Short Answer:

A pumped-storage hydroelectric plant works by storing energy in the form of water. It has two reservoirs at different heights. During times of low electricity demand, water is pumped from the lower reservoir to the upper one using extra power. During high demand, this water is released back down to run turbines and generate electricity.

This system allows the plant to act like a battery, storing energy and supplying it when needed. It helps in balancing supply and demand, improving the reliability of power systems.

Detailed Explanation:

Working of a pumped-storage hydroelectric plant

A pumped-storage hydroelectric plant is a special type of hydroelectric system designed to store and supply electricity based on demand. Unlike traditional hydroelectric plants, which only generate electricity by using natural river flow or stored water, pumped-storage plants both generate and store electricity.

The idea is to pump water to a higher elevation when there is extra electricity available (usually at night or during low demand). This stored water can then be released to generate power when electricity demand increases (typically during the day or peak hours).

Step-by-step working process

1. Two Water Reservoirs
   The plant has two reservoirs:
   • Upper reservoir – stores water at a higher elevation.
   • Lower reservoir – collects water after it passes through the turbines.
2. Pumping Phase (Storing Energy)
   • During off-peak hours or when surplus electricity is available from the grid (often from renewable sources like wind or solar), pumps are used to lift water from the lower to the upper reservoir.
   • This process uses electricity, but the water gains potential energy by being raised in height.
3. Generation Phase (Producing Energy)
   • During peak electricity demand, the stored water from the upper reservoir is released back down through large pipes called penstocks.
   • As the water flows down, it gains kinetic energy and rotates the turbines connected to generators.
   • These generators then convert the mechanical energy into electrical energy.
   • The water finally returns to the lower reservoir, ready to be used again.
4. Cycle Repeats
   • The process can be repeated daily or even multiple times a day depending on the demand and availability of surplus power.
   • It allows the grid to remain stable and helps prevent power shortages.

Importance in Civil Engineering and Power Management

• Load balancing: Stores excess power and supplies it during high demand.
• Grid stability: Maintains voltage and frequency levels.
• Backup source: Acts as emergency support during sudden outages.
• Supports renewable energy: Balances variable supply from solar and wind.
• Efficient use of energy: Though some energy is lost during pumping, overall system efficiency is around 70–80%.

Advantages

• Clean and renewable energy system
• Quick response to demand changes
• Long operational life
• Low maintenance compared to thermal plants
• Eco-friendly compared to fossil fuel-based storage

Conclusion:

A pumped-storage hydroelectric plant works by moving water between two reservoirs to store energy during low demand and generate electricity during high demand. This system is crucial for modern energy management, especially with the growing use of renewable energy. It ensures a reliable, flexible, and sustainable electricity supply while making efficient use of existing energy resources.