Small Wind Turbine Research Articles

Potential and economic feasibility of a wind power plant in Ciudad Juárez, México

This study investigated the wind energy potential of Ciudad Juárez (Chihuahua, México) for a whole year. The viability of employing three small-scale wind turbine models, including the S-343, Bergey BWC Excel, and AOC 15/50, in Ciudad Juarez, located in the northern Mexican state of Chihuahua in Mexico, is studied in the first stage using RETScreen software. The performance of these three turbine models was subjected to sensitivity analysis in the following study stage using the three defined economic scenarios, assuming a 7% inflation rate, a 9% discount rate, a 7% fuel cost escalation rate, and a 20-year project duration. Finally, the circumstances under which these turbines operate in Ciudad Juarez are discussed economically. Findings indicate that the study site is not economically appropriate, not even for the installation of specific small wind turbines. Finally, it was suggested that the viability of adopting alternative renewable energy systems, such as solar and hybrid systems (photovoltaic wind), be examined in the upcoming study in Ciudad Juárez.

Analysis on aerodynamic performance of mine horizontal axis wind turbine with air duct based on breeze power generation

Developing wireless sensor networks based on breeze power generation is of great significance to promote the development of intelligent mines. In this paper, a small horizontal axis wind turbine with air duct was designed for the underground environment of coal mine. The aerodynamic performance of the wind turbine was analyzed by constructing a three-dimensional solid model of the wind turbine. The results show that under the condition of low wind speed underground, the air flow entering the air duct in the outer basin is accelerated and rectified, and the velocity near the impeller increases. The pressure value at the front end of the blade is the largest and the pressure value at the rear end of the blade is the smallest. A certain range of negative pressure zone is formed at the rear end of the impeller, which is conducive to the operation of the wind turbine. After the air flow passes through the impeller, the speed decreases and the speed is the lowest near the rotating shaft of the impeller. Inner basin: the air flow velocity increases gradually along the radial direction of the impeller centre. The pressure at the front end of the blade is greater than the atmospheric pressure, which is conducive to promoting the stability and sustainability of the wind flow and facilitating the operation of the wind turbine. When the wind speed reaches the rated wind speed of the wind turbine, the power, torque and output power of the wind turbine increase, which can provide effective power generation. Compared with other aerofoils, NACA5505 air foil has higher lift drag ratio and thrust coefficient, and is more suitable for downhole low wind environment. Compared with the wind turbine without air duct, the wind turbine with air duct has higher wind energy conversion and output power at low Reynolds number, which verifies the feasibility of the wind turbine with air duct. In the case of low incoming wind speed and no expansion of the size of the wind turbine, improve the output power of the wind turbine and meet the intrinsic safety requirements of the wind turbine. The research can provide technical support for the continuous power supply of wireless intelligent sensors in the mine environment, and provide scientific basis for mine safety production and fine management, which has long-term economic and social benefits.

Numerical study on flow characteristics of shroud with and without flap for wind turbine applications

Shrouded wind turbines have the shroud added to the rotor’s circumference, enhancing wind power compared to conventional wind turbines. This article aims to design a shorter aerofoil cross-sectional enclosure for the wind turbine that improves average velocity and reduces drag, duct material volume, and tower load. Numerical simulations were performed to understand the characteristics of shroud alone and shroud with flap using ANSYS Fluent in the operating regime of the small wind turbine. The influence of the shroud’s length-to-diameter L/ D ratio and angle on the performance was analyzed using a one-factor-at-a-time (OFAT) approach, and the optimum values were found. Then the analysis was performed by including the flap at the exit of an optimized shroud. The shroud with flap results showed enhanced average velocity, increased mass flow rate, and higher drag forces than a single long shroud. In order to reduce the drag coefficient, the enclosure geometrical parameters were analyzed using the Design of Experiments (DOE) approach. The results show that the shroud L/ D ratio significantly affects the average velocity. Moreover, the optimum combination was found as shroud L/ D ratio=0.4, shroud angle=9°, flap L/ D ratio=0.2, flap angle=16°, and radial distance of 0.2 R. The proposed combination helps to get an acceleration factor of 1.78, a drag coefficient of 1.84, and a material volume of 0.7×10−3 m3. It was found that the optimal ratio of shroud L/ D could be between 0.3 and 0.6, resulting in a higher acceleration factor, lower material volume, and shorter length. The drag forces acting in the shroud alone and shroud with flap were studied by analyzing the forces in every section. The results show that the negative drag force acts in the shroud’s inner leading edge.

