Small-sized Wind Research Articles

Dynamic analysis of a small-sized wind turbine in the Midwest of Brazil

Dynamic analysis of a small-sized wind turbine in the Midwest of Brazil

Continuous input current buck DC/DC converter for small-size wind energy systems featuring current sensorless MPPT control

For decentralized electrification in remote areas, small-sized wind energy systems (WESs) are considered sustainable and affordable solution when employing an efficient, small-sized component converter integrated with a less-sophisticated, cost-effective MPPT controller. Unfortunately, using a conventional buck DC/DC converter as a MPP tracker suffer from input current discontinuity. The latter results in high ripples in the tracked rectified wind power which reduces the captured power and affects system operation especially in standalone applications which are self-sufficient and independent of grid support. Furthermore, these ripples propagate to the machine side causing vibration and torque stress which impacts turbine performance and safety. To solve this issue, a large electrolytic capacitor is placed at the buck converter input to buffer these ripples, yet at the cost of larger size, losses and reduced reliability. Oppositely, the developed C1, D4 and D6 buck converters have the merit of continuous input current at small component-size. In this paper, dynamic modelling of these three converters is developed to select the one with the least input current ripples to replace the traditional buck converter in the considered WES system. Consequently, fluctuations in the tracked power are minimized and the large buffer capacitor is eliminated. This enhances system lifetime, reduces its cost and increases tracking efficiency. Moreover, mechanical power and torque fluctuations are minimized, thus maintaining machine protection. Furthermore, a sensorless MPPT algorithm, based on converter averaged state-space model, is proposed. Being dependent on variable-step P&O algorithm, the proposed approach features simple structure, ease of control and a compromise between tracking time and accuracy besides reduced cost due to the eliminated current sensor. Simulation results verified the effectiveness of the selected converter applying the proposed MPPT approach to efficiently track the wind power under wind variations with cost-effective realization.

Design of a small-scale wind tunnel for the study of horizontal-axis wind turbine blades

The paper considers the details of design and construction of a small-sized wind tunnel with an open circuit and a closed test section for investigating the blades of horizontal-axis wind turbines. The effect of different types of jet straighteners on the turbulence of the flow in the test section has been studied. Turbulence flow distributions Tu at Reynolds numbers Re from 5·103 to 2·104 are obtained using Laser Doppler Anemometry methods. As a result, the wind tunnel design with average flow turbulence of 1.6 % is obtained. The flow visualization of NACA 64-618 airfoil at Re = 5·103 is obtained.

Assessments regarding the performances of wind turbines from the roofs of buildings

In the current energy context, wind energy remains the main renewable energy source. Greater attention should be paid to small-sized wind turbines, mounted on the roofs of buildings, for their many advantages: easy to construct, do not require additional space, easy maintenance, eliminate losses from the system and transport costs, can provide alone or in addition to energy solar, the entire energy need of buildings, etc. The present paper analyzes three models of wind turbines that can be placed on the roofs of buildings: crossflow wind turbine Banki, ridge blade turbine and aeroMINE model. The analysis refers to their constructive solutions, the working principle, the optimal design for a good power coefficient and the energy that can be obtained with these small turbines for urban applications and not only.

Orta ve Küçük Ölçekli Rüzgar Türbinlerinin Yaşam Döngüsü Boyutunda Sürdürülebilirliği: Literatür Taraması

With the growing interest in renewable energy systems, studies on the sustainability of small-scale wind turbines have been published in recent years. A literature review was conducted in this study to compile scientific studies conducted to evaluate the environmental effects of medium and small-sized wind energy systems using the life cycle assessment. Life cycle assessment is a method of evaluating the environmental sustainability of a product, process, or system that is becoming more important in the context of decisions and policies in the energy sector. The environmental effects of medium and small-sized wind turbines on the life cycle size have been investigated in this study, which looked at studies conducted since 2004. The vast majority of these studies conducted environmental sustainability assessments based solely on a few environmental impact indicators such as global warming potential. There are only a few studies that consider a wider range of environmental effects. The collection and analysis of studies examining the life cycle environmental sustainability of medium and small-scale wind turbines are important for determining the future vision of small-scale energy production systems.

