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Hydroelectric Power Plant

July 11, 2020

It is the power produced from falling water, fast-running water, rain, or metaled snow. And it’s one of the oldest and cheapest renewable energy sources used for producing energy. Additionally, they are for irrigation as well as the operation of various mechanical devices.

For instance, a gristmill, textile mills, domestic lifts, trip hammers, and dock cranes. Approximately, 10% of hydroelectric power plants come from the nation’s energy.  Thus, it is important to understand how this hydroelectric plant works.

However, we will begin by delving into the history of the hydroelectric power plant.

History of hydropower

Firstly, hydroelectric energy has been in use for centuries. For instance, ancient Greeks used water wheels to grind wheat into flour as the water wheels pick up the flowing water in buckets located around the wheel. The kinetic energy from this water turns the wheel to convert it into mechanical energy to run the mill.

However, the Roman Empire used water-powered mills to produce flour from grain and for sawing timber and stone.

By the nineteenth century, the first electric generator that could be used with hydraulics. In the late 19th century, hydropower became a source for generating electricity.

In 1879 Niagara Falls had the first hydroelectric power plant. Then in 1881, they powered the street lights in the city of Niagara Falls by hydropower. The United States in 1882 began operating the world’s first hydroelectric power plant in Appleton, Wisconsin.

In the 1830s, the US canal-building used hydropower. It was to provide energy to transport barrage traffic up and down steep hills using inclined plane railroads.

James R.Francis in 1848 transformed the open water moved wheel into an enclosed turbine that is, water motor.  then they improve these designs to create a turbine with 90% efficiency.

In 1870 Laster Allan Pelton developed a high-efficiency Pelton wheel impulse turbine that utilized hydropower from the high headstreams. A characteristic of the mountainous California interior.

How to generate electricity from water

Electricity produced by the hydroelectric power plant is simply similar to electricity produced by coal power plants. Both plants use a power source to turn the turbine, which in turn turns the metal shaft connected to an electric generator to produce the electricity.

But the difference between hydroelectric and coal power plants is that the water which is an easily renewable source keeps flowing.

There are also once-through cooling systems that use cooling systems to draw water from a lake, river, aquifer, or ocean to cool steam. Then virtually return all of it to the source although at a higher temperature.

Also, the dams are constructed with a special passageway that is sloped downward to create a flow of the falling water. So the turbine turns by the force of this flowing water. Then the turbine, in turn, spins the metal shaft of the electrical generator to produce the electricity.

The following are other means of modern energy production.

Rain power

The energy in the falling raindrop isn’t a lot to produce electricity. The French Atomic Energy Commission built a device with a special plastic to convert the vibrational energy of the raindrop turning it into electricity. The generated electricity is not much but enough to power a couple of standard laser pointers.

Hydrogen fuel

Hydrogen fuel can be turned into electricity with a fuel cell. Also, it isn’t easy to get pure hydrogen, thus researchers are working on ways to split hydrogen from water without using more energy.

Seawater-derived jet fuel

The U. S. Navy developed a method for turning the seawater into jet fuel. Additionally, the electricity is used to split water into hydrogen and oxygen. Then the hydrogen is combined with carbon dioxide and dissolved in the water to produce a hydrocarbon (aka jet fuel).

Solar-wind hybrid

This method was patented back in 1975 as they built a really tall tower with an upper lip. Over this lip, there was a fine mist of water that absorbs heat from the air and evaporates. So a dense, cool airflow to the bottom of the structure drives a huge turbine that produces electricity.

This method works best in hot, arid places where there is a lot of water.


Power is produced in geothermal from the heat inside the earth.  So we can exploit sites where there are deeper rocks below the surface and pump down cold water through wells.  This is to be heated and then the water is extracted from other wells.

Thus, under special conditions of pressure and temperature is turned into steam which is used to drive generators and produce electricity.


The difference for biofuels is that they don’t need any additional application of water before being harvested. It is believed that by the year 2030, 8% of U. S. freshwater may go to biofuel production.


We pump water in hydraulic fracturing deep underground to create cracks to allow access to trapped oil or natural gas. Unfortunately, in some countries diverting water for freaking is depleting already in stressed supplies.

How does hydroelectric power work

We can simply illustrate how hydroelectric power works by the parts of the hydroelectric power plant. They are;

Dam: It is used to raise the level of water in the river. It enables to create the falling water and controls the flow of water and the reservoir store the energy.

