Performance and Economic Analysis of Multi-Rotor Wind Turbine

Power production of a wind turbine is dependent upon its rotor size and at present wind turbines with large rotor diameter (>175 m) are available in the market. However major problems associated with such large size conventional turbines are their cost & noise pollution. Due to these reason researchers have diverted their attention towards lower sized equivalent multi-rotor wind turbines. These turbines are found to be cheaper and good performers. Keeping it in view, in this paper an effort has been made to compare the energy yield and economics of two types of wind turbines i.e. single rotor & multi rotor wind turbine. Power, energy and cost models as proposed are used to determine the annual energy yield and economics of multi-rotor turbines. Simulation results as presented in this paper justify the suitability of multi-rotor wind turbine in place of single rotor configuration. Such turbines deliver more energy yield with low installation cost in contrast to single rotor turbines

Power curve and wake analyses of the Vestas multi-rotor demonstrator

Numerical simulations of the Vestas multi-rotor demonstrator (4R-V29) are compared with field measurements of power performance and remote sensing measurements of the wake deficit from a short-range WindScanner lidar system. The simulations predict a gain of 0&thinsp;%–2&thinsp;% in power due to the rotor interaction at below rated wind speeds. The power curve measurements also show that the rotor interaction increases the power performance below the rated wind speed by 1.8&thinsp;%, which can result in a 1.5&thinsp;% increase in the annual energy production. The wake measurements and numerical simulations show four distinct wake deficits in the near wake, which merge into a single-wake structure further downstream. Numerical simulations also show that the wake recovery distance of a simplified 4R-V29 wind turbine is 1.03–1.44&thinsp;Deq shorter than for an equivalent single-rotor wind turbine with a rotor diameter Deq. In addition, the numerical simulations show that the added wake turbulence of the simplified 4R-V29 wind turbine is lower in the far wake compared with the equivalent single-rotor wind turbine. The faster wake recovery and lower far-wake turbulence of such a multi-rotor wind turbine has the potential to reduce the wind turbine spacing within a wind farm while providing the same production output.</p

Low-Cost, Low-Weight Test Rig Design for a Laboratory-Scale Twin Rotor Wind Turbine

Multi-Rotor Wind Turbine (MRWT) has been proven advantageous over Single-Rotor Wind Turbine (SRWT) in many aspects. In order to study the performance of MRWT over SRWT, this work presents a low-cost and low-weight design for a test rig for laboratory-scale wind turbine configurations. The configurations under study are a single-rotor, and a twin-rotor of the same size with a diameter of 30 cm. Aerodynamic loads have been calculated using the Blade Element Momentum (BEM) method, then the loads were used for stress analysis over the test rig proposed. The test rig is designed on Solidworks and the aerodynamic and inertial loads were applied for static structural analysis. The analysis showed that both configurations are safe against failure and the deflections were reasonable to ensure low vibrations which may affect the turbine performance. The single-rotor configuration test-rig is about 16 gm in mass, with a 1.67 factor of safety, while the twin-rotor configuration weighs 360 gm with a factor of safety of 3.7

Simulation study on the performance of a counter-rotating savonius vertical axis wind turbine

Wind power is an energy source that is becoming an alternative to burning fossil fuels that may harm the environment during operations due to the emission of harmful gases. In this study, simulation and performance investigations of a counter-rotating vertical axis wind turbine (VAWT) based on the Savonius S-type rotor have been analysed through a computational simulation approach. The foremost motive of this study is to widen the operating wind speed range of the counter-rotating concept in a VAWT while enhancing the conversion efficiency of a single-rotor VAWT system. The 3D simulations were performed based on the K-omega shear stress transport (SST) turbulence model. The results have shown that the counter-rotating model possesses better performance characteristics in terms of torque, power and their corresponding coefficients compared to a single-rotor design of a wind turbine. A maximum output of more than two times was obtained from the new CRWT system compared to that of a single-rotor wind turbine (SRWT). Moreover, the output of the top rotor was higher than the bottom rotor due to the increased higher rotational speed of the top rotor

Numerical Investigation of Aerodynamic Performance and Loads of a Novel Dual Rotor Wind Turbine

