Hydro in Europe: Powering Renewables - Full Report - Eurelectric

There are two types of storage hydropower plants:
a) hydropower plants with a storage reservoir; and
b) pumped storage hydropower plants.
The larger the reservoir of a hydropower plant, the more storage it can provide.
Conventional reservoir-type hydropower plants generally have a more significant
storage capacity in terms of volume than pumped storage plants. Pumped storage
plants are used for short-term activities (within a day or week) and can adapt to
electricity system needs very quickly. Larger conventional reservoirs are used for longterm
storage but have in most cases also capacity to participate in short-term
activities.
a) hydropower plants with a storage reservoir
Reservoir-type hydropower plants involve impounding water behind a dam. This
enables flow regulation throughout a season or the year. Hydropower plants with large
reservoirs can provide flow regulation even on a multi-annual basis. Large reservoirs
not only provide an energy reserve to satisfy electricity demand during dry seasons
and/or periods of peak demand, but they also allow the retaining of more water.
Reservoir-type hydropower plants are typically used for highly variable flows in the
middle reaches of a river, or as energy storage in the upper reaches of a river.
Reservoir-type hydropower plants on gorge or canyon systems also deliver high
capacity.
Pictures 3 and 4 show examples of reservoir-type hydropower plants.
Picture 3 Orellana – a reservoir plant in Spain
Source:
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Picture 4 Blåsjø reservoir of the Ulla-Førre
hydropower scheme in Western Norway
Source: Statkraft 2011
The generating stations of reservoir-type hydropower plants are usually located at the
dam toe, although they can sometimes be found further downstream. In the latter
case the power plant is often connected to the reservoir by tunnels or penstocks (gates
for water).