What Is Hydro Energy Power?

What is hydro energy power?

Hydroelectric power, also known as hydropower, is electricity generated from moving water. Hydropower has a long history dating back to the late 19th century when the first hydropower plant opened on the Fox River in Wisconsin in 1882 (Hydropower and Modernisation in Twentieth-Century Ghana).

Hydropower plants capture the energy of flowing water to generate electricity. Typically, they use a dam to store river water in a reservoir. The water flows through an intake and pushes against turbine blades in the hydropower plant, causing them to turn. The turbine spins a generator to produce electricity. The electricity is then transmitted through power lines to homes, businesses, and industries (Dams: history and purpose).

Hydropower is considered a renewable energy source because it relies on the water cycle. As long as there is a flow of water, electricity can be generated.

Hydroelectric Power Sources

There are three main types of hydropower facilities:

Impoundment facilities use a dam to store water in a reservoir. Water released from the reservoir flows through a turbine, spinning it, which in turn activates a generator to produce electricity. The Grand Coulee Dam in Washington is an example of an impoundment facility, one of the largest hydropower dams in the United States. As of 2020, hydroelectric power from dams accounted for 44% of total U.S. hydroelectric generation1.

Diversion facilities channel a portion of a river through a canal or penstock to turbines and generators. An example is the Robert Moses Niagara hydropower plant, which diverts water from the Niagara River to produce electricity.

Pumped storage facilities pump water from a lower reservoir to a higher reservoir when electricity demand is low. During periods of high demand, power is generated by releasing the stored water through turbines back down to the lower reservoir. For example, the Brâtum pumped storage plant in Norway has an upper reservoir located inside a mountain.

Some of the major rivers used for hydropower in the United States include the Colorado River, Columbia River, and Mississippi River. The Columbia River has 14 hydroelectric dams, which together account for a large portion of renewable energy generation in the Pacific Northwest2.

Advantages of Hydropower

Hydropower has several key advantages that make it an attractive energy source:

Renewable – Hydropower is considered a renewable energy source because it relies on the water cycle. Rain and snow regenerate the water in rivers and reservoirs used to generate electricity.[1]

Reliable – Hydropower can generate electricity 24/7 and adjust output to meet demand. Reservoir storage capacity makes it a dependable source of electricity.[2]

Cost-effective – After a hydropower plant is built, electricity generation is inexpensive compared to fossil fuels. Maintenance costs are low relative to other technologies.[1]

Emission-free – Hydropower does not burn fuel, so it produces no air pollution or greenhouse gases. It has one of the lowest carbon footprints of any energy source.[2]

[1] https://www.energy.gov/eere/water/benefits-hydropower
[2] https://www.enelgreenpower.com/learning-hub/renewable-energies/hydroelectric-energy/advantages

Disadvantages of Hydropower

While hydropower is a renewable energy source with many benefits, there are some downsides to be aware of:

One key disadvantage is the impact constructing dams and hydropower facilities can have on rivers and local wildlife habitats. Building a dam floods areas upstream and alters water levels downstream, which disrupts the natural flow of the river. This impacts the local ecosystem by changing water temperatures, nutrient levels, sediment transport, and more. Many species that are adapted to the natural flow can struggle to survive.[1]

Another disadvantage is that suitable hydropower dam sites are geographically limited based on topology and water sources. While hydropower is renewable, facilities require specific terrain and rivers to effectively generate electricity. This makes expanding hydropower’s share of energy production challenging compared to other renewable sources that can be more widely built, like wind or solar farms.

Output levels at hydropower dams can also vary based on precipitation and droughts. During periods of drought, the amount of electricity generated can decline when water levels drop. This can make hydropower generation less consistent than other sources.[2]

Hydropower Generation Process

Hydropower plants generate electricity by using the energy from flowing water to turn turbines. Here’s how the hydropower generation process works:1

The process starts by directing water from a high-elevation reservoir through intake gates that control water flow. The water is channeled through a penstock, which is a pressurized tunnel or pipe. As the water flows through the penstock, it gains speed and kinetic energy. At the end of the penstock, the high-velocity water spins hydraulic turbine blades, which converts the kinetic energy of the moving water into mechanical energy. The turbine is connected to a generator, so as the turbine spins, it rotates magnets within the generator. This motion of the magnets induces a voltage that generates electricity. Generators convert this mechanical energy from the spinning turbine into electrical energy that can be used in homes, businesses, and industries.

