## 1 Introduction
For example, [PERSON] [27] investigated the self-starting capability of an H-Darrieus rotor with S1046 profile blades using CFD, varying the rotor solidity and combining it with a Savonius rotor in a hybrid design. It was found that with a solidity greater than 0.25, the two-bladed Darrieus rotor is capable of self-starting. However, the maximum power coefficient slightly decreased with an increase in solidity from 0.1 to 0.25. There is still a lack of quantitative data on self-starting, torque, and power coefficient with increased rotor solidity to gain a full understanding of the performance of high-solidity asymmetrical-blade H-Darrieus rotors at low wind speeds. Therefore, this paper aims to study the effect of rotor solidity (from 0.8 to 1.2) on the performance and self-starting of a three-bladed H-Darrieus rotor with S1210 profile blades under various low wind speed conditions. The main goal of this study is to determine a design with better self-starting characteristics, dynamic torque, and optimal power coefficient compared to existing solutions. The work in [28] focuses on the aerodynamic performance of vertical-axis wind turbines (VAWTs) using NACA 4415 and NACA 0021 blade profiles. The study varied flow parameters such as velocity and angle of attack. Experimental results showed that NACA 4415 exhibited a higher maximum lift coefficient than NACA 0021, with stall occurring at an angle of attack of 16\({}^{\circ}\) for NACA 4415 and 18\({}^{\circ}\) for NACA 0021. Reference [29] experimentally investigates the effect of blade pitch angle (\(\beta\)) on improving the performance (self-starting and dynamic characteristics) of an asymmetrical H-Darrieus rotor with NACA 63,415 blade profiles under low wind speed conditions (5.0 and 6.0 m/s). It was found that changing the blade pitch angle from negative to positive values enhanced rotor performance. Reference [30] investigates the performance of a three-bladed H-Darrieus rotor with asymmetrical S1210 blades at various rotor solidity values (ranging from 0.8 to 1.2) and wind speeds. The focus is on self-starting characteristics, static and dynamic torque, and power coefficient (Cp) under low wind speed conditions. The study showed that high rotor solidity improves overall performance. The optimal rotor solidity for maximum Cp was found to be 1.0, with a maximum Cp of 0.32 achieved at a wind speed of 5.7 m/s. A comparison with H-Darrieus rotors with symmetrical and asymmetrical blades is also presented, demonstrating that the investigated rotor is suitable for small-scale applications such as water pumping or grinding that require high torque, despite a reduced operating range. Reference [31] presents research on the influence of blade profiles on the starting characteristics and overall efficiency of an H-Darrieus rotor under low wind speed conditions (4, 6, and 8 m/s). The focus is on comparing three blade types: two asymmetrical (S815 and EN0005) and one symmetrical (NACA 0018). Experimental investigations were conducted on a three-bladed H-Darrieus rotor using a centrifugal fan. The effects of flow non-uniformity and turbulence intensity were also considered. Results showed that the rotor with S815 asymmetrical blades exhibited higher dynamic torque and power coefficient (Cp) compared to rotors with EN0005 and NACA 0018 blades, making it more efficient for low wind speed applications. Another important factor for self-starting is the number of rotor blades. Optimizing the number of blades will result in good starting characteristics and high performance.