Hydroelectric Power Generation - Renewable Energy: Technology, Economics and Environment - page 366

Inflow of water

Runner

Tailwater

Fig. 8.13 Operation principle of a cross-flow turbine (see /8-6/)

Water wheels. As turbines are the most expensive parts of a small hydroelectric
power station, water wheels can still be used if discharges are very small. They
are suitable for heads of a maximum of 10 m; for lower heads there are hardly any
technical limits. Discharges up to approximately 2 m 3 /s can be used with a single
conventional wheel. Water wheels can reach efficiencies of 70 or 80 %. Under-
shot, middle-shot and overshot water wheels are used - according to the available
head (Fig. 8.14).

Headwater Headwater

h h

h h h

Tailwater Tailwater

h h

h h h

Fig. 8.14 Types of water wheels (see /8-6/)