Hydropower Capacity and Usage

Currently, global installed hydropower capacity is estimated at over 1,300 gigawatts (GW) as of 2022, with China, Brazil, and Canada representing the countries with the highest capacity. China has the most installed hydropower worldwide with over 380 GW, accounting for over a quarter of total global capacity. Brazil and Canada follow with 109 GW and 81 GW respectively. Other top countries include the United States, Russia, and India.[1]

Hydropower accounts for over 16% of total electricity generation globally and makes up 71% of all renewable energy. In Europe, hydropower contributes roughly 15% of the total electricity mix. Some countries rely on hydropower for the vast majority of their renewable electricity, with Norway generating over 95% of its renewable electricity from hydro resources.[2] The abundance of water resources and high capacity dams allow countries with favorable geography to utilize hydropower on a large scale.

Notable Hydropower Projects

Some of the most noteworthy and famous hydropower facilities around the world include:

Three Gorges Dam – This massive dam on the Yangtze River in central China is the world’s largest power station in terms of installed capacity at 22,500 MW. The dam is controversial due to displacement of communities and environmental impacts, but generates enormous amounts of electricity.

Itaipu Dam – Located on the Paraná River bordering Brazil and Paraguay, Itaipu is the world’s second largest hydroelectric power plant with an installed capacity of 14,000 MW. The joint project between the two countries supplies 17% of Brazil’s electricity.

Guri Dam – This giant dam in Venezuela has a capacity of 10,235 MW, making it one of the largest hydroelectric facilities on the planet. The dam provides 73% of Venezuela’s electricity.

Grand Coulee Dam – Built on the Columbia River in Washington State, USA, Grand Coulee is among the world’s largest hydropower plants with 6,809 MW of capacity. It is a major source of electricity and irrigation water in the western United States.

Sayano–Shushenskaya Dam – Located in southern Siberia, Russia, this is the largest power plant in Russia and among the top 10 biggest in the world. The dam has an installed capacity of 6,400 MW and provides a substantial portion of Siberia’s electricity supply.

Small-Scale and Micro Hydropower

Small-scale hydropower systems generate up to 10 megawatts of electricity using hydro turbines and water pipes. These systems are appealing for remote communities, rural areas, and isolated grids that lack connection to a widespread power network. Small hydropower systems provide a local, renewable energy source without requiring a large dam or reservoir.

Micro hydropower specifically refers to systems under 100 kilowatts. Micro hydropower can provide electricity to small villages, rural areas, and even individual homes that are off-grid. These small systems take advantage of low-head, run-of-river sites to generate modest amounts of electricity. Small streams, pressure pipelines, irrigation canals, or other water conveyance structures are used to divert water to micro hydropower turbines. https://earthship.com/2020/03/28/micro-hydro-power-pros-and-cons/

The main benefits of micro hydropower for remote areas include:

  • Provides a local source of electricity from small streams and rivers, without requiring a large dam
  • Can serve isolated, rural communities and households that lack grid connection
  • Renewable energy with minimal operational costs after installation
  • Lower cost than extending power lines over long distances

With modest infrastructure requirements, micro hydropower provides an accessible way for off-grid communities to generate their own electricity. The small scale makes these systems economical for meeting basic electricity needs in rural areas disconnected from the main grid.

Future of Hydropower

Hydropower is still the largest source of renewable energy globally, and has significant potential for future growth and expansion. According to the International Hydropower Association, untapped hydropower resources could nearly double the global hydropower capacity to more than 2,000 GW by 2050 (Source). With greater investment and hydro project development, hydropower capacity is projected to grow 50% by 2050, especially in Asia, Africa and Latin America.

Innovations in hydropower technologies and plant modernization will enable greater efficiency and power generation capabilities. Upgrades to existing infrastructure, new pumped storage facilities, and advances in turbine, control systems and materials technologies will help maximize output. Emerging innovations like hydrokinetic turbines and in-stream turbines that generate power from river currents show promise for small-scale hydropower growth.


In summary, hydropower is an important renewable energy source that generates electricity by utilizing the natural water cycle and flow of rivers. Hydropower plants capture the kinetic energy of flowing water by diverting it through turbines, which turn generators to produce electricity. The main types of hydropower facilities include impoundment, diversion, pumped storage, and low-head/micro hydropower plants.

The key advantages of hydropower include its renewability, reliability, flexibility, low operating costs, and lack of greenhouse gas emissions. It currently provides around 16% of the world’s electricity supply. However, hydropower also has some drawbacks, such as high upfront capital costs, potential social and environmental impacts, and vulnerability to droughts. Overall, hydropower is likely to remain a major component in the global renewable energy mix going forward, especially with development of new large-scale projects and micro hydropower applications.

As an emissions-free and renewable power source, hydropower will be an important technology for combating climate change and transitioning the world to sustainable energy. With careful planning and environmental mitigation, hydropower can provide clean and reliable electricity to support both industrial development and rural electrification needs globally.

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