## 1 Introduction
According to the recent literature on self-starting ability of the H-Darrieus wind turbine, [PERSON] et al. [16] and  
Figure 1: Wind profile in the internal boundary layer in a built environment [6]. [PERSON] et al. [17] demonstrated that it is possible to have a self-start three-bladed H-rotor VAWT using a fixed geometry and symmetrical airfoils. This study was confirmed by [PERSON] et al. [18] and by using a numerical code they evaluated the transient behavior of H-Darrieus turbines under generic wind conditions in terms of velocity and direction. They also investigated the influence of the airfoil type and the blade shape on the startup capabilities of the rotor as a function of the initial position of the rotor and the oncoming wind velocity. [PERSON] [19] reported that the self-starting torque and low speed torque problem of VAWTs can be overcome either by passive variable pitch or by a combination of suitable blade airfoil sections. [PERSON] et al. [16] asserted that a lightly loaded, three-bladed rotor always has the potential to self-start under steady wind condition. Similar studies on the self-starting ability of VAWTs are reported in [20; 21; 22]. The VAWT operates with any horizontal wind direction (Figure 2). The VAWT is further sub-divided into two distinct types, i.e., the lift type (often refer to as Darrieus turbines) in Figure 2a which uses the lift force acting on the blades to rotate the rotor and generate power [11], and the drag type (Savonius rotor) in Figure 2b which consists of cup-shaped half, hollow cylinders fixed to a central rotating shaft, and the torque is generated due to the drag force acting on the half cylinders [23]. Wind turbine performance is commonly characterized by the relationship of the coefficient of power (\(C_{\text{p}}\)) and the tip speed ratio (TSR). The \(C_{\text{p}}\) of a wind turbine is defined as the ratio of the actual power extracted by the rotor to the theoretical power available. The \(C_{\text{p}}\) represents the efficiency of a wind turbine. It describes how much power can be extracted from the wind by a wind turbine. It varies from one wind turbine to another. According to the Betz limit, the theoretical \(C_{\text{p}}\) value of a wind turbine is 59.3%. The \(C_{\text{p}}\), of the CAWT is calculated using Equation (2). \[C_{p}\ =\ \frac{P}{0.5.\rho.A.U_{\infty}^{3}} \tag{2}\]  
where \(P\) is the power generated by the turbine (W); \(\rho\) is the density (1.23 kg/m\({}^{3}\)); \(A\) is the swept area of the rotor (m\({}^{2}\)); and \(U_{\infty}\) is the free stream wind speed (m/s). The \(C_{p}\) varies with the TSR, (\(\lambda\)). The \(C_{\text{p}}\) values increases with increase in \(\lambda\). The \(C_{\text{p}}\) reaches its maximum at a certain \(\lambda\) and then decreases with increase in \(\lambda\). The TSR (\(\lambda\)) is the ratio of the mean blade tip speed to the wind velocity. The TSR is calculated using Equation (3). \[\text{TSR}=\lambda=\frac{\Omega}{U_{\infty}}=\frac{\omega r}{U_{\infty}} \tag{3}\]  
where \(r\) is the radius of the rotor (m); \(\omega=2\pi f\) is the angular velocity (rad/s); and \(f\) is the rotational frequency (H\({}_{\text{z}}\)). Figure 2: Two distinct types of VAWT operating under any horizontal wind direction [24]. (**a**) Darrieus rotors; (**b**) Savonius rotor.