Performance appraisal of a small wind turbine under the use of three rotor hub configurations

Performance appraisal of a small wind turbine under the use of three rotor hub configurations

MODELING OF A CVT TRANSMISSION AND DYNAMIC CHARACTERISTICS

This paper briefly describes a newly designed stepless transmission to cope with external loads. A detailed computer model is presented to investigate the technical feasibility of the proposed dismantling scheme. The selected key design variables and constraints are those relevant for the practical application of a small wind turbine gearbox. The corresponding dynamic model was developed using ADAMS. Simulation studies and preliminary discussions were conducted to validate the proposed design solution.

New developments in small scale wind turbines

Considering the global socio-economic context, the pressure on natural resources and of course the effects that exploitation has on natural ecosystems and fauna is more and more evident. The use of renewable energy sources, together with improvements in energy efficiency, can help reduce energy consumption, reduce greenhouse gas emissions and, consequently, prevent dangerous climate change. The integration of renewable energy sources in urban areas and in everyday life is a viable solution. The present paper focuses on the presentation of small-scale wind systems integrated in urban areas and not only to capitalize any energy as efficiently as possible.

Experimental and Numerical Investigation of the Effect of Blades Number on the Dynamic Response of a Small Horizontal-Axis Wind Turbine

The new energy scenario is rising a strong interest towards the distributed production from renewable sources; among them, wind seems to be one of the most interesting and at the same time critical due to the challenges of the conversion technology. Operation of small wind energy conversion systems is generally very complex due the extremely variable regime of operation and the high turbulent wind, so that a deep knowledge of the dynamic response of such devices is crucial not only for optimising their performances but also to make them comfortable to be used in residential areas. For these reasons, the present work is focused on analysing the effect in changing the number of blades on a small horizontal axis wind turbine through an experimental campaign in the wind tunnel. The turbine dynamics has been characterised running some “wind ramp” tests and analysing the rotor capability in following the wind as well the vibrations transmitted by the turbine during the operation. Results demonstrate that a higher number of blades, despite a small decrease of performance, can make the machine more efficient in operating at low wind regimes. At the same time, a higher number of blades can make the rotor efficient even at lower speed of rotation, thus limiting the risks of having high magnitude vibrations.

Design Loads in Small Wind Turbines: a Detailed Comparison Between Pitch and Stall Regulation

Small wind turbines (SWTs) have known alternate fortune but can now play a key role in distributed production to foster energy transition. Among the typical features of small machines, the use of stall regulation is a distinctive one, since the ubiquitous variable speed pitch regulation used in utility-scale rotors is hampered by space constraints in small nacelles. This reduced the cost and boosts overall reliability; on the other hand, compromises in the aerodynamic design of the blades must be adopted to ensure smooth power regulation above rated windspeed. This has implications not only on the final Annual Energy Production (AEP) of the rotors, but also on loads. The current study aims at investigating the differences in peak loads between a stall and a pitch regulated SWT. The UNIFI 50kW SRWT, a reference turbine designed by Università degli Studi di Firenze, is used as a case study thanks to the fact that is available both with stall and pitch control options. Differently from most of the studies to date, simulations are carried out for a variety of power production and parked load cases, significant for extreme loading of the rotor and tower of the wind turbine, thus strongly impacting on the design. Results demonstrate how a pitch-regulated machine can ensure a significant reduction of the main maximum loads, thus paving the way for more optimized and cost-effective designs of future SWTs.

