Natural Wind Speed Research Articles

Entransy analysis optimization of cooling water flow distribution in a dry cooling tower of power plant under summer crosswinds

The performance of natural draft dry cooling tower (NDDCT) of a coal-fired power generating unit is susceptible to ambient conditions, such as natural wind and temperature. An approach was proposed to relieve the adverse effects of ambient wind, which was the optimization of waterside flow re-distribution among heat exchangers of NDDCT under natural wind. With the help of entransy balance equations that described the heat transfer processes in each heat exchanger sector and condenser, all 20 influencing factors were considered to establish the optimization mathematical model of whole system, including both of the steam turbine subsystem and dry cooling system. A practical 660 MW dry cooling supercritical power generating unit was selected as object. The flow and heat transfer of NDDCT by natural wind effect were obtained numerically with verification. The results indicated that the performance of NDDCT could be improved by optimal distribution of waterside flow rate among the heat exchangers at any wind speed, especially at high wind speed. The comprehensive saving of power output coal consumption could be acquired although the pump power would raise by optimal water flow distribution. The decrease of coal consumption could reach 0.74 g/kWh at the natural wind speed of 12 m/s.

Flow deflectors to release the negative defect of natural wind on large scale dry cooling tower

In order to reduce the unfavorable impacts of natural wind, the arc curved air flow deflectors were proposed to be settled around the natural draft dry cooling tower. Based on 2 × 600 MW indirect air cooling power generating units, the thermo-fluid models of the natural draft dry cooling tower coupled with condenser of turbine are developed, by which the cooling performances are investigated at natural wind speed ranged from 0 to 20 m/s. The numerical results with experimental validations illustrate the thermo-fluid performance distributions of different cooling sectors around the dry cooling tower. It can be obtained that in the presence of ambient natural wind, the proposed deflectors could extend the positive effects of natural wind, leading to the decrease of outlet temperature of circulating water and back pressure of turbine. Compared to the case without deflectors, the total air mass flow rate could be increases by 50.26%, the outlet temperature of circulating water could be decreased by 10.73 °C and the back pressure of turbine could be decreases by 7.33 kPa when the wind speed is 20 m/s. In the absence of wind, the changes of air mass flow rate, heat rejection, outlet water temperature and back pressure are all no more than 0.5% compared with that without the deflectors, implying almost no negative impacts of the proposed deflectors under various operating conditions. The natural wind direction has little influence on the performance of natural draft dry cooling tower with deflectors.

Wind Speed Affects Pollination Success in Blackberries

Pollination of wild plants and agricultural crops is a vitally important ecosystem service. Many landscape and environmental factors influence the pollination success of crops, including distance from natural habitat, wind speed, and solar radiation. Although there is a general consensus that increasing distance from forest decreases pollination success, few studies have examined the influence of specific environmental factors. In this study, we examined which environmental factors influence the pollination success of blackberries (Rubus glaucus). We measured the number of fruitlets per berry, a proxy for pollination success, as well as the weight and sweetness of each berry. Our results indicate that number of fruitlets is positively correlated with wind speed, but number of unripe red berries per bush is negatively correlated with wind speed. In addition, sweetness increased with increasing numbers of red berries per bush but was lower when flowers and berries were present, though this result should be considered with caution due to methodological limitations. Our findings suggest that a little studied environmental factor, wind, has a large impact on the number of fruitlets in blackberries. Although our findings should be confirmed in other locations to draw broader conclusions, they suggest that producers should consider the effect of wind on blackberry yield to optimize blackberry production.

Development of a Butterfly Wind Turbine with Mechanical Over-Speed Control System

Based on a concept of “cost reduction by large rotor and small generator”, a kind of small vertical axis wind turbine (VAWT) called a butterfly wind turbine (BWT) has been developed with rotor diameter of 7 m and five looped blades. One of the features is a mechanical system which can twist each blade of a VAWT by using the centrifugal force acting on the blades in order to prevent over-speeding of the rotor. An electric power generation system that combines the BWT utilizing the over-speed control system (OCS) with a coreless generator connected to a three-time increasing gear unit is constructed in this study. The performance of the BWT power-generation system is predicted by the blade element momentum (BEM) theory. The final goal of this research is to show the feasibility of the low-cost VAWT power generation system with the proposed OCS. From the results of a series of forcible rotation experiments of the BWT rotor that is driven by an induction motor in very low wind speed condition, it is shown that the twist movement of the blades is improved by the design of the OCS that considers the observed radial force deprived of the centrifugal force and the pre-compression of springs. In the generation experiments with the final design of the OCS, the expected twists of the blades are observed for the first time in strong natural wind speed over 18 m/s.

