CIVIL ENGINEERING FORMULAS

HYDRAULICS AND WATERWORKS FORMULAS 337

whereQflow rate, ft^3 /s (m^3 /s)
c empirical discharge coefficient dependent on throat velocity and
diameter
d 1 diameter of main section, ft (m)
d 2 diameter of throat, ft (m)
h 1 pressure in main section, ft (m) of water
h 2 pressure in throat section, ft (m) of water

HYDROELECTRIC POWER GENERATION

Hydroelectric power is electrical power obtained from conversion of potential
and kinetic energy of water. The potential energy of a volume of water is the
product of its weight and the vertical distance it can fall:

(12.141)

wherePEpotential energy
Wtotal weight of the water
Zvertical distance water can fall

Power is the rate at which energy is produced or utilized:

1 horsepower (hp)550 ftlb/s

1 kilowatt (kW)738 ftlb/s

1 hp0.746 kW

1 kW1.341 hp

Power obtained from water flow may be computed from

(12.142)

(12.143)

where kWkilowatt
hphorsepower
Qflow rate, ft^3 /s (m^3 /s)
wunit weight of water62.4 lb/ft^3 (998.4 kg/m^3 )
heffective headtotal elevation difference minus line losses due to
friction and turbulence, ft (m)
%efficiency of turbine and generator

kW

%Qwh

738



%Qh

11.8

hp

%Qwh

550



%Qh

8.8

PEWZ