Hydroelectric energy - Energie EDF

How
a hydro plant
works
The principle is simple and relies on the force of gravity:
potential energy from water contained in dams is
converted into mechanical energy by means of a turbine,
which is in turn converted into electrical energy using a
generator.
The dam is used to store up large quantities of water by
forming a lake (1). When the sluice gates are opened, the
water fl ows into a penstock or channel (2) which directs it
towards the power plant. The water causes the turbine to
rotate (3). The turbine drives the generator (4), which
generates electrical current. This current is rectifi ed by a
transformer (5) before being transmitted along highvoltage
power lines. Outside the power plant, the water
returns to the river via the tail-race (6).
HOW A HYDRO PLANT WORKS
Storage reservoir
1
Tunnel
Dam
2
Penstock
3
Turbine
4
Generator
5
Transformer
6
Different plants for different
landscapes
Hydro plants come in a
variety of forms, depending
on the layout of the
waterway, the terrain or the
water head:
– Mountain sites with a steep
gradient, such as the Portillon
plant in the Pyrenees (1,420 m
head in a penstock), but with
a low fl ow rate;
– Medium-head plants with a
higher fl ow rate;
– Run-of-river plants, with a
slight gradient (10-15 m) but a
very high fl ow rate, as found
in large rivers (Rhine, Rhône,
Isère, Durance, etc.);
– Pumped-storage plants,
pumping water downhill
during peak periods and
pumping water uphill during
quiet periods;
–Tidal plants, such as la Rance
in Ille-et-Vilaine, driven by the
tides.
Depending on the type of
dam (arch dam, weight,
abutments, rock fi ll or earth
dam, moveable dam, high,
medium or low-head dam),
three types of turbine are
essentially used: Pelton,
Francis and Kaplan
respectively.
DID YOU KNOW?
AVAILABLE CAPACITY
Available capacity (kW) is a
combination of two factors:
water head (m) and derived
fl o w ( m 3 /s).
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