Typically a large system that uses a dam to store water in a reservoir. Electricity is produced by releasing water from the reservoir through a turbine, which activates a generator. Storage hydropower provides base load as well as the ability to be shut down and started up at short notice according the demands of the system (peak load). It can offer enough storage capacity to operate independently of the hydrological inflow for many weeks or even months. Hydropower schemes with large reservoirs behind dams can store significant quantities of water and effectively act as an electricity storage system. As with other hydropower systems, the amount of electricity that is generated is determined by the volume of water flow and the amount of hydraulic head available.
The advantage of hydropower plants with storage is that generation can be decoupled from the timing of rainfall or glacial melt. For instance, in areas where snow melt provides the bulk of inflows, these can be stored through spring and summer to meet the higher electricity demand of winter in cold climate countries, or until summer to meet peak electricity demands for cooling. Hydropower schemes with large-scale reservoirs thus offer unparalleled flexibility to an electricity system.
The design of the hydropower plant and the type and size of reservoir that can be built are very much dependent on opportunities offered by the topography and are defined by the landscape of the plant site. However, improvements in civil engineering techniques that reduce costs mean that what is economic is not fixed. Reduced costs for tunnelling or canals can open up increased opportunities to generate electricity.
Hydropower can facilitate the low-cost integration of variable renewables into the grid, as it is able to respond almost instantaneously to changes in the amount of electricity running through the grid and to effectively store electricity generated by wind and solar by holding inflows in the reservoir rather than generating. This water can then be released when the sun is not shining or the wind not blowing. In Denmark, for example, the high level of variable wind generation (>20% of the annual electricity production) is managed in part through interconnections to Norway where there is substantial hydropower storage (Nordel, 2008a).
Advantages of storage Hydropower project
1. Storage Hydropower project can be used for multipurpose i.e.(Drinking water, Irrigation,recreation,generate electricity, improvefishery population etc)
2. Operation , running and maintenance costs are low.
3. Advantage to get more head.
4. No fuel is burnt and the plant is quite neat & clean.
5. No waste or pollution produced.
6. Generating plants have a long lifetime.
7. Much more reliable than wind, solar or wave power.
8. Water can be stored above the dam ready to cope with peaks in demand.
9. Once the dam is constructed, electricity can be produced at a constant rate.
10. Hydroelectric turbine-generators can be started and put "on-line" very rapidly.
11. Electricity can be generated constantly.
Disadvantages of storage Hydropower project
1. Very land-use oriented and may flood large regions.
2. The dams are very expensive to build. However, many dams are also used for flood control or irrigation, so building costs can be shared.
3. Capital cost of generators, civil engineering works and cost of transmission lines is very high.
4. The construction period is normally long.
5. Finding a suitable site can be difficult - the impact on residents and the environment may be unacceptable.
6. Fish migration is restricted.
7. Fish health affected by water temperature change and insertion of excess nitrogen into water at spillways
8. Available water and its temperature may be affected
9. Reservoirs alter silt-flow patterns.
10. High construction risk.
11. Expensive Investigation
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