Temperature - European Investment Bank

WEST AFRICAN POWER POOL (WAPP) PÖYRY ENERGY LTD.
Mount Coffee HPP ESIA and RAP 2012-09-18
ESIA Report Page 41
m³/s
4'000
3'500
3'000
2'500
2'000
1'500
1'000
500
Figure 8-4: River flow and plant operating conditions
During part of this period (14%, see Chapter 16.2.3), an operation pattern including load
following will be chosen. The flow in the tailrace channel would vary from potentially
minimum flow (about 34 m 3 /s; only one turbine operating at part of its capacity) to
nearly maximum flow (340 m 3 /s; all units operation at full capacity). Within the low
flow season (discharge below 190 m 3 /s), which occurs on 39% of the time, the plant
will operate in some kind of a pseudo load following scenario. During 7.2% of the time
there is not enough water to operate one unit even with 40% capacity, and during this
time the power plant would have to be shut down for about 4 h for each hour of
operation.
8.2.3 Residual Flow
8.2.3.1 Need for Residual Flow
St. Paul River flows exceedance curve
0
0.00 20.00 40.00 60.00 80.00 100.00
% exceedance
river flow
4 units 100%
load following
Presently, at the project site water is flowing through two ways, namely (i) through the
spillway and in the original river bed, which splits into several branches below the dam
site, and (ii) through the breach in the embankment dam into the tailrace channel (see
following Figure).