Ramesh K Agarwal
Wind has been used as a source of power by human society centuries before the dawn of commercial revolution. Since the start of the economic age, the fossil fuels have dominated as a source of energy. Only in last couple of decade or so, because of concerns about global warming, there has been increased emphasis on using wind as a source of clean, renewable and sustainable energy source. This talk will describe the potential of wind as a crucial source of energy since it's available round the globe at sufficient velocities to get significant amount of power. It is well established that the facility generated by a Horizontal-Axis turbine (HAWT) may be a function of the amount of blades B, the tip speed ratio λ (blade tip speed/ wind free stream velocity) and therefore the lift to tug ratio (CL/CD) of the airfoil sections of the blade. The airfoil sections utilized in HAWT are generally thick airfoils like the S, DU, FX, Flat-back and NACA 6-series of airfoils. These airfoils vary in (CL / CD) for a given B and λ, and thus the facility generated by HAWT for various blade airfoil sections will vary. This lecture will show the effect of different airfoil sections on HAWT performance using the Blade Element Momentum (BEM) theory. The relatively thick airfoils DU 91-W2-250, FX 66-S196-V1, NACA 64421, and Flat-back series of airfoils (FB-3500-0050, FB3500-0875, and FB-3500-1750), both original and optimized, are considered and their performance is compared with S809 airfoil used in NREL Phase II and III wind turbines; the lift and drag coefficient data for these airfoils sections are available. The output power of the turbine is calculated using these airfoil section blades for a given B and λ and is compared with the first NREL phase II clinical trial and Phase III
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