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This paper reports the design and characterization of a small-scale wind energy portable turbine (SWEPT) targeted to operate below 5 m/s wind speed. Aerodynamic performance characteristics of SWEPT were extensively examined using the wind tunnel experimentation and it was found that the maximum coefficient of performance of 14% occurred at the tip...
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... the flowing fluid respectively, c denotes the chord length of the airfoil and v is the wind speed. Reynolds number is proportional to the chord length and the wind speed. For the small scale wind turbines, these two factors have very small value and therefore they operate at much lower Reynolds number as compared to the large scale wind turbines. Fig. 1 shows the effect of Reynolds number on the lift and drag coefficients for NACA 0012 airfoil (Musial and Cromack, 1988). It is very interesting to note that the maximum lift coefficient decreases with decrease in Reynolds number while the drag coefficient increases when Reynolds number is reduced. This implies that the lift to drag ...
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... Separation of the flow is generally not desirable because it deteriorates the performance of the device. The attachment and detachment of the flow are not only controlled by the expansion angle but also by the length of the diverging section. Flow may remain attached even at larger expansion angle, if length of the diverging section is smaller. Fig. 10 and 11 show the velocity contours obtained during post- processing of CFD results. Violet region near the wall of the diffuser in some of the contours shows flow separation. All the contours of Fig. 10 Fig. 9. Contours of Fig. 11 show the effect of diverging section length on flow separation. At y 2 ¼12 o , flow separates when L 2 ¼ 1.0 D but ...
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... by the length of the diverging section. Flow may remain attached even at larger expansion angle, if length of the diverging section is smaller. Fig. 10 and 11 show the velocity contours obtained during post- processing of CFD results. Violet region near the wall of the diffuser in some of the contours shows flow separation. All the contours of Fig. 10 Fig. 9. Contours of Fig. 11 show the effect of diverging section length on flow separation. At y 2 ¼12 o , flow separates when L 2 ¼ 1.0 D but it is still attached to the wall of diffuser when L 2 ¼0.5 D. The consequence of this effect is clear in Fig. 9, velocity augmentation factor U=U o decreases when y 2 Z 12 o at L 2 ¼1.0 D but it ...
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... section. Flow may remain attached even at larger expansion angle, if length of the diverging section is smaller. Fig. 10 and 11 show the velocity contours obtained during post- processing of CFD results. Violet region near the wall of the diffuser in some of the contours shows flow separation. All the contours of Fig. 10 Fig. 9. Contours of Fig. 11 show the effect of diverging section length on flow separation. At y 2 ¼12 o , flow separates when L 2 ¼ 1.0 D but it is still attached to the wall of diffuser when L 2 ¼0.5 D. The consequence of this effect is clear in Fig. 9, velocity augmentation factor U=U o decreases when y 2 Z 12 o at L 2 ¼1.0 D but it continues to increase for ...
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... steps. First, a proto- type was constructed using metallic sheet and then this prototype was used as mold to make actual diffuser using fiber reinforced plastics by hand lay-up process. The composite consists of three layers of fibers: one layer of glass fiber sandwiched between two layers of carbon fiber with epoxy resin as the bonding agent. Fig. 12 shows the diffuser mold constructed from metal sheet and the final product made up of carbon and glass fiber reinforced ...
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... tunnel experiment was conducted on diffuser without turbine inside to know the actual velocity augmentation. The details of the experimental set-up and wind tunnel experiment will be discussed in the next section. In this section, we will compare the numerical data on the velocity augmentation factor with the experimental performance. Fig. 13 depicts the velocity augmentation factor at the center of the throat of the diffuser found experimentally and calculated numerically. It can be seen that the velocity augmentation factor U/U o is almost constant with the wind speed. Numerical results are, however, slightly higher than the experimental data. One of the reasons for this ...
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... was PASPORT, Model PS-2174 (PASCO, USA). The output voltage of the wind turbine generator was measured using 'RadioShack Digital Multi-meter'. The resistance box used to study the performance of the wind turbine at various loading conditions was an electro- nically controlled resistance box named 'ohmSOURCE Model OS-260' by IET Labs, Inc. Fig. 14 shows the experimental set-up and schematic diagram of the wind tunnel experimentation. The generator of the wind turbine was connected to the voltmeter which was connected to the resistance box in parallel. At a fixed wind velocity, the load resistance can be varied using the resis- tance box and corresponding output voltage can be ...