Turbine: The turbine spins as a result of the force of the falling water to convert the kinetic energy of this water into mechanical energy.

Generator: the generator is connected to the turbine by shafts and gears so it spins when the turbine spins and converts the mechanical energy into electrical energy. The generator work follows the principle of Faraday. It says that when a magnet is moved to past a conductor it’ll cause electricity to flow.

Transmission lines: This transmits electricity stepped up by transformers from hydropower plants to homes, hospitals, and businesses.

Hydroelectric Power Plant Components

Types of hydropower plants:

1- We can simply classify hydropower plant, according to facilities for generating hydropower, that is, the way of operation of the plant. There are four main types and here are they:

Impoundment plant (storage hydropower plant)

This facility is a large hydropower system that uses dams to store river water in a reservoir, then we use this water to turn the turbines. They in turn rotate the generator to produce the electricity.

Transmission lines are used to connect this electricity to homes, hotels, hospitals & businesses. The dam store water until needed for usage. A penstock carries water to the turbines and the generators connected with turbines are turned by the force of the water to automatically generate electricity.

Diversion hydro plants

Diversion plants or run-of-river plants don’t require dams to store water as they divert portions of the water into the canals from the river. They are used to supply power to the baseload.

The main advantage of this plant is that it reduces the need for constructing large reservoirs. Since they use small water ponds to meet the immediate loads. This also reduces the initial cost compared to the storage plant.

Pumped storage plants

It is the most common type of hydro plants and it fairly works like a battery as it stores the energy produced by solar, wind, nuclear, and other power sources.  This plant requires a dam to store the water in a reservoir then the water is carried by penstocks to turn turbines to generate electricity.

We use the pumps to cycle harnessing water between a low and upper reservoir to make up energy in times of low demand. There is a release back of the water to the lower turbine when the demand is high.

And the pumped storage plant is capable to supply the peak load at a low cost. So, the efficiency of this plant varies between 70-80%, and that increase the revenue.

Tide (tidal) power hydroelectricity:

Tide power hydroelectricity or offshore hydroelectricity is a technology that uses the power of the waves or the tidal currents from seawater to generate electricity.

The main advantages of this technology are:

  • We can stop the generation of electricity on the basis of requirement.
  • We use water wheels instead of dams which decrease investments
  • It gives a constant power supply.
  • It’s cheaper than many other types.

There is also an unknown type of hydroelectric power plant which is:

Underground hydropower plant

We construct this plant below the upper level of the water. It works on the basis of the natural height difference generated by the use of two waterways (waterfall or mountain lake).

This plant is safe against any external factors like rock or earth slips or snow avalanches. Also, they don’t affect the site scenic beauty.

2– We can also classify hydroelectric power plants according to size. They are;

Large hydro plants

They are plants capable to produce more than 30MW.

Small hydro plants

They are plants that produce 10MW or less of power which is enough to supply home, farm, ranch, or a village.

Micro-hydro plants

They are plants capable to produce up to 100KW and they also supply a village, home, ranch, or farm.

The layout of the hydropower plant

The layout of the hydroelectric power plant is simply all the main and assistance components of the hydroelectric power plant. Here is the importance of each component:

Water reservoir

It is very necessary for the hydroelectric power plant to continuously have water. Thus, the use of reservoir to store water collected from watersheds or catchment areas during the rainy season.


It is used to increase the height of the water level behind it and increase the working head of the power plant. And it also controls the outing run of the water.

Control Gate

We use the control gate penstock to control the water flows from the reservoir through the penstock to the turbine. A maximum amount of water is released through the penstock when the control gate is fully opened.


It provides a release of floodwater from a dam and prevents over toping of the dams which may cause damage or failure of dams. This spillway may be an uncontrolled type, that is, it starts releasing water when the water rises above the particular level. Or, a controlled type, that is regulation of the water flow.

Surge tank

It is a small reservoir or tank opened at the top, and we usually provide this surge tank with high or medium head power plants. When we require a long penstock, we fit it between the reservoir and the powerhouse. We use the surge tank to reduce the sudden rise of pressure in the penstock.

It provides excess water needed when we suddenly open the control gates to meet the increase in load demand.

Pressure tunnel

It is used to facilitate the flow of water from the reservoir to the surge tank.


