collaboration is needed to develop accurate short-term and long-term prediction methodologies. Several methods have been proposed and implemented for the prediction of solar and geomagnetic activity indices, but problems in predicting the exact time and...
Dynamic behavior and transient stability analysis of fixed speed wind turbines
, Article Renewable Energy ; Volume 34, Issue 12 , 2009 , Pages 2613-2624 ; 09601481 (ISSN) ; Parniani, M ; Sharif University of Technology
Abstract
This paper analytically investigates the dynamic behavior of fixed speed wind turbines (FSWTs) under wind speed fluctuations and system disturbances, and identifies the nature of transient instability and system variables involved in the instability. The nature of transient instability in FSWT is not similar to synchronous generators in which the cause of instability is rotor angle instability. In this paper, the study of dynamic behavior includes modal and sensitivity analysis, dynamic behavior analysis under wind speed fluctuation, eigenvalue tracking, and using it to characterize the instability mode, and investigating possible outcomes of instability. The results of theoretical studies...
Experimental investigation of new designs of wind towers
, Article Renewable Energy ; Volume 33, Issue 10 , 2008 , Pages 2273-2281 ; 09601481 (ISSN) ; Mazidi, M ; Dehghani, A. R ; Sharif University of Technology
2008
Abstract
Two new designs of wind towers were tested side by side with a conventional wind tower in the city of Yazd, Iran. All the towers were of identical dimensions. The two new designs were one with wetted column, consisting of wetted curtains hung in the tower column, and the other one with wetted surfaces, consisting of wetted evaporative cooling pads mounted at its entrance. The air temperature leaving the wind towers with evaporative cooling provisions were much lower than the air temperature leaving the conventional design, and its relative humidity much higher. The air-flow rate was reduced slightly in these new towers. It was found that the wind tower with wetted column performs better with...
Internalizing the social cost of noise pollution in the cost analysis of electricity generated by wind turbines
, Article Wind Engineering ; Volume 30, Issue 6 , 2006 , Pages 521-529 ; 0309524X (ISSN) ; Bahadori, M. N ; Sharif University of Technology
2006
Abstract
The Social Cost of nuisance noise from a wind turbine is defined here as the additional cost to reduce the noise level at a receptor to an exceptable, non-nuisance value, i.e. to mitigate this cost. This acceptable sound level is considered to be 35 dB. Our example is a 10-kW (nominal power) wind turbine considered to supply the electrical energy needs of a 3-storey residential building in Tehran and Manjil. The turbine generates sound at 75 dB. To reduce the sound level at the third floor of the building to 35 dB, it was necessary to increase the height of the turbine from 24 m to 48 m. The initial installed cost of the turbine thereby increased from US$45.000 to US$55,000. The cost of...
Performance of a standalone wind-hydrogen power system for regions with seasonal wind profile: A case study in Khaf region
, Article Sustainable Energy Technologies and Assessments ; Vol. 7 , September , 2014 , pp. 265-278 ; ISSN: 22131388 ; Rezaei Mirghaed, M ; Roshandel, R ; Sharif University of Technology
Abstract
The present study was aimed at performance and energy analysis of a hybrid wind-hydrogen power system. Such system consists of wind turbines, batteries for the short time energy storage, electrolyzer, fuel cell and hydrogen tank for long time energy storage. The proposed configuration is used to supply energy demand of a region with discrete seasonal wind speed regime. Temporary wind energy profiles restrict using batteries for electricity storage as they lose much electrical stored energy for the long time. Based on direct wind turbine usage, batteries and hydrogen storage, different energy supply strategies are introduced and analyzed to power the household electricity demand. The energy...
Starting improvement of micro-wind turbines operating in low wind speed regions
, Article International Journal of Green Energy ; Volume 14, Issue 11 , 2017 , Pages 868-877 ; 15435075 (ISSN) ; Gooya, M ; Hosseini, S. V ; Pourrajabian, A ; Sharif University of Technology
Abstract
The study deals with the design and optimization of external and internal geometry of micro-wind turbines blades. A specified objective function which consists of the power coefficient and the starting time was defined and the genetic algorithm optimization technique in conjunction with the blade-element momentum theory was adopted to find the geometry of the blades including the distributions of the chord, the twist angle and also the shell thickness. Moreover, the allowable stress of the blades was considered as a constraint to the objective function. Results show that a reasonable compromise is achievable such that the starting time of the blades reduces noticeably in return for a small...
Experimental investigation of blade number and design effects for a ducted wind turbine
, Article Renewable Energy ; Volume 105 , 2017 , Pages 334-343 ; 09601481 (ISSN) ; Kamali Monfared, R ; Rad, M ; Sharif University of Technology
Abstract
Over the recent decades, many different ducted turbines have been designed to augment efficiency of wind turbines. The design and number of blades are the most important parameters to optimize efficiency of wind turbines. In this paper, effects of design, number and attack angles of blades on rotational speed are experimentally studied in a duct which increases wind velocity up to 2.46 times numerically and 2.32 times experimentally as great as far-field flow. In order to realize this, 3 different types of aerodynamic blades were designed and then, 2-bladed, 3-bladed and 4-bladed impellers were created by these blades; finally, 9 impellers were built on aggregate. The rotational speed of...