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... and then it was allowed to rotate and accelerate freely to its maximum constant speed. The rpm of the turbine blade, while it was accelerating, was recorded at the time interval of 100 ms using the optical tachometer. The curve fitting method was then employed to find the 6th degree polynomial equation which describes the rpm as function of time. Fig. 15 shows the angular speed of the wind turbine at the wind speed of 3.2 m/s. The time derivative of the velocity gives the acceleration which multiplied by the moment of inertia provides the torque. Fig. 16 shows the variation of torque and the angular speed as a function of time at four different wind speeds. Torque is highest when the ...
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... tachometer. The curve fitting method was then employed to find the 6th degree polynomial equation which describes the rpm as function of time. Fig. 15 shows the angular speed of the wind turbine at the wind speed of 3.2 m/s. The time derivative of the velocity gives the acceleration which multiplied by the moment of inertia provides the torque. Fig. 16 shows the variation of torque and the angular speed as a function of time at four different wind speeds. Torque is highest when the wind turbine is stationary and it slowly decreases to zero as the wind turbine speeds up to its maximum rpm. The mechanical power is zero at t ¼0 because rpm is zero. It reaches maximum at time interval ...
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... moves up and leftward as wind speed is increased which implies that not only the magnitude of the maximum mechanical power is higher but also the response of the wind turbine is better. The angular speed at which a wind turbine generates the maximum power is called its optimal rpm. The mechanical power as a function of angular speed is shown in Fig. 17. It is interesting to note that even though the optimal rpm increases with increase in the wind speed but it is always near about 60% of the maxi- mum rpm. The best possible overall output power from a wind turbine cannot be achieved unless and until the rated rpm of the generator is well synchronized with the turbine's optimal ...
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... P is the mechanical power generated by the wind turbine, r is the density of the wind, A is the swept area by the rotor and U 1 is the free wind speed. The coefficient of perfor- mance as a function of the tip speed ratio (shown in Fig. 18) depicts the response of the wind turbine under various operating conditions. It can be observed in Fig. 18 that the coefficient of performance initially increases with the increase in the value of TSR, reaches maxima, and then decreases. This can be explained by noticing that when TSR is small it corresponds to the situation when the ...
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... P is the mechanical power generated by the wind turbine, r is the density of the wind, A is the swept area by the rotor and U 1 is the free wind speed. The coefficient of perfor- mance as a function of the tip speed ratio (shown in Fig. 18) depicts the response of the wind turbine under various operating conditions. It can be observed in Fig. 18 that the coefficient of performance initially increases with the increase in the value of TSR, reaches maxima, and then decreases. This can be explained by noticing that when TSR is small it corresponds to the situation when the wind turbine is rotating very slowly and almost all wind just passes across the blades without much power ...
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... overall performance of a small-scale wind turbine is dependent upon all its components. Fig. 19 shows the rpm of the turbine blades under different loading conditions at six different wind speeds. It can be seen that SWEPT starts at very low wind speed of 2.7 m/s. It runs between 300 rpm and 800 rpm under the normal loading condition. The gear train has gear ratio of 80:10 and it thus allows the generator rotor to run in the ...
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... explained earlier, a diffuser is essentially a wind accelera- tion system which, by virtue of its shape, creates sub-atmospheric pressure near exit and thus induces greater mass flow rate through the turbine. Fig. 13 shows that the optimized diffuser has velocity augmentation factor of about 1.2. Theoretically, power output of a horizontal axis wind turbine is proportional to the cube of upstream wind speed, which entails that the power output of ducted SWEPT should be around 1.7 times higher than the power generated by SWEPT without a diffuser. ...
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... Fig. 13 shows that the optimized diffuser has velocity augmentation factor of about 1.2. Theoretically, power output of a horizontal axis wind turbine is proportional to the cube of upstream wind speed, which entails that the power output of ducted SWEPT should be around 1.7 times higher than the power generated by SWEPT without a diffuser. Fig. 21 shows the power output of the ducted SWEPT at various wind speeds and load resistances. The optimal power output of SWEPT with and without diffuser at various wind speeds has been compared in Fig. 22. It can be noted that the power augmentation factor P/P o is in the range of 1.4-1.6, which is lower than the expected value of 1.7. The ...
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... such as geometric parameters (like rotor diameter, blade twist angle, chord length and number of blades), aerodynamic properties (like lift and drag coefficients) and operating conditions (like wind speed and rpm of the rotor). Abe and Ohya, (2004) determined the value of C t using disk loading method and showed that the acceleration factor U/U o Fig. 19. Angular speed as a function of load resistance. decreases with increase in value of C t . Besides loading, there are some other factors, mainly the aerodynamic losses associated with nacelle drag, hub/tip losses and blockage to flow because of diffuser, which can be the reason for the poorer performance of the ducted SWEPT at higher ...
