Hydroelectricity Meaning, History and Working Principle Fully Explained

Hydroelectricity is electricity generated from dynamic processes involving water or any similar hydraulic fluid.

This article discusses hydroelectricity according to the following outline;


-Hydroelectricity Meaning: 9 Ways to Define Hydropower

-History and Prospects of Hydroelectricity

-Hydroelectricity Working Principle: A Summary Describing how Hydroelectricity Works











Hydroelectricity Meaning: 9 Ways to Define Hydropower

Hydroelectricity is electricity which is produced as a result of some form of fluid motion, usually involving water, within a mechanical conversion system.

In line with the above definition, it is important to highlight the significance of energy conversion and electricity generation in hydroelectric processes, as done in the following definition;

Hydroelectricity is power which results from electricity generation processes where the kinetic energy of falling and flowing water is converted to mechanical energy which drives an electromagnetic system [1].

Given that the main hydraulic fluid required to generate hydroelectricity is water, the concept can be defined with respect to this factor, especially in terms of its sources and dynamics;

Hydroelectricity is electric power which is generated when water from a river (or any other water body) is controlled and mobilized through a dam, and used to drive an electro-mechanical system [5].

The role of dams and other equipment in the process of generating hydroelectricity, usually involves some form of energy conservation and capture, in a manner that is almost similar to the function of cogeneration systems. This is highlighted in the following definition;

Hydroelectricity is a form of electricity that is produced from a conservative hydraulic process whereby a fluid (usually water) is recycled in a gravity-driven kinetic and sustainable system, yielding energy that is supplied to a generator.

One of the implications of the conservative nature of a typical hydroelectric system, is that the hydroelectric process is relatively sustainable, as stated in the above definition. These attributes are further addressed in the following definition;

Hydroelectricity is electricity produced from a renewable process which uses energy from fluid motion to operate an electromagnetic system in a sustainable manner.

It is apparent from the above, that hydroelectric power systems can be categorized as a renewable energy technology, and should be considered similar to other technologies that are geared toward sustainable development, such as energy management systems and energy efficient technologies.

The next definition describes hydroelectricity as a tool for addressing unsustainable energy technologies and preserving the environment;

Hydroelectricity is a form of electric power which is generated from renewable hydraulic systems, as an alternative to fossil fuels, and as a means of addressing environmental degradation, global warming and climate change, among other problems that affect global sustainability.

Working principle of hydroelectric power generation may be included in the definition of hydroelectricity;

Hydroelectricity is power generated from a system which works based on a sustainable process of fluid capture and mobilization, energy conversion, and electromagnetic induction.

A required step to understand the working principle of hydroelectric systems is to identify the basic components of these systems, which are mentioned in the definition below;

Hydroelectricity is electricity generated from the combined operation of a fluid reservoir or source, a diversion and control unit, a turbine, and an electric generator.

In the above definition, turbine and generator are mentioned as separate components because their individual functions in a hydroelectric system are distinctive.

Lastly, hydroelectricity can be defined based on its role and significance as a form of power that is used globally;

Hydroelectricity is a renewable form of electricity which is generated commercially and accounts for 16 to 20 percent of global power supply [2].

World Electricity Generation 2015 Record showing Hydroelectricity at 16.4% (Credit: Delphi234 .CC0 1.0.)
World Electricity Generation 2015 Record showing Hydroelectricity at 16.4% (Credit: Delphi234 .CC0 1.0.)


History and Prospects of Hydroelectricity

Although hydroelectricity generation is a relatively-modern practice, the use of water as a source of energy for various purposes has been performed since ancient times.

Records indicate the prehistoric use of hydropower in various continents of the world including Africa, Asia and Europe. Examples of these applications include grain-grinding which was performed using hydropower-driven mills in Ancient Greece [8], and irrigation with hydropower systems in North Africa.

