Page 275 - Handbook of Energy Engineering Calculations

construction of such a plant.

Calculation Procedure:

1. Analyze the available head
Most small hydro-power sites today will have a head of less than 50 ft (15.2
m) between the high-water level and tail-water level, Fig. 2. The power-
generating capacity will usually be 25 MW or less.

FIGURE 2 Vertical Francis turbine in open pit was adapted to 8-m
head in an existing Norwegian dam. (Power.)

2. Relate absolute head to water flow rate
Because heads across the turbine in small hydro installations are often low in
magnitude, the tail-water level is important in assessing the possibilities of a

given site. At high-water flows, tail-water levels are often high enough to
reduce turbine output, Fig. 3a. At some sites, the available head at high flow
is extremely low, Fig. 3b.