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The Diffuser Augmented Wind Turbine (DAWT)
is an innovative mean to increase the power harvested by
wind turbine. By encompassing the rotor with a diffusershaped
duct it is possible to increase the flow speed
through the turbine by about 40-50%. The study presents
the development of a numerical model and its validation
by the experiments performed...
Citations
... These turbines are more sensitive to wind direction than VAWTs, hence they are often placed at higher altitudes. Between 50% to 60% efficiency [19] is the sweet spot for these turbines. ...
Wind energy provides a sustainable solution to the ever-increasing demand for energy. Micro-wind turbines offer a promising solution for low-wind speed, decentralized power generation in urban and remote areas. Earlier researchers have explored the design, development, and performance analysis of a micro-wind turbine system tailored for small-scale renewable energy generation. Researchers have investigated various aspects such as aerodynamic considerations, structural integrity, efficiency optimization to ensure reliable and cost-effective operation, blade design, generator selection, and control strategies to enhance the overall performance of the system. The objective of this paper is to provide a comprehensive design and performance review of horizontal and vertical micro-wind turbines. The study begins with an overview of the current landscape of wind energy across the globe and India in particular, highlighting key challenges and opportunities. Numerical and experimental studies were used to validate the designs. Horizontal Axis Wind Turbines (HAWTs) with ducts or shrouds are suitable for microscale and low-speed applications. Researchers investigated the position and location of the turbines to enhance their performance in urban settings. Airflow and airfoil noise produce aerodynamic noise, which is the most significant disadvantage of wind turbines. The findings provide valuable insights for stakeholders interested in advancing micro-wind turbine technology. The highlighted research opportunities may be pursued further to improve the efficiency, reliability, and overall performance of micro-wind turbines.
... The power coefficient measures the amount of mechanical power generated by the wind turbine relative to the total available wind power. Mathematically, it is determined using the following expression [19,20]: ...
The societal and economic reliance on non-renewable energy sources, primarily fossil fuels, has raised concerns about an imminent energy crisis and climate change. The transition towards renewable energy sources faces challenges, notably in understanding turbine shear forces within wind technology. To address this gap, a novel solution emerges in the form of the ducted horizontal-axis helical wind turbine. This innovative design aims to improve airflow dynamics and mitigate adverse forces. Computational fluid dynamics and experimental assessments were employed to evaluate its performance. The results indicate a promising technology, showcasing the turbine’s potential to harness energy from diverse wind sources. The venturi duct aided in the augmentation of the velocity, thereby increasing the maximum energy content of the wind by 179.16%. In addition, 12.16% of the augmented energy was recovered by the turbine. Notably, the integration of a honeycomb structure demonstrated increased revolutions per minute (RPM) by rectifying the flow and reducing the circular wind, suggesting the impact of circular wind components on turbine performance. The absence of the honeycomb structure allows the turbine to encounter more turbulent wind (circular wind), which is the result of the movement of the fan. Strikingly, the downwash velocity of the turbine was observed to be equal to the incoming velocity, suggesting the absence of an axial induction factor and, consequently, no back force on the system. However, limitations persist in the transient modelling and in determining optimal performance across varying wind speeds due to experimental constraints. Despite these challenges, this turbine marks a significant stride in wind technology, highlighting its adaptability and potential for heightened efficiency, particularly at higher speeds. Further refinement and exploration are imperative for broadening the turbine’s application in renewable energy generation. This research emphasizes the turbine’s capacity to adapt to different wind velocities, signaling a promising avenue for more efficient and sustainable energy production.
... Furthermore, by enclosing the turbine within a nozzlediffuser shroud, this enhancement could be further extended to 63% [112]. [113] introduced a portable small-scale wind turbine designed to operate at wind speeds below 5 m/s. This turbine comprises only a nozzle and a diffuser. ...
... Furthermore, by enclosing the turbine within a nozzle-diffuser shroud, this enhancement could be further extended to 63% [112]. Kishore et al. (2013) [113] introduced a portable small-scale wind turbine designed to operate at wind speeds below 5 m/s. This turbine comprises only a nozzle and a diffuser. ...
... Furthermore, by enclosing the turbine within a nozzle-diffuser shroud, this enhancement could be further extended to 63% [112]. Kishore et al. (2013) [113] introduced a portable small-scale wind turbine designed to operate at wind speeds below 5 m/s. This turbine comprises only a nozzle and a diffuser. ...
