Wind Power Generation - Renewable Energy: Technology, Economics and Environment - page 336

To convert wind power into hydraulic energy, hydraulic capacity is of particu-
lar importance. It is the product of water density, local gravity, water flow and de-
livery head. Hence, a large volume flow at low flow height or a low volume flow
at high flow height can be obtained. Whereas the former usually applies to irriga-
tion and drainage, the latter is true for potable water supply.
For the described systems predominantly piston pumps as well as single or
multi-stage centrifugal pumps are used. However, also diaphragm pumps, eccen-
tric worm pumps and chain pumps may be applied.
For system dimensioning, the ideal combination of pump and turbine results
indispensable. For this purpose torque characteristics of wind turbine and pump
need to be compared. By adapting the respective pump and turbine design on the
one hand, the operating speed of the wind turbine and the pump may be adapted
by appropriate transmission reduction. On the other hand, adequate torque adapta-
tion ensures a favourable start of the wind pump.
In order to understand wind pump operation, the respective characteristic flow
curve of the wind pump system and the interdependence of wind speed and vol-
ume flow are important. Fig. 7.24 illustrates the characteristic flow curve for
combinations with piston and centrifugal pumps. Extraction only starts at a certain
minimum wind speed. With the piston pump volume flow increases rapidly upon
slight wind speed alternations, whereas, at a higher level, volume flow is only
slightly increased by enhanced wind speed. For the centrifugal pump, by contrast,
the characteristic curve is almost linear over a large part of the wind speed curve.
While wind pumps have been applied for irrigation and drainage in Europe in
the past centuries, they are currently predominantly used in developing and newly
industrialised countries.

Piston pump Piston pump Centrifugal pump Centrifugal pump

Kreiselpumpe Kreiselpumpe Kreiselpumpe Kreiselpumpe

Kolbenpumpe Kolbenpumpe Kolbenpumpe Kolbenpumpe

Minimum
wind speed

Minimum
wind speed

Wind speed Wind speed Minimum

wind speed

Minimum
wind speed

Wind speed Wind speed

Mindestwindgeschw. Mindestwindgeschw. Mindestwindgeschw. Mindestwindgeschw.

Windgeschwindigkeit Windgeschwindigkeit Windgeschwindigkeit Windgeschwindigkeit

Mindestwindgeschw. Mindestwindgeschw. Mindestwindgeschw. Mindestwindgeschw. Windgeschwindigkeit Windgeschwindigkeit Windgeschwindigkeit Windgeschwindigkeit

Fig. 7.24 Characteristic curves of wind pump systems based on a piston pump and a cen-
trifugal pump

Wind-diesel systems. Wind-diesel systems are used for very small systems of ca-
pacities below 100 kW and even for isolated grids designed for cities or whole
islands and reach maximum capacities of 10 MW. The major problem encountered