The objective of this paper is to numerically investigate the effects of the atmospheric boundary layer on the aerodynamic performance and loads of a novel dual-rotor wind turbine (DRWT). Large eddy simulations are carried out with the turbines operating in the atmospheric boundary layer (ABL) and in a uniform inflow. Two stability conditions corresponding to neutral and slightly stable atmospheres are investigated. The turbines are modeled using the actuator line method where the rotor blades are modeled as body forces. Comparisons are drawn between the DRWT and a comparable conventional single-rotor wind turbine (SRWT) to assess changes in aerodynamic efficiency and loads, as well as wake mixing and momentum and kinetic energy entrainment into the turbine wake layer. The results show that the DRWT improves isolated turbine aerodynamic performance by about 5%–6%. The DRWT also enhances turbulent axial momentum entrainment by about 3.3 role= presentation style= box-sizing: inherit; display: inline; line-height: normal; text-align: left; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; \u3e3.3 %. The highest entrainment is observed in the neutral stability case when the turbulence in the ABL is moderately high. Aerodynamic loads for the DRWT, measured as out-of-plane blade root bending moment, are marginally reduced. Spectral analyses of ABL cases show peaks in unsteady loads at the rotor passing frequency and its harmonics for both rotors of the DRWT

Development and Performance Investigation of a Unique Dual-rotor Savonius-type Counter-rotating Wind Turbine

Wind power is sustainable and prevalent virtually all over the globe. However, the conversion efficiency of the conventional single-rotor wind turbine (SRWT) is still far from satisfactory. The dual-rotor counter-rotating concept is among the reliable techniques used to enhance the efficiency of a wind energy conversion device for its renowned effectiveness. This study aims to investigate the performance of a Savonius dual/twin-rotor system, particularly in low-speed wind conditions while employing the counter-rotating technique. The evaluation of this technique is presented in terms of aerodynamic characteristics, including the power and torque coefficients. The results have shown that the new concept was able to improve the performance of the system extensively and was capable of operating in a lower wind speed condition. Compared to a single-rotor system, an additional 42% more torque was possible owing to the existence of a second rotor in the new system. The results have also revealed that the conversion efficiency of the system has been enhanced substantially. A corresponding average power coefficient of up to 28% was achieved. The present technique is thought to be promising for wind energy conversion systems, including sites with poor wind conditions

Experimental and numerical investigations on the flow characteristics of rotary machineries

The research work described in this thesis includes two topics: 1). An experimental and computational study on the aerodynamic and acoustic characteristics of case fans for computer cooling applications; and 2). A comparative study on the aeromechanic performances and wake characteristics of innovative dual-rotor wind turbines (DRWTs) and conventional single-rotor wind turbine (SRWT). For the first topic, by using a commercially-available cooling fan as the baseline, a number of acoustically tailored modifications were implemented in order to reduce the noise level of the cooling fan, which includes optimizing the rotating blades and guide vanes according to axial fan design theory, adding an intake cone in the front of the hub to guide the airflow into the axial fan smoothly, and reducing the tip clearance to lower the noise generation due to tip vortex structures. In order to assess the effects of the modifications on the fan noise reduction, a comparison study was conducted to measure the sound pressure level (SPL) and the sound spectra of the newly designed axial fan in an anechoic chamber, in comparison to that of the baseline fan. The measurement results of our preliminary study revealed that, at the same flow rate, the SPL of the newly designed fan would be up to 5 dB lower than that of the baseline fan. The spectra results demonstrated that the sound power energies in both of peak frequency and broadband frequency for the baseline fan were higher than that of the newly designed fan regardless of flow rate. In addition, a digital particle image velocimetry (PIV) system and numerical simulation were also used to conduct detailed flow field measurements to reveal the inner and outer flow characteristics and unsteady vortex structures associated with the modifications. For the second topic, a comprehensive study was conducted to investigate the aerodynamics and wake characteristics of innovative dual-rotor wind turbines (DRWTs) consisting of twin-rotor, co-, and counter-rotating configurations, in comparison to a conventional single-rotor wind turbine (SRWT). In addition to measuring the dynamic wind loads acting on the SRWT and DRWT models, a Cobra Probe Anemometry, a conventional 2D and a stereoscopic Particle Image Velocimetry (PIV) system were used to attain the detailed flow field measurements to quantify the flow characteristics in the turbine wakes and to quantitatively visualize the time evolution of the unsteady vortex structures in the wake flows. Furthermore, the power outputs of a duplicate model turbine operating in the wakes behind the DRWT and SRWT models at different downstream locations were also measured and compared quantitatively. The detailed flow field measurements were correlated with the dynamic wind loads and power output measurements to elucidate the underlying physics to explore/optimize design paradigms for higher total power generation and better durability of the wind turbines