Actual hydroelectricity generation can be traced back to the late eighteenth century, during which Bernard Forest de Bélidor; a French engineer, published his findings on architectural designs for hydraulic systems based on horizontal and vertical axis models [12].

In the late nineteenth century, efforts by engineers and researchers such as the American engineer James Francis, led to the early practical model of a hydroelectric turbine [10]. In the 1880s, this model was used for street lighting and flour milling in parts of the United States.

Fortunately, the development of hydroelectricity coincided with early discoveries in the field of general current electricity, and the first hydroelectric systems were designed to generate direct current. Subsequent discovery of alternating current enabled hydroelectric systems to operate with more efficiency of electricity generation and transmission.

In 1882, Edison’s Vulcan Street Plant; a hydroelectric system, commenced operations in Wisconsin [11].

The Reclamation Act was passed in 1902 as part of measures to optimize hydroelectricity generation through the implementation of conservative methods and practices [3].

Hydroelectricity accounted for approximately 40% of all electric power in the United States by the year 1920 [7]. In that same year, the building of hydropower plants by the U.S Army Corps of Engineers was authorized. Large hydropower plants became integrated systems which served multiple purposes in agriculture, electricity generation, and water resource management.

In the 1920s and 1930s, various hydroelectric technological systems as well as agencies were established.

Hoover Dam was completed in 1936 on the Colorado River; as a component of one of the most famous hydroelectricity generation systems with an initial capacity of 1,345 MW [16]. Other major hydropower dams include the Itaipu Dam (14 GW), completed in 1984, and the Three Gorges Dam (22.5 GW) completed in 2008 [6].

The twenty-first century has seen more developments in the field of hydroelectricity, with the establishment of more power plants and hydropower agencies. Hydroelectricity generation is seen as an important factor in the effort to achieve global sustainability, alongside innovative technologies like improved wind turbines and electric cars.


Hydroelectricity Working Principle: A Summary Describing How Hydroelectricity Works

Hydroelectricity works based on the principle of hydrodynamic energy conversion, which involves a three-step process of fluid capture/mobilization, energy transformation, and electromagnetic induction.

Each of these three steps is discussed as follows;

1). Fluid Capture and Mobilization

In order for the hydraulic fluid (which is usually water) in a hydroelectric system to produce energy, it must first be captured and mobilized.

This simply means that the flow of the hydraulic fluid must be controlled to suit the preference of the user and the requirements of the hydroelectric system.

Some components of a hydroelectric power system are designed to handle fluid capture and mobilization. These include the reservoir, dam, catchment area, penstock(s), and surge tank.

In most hydroelectric systems (which depend on water as a hydraulic fluid), the reservoir and catchment are used for fluid capture, whereby a section of a larger body of the fluid is segregated, to be used for electricity generation.

Fluid capture is important because it makes the process of generating hydroelectricity to be sustainable and less-complicated. It also ensures that the mobilization of the fluid and the amount of hydro-power which the system generates, can be predicted and adjusted with relative ease.

Two components of a hydroelectric power plant that are important for fluid mobilization are the surge tank and penstocks.

Basically, the surge tanks controls hydraulic pressure and ensures that fluid flow is efficient [14], thereby protecting the penstocks from damage. The penstocks on the other hand, are reinforced conduits that serve as flow pathways for hydraulic fluid to reach the turbine [9].

Aside the surge tank and penstocks, a dam is needed to control the flow of the hydraulic fluid [15]. In order for the system to operate efficiently, the dam must be able to control sufficiently-large volumes of fluid and provide large water head (the height of water in the enclosure) that can be used to produce energy.

Hydroelectricity Working Principle: A Reservoir for Water Capture (Credit: Krish Dulal 2011 .CC BY-SA 3.0.)
Hydroelectricity Working Principle: A Reservoir for Water Capture (Credit: Krish Dulal 2011 .CC BY-SA 3.0.)


