Preliminary study on the matching characteristics between wind wheel and pump in a wind-powered water pumping system

Abstract

In a wind-powered water pumping system, the water pump is driven directly by a wind wheel without any control system, other than a gear box. Thus, there exists a dynamic balance between the torque provided by the wind wheel and that accessed by the water pump. That is, the torque produced by the wind wheel will often be larger or smaller than that required by the pump. If so, the system will accelerate or decelerate, thus increasing or decreasing the torque provided by the wind wheel, which will then result in an increase or a decrease in that accessed by the pump until equilibrium is re-established. In addition, the amount of water that can be pumped corresponds directly to the effective power of the wind wheel, whereas the output torque and actual power from the wind wheel depend only on its rotation rate, which is a function of the wind speed. Hence, once a good match is obtained between the torque and the power provided by the wind wheel and those required by the pump, the entire system can operate most efficiently, maximizing the amount of water lifted by the pump. On the other hand, unlike steam or gas turbines, whose performance characteristics under different operating conditions have long been a popular subject for research, there are as yet very few studies of the characteristics of wind wheels under varying wind conditions, even though the wind changes continuously in speed and direction. Therefore, the primary purpose of this paper is to provide a preliminary investigation of wind wheel performance under time-varying wind conditions, while also studying the matching characteristics between a wind wheel and a water pump. The present paper is thus intended to help design and select a pump optimized for a wind-powered water pumping system, which could operate efficiently over a wide range of wind speeds.