Worked Example 12.3
The monthly flow of a river supplying water to a power plant in 14 succes-
sive 4-week periods of the driest year is as follows:
Period 1234567891011121314
(4 weeks)
Flow
(m^3 s^1 ) 1.14 0.58 0.68 0.78 0.94 1.16 0.56 0.56 0.5 0.67 1.36 1.65 1.49 0.83
- Calculate the volume of reservoir storage to be provided to maintain
the highest uniform output throughout the year, and calculate the
continuous power if available head is 40 m.
- If a reservoir of only half the required capacity can be provided, how
much power is to be supplied by an auxiliary plant to produce the
continuous power in 1?
- How many turbines and what type and specific speed units would
you install for the power in 1?
Solution
To plot the mass curve the cumulative volumes of flow need to be calcu-
lated:
Period Flow rate ∑Flow rates ∑Volumes ∑Outflows ∑Balance
(4 week) (m^3 s^1 )(m^3 s^1 )( 106 m^3 )( 106 m^3 ) volumes
( 106 m^3 )
1 1.14 1.14 2.76 2.23 0.53
2 0.58 1.72 4.16 4.46 0.30
3 0.68 2.40 5.80 6.69 0.89
4 0.78 3.18 7.69 8.92 1.23
5 0.94 4.12 9.97 11.15 1.18
6 1.16 5.28 12.77 13.38 0.61
7 0.56 5.84 14.13 15.61 1.48
8 0.56 6.40 15.48 17.84 2.36
9 0.50 6.90 16.69 20.07 3.38
10 0.67 7.57 18.31 22.30 3.99
11 1.36 8.93 21.60 24.53 2.93
12 1.65 10.58 25.60 26.76 1.16
13 1.49 12.07 29.20 28.99 0.21
14 0.83 12.90 31.21 31.21 0.00
- The uniform draw-off rate
31.21 106 /14 28 24 60 60
536 HYDROELECTRIC POWER DEVELOPMENT
