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Wind Energy
Published in Frank R. Spellman, The Science of Wind Power, 2022
Efficiency is a function of how fast the rotor turns. The tip-speed ratio (TSR) is an extremely important factor in wind turbine design. Tip-speed ratio is the ratio of the speed of the rotating blade tip to the speed of the free-stream wind (see Figure 5.4). Stated differently, TSR is the speed of the outer tip of the blade divided by wind speed. There is an optimum angle of attack which creates the highest lift to drag ratio. If the rotor of the wind turbine spins too slowly, most of the wind will pass straight through the gap between the blades, therefore, giving it no power! But if the rotor spins too fast, the blades will blur and act like a solid wall to the wind. Moreover, rotor blades create turbulence as they spin through the air. If the next blade arrives too quickly, it will hit that turbulent air. Thus, it is actually better to slow down the blades. Because the angle of attack is dependent on wind speed, there is an optimum tip-speed ratio. TSR=ΩR/V
Force-System Resultants and Equilibrium
Published in Richard C. Dorf, The Engineering Handbook, 2018
Figure 7.72 and Equation (72.10) and Equation (72.11) illustrate several important points. First, increasing the shaft speed, Ω, will significantly increase the force up to the point where the inflow angle, ϕ, becomes so small that the term CLsinϕ-CDcosϕ in Equation (72.10) starts to decline faster than the (Ωr)2 term is increasing. This generally limits optimal rotor blade tip speeds to less than ten times the freestream wind speed, while most modern wind turbine rotor blades are optimized for a Tip Speed Ratio, X=ΩR/V, of between five and eight. Second, for relatively high tip speed ratios, mid-span and outboard regions of the blade will experience significantly higher out-of-plane forces than in-plane loading.
Wind Turbine Control
Published in Thomas Corke, Robert Nelson, Wind Energy Design, 2018
Standard control of wind turbines have focused on changing the pitch of the rotor and control of the rotor rpm in order to maintain an optimum tip speed ratio. The standard practice for rotor pitch control is to have a fixed pitch angle for Region II wind speeds (Vcut-in ≤ V∞ ≤ Vrated), then to change the pitch to maintain a constant rated power for Region III wind speeds (Vrated ≤ V∞ ≤ Vcut-out). The fixed pitch in Region II wind speeds is intended to maximize the average efficiency over the wind speeds from cut‐in to rated. However, as will be apparent, for a rigid rotor with fixed twist and constant pitch, the optimum (Betz) efficiency is only approached at best at a single wind speed. As a result, present generation wind turbines generally fall well short of optimum performance.
Enhanced radial fuzzy wavelet neural network with sliding mode control for a switched reluctance wind turbine distributed generation system
Published in Engineering Optimization, 2019
Chih-Ming Hong, Chiung-Hsing Chen
By using (5), the typical versus curve is shown in Figure 2. In a wind turbine, there is an optimum value of tip speed ratio that leads to maximum power coefficient .
Effect of solidity and airfoil on the performance of vertical axis wind turbine under fluctuating wind conditions
Published in International Journal of Green Energy, 2019
Bhargav Mantravadi, Unnikrishnan D., Karthik Sriram, Akram Mohammad, Laxman Vaitla, Ratna Kishore Velamati
Tip speed ratio (TSR) is the ratio of the tangential speed of the blade to the free stream velocity of the wind . Mean tip speed ratio is given by Equation (11), where is the mean speed of the fluctuating wind.