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... Furthermore, by enclosing the turbine within a nozzle-diffuser shroud, this enhancement can be further extended to 63% [112]. [113] introduced a portable small-scale wind turbine designed to operate below a 5 m/s wind speed. This turbine comprises only a nozzle and diffuser. ...
... Schematic view and CFD streamlines for flow around a flanged diffuser[110].Kishore et al. (2013) ...
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The development of renewable and clean energy has become more crucial to societies due to the increasing energy demand and fast depletion of fossil fuels. A state-of-the-art design for an augmented wind turbine has been introduced in the past years to increase the efficiency of compact horizontal axis wind turbines, exceeding the ideal Betz's limit of the maximum energy captured from the wind. The optimization of the flanged diffuser-so-called diffuser augmented wind turbine DAWT-is investigated numerically using the multi-objective genetic algorithm "MOGA". A 2D computational model is developed using ICEM CFD and solved by ANSYS Fluent. The Turbulence model selected is shear stress transport K-omega, with a pressure-based solver and a coupled algorithm scheme. The optimization objectives are to maximize the velocity ratio at the shroud throat and minimize shroud form dimensions. 517 design points were solved, and the design dimensions were categorized into four types: compact, small, medium, and large design. The results showed that the diffuser dimensions are the main parameters to increase velocity inside the shroud throat, where a long diffuser with a low converging angle drags more air inside the shroud, reaching in some cases more than double the upwind velocity. While the nozzle and flange are also effective in the different design types. It was found that a super long diffuser with a length ratio of 2.9 LD to throat diameter D is optimal with a diverging angle of 7.6˚, accompanied by a nozzle of ratio 1.2 LN/D and 12.6˚ converging angle and a flange length ratio of 0.6 LF/D. This optimal design increased the velocity ratio by almost 2.5 times.
... Unlike European countries where wind speed are considered high, wind energies has emerged in generating electricity [4] and assisting in water pumps [5,6] because of their high efficiency output in comparison to other natural resources. A convenient geographical location where wind shear level and sufficient wind speed are some of the key factors for wind turbines to deliver large amount of power generated. ...
The wind condition in Malaysia is in the low-speed category with an average speed of 1 ms⁻¹ to 4 ms⁻¹. Effect of ground level relies significantly on the wind speed distribution. Despite these conditions, it is less suitable for the development of horizontal wind turbine as an energy source. The obvious weakness is the lack ability to self-start and predict the wind direction thus affects the energy efficiency output. To overcome this problem, improvement of the vertical axis wind turbine design is observed to be the solution in replacing horizontal axis wind turbine. Hence, this study is to investigate a suitable type of vertical axis wind turbine blade design for the best performance RPM output in a low-speed wind environment. The investigation was conducted in a Longwin LW-9300R subsonic wind tunnel at 0 ms⁻¹ to 10 ms⁻¹ wind speed condition from three wind turbine blades specified as Solid Harmony, Scoop Harmony and Conventional Savonius blade with angle of 90º, 135º and 180º to determine the highest RPM productivity. Result shows that Scoop Harmony blade delivers the highest RPM blade output while Savonius 180º is seen to have the highest self-start blade achieved at 64 rpm at 1 ms⁻¹ wind speed. However, Solid Harmony shows an acceptable range TSR of 0.5 with difference of 23% lower than Scoop Harmony. This shows that both Scoop Harmony has a higher performance RPM but Solid Harmony still has the potential design to be applied at low-speed condition due to its low TSR output.
... Part two of the model verifies the reliability of the turbine performance across the entire wind speed range once the blades have been optimized. As mentioned by Kishore et al. [57], a WT power coefficient may drop significantly as wind speed increases, despite operating very efficiently at its design point. ...