Study on Optimization of Semi-lateral Ventilation Mode of Fire in the Nantong Seyuan Road Tunnel

Abstract The fire field simulation tool FDS is used to simulate and compare the different fans operating conditions of the semi-transverse ventilation of the proposed Nantong Seyuan Road Tunnel. The fire source is located at the most unfavorable position of the main road and the ramp. The heat release rate is 20 MW and the grid size is 0.2 m. Considering the natural wind speed of 1 m / s and 2 m / s, the air volume of the single fan is 20 m3 / s. The results showed that: (1) The flue gas temperature at the ceiling above the fire sources of all conditions was significantly higher than 100 ℃; when from the fire source area more than 10 m, the CO concentration was not more than 100 ppm and the height of the smoke layer was more than 2 m; (2) Opening the air feed fans was not conducive to reduce the flue temperature at the safe height. (3) Increasing the number of exhaust fans on both sides of the fire source was conducive to flue gas emissions; (4) when the exhaust fans were turned on, the addition of the ramp jet fan can not be significantly to reduce the flue gas temperature at the ramp. The aim of this study is to provide a theoretical basis for the optimization of the semi-transverse ventilation model of the fire in the Nantong Seyuan Road Tunnel.

Economic Analysis of Hybrid Wind/PV/Diesel/ESS System on a Large Oil Tanker

Due to the global concern on the increasing amount of fossil energy consumed by traditional ships, the application of renewable energy into a ship power system provides a new solution to improve the energy efficiency and to reduce the greenhouse gas emissions. This study proposes a stand-alone power system on a large oil tanker including wind generation system, photovoltaic generation system, the diesel generator, and the energy storage system (ESS). Unlike on land, the wind generation on the shipboard not only relies on the natural wind speed but also the ship's course and speed. The installation of the wind turbines on the board is optimally designed, which takes the relative speed into account. In order to mitigate the intermittence of the renewable energy generation, a lead–acid battery serves as the ESS to enhance the stability of the ship power system, and the size is optimized by the multi-objective particle swarm optimization to minimize the whole system cost and CO2 emissions. Additionally, variations of the ship loads are considered with respect to the different operational conditions. Various cases are compared in detail to demonstrate the applicability of the proposed algorithm.

Operation of air-cooling CHP generating unit under the effect of natural wind

The influences of natural wind on the thermo-fluid performance of 300MW air-cooling combined heat and power (CHP) generating unit were investigated both numerically and experimentally. The CHP unit operated with only partial air cooling condensers (ACCs) in work under the winter chill environment. The physico-mathematical model was established for air flow and temperature fields of air-cooling island, in which only natural convection was considered while the axial flow fans of ACCs stopped. Variations of heat rate of ACCs with natural wind direction and speed were acquired. The results indicated that the heat rate varied significantly both with hot plume recirculation and reversed air flow to ACCs caused by natural wind. However, different from the normal operated air cooling power generating unit, the total heat rate of ACCs might increase due to the reversed flow for all axial flow fans stopped. Based on the observations, a case study was executed for the CHP unit with partial power generating load under natural wind conditions. The optimal operating schemes of the ACCs, as well as the rotating speed of the axial flow fans under various ambient wind conditions were obtained to satisfy heat supply of urban heating network, and also to maintain economic operation of the CHP unit. The numerical results were verified by the experiments.

Experimental investigation on thermal performance of natural draft wet cooling towers employing an innovative wind-creator setup

Natural draft wet cooling towers are one of the most widely-used types of wet cooling towers in the large-scale power plants. In the present research, the heat transfer performance of natural draft counter-flow wet cooling towers is investigated under cross-wind and windless conditions by virtue of an innovative wind-creator setup provided so as to implement intrinsic features of the natural wind speed profile precisely. As a matter of fact, this investigation will focus on the influences of cross-wind velocity, inlet water temperature and water flow rate on the water temperature difference and cooling efficiency of the studied cooling tower, with an emphasis on the role of wind speed features. Interestingly, a twofold trend is exhibited by the water temperature difference and cooling efficiency with respect to variation of the cross-wind velocity. Furthermore, to have a more applicable study, regression analysis of the experimental results is utilized for the sake of developing general mathematical equations and thus facilitating further analyses. Finally, these mathematical equations are employed in order to recommend a guideline for the purpose of reaching optimum operating conditions of natural draft wet cooling towers.

