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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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In pumped storage
Power is produced by means of pumps
Water is stored by pumping to high pressures
Downstream water is pumped up-stream during off load periods
Water is re circulated through turbine
Downstream water is pumped up-stream during off load periods
A pumped storage plant functions as an energy storage system that converts off-peak electrical energy into potential energy by pumping water from a lower reservoir to an upper reservoir. During peak load hours, this stored water is released through turbines to generate electricity to meet the grid demand.
A pumped storage plant functions as an energy storage system that converts off-peak electrical energy into potential energy by pumping water from a lower reservoir to an upper reservoir. During peak load hours, this stored water is released through turbines to generate electricity to meet the grid demand.
P=ηρgQH — where P is power, η is efficiency, ρ is density, g is gravity, Q is flow rate, and H is head.
During low demand (off-load) periods, surplus electricity from the grid is used to drive motor-pump sets, lifting water to the upper reservoir. When peak demand occurs, the process is reversed: water flows back to the lower reservoir through the penstock, spinning a turbine-generator set to supply power to the grid.
Used for grid stabilization and peak load shaving.
The round-trip efficiency of modern pumped storage plants is typically between 70% and 85%.
Acts as a large-scale energy storage mechanism.
Often uses reversible pump-turbines (Francis type) to save costs.
Rapid response to load changes
High reliability for grid frequency regulation
Long operational life
High initial capital investment
Requires specific geographical conditions
Energy losses during pumping/generating cycles
Grid peak load management
Frequency stabilization of the national grid
Black start capability for power systems
The storage capacity is directly proportional to the volume of water stored and the height (head) of the upper reservoir.
Option A is incorrect because pumps do not produce power; they consume it. Option B is incorrect as water is stored by elevation (potential energy), not high pressure. Option D is partially true but incomplete; the distinct characteristic is the bi-directional pump-turbine operation between reservoirs.
C is correct — Downstream water is pumped up-stream during off-load periods to store potential energy for later peak-hour generation.
Always remember that pumped storage is not a primary energy source, but an energy storage device; the system efficiency ηtotal=ηpump×ηturbine×ηtransmission is always less than 1.