div>In recent years, the number of electric vehicles (EVs) has grown rapidly, as well as public interest in them. However, the lack of sufficient range is one of the most common complaints about these vehicles, which is particularly problematic for people with long daily commutes. Thus, this article proposed a solution to this problem by installing micro wind turbines (MWTs) on EVs as a range extender. The turbines will generate electricity by converting the kinetic energy of the air flowing through the MWT into mechanical energy, which can have a reasonable effect on the vehicle aerodynamics. The article uses mathematical modelling and numerical analysis. Regarding the modelling, a detailed EV model in MATLAB/SIMULINK was developed to analyze the EV performance using various driving cycles in real time. In terms of numerical analysis, a detailed computational fluid dynamics (CFD) model has been implemented on a sample EV (Kia Soul) and an MWT using the Moving Reference Frame (MRF) method to act as a virtual wind tunnel in order to investigate the aerodynamic performance. The optimum location for the turbines to be installed has been identified on the front bumper of the car. The MWT has been designed from scratch using Qblade and Xfoil solvers by testing many foil sections and blade parameters to find the best design for the vehicle speed range. After using the designed turbine numerical results and implementing them into the EV model in MATLAB/SIMULINK, the results become more accurate. The vehicle efficiency increased by 13.1% at the Federal Test Procedure (FTP) highway driving cycle with five MWTs installed in the front bumper of the car, and its range increased by 24 km on a full charge; however, three MWTs have been studied in the CFD analysis to investigate the effect of the system on the vehicle drag coefficient, which is considered as the main trade-off of the proposed work. The analytical and numerical errors, points of strength, and weaknesses in each method and model have been determined to verify the entire work.</div
... Model turbin yang diperkenalkan mampu menghasilkan C p yang lebih tinggi berbanding turbin angin jenis lain. (Kishore et al. 2013) membangunkan turbin tenaga mudah alih berskala kecil yang diberi nama SWEPT ( small wind energy portable turbine) dan dilengkapi dengan peresap angin. Mereka mendapati bahawa turbin tersebut mempunyai kelajuan angin cut-in yang rendah, iaitu pada 2.7 m/s serta mampu menghasilkan 0.83W tenaga elektrik pada kelajuan angin terkadar 5 m/s. ...
Wind energy is one of the renewable energy resources that is gaining attention from industry players and researchers. In the last few years, there is an increasing interest in small-scale wind turbines as a power generator in built environments as the urgency to reduce carbon footprint in urban areas increases as well as reducing adverse effects of fossil fuels on human health and the environment. Generally, wind turbines can be categorized into two categories which are horizontal axis wind turbines (HAWTs) and vertical axis wind turbines (VAWTs). VAWTs have good potentials to be developed considering their suitability to be used in complex wind conditions associated with built environments. However, the number of research, publications, as well as basic understanding of flow phenomena associated to the performance of VAWTs such as dynamic stall, flow separation, flow curvature effect and blade-wake interaction are scarce. These flow phenomena are attributed by operational and geometrical parameters that significantly affect the overall performance of VAWTs that includes turbine power generation and aerodynamic characteristics. This paper provides a review and discussion of the effects of various design parameters such as blade profile, blade pitch angle and turbine solidity on the performance of VAWTs and serves as a basic guideline to the designer in designing an ideal VAWT
... With progressive practices, the measurement of data acquisition proved to be very precise. Kishore et al. (2013) developed a portable turbine that was capable of starting at a wind speed of 2.7 m/s. The turbine, which functioned with a low Reynolds' number, exhibited an entirely different lift coefficients. ...
... Including a duct with a converging portion leading to the wind turbine can concentrate the wind flow towards the rotor. They also discovered that, when compared to other arrangements, a cone angle of 15° provided considerable acceleration (Kishore et al. 2013). As a result, a rotating unidirectional INVELOX with a slightly modified structure of patented turbine intake tower (Examiner and Verdier 2010) is designed to ensure a flat and unobstructed flow to avoid the wake on the boundaries with better flow concentration for low-density environments (isolated buildings) as shown in Fig. 1 and high-density environments as shown in Fig. 2. Eight different-shaped parts constitute the modified unidirectional INVELOX. ...
Renewable energy sources are becoming more widely used in the pursuit of a sustainable future. Wind energy is considered one of the most significant renewable energy sources. There have been several attempts to streamline wind turbines such that they blend nicely with the urban environment. Increased velocity in an omnidirectional pattern proved to be unique instrumentation for increasing velocity using mass conservation principles. In the traditional model INVELOX, the velocity reduction is mainly due to turbulence and free air movement in all directions. To overcome these issues, the traditional INVELOX wind turbine is modified with a unidirectional rotating head. Further improvement in velocity, three modifications such as introducing the swirl component in the midsection, twisting the midsection, and introducing a flange at the end of the unidirectional rotating INVELOX were carried out. The numerical investigation of each model is analysed using computational fluid dynamics under Indian environmental conditions. The unidirectional, uniform midsection INVELOX with the flanged diffuser exhibited a better speed ratio of 2.25. Experimental investigations were carried out on the better numerical design of unidirectional INVELOX. The experimental findings from the optimized INVELOX were compared to the numerical results with an estimated maximum error of 4.08%. In this paper, we propose a system that can gather air at higher altitudes while still operating at ground level. The manuscript focuses on the importance of increasing wind speed in urban environments, even in the face of adversity.