Analysis and Simulation of Wind Turbine Optimal Control Considering wind Turbulence Characteristics

A maximum power point tracking (MPPT) algorithm of wind turbines considering wind turbulence characteristics is presented in this paper. The turbulence characteristics of natural wind are analyzed, and the natural wind speed model is established. A MPPT algorithm based on extremum-seeking control (ESC) is proposed, which considers the turbulence characteristics containing in wind speed. The goal of the MPPT algorithm is to keep the wind turbines running at the maximum wind energy utilization coefficient point stably. The algorithm is modeled and analyzed, and the simulation results show that the MPPT algorithm is correct and effective.

Experimental study of wind-induced sediment suspension and nutrient release in Meiliang Bay of Lake Taihu, China.

Wind-induced sediment suspension and nutrient release is an important source for shallow eutrophic lakes. This work studies the quantitative relationship between wind speed and sediment release rate in Meiliang Bay of Lake Taihu, China, using field observations and indoor simulations. Natural wind, water flow, and water quality conditions were synchronously monitored to establish the relationship between wind speed and sediment release rate. Sediment suspension processes under different wind speeds were also simulated in a specially designed reactor. We then established the relationship between natural wind speed and indoor-simulated sediment release rate through hydrodynamic conditions (expressed using water shear stress). The indoor experiment was a supplement to the field observations. The results showed that (1) the critical wind speeds at which sediment became suspended and demonstrated maximum suspension were approximately 3-4 and 8 m s(-1), respectively; (2) the relationship between wind speed and suspended sediment (SS), total nitrogen (TN), and total phosphorous (TP) release rate could be expressed by exponential functions (SS release rate: y = 1.287e(0.177x) , R (2) = 0.981; TN release rate: y = 7.55e(0.363x), R (2) = 0.981; TP release rate: y = 0.381e(0.186x), R (2) = 0.945); and (3) the critical (wind speed, 8 m s(-1)) release rates of SS, TN, and TP were 1000, 5.8, and 2.2 g m(-2) day(-1), while the maximum (wind speed, 16 m s(-1)) rates were 5000, 24.7, and 5.4 g m(-2) day(-1), respectively.

Numerical Simulation on Finned Heat Pipe under the Condition of Convection

This paper intends to use Gambit software to set up different mathematical models for the finned heat pipe, separately from the perspectives of three-dimensional, steady-state, natural and mixed convection. And then, it also uses Fluent software to do numerical simulation on the influence of different fin spacing, fin height and fin angle under the conditions of natural convection and different horizontal wind speed on heat transfer performance of fin under the conditions of mixed convection. The results show that, under the condition of natural convection, increasing the fin spacing, fin height and fin angle with the horizontal angle can improve the heat transfer performance of finned heat pipe; Under the condition of mixed convection, with the increase of horizontal wind speed, on which the horizontal wind speed has a greater influence, the heat transfer rate and heat transfer coefficient of fin present approximately linear increase.

Experimental Study the Affection of the Dust Emission on Sand Stockpile by the Height of Windbreak Wall and Wind Speed

Based on the perspective of saving investment and reducing dust emission, the method of experimental study and the working principle of windbreak wall were adopted in this paper to explore the affection of the dust emission on sand stockpile by the height of windbreak wall and natural wind speed. According to the experimental testing, the data processing and analysis by the origin software, the studied results indicated that, the dust emission of the same particle size of powder (sand) increased with increasing the wind speed, the dust emission of the same particle size and the same wind speed of powder reduced with increasing the height of the windbreak wall., When the height of windbreak wall is 5/6 times of the height of the stockpile for a certain height of the bulk stockpile, the dual purposes of the minimum dust emission of bulk stockpile and saving investment could be gained. In the practical engineering application, the height of the windbreak wall should be chosen according to the actual situation (the density of the stockpile, particle size as well as the local wind speed).

