PDF - 9Mo - Grande Dixence SA

GD. P.60The challengesof hydropowerInstant response to demandThe miracle is still there but no-one pays attention toit any more. No-one thinks about the technologicalprowess that enables a switch to be activated by justa click, so lighting a room or powering up a televisionset. Are consumers at all aware that power from theFionnay and Nendaz plants is injected on the transmissiongrid at their demand?In Switzerland, basic electricity is provided by nuclearenergy, which covers 40% of the total consumption.Run-of-the-river power plants supply 25% of the requirements.Some conventional thermal power plantsstill account for 4 to 5%. The remainder, almost onethird of consumption, is covered by stored energy plants(hydro). Clearly a much higher proportion than ourneighbours, who are more reliant on nuclear and fossilenergy.Because electricity cannot be stored, except in verysmall quantities, the hydropower plants play an essentialrole. They are the only generating plants capableof injecting considerable power into the grid within afew minutes. They are also the only plants able to holdin reserve the energy surpluses needed to meet a demandthat varies from hour to hour, from day to day,from season to season.The dams are the only “canned” variety of electricity.Production occurs only on demand, and there are noenvironmentally harmful emissions. This green energyis a security for future generations.Electricity generation in Switzerland – 2004Contribution of the different types of plantsIt was to cope with the increasing demand of consumersthat dams like Grande Dixence were built.Although basic consumption is met by the electricitygenerated by nuclear and run-of-the-river power plants,the storage dams supply a reserve of energy that isdelivered on demand.30%40%The Grande Dixence version of the hydropower missionis therefore to cover consumption peaks. Theyoccur in winter, mainly between January and March,and especially on weekdays between eight in themorning and eight in the evening, when there is thehighest concentration of human activity. Maximumpeaks are generally reached at mealtimes.4,7%25,3%Nuclear power plantsHydropower plants (stored water)Run-of-the-river power plantsConventional thermal power plants