Recommendation for strut designs of vertical axis wind turbines: Effects of strut profiles and connecting configurations on the aerodynamic performance

The strut is a necessary support structure that connects the vertical axis wind turbine blade to the rotating shaft and transfers the torque, and is one of the key factors affecting the aerodynamic performance of the wind turbine. However, research on struts is limited and the appropriate strut design remain uncertain. Therefore, in this paper, the struts of a straight-bladed vertical axis wind turbine are investigated by a three-dimensional computational fluid dynamics approach, to find the appropriate strut design parameters that minimize the impact on the aerodynamic performance. Thirty strut profiles with different chord lengths, thicknesses, areas, and streamlined shapes were parametrically created and analyzed, including a novel strut-specific profile proposed in this paper. Furthermore, all strut connecting parameters, such as spanwise and chordwise positions, connecting angle and fairing were investigated. The results show that the power loss of a vertical axis wind turbine has a relatively linear relationship with the dimensionless absolute thickness of the strut within a certain range. The strut chord length is another important influencing factor. Equal chord lengths of the strut and the blade should be avoided as much as possible. The proposed novel olivary strut profile has lower drag characteristics and more favorable geometrical structural properties compared to the most used NACA airfoil. The influence of the spanwise connecting position (within the range around the blade quarter span) is minor. But the chordwise position has a significant effect, and special attention should be paid to avoid the strut maximum thickness position connecting with the blade aerodynamic center, which will result in the greatest performance degradation. Analysis of the connecting angles shows that inclined struts are suitable for small wind turbines. The fairing is effective when the strut chord length is equal to or longer than the blade chord length. With these results, a set of recommended design parameters for vertical axis wind turbine struts is presented.

Potential of Small-wind Turbine for Power Generation on Offshore Oil and Gas Platforms in Malaysia

On most of the offshore oil and gas platforms, the current means of generating power are through the use of generators i.e. gas turbines and diesel power generators, or micro-generators for some smaller equipment. These generator sets are less reliable, especially on unmanned platforms. Hence, the deployment of renewable energy, such as the use of wind turbines, would be better for energy security, economic development and also protection of the environment. Instead of using wind power to power up the whole platform, small wind turbines can be utilised to power up some utilities and instrumentations on the platform, while having generators as back up, as the wind speed is beyond control. However, the capability of a small wind turbine in generating enough power is constantly under doubt as it is yet to be widely employed and only meagre data is available. This is caused by the issue of having insufficient studies regarding the implementation of small wind turbines for power generation on offshore oil and gas platforms. Hence, this paper studied the capability of small wind turbines for power generation on offshore platforms in Malaysia. Several models of small wind turbines were selected and their abilities in generating power to fulfil the annual energy consumption on a typical offshore platform were examined through precise calculations. The common offshore locations in Malaysia were identified and the average wind speeds from 2017 to 2019 at these locations were analysed. The result shows that certain models of small wind turbines are able to provide a significant amount of power for an offshore platform especially to power up the low power machineries. It was found that Kerteh, Terengganu is the most suitable offshore location to harness wind power due to its averagely high wind speed throughout the year. The highest amount of energy that can be produced was around 1445kWh per annum at Kerteh by the small wind turbine with the largest swept area and the lowest cut-in speed. This paper aims to serve as numerical validation on the plausibility of integrating small wind turbines for the generation of electricity on offshore platforms in Malaysia while also providing the recommended locations that are suitable for this region.

