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Figure 11.10. The vane pump works by using vanes that slide outward by centrifugal force to form
sealed ‘capsules’ of fluid between adjacent vanes and the casing (Used with permission of the
McGraw-Hill Companies, Platt, R.A. & Little, C.W.J. (2001), ‘Vane, gear and lobe pumps’, , in
Karassik, I.J., Messina, J.P., Cooper, P. & Heald, C.C., Pump Handbook, McGraw-Hill, pp. 3.123–
3.154).
Figure 11.11. Performance curves of a typical rotary positive displacement pump
(Used with permission of Halcrow & Partners, 1981).
11.4 MOTORS
11.4.1 Introduction
Small motors (< 2 kW) of high efficiency that are well suited to photovoltaic water
pumping are still relatively rare. Fig. 11.12 shows the typical fall off in performance
as motor size decreases, which compounds the problem of reduced pump efficiency at
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