Handbook of Civil Engineering Calculations

eliminates half of the pumps that might be selected and results in oversized pumps op-

erating at lower efficiency.

This procedure is the work of John H. Doolin, Director of Product Development, Wor-

thington Pumps, Inc., as reported in Chemical Engineering magazine.

SMALL HYDRO POWER CONSIDERATIONS

AND ANALYSIS

A city is considering a small hydro power installation to save fossil fuel. To obtain the
savings, the following steps will be taken: refurbish an existing dam, install new turbines,
operate the generating plant. Outline the considerations a designer must weigh before un-
dertaking the actual 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. 15. The power-generating capacity will usu-
   ally be 25 MW or less.


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. 16a. At some
   sites, the available head at high flow is extremely low, Fig. 166.

FIGURE 15. Vertical Francis turbine in open pit was adapted to 8-m head

in an existing Norwegian dam. (Power.)

Tai!water level

Francis

turbine

Generator

High water Gearbox

level