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Wind Turbines
Published in V. Dakshina Murty, Turbomachinery, 2018
As described earlier, VAWT are wind turbines that generate power from rotors that are vertical. In such machines, since the torque-generating surfaces move in the wind direction, the blade speeds are always less than wind speed. Consequently, the speeds of VAWT are lower than those of the horizontal axis-type turbines. Also, during part of the revolution, the motion of the blades is against the wind which results in lower power output. This can be corrected partially by the use of a blanking arc. All these features make VAWT suitable for lower-power applications when compared with the horizontal type of turbines.
Generator Driver Applications and Selection
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
The prime mover in a modern WECS is the wind turbine. Electricity is produced as the wind imparts a force that turns the rotor blades, which spins a shaft that drives an electric generator. Turbines are classified as either horizontal-axis wind turbines (HAWTs) or vertical-axis wind turbines (VAWTs). The design of HAWTs, which dominate the WECS electric generation market, is similar to historic windmills, with a propeller type rotor on the axis. The axis of rotation is horizontal and roughly parallel to the wind stream. The blades on the horizontal drive shaft may be facing into the wind (an upwind turbine) or the wind may hit the supporting tower first (a downwind turbine). A yaw drive is used with upwind turbines to keep the rotor facing into the wind as the wind direction changes. Downwind turbines do not require a yaw drive, since the wind blows the rotor downwind. More modern two- and three-blade HAWTs run at high tip speed ratios that allow them to achieve very high electric power conversion ratios. These turbines generally operate with a constant blade pitch (or orientation) angle, but can be designed so that the blade pitch is continuously controlled to maintain constant speed and target power output.VAWTs, which are far less common for modern electric generation applications, feature an axis of rotation that is vertical to the ground and roughly perpendicular to the wind stream. They are similar to traditional waterwheels, with the fluid arriving at a right angle to the rotation axis. While less efficient than HAWTs, they feature a simple, durable design and have the advantage of having all of the drive train and generator components at ground level.
Renewables—The Future’s (only) Hope!
Published in Anco S. Blazev, Energy Security for The 21st Century, 2021
Vertical-axis wind turbines (or VAWTs) are different from the horizontal turbines in that the main rotor shaft is positioned vertically. The advantage here is that the turbine is fix-mounted and does not need to be reoriented into the wind to be effective. This is particularly advantageous on sites where wind direction is highly variable.
Performance investigation of cavity shaped blade on H-Darrieus wind turbine in built environmental condition
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Anal Ranjan Sengupta, Yogesh Kumar, Agnimitra Biswas, Rajat Gupta
Vertical axis wind turbines (VAWTs) demonstrate several vital advantages over horizontal axis wind turbines, like cost effectiveness, simpler design, less noisy, omni-directionality, lower maintenance requirements, etc. For these advantages, deployment of H-Darrieus VAWT is comparatively easier in case of the built environmental condition to extract sustainable wind energy. But H-Darrieus rotor’s self-starting ability and power coefficient is poor in the built environment having lesser wind velocities. To address these issues, several researches have been done to increase its static and dynamic performances in low wind speed condition by various ways for e.g., by increasing the blade numbers, modification of blade shape, implementing some augmenting devices, optimizing the turbine solidity and aspect ratio, improving the blade pitch angle etc.
Electricity generation from the high-speed wind of the spillway in a hydroelectric power station
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Electricity can be generated by wind turbines when wind strikes the blade at the specific angle known as the angle of attack. Main parts of a wind turbine are blades, hub, shaft, gearbox, pitch angle control, yaw angle control, rotor, and generator (Mahadanaarachchi and Ramakuma 2008). Electrical power generated mainly depends on wind speed and height of the installed system above ground surface (Billinton and Bai 2004) (Alkuhayli, Raghavan, and Chowdhury 2012) (Liang, Su, and Liu 2010) (Wan, Ela, and Orwig 2010). Wind turbines are of different types i.e. horizontal axis wind turbines (HAWT) and vertical axis wind turbines (VAWT). In horizontal axis wind turbine, the axis of the hub is in the horizontal direction. Whereas, in vertical axis wind turbine the axis of the hub is in vertical direction. Each type of wind turbine has its own application and benefits, but mostly horizontal axis wind turbines are used because of higher efficiency, ease of operation and maximum energy extraction from wind (Xie et al. 2017) (Wang, Liu, and Kolios 2016) (Hand and Cashman 2018).
The development and utilization of microgrid technologies in China
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2019
Horizontal Axis Wind Turbine (HAWT) is widely used in onshore and offshore wind farm. But in urban area, the utilization of HAWT is limited by the disadvantage of high center of gravity which makes it hard to be moored, and large space is also needed for the wind turbine to yaw with the change of wind direction. Vertical Axis Wind Turbines (VAWTs) are of interest as a potential wind turbine to be installed on top of the building in urban area, because a relatively low center of gravity can be designed, and load-reducing alternative anchoring topologies can be used. Furthermore, it can maintain rotating in the same direction without complex yaw control system to collected wind energy when the wind direction changes. These advantages make it suitable for urban area where the space is limited and the wind flow turbulent intensity is higher than that of rural and offshore area.