Excerpt from "Wind Water Pumping" AEI Information CD
The pumping of water and boats with sails are the oldest and longest term use of wind power. The two common examples of mechanical water pumping are the Dutch windmill for pumping large volumes of water from a low lift and the farm windmill for pumping small volumes of water from a high lift. The Greeks and Persians used a sail wing type of water pumper with a bucket-ladder type of pump, but these were used mainly in the Mediterranean.
For mechanical windmills or wind turbines the important considerations are the power in the wind and how can that power be transferred by the system. This means that the characteristics of the wind turbine (primarily the rotor) and the characteristics of the pump are combined in an operating system. The efficiency depends on this load matching. In both cases the pump is a positive displacement type pump. The Dutch windmill employed a screw pump and the farm windmill uses a reciprocating pump (piston).
The primary components of the wind-water pumping system are the rotor, drive train (may involve gears), tower and pump. The type of pump in many cases dictates the
mode of operation of the rotor and how the rotational shaft power is transferred to pump power. Of course the size of the system depends on the dynamic pumping head and the quantity of water to be pumped.
Besides the mechanical system, there is a new system for pumping water with wind power, wind-electric. The wind-electric system can pump enough water for villages and/or small scale irrigation. In the wind-electric system, the rotor drives an alternator at variable voltage, variable frequency. This output is directly connected to an electric motor which drives a pump; a centrifugal or turbine pump. The technology and operation of the mechanical and electrical system differ in terms of the rotor and the pump.
1.1 DUTCH WINDMILL
The Dutch windmills for pumping large volumes of water from a low lift (1 m or less) are a famous attraction. Windmills of the same type were also used for grinding grain and even for sawing wood. These machines were as large as 25 m in diameter and were almost all of wood (Fig. 1.2). They were quite sophisticated in terms of the aerodynamics of the rotor and blades. The miller would rotate (yaw) the top of the windmill so the rotor would be perpendicular to the wind. Other types would have a fan to yaw the big rotor. Speed and power were regulated by the amount of sail that was placed on the rotor frame.
Figure 1.1. Dutch windmill, high volume, low lift with screw (Archimedean) pump.
1.2 FARM WINDMILL
The farm windmill was developed in America for pumping water for residences and livestock from deep underground aquifers. The windmill was developed to work with a reciprocating pump with a small diameter that could be place in a small bore hole. Reducing gears convert the rotary motion of the wind wheel to the up and down motion of the pump. Farm windmills are still being manufactured and are still very important for rural areas, primarily in Argentina, Australia, Canada, Africa and the United States.
1.3 OTHER HISTORICAL WATER PUMPING
The wind turbines with sail wings (Fig 1.2) on the island of Crete are an example of water pumping for irrigation. One of the blades has a whistle on it to notify the operator to change the sail area when the winds are too high.
Figure. 1.2. Water pumping windmills with sailwings, Crete.
The windmills of Piura, Peru pump water from shallow wells for small scale irrigation. They are an example of indigenous technology, since all of the parts are wood and fiber, except for the steel drive shaft and the pump made from old tires. The rotor is fixed in direction to catch the sea breezes (Fig. 1.4), which makes for simple construction.
Figure 1.3. Water pumping windmills of Piura, Peru.