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270 Managing Global Warming

1.0
0.9
2
0.8
1
0.7
3
0.6 4 1 Pelton (two jets)
Efficiency, h 0.5 5 2 3 Kaplan

Francis (low speed)
0.4
0.3 4 5 Francis (high speed)
Propeller
0.2
0.1

0
0.5 1.0 1.4
Relative discharge

Fig. 8.2 Turbine efficiency versus relative discharge for five different turbine types [6].

efficiency curves for these turbines are shown in Fig. 8.2. The efficiency varies very
much with relative discharge; therefore, it is very important to be able to run at or as
close as possible to the “best point,” for most of the time. For a run-of-river plant with
a large variation in inflow, this may be difficult if only one turbine is installed. Increas-
ing the number of turbines will allow a more efficient operation, but will also mean an
increase in cost.
With increasing share of wind and solar power plants, there will also be an increas-
ing pressure on hydropower plants to take more responsibility for load balancing, and
operation outside the best efficiency range. Today, it is an increasingly important
research topic to design turbines that will allow operation over a wider range of flow,
while still keeping efficiency at an acceptable level.

8.3.1 Hydropower project classification

Hydropower projects are usually classified into four major types:
– Run of river (RoR)
– Storage (reservoir) based
– Pumped storage
– Instream technologies (Hydrokinetic)
Hydropower projects can also be classified according to size (pico, micro, small,
large) and head (low, medium, and high), but there is no clear consensus on classifi-
cation by project size (installed capacity, MW) or head due to varying policies in