Owing to the fast development in the energy field, the demands are increasing to improve energy efficiency and lifetime of wind turbine. The wind blades are considered as the most important and expensive part in the wind system. Therefore, it's important to understand deeply the behaviour of turbine blades. In this research paper, full details were presented to analyze and optimize the behaviour and performance of the blade of the small horizontal axis wind turbine (less than 1 KW). QBlade software was used to simulate the wind turbine blade during the working conditions. The mathematical formulations which used in QBlade software were based on the Blade Element Momentum method (BEM). It was studied deeply the effect of design parameters (Twist Angle and Chord length) on the behaviour and performance of the wind turbine. It was used SG6043 airfoil for 10 different sections of 1.17 m blade length. The obtained results were of high accuracy, and it was proved that the QBlade software is reliable to analyze the blades of wind turbine. The paper exhibits the necessary steps to build and optimize the blade of wind turbine, in addition to the features and advantages of the software.

Wind energy is considered one of the most important sources of renewable energy in the world, because it contributes to reducing the negative effects on the environment. The most important types of wind turbines are horizontal and vertical axis wind turbines. This work presents the full details of design for vertical axis wind turbine (VAWT) and how to find the optimal values of necessary factors. Additionally, the results shed light on the efficiency and performance of the VAWT under different working conditions. It was taken into consideration the variety of surrounding environmental conditions (such as density and viscosity of fluid, number of elements of the blade, etc.) to simulate the working of vertical wind turbines under different working conditions. Furthermore, the effect of the design factors was investigated such as the number and size of the blades on the behavior and performance of VAWT. It was assumed that the vertical wind blade works in different sites of Iraq. QBlade software (Version 8) was used to achieve the calculations and optimization processes to obtain the optimal design of vertical axis wind turbines that is suitable for the promising sites. The results proved that accurate results can be obtained by using QBlade software.

Artificial roughness applied to a Solar Air Heater (SAH) absorber plate is a popular technique for increasing its total thermal efficiency (${\eta }_{t-th}$). In this paper, the influence of geometrical parameters of V-down ribs attached below the corrugated absorbing plate of a SAH on the ${\eta }_{t-th}$ was examined. The impacts of key roughness parameters, including relative pitch $p/e$ (6–12), relative height $e/D$ (0.019–0.043), angles of attack $\alpha$ (30–75°), and Re (1000–20,000), were examined under real weather conditions. The SAH ${\eta }_{t-th}$ roughened by V-down ribs was predicted using an in-house developed conjugate heat-transfer numerical model. The maximum SAH ${\eta }_{t-th}$ was shown to be 78.8% as predicted under the steady-state conditions of Re = 20,000, solar irradiance G = 1000 W/m², p/e = 8, e/D = 0.043, and α = 60. The result was 15.7% greater efficiency compared to the default smooth surface. Under real weather conditions, the ${\eta }_{t-th}$ of the roughened SAH with single- and double-glass covers were 17.7 and 20.1%, respectively, which were higher than those of the smooth SAH.