A Study on ventilation characteristics in bidirectional traffic tunnels – with emphasis on the natural ventilation

양방향(대면통행) 터널에 대한 자연환기에 대한 결정기준 및 제트팬 용량 검토기준이 명확하게 정립되지 못한 이유로 1km미만의 터널에 대한 기계환기 여부 및 용량산정에 있어 혼선이 나타나고 있다. 이에 본 연구에서는 자연환기량의 특성을 살펴보고, 최근 진행중인 대면통행 터널의 환기설계 기법을 크게 2가지로 분류하여 분석하였다. 또한 본 연구에서는 양방향 터널에서의 합리적인 환기용량 산출과 자연환기량에 기초한 자연풍속(<TEX>$Vr^*$</TEX>)과 소요풍속(Vreq)과의 관계 검토를 통해 자연환기 방식의 적용 가능성에 대한 연구를 수행하였으며, 향후 양방향 터널의 환기기준 수립에 대한 기초자료 제공을 목적으로 하고 있다. The standards of ventilation system for bi-directional tunnel have not been established now. For this reason, with regard to the bi-directional tunnel below 1km, some problems have been appeared in ventilation capacity designing and in determining whether the mechanical ventilation system is needed or not for each case. In this study, we examine the characteristics of natural ventilations, analyze ongoing ventilation design cases for bi-directional tunnels and classify those cases into two groups. This study is carried out about the capability of using natural ventilating system by calculation of reasonable ventilation capacity in bi-directional tunnel and review of relationship between natural wind speed (<TEX>$Vr^*$</TEX>) and required speed(Vreq). This paper aims at providing a basis data for bi-directional tunnel ventilation design standards.

Wind Tower System With a Helical Wind Deflecting Structure, Computational Fluid Dynamics, and Experimental Studies

A wind tower system having a three dimensional heliacal wind deflecting structure is studies in this work. The purpose of the helical structure is to increase the natural wind speed and direct the follow of the wind toward two columns of horizontal-axis rooftop-size wind turbines that are installed in the grooves of the helical structure, diametrically opposed to each other. Computational fluid dynamics analyses were conducted to determine the influence of the helical structure on the wind speed reaching the turbines. A wind speed amplification coefficient was determined for a helical structure of 6.7 m outer diameter. The velocity profiles of the wind flow around the helical structure were determined under a postulated wind speed of 4.47 m/s. The flow was modeled as turbulent with a Reynolds Number of 2,052,167. Standard “k–ε” turbulent model with “near wall treatment” and “standard wall function” were adapted in all analysis. A “y+” value of 50 was held constant in all simulation. The grid-size effects on the accuracy of the results were examined. Convergence criterion was satisfied in each case. This study shows that the helical structure having an outer diameter of 6.7 m results in an average wind speed increase factor of 1.52. An experimental wind tower system was fabricated and installed at an elevation of 40 m above the ground. The wind tower system comprised of four identical rooftop size wind turbines, each having 1.6 KW name-plate-rating. A helical wind deflecting structure of 11 m tall, and 7 m in major diameter was used in fabrication of the tower. An active yaw-control mechanism was used to orient the tower into the prevailing wind. The experimental results show that as the result of the use of the wind deflecting structure, an average power amplification factor of 4.69 was obtained for the tower, in comparison with the standard standalone installation of the four wind turbines.

Compensation for the Power Fluctuation of the Large Scale Wind Farm Using Hybrid Energy Storage Applications

This paper proposes an application of superconducting flywheel energy storages (SFESs) to compensate the power fluctuation of the large scale wind farm. Based on the global interest against global warming, the power capacity of the renewable generation, especially wind generation, has been increased steeply. However, since wind generations depend on the natural wind speed completely, the power output cannot be controlled. The power fluctuation caused by the non-controllable output characteristic may create voltage problem for local system and frequency problem for whole power system. To solve those problems, the hybrid application of the large-capacity battery energy storage system (BESS) and the high-speed superconducting flywheel energy storage system (SFES) are considered in Heangwon wind farm in Cheju Island in Korea. Through the case studies based on the site-measured output data, the optimal power and energy capacity of the BESSs and SFES are figured out.