It is a huge reinforced concrete or steel pipe used to carry water from the reservoir to the turbine. As a result of gravity and flowing down of water through the penstock. The potential energy of the water converted into kinetic energy.

Water turbine

A water turbine or hydraulic turbine is used to convert the water-energy into mechanical energy. It is mechanically coupled to an electrical generator by a shaft to produce electricity.

There is an impulse turbine that is used for large heads and reaction turbines that are used for medium and low heads.

Electrical generator

It is mounted in the powerhouse and mechanically coupled to the turbine shaft. It rotates when the turbine blades are rotated to generate electricity. Then we use transformers to step up this electricity for transmission purposes.

Draft tube

It is connected to the outlet of the turbine to allow it to be placed over the tailrace level. It is used to exchange the kinetic energy of the water into pressure energy into the atmosphere.

Tailrace level

It is a waterway (path) used to lead the water discharged from the turbine to the river.


It accommodates the turbine, generator, transformer, and the control room.

Step-up transformer

It is used to raise the voltage produced at the generator terminal to be transmitted to the power consumers.

And to achieve the highest benefits of these components when we select a site for a hydroelectric power plant; we should take into account:

  • The availability of water.
  • Location of the dam.
  • The distance from the load center.
  • Transport facilities.
  • Storage of water.
  • And the head of water.

Uses of hydroelectricity

Having discussed the hydroelectric power plant and how it works to produce the electricity, we now look at other benefits of hydroelectricity.

  • It is for producing electricity. It is a cheap and non-polluting source of energy. Thus, big countries like China, Brazil, Russia; India, and South America completely depend on hydroelectricity for their massive need for energy.
  • It is also used for driving bellows in small blast furnaces and for the extraction of metal ores.
  • Hydro-power is important for agriculture. Such as producing flour from grain, for sawing timber and stone to raise water into irrigation canals.
  • Hydroelectricity is also essential for storing energy as we use pumped hydro storage for grid energy storage. Because hydroelectricity is a cheap option for storing energy, there is already 90 GW of global hydro storage; and with the increased cost of solar and wind energy, the usage capacity will grow.

Biggest countries using hydropower

Hydroelectric power plants are the backbone of many countries for producing electricity.

  • 200GW in China.
  • 89GW in Canada.
  • 80GW in the USA.
  • 70GW in Brazil.
  • 45GW in Russia.
  • 33GW in India.
  • 27GW in Norway.
  • 27GW in Japan.
  • 15GW in Venezuela.
  • And we can’t ignore Paraguay which produces almost 100% of its electricity supply from hydroelectric power.

Advantages of a hydroelectric power plant

When we focus on all details of the hydroelectric power plant we will discover great advantages as:

  •  It produces minimal pollution as it uses water and doesn’t burn fuels.
  • It comes at a low cost as the water used for running the hydro plant is free.
  • It’s a clean renewable source which helps to reduce the greenhouse gas emission.
  • The operation and maintenance cost is relatively low and the parts of the plant need minimal replacement.
  • It’s a reliable source of energy; as the construction of the dams is long-lasting and capable to produce hydroelectric power for 50-100 years.
  • We can control the use of energy according to their requirements. We can reduce the flow of water from the dam if we require less energy. Also, when we require huge energy, we can maximize the water by uncovering water tunnels in a very short space of time.
  • Also, we can use the built dam as a supply of water to the surrounding towns and cities. For instance, use for drinking, washing, bathing, and also irrigation.
  • The hydroelectric dams can be a landmark in the country and bring large volumes of tourists. For example, fishing, boating, and aquaculture purposes) which will provide a boost to the local economy.

Disadvantages of hydroelectric power plant

Nothing is perfect, so it’s ordinary to meet some drawbacks of hydroelectric power plant like:

  • The investment and upfront capital cost is high, almost 20 billion$.
  • The time needed to build and finish a hydroelectric plant is too long. It may up to 18 years.
  • Creating dams may affect the fish habitats which depend on the water current, water level, and access to food.
  • Floods created by the flow of the water from the dam affect the living organism; as the temperature of the water may increase, and the organisms which don’t adapt to this new environment conditions will die.
  • The hydroelectric energy can affect the residences living near the dam, and force them to relocate.
  • Producing hydroelectric energy depends on the weather conditions and the availability of water. The flow of the water may reduce; as a result of the sedimentation in dams and that affects the generation of hydroelectric energy.
  • We need a large area of land to construct a dam, install a power production unit, and transformers.