Electric vehicle battery charging framework using artificial intelligence modeling of a small wind turbine based on experimental characterization

The objective of this paper is to develop a generic electric vehicle battery charging framework using wind energy as the direct energy source. A robust model for a small vertical axis wind turbine based on an artificial neural network algorithm is used for predicting its performance over a wide range of operating conditions. The proposed framework can be implemented at any location worldwide where full prediction of the wind signature is perfectly obtained. In this paper, a small vertical axis wind turbine has been experimentally characterized at different operating conditions, where measured data, output power, and torque have been used to build the model. Once the model has been developed, the model is inserted into the MATLAB/Simulink software tool to predict the charging performance of a battery for an electric vehicle. An rpm controller has been used to achieve the maximum generated power from the wind turbine across the day with various wind speeds. Hence, the generated power is fed to the EV battery charger to implement the constant current constant voltage charging protocol. The charging current reached the desired value in a settling time of 4.5 s, whatever the intermittency of the wind energy. The proposed application of wind energy to EV provides sufficient constant power supported by the utility grid.Graphical

Implantation, Operation Data and Performance Assessment of An Urban Area Grid-Connected Small Wind Turbine

Over the last few decades, and more prominently currently, many countries have launched and reinforced campaigns to reduce CO2 emissions from all human activities and, in the area of energy, promote energy generating technologies from low carbon, renewable sources, especially wind and solar. In recent years, this promotion of renewables can be seen in statistics as well as an extraordinary increase in plants using renewable sources. There is more activity surrounding the use of small devices installed close to consumers, such as small wind turbines (SWT). In cities, the best places to install SWT are tall buildings. The Institute of Energy and Environment (IEE-USP) has installed a 1.8 kW SWT on the University of São Paulo campus in São Paulo, Brazil. Even with low-magnitude winds at the site, the SWT installation was carried out to serve as a didactic apparatus and demonstration initiative of wind energy generation connected directly to the University’s electric grid, which already has other embedded renewable sources installed, namely photovoltaic and biogas plants. The turbine was placed on the roof of the existing High Voltage Laboratory building, leading to an operating height of 35 m. This paper presents previous local wind data measurements using a Lidar system, annual energy yield estimation calculations, and measurements, also bringing all implementation details. It reports and analyzes the operation and energy production data from three full operational years, from 2018 to 2020, discussing and concluding with further improvements of SWT from technical and economic aspects.

Effects of blade number on the aerodynamic performance and wake characteristics of a small horizontal-axis wind turbine

Small-scale horizontal-axis wind turbines (SHAWTs) are powerful equipments for wind energy conversion. Furthermore, the wake vortices generated by SHAWTs are used in structural engineering to potentially mitigate vibrations. The blade number of SHAWTs is an important parameter for determining the wake vortices, and thus, in addition to its impact on power generation, it significantly influences structural vibration control. Consequently, the aerodynamic performance and wake characteristics of SHAWTs, with blade numbers from 2 to 5 and tip speed ratio from 1 to 6, were systematically investigated using large-eddy simulations and wind tunnel tests. A superior SHAWT with a high power coefficient (>35 %) was designed. The near-wake characteristics and wake evolution were highly sensitive to blade number. An increased number of rotor blades resulted in a (i) wider near wake, (ii) faster decrease in streamwise vorticity, and (iii) greater velocity deficit (VD) and turbulence intensity (TI) in the near wake. Furthermore, in the far wake, the unstable positions of the tip vortices and peak positions of the TI were closer to the rotor and the VD recovered faster, causing the wind-speed distribution to transition from W-shaped to V-shaped. The results have significant implications for the design optimisation of wind energy harvesting. Moreover, they are potentially beneficial for the control of structural vibration using SHAWTs.