2). Energy Transformation

There are three main energy conversions which occur in the process of generating hydroelectricity. These are potential-kinetic, kinetic-mechanical, and mechanical-electricity.

Potential-to-kinetic energy conversion occurs at the reservoir and dam, where water capture and mobilization occur. This means that the first energy transformation coincides with the first step in the hydroelectricity generation process.

Water (or any other hydraulic fluid) possesses potential energy while it is in the reservoir [13]. The magnitude of this energy is proportional to the volume of the hydraulic fluid, and the hydraulic head (or level) of the fluid in the reservoir.

As the water flows, it acquires kinetic energy, which is highest as it falls from the dam. This signifies the conversion or transformation of potential energy to kinetic energy.

Factors that determine the magnitude of kinetic energy produced in a hydroelectric system include the volume of hydraulic fluid, velocity of flow, size of the dam, and distance of fall.

The hydraulic fluid now mobilized, is channeled toward the turbine by the penstocks and other fluid flow-control components, where the next phase of energy conversion occurs. This is the conversion of kinetic energy to mechanical energy, and it is facilitated by the rotation of the turbine under the influence of the hydraulic fluid.

Lastly, mechanical energy is converted to electricity through the process of electromagnetic induction.

Hydroelectricity Working Principle: A Dam for Potential-Kinetic Energy Conversion (Credit: Dnirvine 2005 .CC BY 3.0.)
Hydroelectricity Working Principle: A Dam for Potential-Kinetic Energy Conversion (Credit: Dnirvine 2005 .CC BY 3.0.)


3). Electromagnetic Induction

Electromagnetic induction is the final step in the working principle of hydroelectricity generation.

The main components of a hydroelectric system which are involved in this stage are the turbine and generator. These two can be viewed as a single unit, described as a turbine-generator.

In electromagnetic induction, electricity is generated as a result of the continuous motion of a conductor within a magnetic field. The continuous motion is provided by the turbine as it converts kinetic energy from the hydraulic fluid to mechanical energy of rotation.

The generator is usually equipped with a magnetic unit, which may be either a permanent magnet or an electromagnet, that provides the magnetic field required for electricity generation.

Based on the principle of electromagnetic induction [4], the continuous rotation of the turbine (conductor) in the magnetic field causes a flow of current through the conductor.

There are various types of turbines used in hydroelectric systems to generate power. The amount of hydroelectricity which is generated by these systems depends on factors such as the type of turbine, size of the system, speed of rotation and efficiency of the generator.



Hydroelectricity is a renewable form of electricity which is generated when a hydraulic fluid like water is captured, mobilized, and used to drive a turbine generator.

Generation of hydroelectricity dates back to the late eighteenth century, with the early development of hydraulic technological systems.

The working principle of hydroelectricity generation involves a combination of fluid capture/mobilization, energy transformation, and electromagnetic induction.



1). Ajibola, O. O. E.; Ajala, O.; Akanmu, J. O.; Balogun, O. (2018).”Improvement of hydroelectric power generation using pumped storage system.” Nigerian Journal of Technology 37(1):191. Available at: https://doi.org/10.4314/njt.v37i1.25. (Accessed 26 June 2022).

2). Askari, M.; Abadi, V. M. M.; Mirhabibi, M.; Dehghani, P. (2015). “Hydroelectric Energy Advantages and Disadvantages.” Available at: https://www.researchgate.net/publication/275094706_Hydroelectric_Energy_Advantages_and_Disadvantages. (Accessed 25 June 2022).

3). Curtis, T.; Levine, A.; Mclaughlin, K. (2018). “Privilege: Case Studies and Considerations.” Available at: https://doi.org/10.13140/RG.2.2.13023.10402. (Accessed 26 June 2022).

4). Dinis, C. M.; Popa, G. N.; lagăr, A. (2017). “Analysis of synchronous and induction generators used at hydroelectric power plant.” IOP Conference Series Materials Science and Engineering 163(1):012033. Available at: https://doi.org/10.1088/1757-899X/163/1/012033. (Accessed 26 June 2022).

