A Review of Solidity and Rotor Size Effects on Water-Pumping Windmills

The windmill is one of the important applications of wind energy and it is one of the best and the easiest ways to manipulate this wind power and use it for water pumping. The best feature of windmills is their high solidity, which gives high torque at the starting. Therefore, they will be able to lunch at low wind speeds like 2 m/s which gives a great possibility of utilizing, especially in the agricultural countries. This feature has been the focus of attention of researchers and developers over the long years. There are several factors affected by it, the most prominent of which is the number of blades and the diameter of the rotor. Some researchers have tested with different models of different diameters and others did on different numbers of blades. The challenge is how to find a model with an ideal number of blades and diameter that can give us the highest torque value under low wind conditions. In this paper, the multi-bladed horizontal axis wind turbines, which are used for water pumping, are discussed. Besides, the literature review is described, which presented the basic design requirements for windmill rotors as solidity, diameter, and tip speed ratio, also information given about materials that used in manufacture. The investigations of this paper are focused on the effect of the number of blades to reach the main goal and the best performance at located wind speeds.