Editing Windpump (section)

===Poor load matching===

A multi-bladed windmill is a mechanical device with a piston pump. Because a piston pump has a fixed stroke, the energy demand of this type of pump is proportional to pump speed only. On the other hand, the energy supply of a wind rotor is proportional to the cube of wind speed. Because of that, a wind rotor runs at over speed (more speed than needed), yielding a loss of aerodynamic efficiency.

A variable stroke would match the rotor speed according to wind speed, functioning like a "variable-speed generator". The flow rate of variable stroke windpump can be increased two times, compared to fixed stroke windpumps at the same wind speed.<ref name="ena.com.tr">[https://web.archive.org/web/20161223052210/http://www.ena.com.tr/Wind90.pdf Clark, Nolan "Variable Stroke Pumping for Mechanical Windmills", 1990, AWEA Proceedings]</ref>