5). El-Shimy, M. (2019). “CONCEPTUAL ELECTROMECHANICAL DESIGN OF NEW HYDROPOWER PLANTS (RESERVOIR & RUN-OF-RIVER).” Available at: https://doi.org/10.6084/m9.figshare.7752050. (Accessed 26 June 2022).

6). Gleick, P. H. (2008). “The World’s Water 2008-2009. Three Gorges Dam Project, Yangtze River China.” Available at: https://www.researchgate.net/publication/288878019_The_World’s_Water_2008-2009_Three_Gorges_Dam_Project_Yangtze_River_China. (Accessed 26 June 2022).

7). Khayal, O. (2019). “Hydroelectric Power Generation.” Available at: https://www.researchgate.net/publication/334415904_Hydroelectric_Power_Generation. (Accessed 26 June 2022).

8). Kumar, A.; Schei, T.; Ahenkorah, A.; Rodriquez. R. C.; Devernay, J.; Freitas, M.; Hall, D.; Killingtveit, A.; Liu, Z. (2012). “Hydropower.” IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation (pp.437-496). Available at: https://www.researchgate.net/publication/267639314_Hydropower. (Accessed 26 June 2022).

9). Kumar, A.; Singhal, M. K. (2015). “Optimum Design of Penstock for Hydro Projects.” International Journal of Energy and Power Engineering 4(4):216-22. Avaialble at: https://doi.org/10.11648/j.ijepe.20150404.14. (Accessed 26 June 2022).

10). Lewis, B.; Cimbala, J. M.; Wouden, A. M. (2014). “Major historical developments in the design of water wheels and Francis hydroturbines.” IOP Conference Series Earth and Environmental Science 22(1):012020. Available at: https://doi.org/10.1088/1755-1315/22/1/012020. (Accessed 26 June 2022).

11). Okpighe, S. (2010). “HYDRO AND GEOTHERMAL ENERGY.” Available at: https://www.researchgate.net/publication/334764310_HYDRO_AND_GEOTHERMAL_ENERGY. (Accessed 26 June 2022).

12). Petrescu, F. I. T.; Petrescu R. V. (2015). “HYDROPOWER AND PUMPED-STORAGE.” Available at: https://www.researchgate.net/publication/284551465_HYDROPOWER_AND_PUMPED-STORAGE. (Accessed 26 June 2022).

13). Rani, P.; Pandey, N.; Datta, R. (2014). “HYDROELECTRIC ENERGY DEPENDENCY WITH INCREASE SOURCES OF ENERGY CONSUMPTION.” Available at: https://www.researchgate.net/publication/342746673_HYDROELECTRIC_ENERGY_DEPENDENCY_WITH_INCREASE_SOURCES_OF_ENERGY_CONSUMPTION. (Accessed 26 June 2022).

14). Richter, W.; Zenz, G.; Schneider, J.; Knoblauch, H. (2015). “Surge tanks for high head hydropower plants – Hydraulic layout – New developments / Wasserschlösser für Hochdruck-Wasserkraftanlagen – Hydraulische Auslegung – Neue Entwicklungen.” Geomechanik und Tunnelbau 8(1):60-73. Available at: https://doi.org/10.1002/geot.201400057. (Accessed 26 June 2022).

15). Safta, C.; Vasile, L. (2012). “Management of a hydroelectric mobile dam.” Available at: https://www.researchgate.net/publication/265268253_Management_of_a_hydroelectric_mobile_dam. (Accessed 26 June 2022).

16). von Sperling, E. (2012). “Hydropower in Brazil: Overview of Positive and Negative Environmental Aspects.” Energy Procedia 18:110–118. Available at: https://doi.org/10.1016/j.egypro.2012.05.023. (Accessed 26 June 2022).

Similar Posts