A ring-vortex actuator disk method for wind turbines including hub effects

Due to its robustness and simplicity, the simple actuator disk is still the most used and popular method for performance analysis of horizontal axis wind turbines. However, the hub blockage effect is generally disregarded in this approach, thus worsening the accuracy of its results. This is particularly true for small-sized wind turbines whose ratio between the hub and rotor radii can be as large as 25–30%. In order to obtain some insights onto the impact of the hub blockage-effect on the performance prediction, this paper presents a free-wake ring-vortex actuator disk method accounting for an axisymmetric hub of general shape. The fundamental concept of a uniformly loaded disk without wake rotation is adopted. In the proposed method, the flows induced by the disk and the hub are both modelled by ring sheet-vortices which are discretised through a classical panel method. An iterative solution procedure is developed to evaluate the density strength distribution of the sheets and the wake shape. To this aim, the homogeneous Dirichlet boundary condition is used for the velocity just beneath the hub sheet, while the free force condition is imposed all along the wake boundary. The latter is also required to be aligned with the overall flow field. The method is verified comparing its results with those of a Computational-Fluid-Dynamics-based approach, and of the classical axial momentum theory showing a very good agreement in both cases. Finally, some insights on the hub blockage effect are presented showing that, for a small-sized wind turbine, this effect significantly affect the flow distribution all along the blade span. In the analysed cases, the increment in the axial velocity at the disk, due to the hub blockage, goes from 20% in the hub proximity to 2% at the tip. The above values suggest that the hub blockage effect should never be disregarded in the analysis of small-sized wind turbines.

The effects of blade pitch angle on the performance of small-scale wind turbine in urban environments

Due to the growing importance of wind power as a clean and renewable energy source, the use of small-scale wind turbines in urban environments has increased lately. The blade pitch control is an effective method to improve the aerodynamic response of a wind turbine, usually applied to large-scale wind turbines. This study presents the effects of varied blade pitch on the aerodynamic performance of a small-size wind turbine. The blades were sketched out according to the Blade Element Moment (BEM) theory, applying the aerodynamic profile NREL-S809 and designed for a tip speed ratio of eight. To analyze the influence of the blade pitch angle on the energy conversion, a comparative study was carried out varying the pitch angle to five different values. Using the analysis of variance (ANOVA), it was possible to demonstrate that blade pitch control could be an effective method also for small-sized wind turbines. A performance chart from the results of blade pitch experiments shows that the power coefficient varies significantly when the angle changes. As conclusion, it is highlighted that an enhanced behavior could be attained by the use of a pitch angle controller resulting in a better recovery of the energy available in the wind.

104 Development of multi-fan type gust wind tunnel by integration of small-sized wind tunnels

104 Development of multi-fan type gust wind tunnel by integration of small-sized wind tunnels

Small wind turbines: A numerical study for aerodynamic performance assessment under gust conditions

Abstract In the present work, a numerical study aimed to analyse the effect of an extreme loading event on a Horizontal Axis Wind Turbine (HAWT) is performed. A 3D unsteady CFD model of the NREL Phase VI small-sized wind turbine is validated against experimental data, with the incompressible solver of ANSYS Fluent and an unstructured moving mesh strategy. Then the Extreme Operating Gust (EOG) model from IEC 61400-2 is considered as the inlet condition. The results of the aerodynamic response and of the structural ultimate check, based on the IEC guidelines, are presented for both the operating and the parked turbine, in order to underline the benefit of the safety position in terms of lower stress transferred to the critical root section.

Studies on Three-Dimensional Mixed Convection with Surface Radiation in a Rectangular Channel with Discrete Heat Sources

ABSTRACTThe flow behavior and heat transfer characteristics of conjugate heat transfer under mixed convection for a three-dimensional laminar flow in a rectangular channel with six protruding heat sources, mounted on the lower wall of the channel, have been studied numerically and experimentally. At higher temperatures, radiation plays an important role. This work reports the effect of radiation on conjugate mixed convection heat transfer. Air is taken as a cooling medium and is considered to be radiatively non-participating medium. The parameters considered for the study are positions (streamwise and spansise) of the heat sources, Reynolds number, emissivity of the heat sources, and the thermal conductivity of a printed circuit board (PCB) having constant fluid properties with the Prandtl number being 0.707. The Boussinesq approximation has been used. Commercial software ANSYS Fluent has been used for numerical analysis, and experiments have been carried out in a small-sized wind tunnel. The ranges of Reynolds number, emissivity, and thermal conductivity of PCB are 115–690 (corresponding inlet velocity of 0.25–1.5), 0–0.9, and 0.038–1.4 W/mK, respectively. Results indicate that the radiative heat transfer is significant at lower Reynolds number and lower thermal conductivity of PCB. The streamwise spacing of heat sources has larger influence compared to the spanwise spacing.

