Short Answer:

Hydroelectric power plants are classified into different types based on how they store and use water. The main types are storage (dam-based), run-of-river, and pumped-storage power plants. Each type works in a unique way to generate electricity using the natural flow or stored water.

Storage plants store large amounts of water in a reservoir, run-of-river plants use river flow directly without much storage, and pumped-storage plants store and reuse water between two reservoirs to meet changing electricity demands.

Detailed Explanation:

Types of hydroelectric power plants

Hydroelectric power plants convert the energy of moving water into electrical energy. Depending on the way they collect, store, and use water, these plants are classified into various types. Understanding these types is important in civil engineering, as each requires different designs, structures, and site conditions. The main types of hydroelectric power plants include:

Storage (Reservoir or Dam-based) Power Plants

These are the most common and traditional type.

A large dam is built across a river to create a reservoir.
Water is stored at a high level and released when electricity is needed.
The high-pressure water flows through a penstock to rotate turbines and generate power.
These plants can generate electricity on demand and are suitable for base load and peak load.

Advantages:

Can supply electricity consistently.
Helps in irrigation and flood control.
Good for areas with seasonal rainfall.

Run-of-River (ROR) Power Plants

These plants do not store much water.

They use the natural flow of the river to produce electricity.
A small diversion structure or weir is used to channel water to turbines.
There is little or no reservoir, so output depends on river flow.
Suitable for small-scale or remote-area power generation.

Advantages:

Low environmental impact.
Less costly and quicker to build.
No large reservoir or land submergence.

Pumped-Storage Power Plants

These work like energy storage systems.

Have two reservoirs at different heights.
During low demand, water is pumped from lower to upper reservoir using extra electricity.
During high demand, stored water is released to generate electricity.
Acts like a battery, storing and supplying energy.

Advantages:

Helps balance grid supply and demand.
Ideal for supporting renewable energy systems.
Provides quick response during peak demand.

Tidal and Small Hydropower Plants (Additional Types)

Tidal plants use ocean tides to generate power. These are site-specific and rare.
Small hydropower plants are mini versions of the above types, usually below 10 MW, used in rural or hilly areas where large infrastructure is not feasible.

Conclusion:

Hydroelectric power plants are categorized into storage, run-of-river, and pumped-storage types, depending on how water is used for power generation. Each type has its own design, purpose, and benefits. Civil engineers choose the appropriate type based on the geography, water availability, and energy needs of the area. These types make hydroelectric power versatile and suitable for a variety of situations.