Hydro in Europe: Powering Renewables - Full Report - Eurelectric

plants are designed to use either a large flow rate with small head on large rivers with
gentle gradient, or a small flow rate with high head in mountain areas. Pictures 1 and 2
show a low head run-of-river power plant and a high head run-of-river power plant in
northern Norway, respectively.
Picture 1 Freudenau run-of-river power plant in Austria
(a low head run-of-river power plant)
Source: Verbund
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Picture 2 Nore power station – a high head run-ofriver
plant in Norway
Source: IEA
Electricity output of run-of-river power plants depends on the availability of water in
the river and varies considerably throughout the year. Seasons, rainfall or snowmelt all
influence the amount of water available for electricity generation. Because they lack
storage, run-of-river power plants operate under the constraint of precisely controlling
the water level at the intake in accordance with incoming river flow. Run-of-river
hydropower plants without connection to upstream storage typically operate as baseload
power plants since the hydrological forecast is sufficiently good for the timescales
required in the electricity market.
Services
Run-of-river hydro plants have little or no storage capacity. Therefore they offer only
very short-term storage possibilities (few minutes dynamic cycle), thus allowing for
some adaptation to demand, especially for ancillary services such as frequency and
voltage control.
Cascading hydropower schemes – a well orchestrated system
Other, upstream hydropower plants or reservoirs have to be taken into consideration
when looking at the energy output of a run-of-river plant. A constant output from a
run-of-river hydropower plant is possible if the river is already regulated further
upstream by a hydropower plant with storage capacity (thanks to the reservoir). A
commonly used strategy to optimise the energy output of hydropower plants on a
river is to build a large storage reservoir in the upper catchment which will even out
flows for several run-of-river or smaller reservoir plants downstream, as illustrated in
Figure 12. Figures under each plant indicate how high from the sea level they are
located.