Laboratory development of wind turbine simulator using variable speed induction motor

The conventional synchronous generators in wind energy conversion system are now getting replaced by variable speed induction generator to extract maximum power with wide range of wind speed limit. The design and performance of such systems requires a simplified digital simulator, especially for the development of a optimal control solution .The proposed work is to make a prototype of variable speed wind conversion system simulator for a required operational condition under variable wind speed. In this paper variable speed induction motor drive using scalar control is interfaced in wind energy conversion system as an alternative to make the real time wind simulator for wind energy researchers. The basic power curve from wind generator is carried out through d-SPACE and interface of induction motor through an inverter control system. The induction motor is operated in wide speed range using Volt /Hertz speed control scheme. The laboratory prototype consists of 3 kW, 415 Volt, 50Hz induction motor controlled by voltage source inverter for various wind speed. The paper demonstrates the steady state characteristics of wind turbine without dependence on natural wind speed using Volt/Hertz. The basic control strategy is implemented through hardware system. The result verifies that the wind turbine simulator can reproduce the steady state characteristics of a given wind turbine at various wind conditions.

Framework design of a hybrid energy system by combining wind farm with small gas turbine power plants

Owing to the stochastic characteristic of natural wind speed, the output fluctuation of wind farm has a negative impact on power grid when a large-scale wind farm is connected to a power grid. It is very difficult to overcome this impact only by wind farm itself. A novel power system called wind-gas turbine hybrid energy system was discussed, and the framework design of this hybrid energy system was presented in detail in this paper. The hybrid energy system combines wind farm with several small gas turbine power plants to form an integrated power station to provide a relatively firm output power. The small gas turbine power plant has such special advantages as fast start-up, shutdown, and quick load regulation to fit the requirement of the hybrid energy system. Therefore, the hybrid energy system uses the output from the small gas turbine power plants to compensate for the output fluctuation from the wind farm for the firm output from the whole power system. To put this hybrid energy system into practice, the framework must be designed first. The capacity of the wind farm is chosen according to the capacity and units of small gas turbine power plants, load requirement from power grid, and local wind energy resource distribution. Finally, a framework design case of hybrid energy system was suggested according to typical wind energy resource in Xinjiang Autonomous Region in China.

Nonprobabilistic Interval Reliability Analysis of Wing Flutter

DOI: 10.2514/1.39880 The influences of uncertainties on the flutter behavior of aeroelastic wings were investigated. Uncertainties in the structural parameters of the wing and the natural wind speed were quantified by interval numbers. Uncertainty propagation in wing flutter was studied via interval analysis, and the interval estimation of flutter wind speed of the wing was obtained. Further, the reliability of wing flutter was analyzed based on the interval flutter-wind-speed and natural-wind-speed interference model. The ratio of the volume of the safe region to the total volume of the region associatedwiththevariationofthebasicintervalvariablesissuggestedasthemeasureofstructuralnonprobabilistic reliability. Numerical examples were used to illustrate the validity of the presented measurement.

Experimental study of the effect of wind on positive and negative corona from a sharp point in a thunderstorm

Corona discharge measurements made during a thunderstorm on a mountain at an altitude of almost 3300 m above sea level were analyzed for their dependence on the ambient electric field and the local wind speed. The corona current data were taken from an earthed needle point mounted at a height of 3 m above the ground. The coronating point was exposed to natural wind speeds of up to 14 m/s. Comparisons are made with empirical relationships dating back to the mid-1900s and new formulae are provided to describe the effect of wind on the magnitude of corona current measured under natural conditions.

Maximum output power control system of variable‐speed small wind generators

AbstractThis paper proposes a maximum output power control system for variable‐speed small wind generators. The proposed control system adjusts the rotational speed of a single‐phase AC generator to the optimum rotational speed, which yields the maximum output power according to the natural wind speed. Since this adjustment is performed on‐line in order to adapt to variations in wind speed, the rotational speed of the single‐phase AC generator is adjusted by controlling the generated current flowing in an FET (field‐effect transistor) device, serving as the generated power brake, which is linked directly to the single‐phase AC generator. In order to reduce heat loss from the FET device, a PWM (pulse width modulation) controller is introduced. An experimental model of the proposed control system was built and tested, and the validity and practicality of the proposed control system were confirmed by the experimental results. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(1): 9–17, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20692