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Hydropower 273

it is necessary to study environmental and social impacts, in addition to economical
parameters. This will be discussed later in Section 8.10.
If one considers the impact per kilowatt-hour, the picture becomes more compli-
cated. A large hydropower plant could easily have less impact (per kilowatt-hour) than
many small plants of the same capacity combined. This was discussed thoroughly in
reference [1] where the conclusion was that the use of classification according to size
should be avoided, both because there is no clear connection between size and impact,
and also because the definition of what is “small” and “large” varies widely from one
country to another, as shown in Table 8.1.

8.5 Cutting-edge technology

Though hydropower is a mature technology, there is still a need for and room for tech-
nology improvements. Since hydropower is so closely linked to water management,
new requirements and environmental policy changes can have a big impact on hydro-
power projects, and lead to changes for example in flow restrictions and reservoir
operation rules, and require new methods for operation and optimization. One such
example is the European Water Framework Directive, which has a profound effect
on hydropower in many European countries.
With hydropower plants’ long lifetime, typically 80years or more, it will usually be
necessary to upgrade machinery and control equipment several times during a plant’s
lifetime. This gives the possibility to introduce new and improved technology and
increase efficiency. Even civil structures, in particular, dams may need refurbishment
and major upgrades during such a long lifetime, for example, due to new guidelines for
dam safety or climate change impacts.
Cutting-edge technology is not limited to better “hardware” like turbines and gen-
erators, it can also be improved planning and operation tools, and of course improve-
ments in dams, tunnels, and other civil structures. Hydropower generation can be
increased by optimizing different aspects of plant operation, both for individual units
and by better coordination in cascades with many interlinked reservoirs and power

Table 8.1 Definition of “Small hydro” by installed capacity in
some countries [1]
Country Small hydro defined by installed capacity (MW)
Brazil 30
Canada <50
China 50
EU 20
India 25
Norway 10
Sweden 1.5
United States 5–100