II. SIMPLE PAYBACK-PERIOD METHOD AND POTENTIAL
ANALYSIS OF WATER RESOURCES
A. Potential Analysis of Water Resources
The typical equation for determining the generated
mechanical power of a SHP or MHP plant is as below.
P = η × ρ × g × Q × H (1)
where P is the generated power (in W) of water turbine, η is
the efficiency of the turbine, ρ is density of water ( = 1000
kg/m3), Q is water flow rate (in m3/s) through turbine, and H
is the effective water head (in m) of through the water turbine.
Fig. 1 shows the diagram for determining the potential of
an irrigation canal for future installation of MHP plants. This
scheme was proposed by the Ghugoku Electric Power Co.,
Inc., Japan to calculate the value of possible maximum
generated power in each section of an irrigation canal and the
resultant potential is obtained by summing up the values of
possible maximum generated power in each section of the
canal.
When dealing with an irrigation canal with different
values for water flow rate Q and effective water head H,
equation (1) can be further simplified by neglecting the
constants η, ρ, and g. The small section of an irrigation canal
shown on the left-bottom side of Fig. 1 has a constant water
flow rate of Q4b. This small section has a water overfall from
H34b drop to H4b. Hence, the values of Pmax for this section are
respectively
P34b = Q4b × H34b (2)
P4b = Q4b × H4b (3)
Fig. 1 Diagram for potential analysis of an irrigation canal.
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The potential of this small section can be determined by
ΣPb = Q4b × H34b + Q4b × H4b = Q4b × (H34b + H4b) (4)
The potential of a longer irrigation canal with different values
for water flow rate Q and effective water head H may be
easily calculated by using (2)-(4).