- Hydroelectric Power Plant Definition: A hydroelectric power plant is defined as a facility that generates electricity by using the kinetic energy of falling water to rotate a turbine.
- Construction of Hydroelectric Power Plant: Building a hydroelectric power plant involves creating a dam, pressure tunnel, valve house, penstock, powerhouse, and surge tank.
- Advantages of Hydroelectric Power: These plants are cost-effective and environmentally friendly since they don’t need fuel and don’t produce pollution.
- Disadvantages of Hydroelectric Power: The high construction costs and the need for long transmission lines to deliver electricity to where it’s needed can be drawbacks.
- Additional Benefits of Dams: Dams used in hydroelectric power plants can also provide benefits like irrigation support and flood control.
A hydroelectric power station turns the energy of water falling through a head into electricity. Water stored at the upper level holds potential energy. That energy becomes flow in the penstock and then shaft work when the water hits or fills the turbine. A hydroelectric power station is therefore usually built where a dam can create that head, often in hills on a river. Controlled flow from the reservoir drives the turbine, and the turbine shaft turns the coupled alternator.
A hydro electric power plant burns no fuel at the powerhouse. After the dam exists, the working fluid is the stored water head.
No combustion fuel means no fuel bill and no stack gas at the plant, so hydroelectric power plants are classed as low-carbon. Reservoirs can still flood land and emit methane. Civil works are larger than those of a thermal or nuclear power plant, so the build is not simpler.
A hydroelectric power plant can cost more up front than a thermal power plant because of the dam and tunnels. The site must have a usable head and flow, and that site is often far from the load.
Then long transmission lines are needed to reach the load centres.
Those lines add cost.
The same reservoir can supply irrigation and, on some rivers, reduce downstream flood peaks.
A common high-head layout uses six main parts: dam, pressure tunnel, surge tank, valve house, penstock and powerhouse.
The dam is a barrier, often concrete, built across the river. The catchment behind it forms the reservoir.
The pressure tunnel carries water from the dam toward the valve house.
The valve house usually has a main sluice (or inlet) valve and an automatic isolating valve. The sluice sets normal flow. The isolating valve shuts on a sudden load rejection or another trip so the penstock is not left at full flow with the turbine gates closed.
The penstock carries water from the valve house to the powerhouse. Steel is common; concrete and other pipes are also used.
The powerhouse holds the turbines and alternators, plus step up transformers and switchgear that feed the grid.
The surge tank protects the hydroelectric power plant penstock. On this layout it sits just before the valve house. It is an open-top tank. Its overflow level is set above the static reservoir head so a load-rejection surge can rise in the tank instead of bursting the pipe.
That tank takes the water column when the turbine suddenly refuses flow. Governor-controlled gates (wicket gates or a needle) open and close with electrical load. If load is thrown off, the governor closes those gates and the penstock flow must stop. A sudden stop raises pressure. The surge tank lets the water level swing so that pressure stays inside the pipe rating.
