HYDRO POWER : Harnessing Energy From Water

06 Feb 2025

Hydroelectric power is a popular source of clean renewable energy that produces low cost electric power from generators that are driven by mechanical turbines that convert fast-flowing water’s ……

Potential Energy → Kinetic Energy → Mechanical Energy → Electrical Energy

                                                                                                                                                         - Sushil KumarVarshney

Hydropower, or hydroelectric power, is one of the oldest and largest sources of electrical energy, which uses the natural flow of moving water to generate electricity. The water pressure is achieved by the elevation difference, created by storage in a dam or diversion structure.

 Compared to other electricity sources, hydropower has relatively low costs throughout the duration of a project’s lifetime in terms of operation, maintenance, and fuel etc. Equipments used at hydropower facilities often operate for much longer periods of time without needing replacements or major repairsmaking the operation quite economic in the long run.

The installation costs for large hydropower facilities consist mostly of civil construction works for building of the dams, tunnels, other infrastructure and the turbo generator machinery.

In addition to being a clean and cost-effective form of energy, hydropower plants can provide power to the grid immediately, serving as a flexible and reliable form of backup power during major electricity outages or disruptions. Hydropower dams also have important benefits other than electricity generation, such as flood control, irrigation support, water supply, transportation etc. Adding to this list of positives, hydropower is reliable and emits low-to-no greenhouse gases.

Hydro Power Plant Working:

Huge quantity of water available from a river throughout the year, is stored in a large reservoir of a dam at a higher elevation in form of potential energy and led downward through large pipes or tunnels called penstocks to a lower level. The difference in these two elevations is known as the head. Control gates maintain the desired flow of water into the penstock to which are connected Surge tank, Valve, and Nozzle. Initially, the valve is closed. When the water reaches up to a high level to create a desired high pressure then water starts flowing with high kinetic energy and strikes with high pressure to the turbine blades through nozzle, causing the turbine blades to rotate. Thus water’s PE is converted into KE to ME. The rotating turbine shaft then rotates an attached generator. Thus Mechanical energy is converted into Electrical energy. The energy thus generated is sent to the transformers & transmission lines. Transformers convert the AC voltage to a higher voltage for long-distance transmission. The water after rotating the turbine blades is now released to the river or canals via a tailrace. The potential power that can be derived from a volume of water is directly proportional to the working head, so that a high-head installation requires a smaller volume of water than a lowhead installation to produce an equal amount of power.

Main Parts of a Hydro Power Plant

Dam: a structure built across a river or stream to store / retain water

Power House: The building structure that houses all power generating equipments, electrical & mechanical

Headpond: A large reservoir to store huge amount of water throughout the year .

Control Gates: To regulate the downward flow of water. Maximum flow is when fully open Penstock: Water stored at the dam or head pond is released through penstock pipe to the turbine

Valve and Nozzle: The valve controls the water flow to the Nozzle which strikes high pressure water on to turbine blades.

Surge tank: Accumulates water of the pipe during sudden inrush of water when the turbine is stopped. It is a safety tank to avoid the pipe burst.

Spillway: A by pass tunnel or conduit to discharge excess water from the dam during floods

Turbine: Turbine is a mechanical device which converts the water’s high kinetic energy into rotational mechanical energy. Generator: It is directly coupled to the rotating turbine shaft. It generates electricity ( ME to EE conversion )

Tail Race: Carries water after use away from the plant - to the river or canal.

Transformer: Electricity generated is fed to transformer to further send by transmission lines after step up voltage .

Transmission Lines: Carry power from the power plant to distribution agencies / large users.

Hydro Power Plant Advantages:

• Operating cost of the hydroelectric plant including auxiliaries is low, compared with a thermal plant. Annual O&M cost of a thermal plant is appx 5- 6 times that of a hydro plant of equal capacity.

• These are simple in design easy to maintain, pollution-free with zero fuelling cost.

• Life expectancy of a hydroelectric plant is over 100 yrs compared to a thermal plant of 35-45 years.

• No transportation, storage or handling of fuel, ash and smoke / exhaust gases

• No health hazards due to air pollution.

• Hydroelectric plants are quick to respond to change of load compared with thermal plant or nuclear plant.

• Hydro plant machines are robust, mostly run at low rpm, while in thermal plants run at a 3000 rpm.

• Efficiency of hydro plants not much change with age, but considerable reduction in thermal/ nuclear plant

• It does not contribute to air and water pollution to the greenhouse effect

• Hydro station is situated away from developed area / city so the land availability & cost is not a problem.

Hydro Power Plant Disadvantages:

• Capital cost (cost per kilowatt capacity installed) of a hydro plant is much more than a thermal plant.

• It takes much longer years - more than 10 years time for its planning, erection to operation stage.

• Power by a hydro plant depends on water availability from rains. Power reduces during dry seasons

• Site of Hydroelectric station is usually far away from the load center, thus long transmission lines need huge investment and then more transmission losses - which is substantial