Exergy analysis of parabolic trough solar collectors using Al2O3/synthetic oil nanofluid
, Article Solar Energy ; Volume 173 , 2018 , Pages 1236-1247 ; 0038092X (ISSN) ; Shamloo, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
Parabolic trough solar collector (PTC) is one of the most mature and widely used type of solar energy harnessing devices. Therefore, investigation of the effect of various operational conditions on the overall efficiency of these devices has been topic of substantial interest in the recent decade. Moreover, utilization of nanoparticles as a useful additive to the working fluid should be examined thoroughly to optimize the collector's outputs. To do so, in the present study, energy and exergy efficiencies of a typical PTC as a function of several involving parameters are numerically calculated. These parameters are nanoparticle volume fraction (from 0 to 5 percent), environment wind speed...
Some experimental studies on the performance of a rigid wing land yacht model in comparison with VPP
, Article Scientia Iranica ; Volume 16, Issue 4 B , 2009 , Pages 291-300 ; 10263098 (ISSN) ; Had, M ; Sharif University of Technology
2009
Abstract
It is important to understand the flow characteristics and performance of wings for designers who want to have an efficient thrust in a land yacht. In this paper, a comparison of aerodynamic forces obtained by testing the land yacht model in a wind tunnel and by the Velocity Prediction Program (VPP) is presented. The wind tunnel testing of a land yacht is an effective design tool, but at present it is mainly used for VPP validation, which allows for a faster and more efficient design process. The rigid wing land yacht model, which is a radio controlled model, is tested in the national open jet wind tunnel of the Malek Ashtar University of Technology in Iran. The wing data, which is obtained...
Dust concentration over a semi-arid region: parametric study and establishment of new empirical models
, Article Atmospheric Research ; Volume 243 , 1 October , 2020 ; Afshin, H ; Firoozabadi, B ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In recent years, the city of Tehran, Iran's capital, has encountered numerous dust events so that the dust concentration of PM10 has reached even more than 800 μg m−3. This emphasizes the importance of the statistical study of dust in Tehran and the development of correlations for estimating dust concentration of PM10. In the present study, by evaluating the data measured during dust observations over the years 2013–2016 in Tehran, new statistical models are established for estimating PM10 concentration in terms of horizontal visibility and MODIS AOD. Firstly, simple nonlinear regression models between dust concentration of PM10 and horizontal visibility as well as MODIS AOD are developed....
Optimization of a novel photovoltaic thermal module in series with a solar collector using Taguchi based grey relational analysis
, Article Solar Energy ; Volume 215 , 2021 , Pages 492-507 ; 0038092X (ISSN) ; Parcheforosh, A ; Salari, A ; Ma, T ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
The solar collectors absorb solar irradiation and then produce thermal energy; however, they cannot generate electrical power. Electricity and thermal energy can be produced by the photovoltaic thermal module, simultaneously, while the outlet temperature of the photovoltaic thermal module is not usually high enough to provide thermal requirements of a building such as hot water or space heating. This work proposes a novel compound system created by the connection of a solar collector in series with a photovoltaic thermal module to resolve the issue of low outlet temperature in the photovoltaic thermal module and lack of electrical power in solar collectors. To examine the feasibility of this...
Identification of the dynamics of the drivetrain and estimating its unknown parts in a large scale wind turbine
, Article Mathematics and Computers in Simulation ; Volume 192 , 2022 , Pages 50-69 ; 03784754 (ISSN) ; Moradi, H ; Sharif University of Technology
Elsevier B.V
2022
Abstract
In this paper, the drivetrain identification problem of a horizontal axis gear-driven wind turbine has been considered. The identification problem leads to a precise model of the drivetrain of the wind turbines which plays a key role in the production and transmission of electrical energy. This process consists of two stages: First, offline identification which needs the input–output data from the drivetrain system. These data are obtained from the FAST code. FAST (Fatigue, Aerodynamics, Structures, and Turbulence) is a valid aeroelastic code in the simulation aeroelastic field of offshore and onshore wind turbines. In region 2 (wind velocity is between the cut-in and rated velocities), the...
Toward design and fabrication of wind-driven vehicles: Procedure to optimize the threshold of driving forces
, Article Applied Mathematical Modelling ; Volume 37, Issue 1-2 , 2013 , Pages 50-61 ; 0307904X (ISSN) ; Rad, M ; Sharif University of Technology
2013
Abstract
Wind energy has been continuously considered as a green, available, and economical alternative source of energy. For centuries, the transformed wind energy to drag-force has been used for transportation in watercrafts. With improvement of aerodynamics, the airfoil was invented to create and use a higher magnitude aerodynamic force, lift-force, in order to elevate airplanes. Later, the lift-force was horizontally applied as the thrust force in land/water wind-crafts. Whereas in airplanes horizontal airfoils (wing) create a vertical lift-force, installed vertical airfoils (wing-sail) produce a horizontal lift-force in wind-crafts. Therefore, this force can be used as thrust (driving) force in...