最優秀論文賞：風車のソリディティとエネルギー変換効率の関係

Today, we must develop alternative energies. However, Japan does not have enough land to build large power plant. Therefore we studied about small-sized wind power generation for the purpose of developing a windmill which is suitable for the wind condition of its installed location.

Performance Experiment of Small-Sized Wind Power Generation Using Outdoor Air and Exhaust

AbstrctThis study explains the experiment for evaluating the performance of small-sized wind power generators, in which outdoor air that increases with height of high-rise apartment buildings is induced into the exhaust openings of kitchens and bathrooms. This outdoor air generates an ascending air current and a certain amount of electric energy, which are needed for operating buildings. To apply small-sized wind power generators to exhaust openings of kitchens and bathrooms in existing apartment buildings, a constant driving wind velocity of 3 m/s is required. Performance experiments in laboratories and application experiments on building rooftops, in which outdoor air induction modules were applied to existing exhaust openings of kitchens and bathrooms, show that when outdoor air and exhaust wind velocity are lower than 2 m/s, a driving wind velocity of higher than 3 m/s, which is needed to generate wind power, can be obtained. Furthermore, the generated amount increases by 29%.

1204 小型垂直軸風車によるダクト排気流発電に関する基礎的研究(流体工学II)

1204 小型垂直軸風車によるダクト排気流発電に関する基礎的研究(流体工学II)

0501 対称形ケーシングを有するクロスフロー風車のCFD解析

Cross-flow wind turbine has a characteristic of high torque coefficient at low tip speed ratio, good self-starting, low noise and high stability. Therefore, it attracts attention as the city type small-sized wind turbine for urban district. However it is serious problem that the maximum power coefficient is extremely low as 10% compared with other smallsized wind turbines. In this research, in order to improve the performance of a cross-flow wind turbine, a symmetrical casing is installed to it. Then the internal flow is investigated, and the effect of the symmetrical casing on the performance of the turbine is clarified by CFD simulation.

Wind Potential Analysis in Brasov Built Environment

Implementing renewables in the built environment represents a must, considering the target of Nearly Zero Energy Buildings set by the European legal frame, starting with 2020. One specific feature of the built environment is that it additionally imposes constraints, and can distort the renewable energy potential, particularly the wind energy. Therefore, the development of optimized, efficient small wind turbines requires on-site monitoring and, further on, models developed/adjusted according to these. Thus, the main purpose of this study is the analysis of the available wind potential in the built environment – particularly in theColinaCampus of the Transilvania University, in order to implement small wind energy conversion systems. Wind data are collected during one year (2013) from the meteorological station from Brasov - Ghimbav (located 8 km far from Brasov), and from a second weather station, which is mounted on the rooftop of the university building in Brasov city (University hill). The results indicate that the area has a promising wind potential for the implementation in this built environment of small-sized wind turbines, which can start operating from 0.8 m/s and producing electricity from min. 1.8 m/s.

A Study on the Application of Small Wind Power System with Combined Ventilator in Super High-Rise Apartment

This is an elementary study on the application of small-sized exhaust wind power generation to exhausters on the rooftop of high-rise apartment buildings, Here, CFD (Computational Fluid Dynamics) simulation is performed to determine the effect of multi-diffusers for exhaust wind velocity amplification and external wind attraction; the experiments are conducted using miniatures and actual mock-ups. The results of the study are summarized as follows. From the simulation of multi-diffusers for exhaust and ventilation, the wind velocity increased with a greater number of installations of devices, where up to eight was possible and about six was found to be appropriate. In simulation of exhaust effect, an increase in the external wind velocity leads augmentation in the exhauster wind velocity; in particular, it was confirmed that even when there was no exhaust wind (0m/s), there was an exhaust air rise effect due to inflow of the external wind, itself. In the results of experiments with miniatures and mock-ups, the exhauster discharge wind velocity increased due to the external air inflow in the apartment building exhauster, confirming the existence of an exhaust effect. The wind velocity increase rate was greater at the upper part than at the lower part, leading to the prediction that it would be possible to secure over 3m/s, the initial operation wind velocity of small wind power.

