Page 270 - Handbook of Energy Engineering Calculations

turbines to deliver, and use, stored water during off-peak and on-peak hours.
Further, the terrain at the installation must be such that there is a significant
elevation difference, H, between upper and lower reservoirs, and a minimum
horizontal distance, L, to reduce piping energy losses.
Values of L/H less than 2 are considered very favorable. Most existing

pumped-storage plants have L/H ratios of between 4 and 6; some are nearly
as high as 10. To overcome site problems where there is not enough
difference in the reservoir elevations, underground storage may be an

alternative option. The upper reservoir is placed at, or near, ground level. To
provide sufficient hydraulic head, the lower reservoir is in underground
natural caverns, abandoned mines, or other underground cavities. The
existing terrain must have such features for such an underground system to be
developed.† Use Table 1 as a guide to hydroturbine types and the typical

head ranges they are used for.‡

TABLE 1 General Arrangements of Turbine Installations and Usual
Head Limits Employed

Small-Scale “Clean Energy” Hydro Site Analysis

A newly discovered hydro site provides a potential head of 65 ft (20 m). An
output of 10,000 kW (10 MW) is required to justify use of the site. Select
suitable equipment for this installation based on the available head and the