**1. Introduction**

Wind turbines have been around for more than a century now. Moreover, the idea of harvesting energy from wind has existed for even longer. Charles F. Brush invented the first automatic wind turbine for power generation in 1887. That does not mean that the technology has stagnated or remained unchanged. Since then, many scientists have improved the early designs, typically made out of wood and later aluminum. These days, the materials used are as exotic as the design, involving manufacturing processes, such as resin-transfer molding to create fiber-reinforced composites [1]. Even the designs themselves have changed radically. We have vertical axis wind turbines (VAWT) and horizontal axis wind turbine (HAWT) [1, 2]. Both have pros and cons, but for this chapter, HAWT will be the main focus owing to their relative popularity, high efficiency, and simplicity. **Figure 1** shows HAWT and VAWT for comparison.

Renewable energy is projected to hit 31% of all energy generation by 2035 across the world. Out of this, a quarter will be from wind power alone [3] with a high projected growth rate. However, the wind turbine blade is one complex piece of engineering that requires its own attention. It is a significant portion of the entire cost of the machine. The blades are indeed immense and have subtle curves. The fundamental aim of this chapter will be to see how these curves affect the wind turbine blade performance. The theory of the blades will be explained first, followed by design

**Figure 1.**

*HAWT and VAWT side by side (image from iStock/purchased for use).*

in CAD. Then the blade performance will be estimated roughly using the blade element and momentum (BEM) theory. Then, extensive simulations will be performed in ANSYS Fluent to determine the exact characteristics. The same will be verified and validated by our earlier estimates obtained by BEM theory.

The chapter has been designed concisely and easy to follow, so that it will be comprehensible for newcomers yet contain essential data for the experts. It is divided as follows: Firstly, we will look at BEM and perform the initial estimation of blade characteristics. The exact "curves" of the blades will be determined using simple equations solved in MATLAB. We will use NREL-S Series Airfoils (the "curves"), namely, S815, S825, and S826 for root, primary & tip portions, respectively. The geometry will require specific parameters of the airfoils. Here, QBlade and XFoils will prove particularly handy for determining these parameters and assist in blade design. This step will be followed by CFD logic and ANSYS Fluent working methods. Particular attention will be given to Navier-Stokes Equation in rotational domain and how it differs from the common coordinate form. After this, the CAD modeling will be touched on briefly as it is highly software dependent. After that, the Fluent simulations will be performed, and the various performance parameters will be noted. Finally, the results obtained will be compared with the estimates produced earlier.