전산유체역학해석을 통한 고속도로 주행차량 유도풍의 풍력발전 적용 가능성에 관한 연구

In this study, analytical works for the induced winds due to traveling vehicles on highway have been conducted by Computation Fluid Dynamics (CFD). The traveling condition was considered in two cases: (a) single direction and (b) bi-direction. The analysis was focused on the effects of the induced winds on the upper part of a median strip while the aerodynamic characteristics of the vehicles were directly analyzed in the previous studies. From the analysis results, it has been found that the maximum magnitude of the induced winds was 2.2 m/s when the vehicles travel with the speed of 50 km/h. Additionally, 4.0 m/s and 5.3 m/s were obtained with the speed of 90 km/h and 120 km/h, respectively. Especially, the induced winds was generated about 84% of the vehicle speed at 1.0 m above from the median strip when the vehicles travel with the speed of 120 km/h. The induced winds was maintained during the very short period while the traveling. conclusively, it is noted that the wind power generation can be possible by using the small-sized wind power generators installed on median strips throughout the analytical results in this study.

Performance analysis of indirect vector control algorithm for small-sized wind turbine induction generator

A power limitation on a small-sized of a stallregulated wind turbine is presented. The turbine is designedwith a rated power of 25kWatt and operating in variablespeed. The turbine is designed to use a 30kWatt SquirrelcageInduction Generator (SCIG) to generate electricity. Acontrol algorithm using Indirect Vector Control (IVC) hasbeen designed, and the performance has been analysed. Agood result is achieved where the power can be limited atthe rated value during high wind velocity. The comparisontransient response when the different controller's gain istuned is also demonstrated. This proposed design is to beused in the stall regulated wind turbine, with active speedcontrol.

CFD Investigation on the aerodynamic characteristics of a small-sized wind turbine of NREL PHASE VI operating with a stall-regulated method

The objective of this investigation is to clearly understand the aerodynamic characteristics of a small-sized wind turbine of NREL Phase VI, operating with a stall-regulated method using CFD code. Based on this, it is possible to provide turbine designers with the aerodynamic design data to increase efficiency and improve performance in the design phase of future small-sized wind turbine blades. Moreover, a comparison was made between experimental datasets, in order to verify the reliability and validity of the analysis results. The first height in the normal direction from the surface of a rotor blade is about 0.2 mm, and the average value of y+ is about 7 at 7 m/s. The domain is chosen to consist of only two hexahedral mesh regions, namely the interior region, including the wind turbine blade, and the external region excluding the rectangle. The total cell number of the numerical grid is about Ng = 3.0 × 106. Five different inflow velocities, in the range Vin = 7.0−25.1 m/s, are used for the rotor blade calculations. The calculated power coefficient is about 0.35 at a TSR of 5.41, corresponding to 7 m/s, and showed considerably good agreement with the experimental measurements, to within 0.08%. It was observed that the 3-D stall begins to generate near the blade root at a wind speed of 7 m/s. Therefore, root design approaches considering the appropriate selection of the angle of attack and the thickness are very important in order to generate the stall on the blade root. Through a clear understanding of aerodynamic characteristics of a small-sized NREL Phase VI wind turbine, it is expected that this useful aerodynamic data will be made available to designers as guidance in designing stall-regulated wind turbine blades in the development phase of small-sized wind turbine systems in the future.

소형 풍력발전 시스템을 위한 CRIO 기반의 실시간 제어 시스템 설계 및 다양한 형태의 MPPT 알고리즘 성능 비교 분석

The small-sized wind turbine generating system with the output power less than 10kW, which can be installed in some areas of hills, parks, and cities due to its flexibility, is one of the progressive research and development fields in renewable energy. It is important for the small wind turbine generators to have low cost, high reliability as well as high efficiency. To meet these requirements, development of various maximum-power-point-tracking (MPPT) control schemes should be required. Generally, the output of the controller can be connected to a 48V battery to supply power to a DC load. In this work, the design and implementation of an FPGA-based MPPT controller for small-sized wind turbine generating system is presented. For the verification of the practical performance of various MPPT algorithms, CRIO controller from NI has been used.