Characterization of Aerodynamics of Small Wind Turbine Blade for Enhanced Performance and Low Cost of Energy

During a turbine’s lifetime, minimizing the cost of power production should be the primary aim in addition to attaining high technical efficiency. Thus, this paper was aimed at enhancing the aerodynamic efficiency of a site-specific small wind turbine considering the cost of energy as one of the design parameters. The wind distribution of a specific site was employed to characterize the wind using the Weibull distribution method. The aerodynamics of a typical 5 kW wind turbine blade were investigated by implementing a blade element method (BEM) using a MATLAB code that applied the advancements and improvements with different modifications and which was validated by engaging computational fluid dynamics (Ansys-Fluent). The optimal pitch angle was then employed to further promote the performance characteristics of the blade. The cost of energy was reformulated in terms of rated power considering a cost variation of the main components that deviates with the rated power. Accordingly, the performance parameters were investigated against a varying rated power and the relative cost of energy, achieving a maximum power coefficient of 55.37% at a lower cost of energy. Moreover, annual energy production of approximately 18 MWh with a corresponding capacity factor of approximately 41% was achieved at a lower cost of energy. These findings demonstrate that the selected modelling, analysis procedures, and modifications enhance the aerodynamic performance characteristics and lower the cost of energy of the small wind turbine blade, which promotes the affordability and energy harnessing capability of small wind turbines.

Influence of height ratio in groups of buildings of unequal height on micrositing of urban-SWTs

Roof-mounted small wind turbines (SWTs) in groups of buildings is an efficient method to expand urban wind energy. In order to 1) identify the value of the height ratio λ (λ = h/H, where h is the average surrounding building height and, H is the target building height) at which the influence of surrounding buildings on wind is minimized and 2) confirm the optimal location and installation height for roof-mounted SWTs in groups of buildings of unequal heights, we assess wind velocity and turbulence intensity above rooftops over five groups of buildings of unequal height by computational fluid dynamics (CFD). The rooves of low-rising buildings are not ideal installation locations for SWTs due to the high installation height needed to make them effective. The influence of surrounding buildings on wind behavior above the roof of the tallest building in a group of buildings of unequal height can be neglected when λ ≤ 0.6. Therefore, the tallest building in the building group with λ ≤ 0.6 should thus be considered an isolated building when micrositing SWT placement using CFD. This finding can be used to use CFD methods to simulate wind behaviors in urban environments.

Multi-Scale Numerical Assessments of Urban Wind Resource Using Coupled WRF-BEP and RANS Simulation: A Case Study

Urban wind resource assessments (WRAs) contribute to the effective exploitation of wind energy and thus are of significant importance to the sustainable development of cities. To improve the simulation accuracy of urban wind flow with high spatial resolution, this study implemented a multi-scale numerical assessment of the wind power potential in a highly-urbanized region with realistic terrain conditions by integrating the Reynolds-averaged Navier-Stokes (RANS) equations into the Weather Research and Forecasting (WRF) model with Building Effect Parameterization (WRF-BEP). The sensitivity analyses are first conducted to obtain an appropriate combination of physical parameterization schemes in the WRF-BEP model. Then, the wind tunnel tests are performed to validate the computational accuracy of urban wind flow using the RANS equations. Based on a close examination of the urban wind flow resulting from the coupled WRF-BEP and RANS simulations, the integration of micro-wind turbines into the building skin is not recommended in the highly-urbanized region. Furthermore, five optimum roof installation locations with low turbulence intensities (smaller than 18%) and high wind power densities (approximately 220 W/m2, 260 W/m2, 270 W/m2, 300 W/m2 and 400 W/m2, respectively) are identified. Finally, the important effects of the terrain conditions, planetary boundary layer (PBL) parameterization schemes and turbulence models on WRAs are discussed. The results of WRAs in this multi-scale numerical case study presented a systemic approach to effectively determine the installation locations of micro-wind turbines that possess the greatest potential to harness wind energy in a realistic highly-urbanized area.

An Investigation of Design and Simulation of Horizontal Axis Wind Turbine Using QBlade

Abstract The wind turbine blade design is important in obtaining an effective wind turbine. In the field of wind energy, it is essential to understand the design and parameters affecting the blades of the wind turbine in order to obtain a successful design. However, most of the parameters are dependent on each other and this makes the design of wind turbines a challenging task. This research paper used the QBlade software to analyze and optimize the behavior of the small horizontal axis wind turbine. The software applies the Blade Element Momentum Theory (BEM) to study the wind turbine blades by calculating the drag and lift coefficients which were achieved by dividing the blades into 10 ascending segments. The twist angle and chord length of the blade are optimized to get the highest performance. Among the various airfoil types, the SG-6041 airfoil type was selected to build the blade structure. The calculated power coefficient was almost 0.4, which is considered high given that it was calculated under 10 m/s average wind speed and 1-meter length blade conditions. Where all the results are logical and reasonable, the software is proven to be reliable. The paper also evaluates the wind characteristics in different locations in Iraq in order to find the most optimal promising locations in Iraq.

Current status and grand challenges for small wind turbine technology

Abstract. While modern wind turbines have become by far the largest rotating machines on Earth with further upscaling planned for the future, a renewed interest in small wind turbines (SWTs) is fostering energy transition and smart grid development. Small machines have traditionally not received the same level of aerodynamic refinement as their larger counterparts, resulting in lower efficiency, lower capacity factors, and therefore a higher cost of energy. In an effort to reduce this gap, research programs are developing worldwide. With this background, the scope of the present study is 2-fold. In the first part of this paper, an overview of the current status of the technology is presented in terms of technical maturity, diffusion, and cost. The second part of the study proposes five grand challenges that are thought to be key to fostering the development of small wind turbine technology in the near future, i.e. (1) improving energy conversion of modern SWTs through better design and control, especially in the case of turbulent wind; (2) better predicting long-term turbine performance with limited resource measurements and proving reliability; (3) improving the economic viability of small wind energy; (4) facilitating the contribution of SWTs to the energy demand and electrical system integration; (5) fostering engagement, social acceptance, and deployment for global distributed wind markets. To tackle these challenges, a series of unknowns and gaps are first identified and discussed. Based on them, improvement areas are suggested, for which 10 key enabling actions are finally proposed.

Experimental study of turbulence intensity on the wake characteristics of a horizontal-axis wind turbine

ABSTRACT A time-resolved particle image velocity (TR-PIV) system was used to test the wake flow of a small horizontal-axis wind turbine at tip speed ratios (TSRs) in the range of 4–6 under uniform inflow and turbulent inflow in order to study the impact of turbulence intensity on wind turbine wake characteristics. The impact of incoming turbulence on the wake structure of a wind turbine and its mechanism was examined by comparing and analyzing the turbulence properties of the wake flow, including velocity field, vortex structure, additional turbulence intensity, and energy distribution coefficient. It was found that tip vortex structure remained intact in the range of 9 R under uniform inflow, and the longitudinal distribution of turbulent intensity had double peaks, indicating that it was in the near wake zone. Under turbulent inflow, the three vortex systems could not be distinguished at the position of 5 R, and the longitudinal distribution of turbulent intensity did not have peaks, the wake vortex system was broken and the wake transitioned to the far wake zone. With the increase in the turbulence intensity and tip speed ratio, the contribution of the longitudinal component of turbulence intensity to the turbulent kinetic energy increases, which is also the reason for the rapid wake recovery. Additionally, the recovery of the wake velocity was sped up in the range of 3 R and gradually decreased after 3 R.

Structural and modal analysis of small wind turbine blade using three different materials

The aim of the research is to investigate and compare the performance of small wind turbine blades made using three different materials by performing structural analysis. Also, it investigated the vibration characteristics of these blades. SOLIDWORKS software was used to create the three-dimensional model of the blade, which was then exported to ANSYS softwarein order to achieve the numerical simulation based on the Finite element method. In this work, three different materials Aluminum alloy (Al-2024), Glass fibre reinforced epoxy (GRFP), and Carbon fibre reinforced epoxy (CFRP) were selected to build the body of the blade parts. The structural analysis result shows that the CFRP gave the lowest deformation and highest stress whereas GRFP and AL-2024 gave almost similar results. Modal analysis results show that GFRP has lower modes of vibration than other materials.