What Do Most Hydropower Plants Rely On?
Hydropower is an important source of renewable electricity generation globally and in the United States. Hydropower relies on flowing water to generate power at plants located on rivers, streams, or constructed waterways like canals. In this article, we will provide an overview of how most hydropower plants work, including their main components like dams, turbines, and generators. We’ll also explore the water supply needs of hydropower plants and their generating capacity.
Hydropower Basics
Hydropower is a form of renewable energy that relies on water’s flow or its elevation to generate electricity. Hydropower plants capture the energy of flowing water to produce electric power.
Most hydropower plants rely on a dam along a river or stream to create a reservoir. Water in the reservoir flows through a turbine, which spins a generator to produce electricity. The amount of electricity that can be generated depends on how far the water drops and how much water moves through the system.
As water flows downstream past the dam, some of that energy gets “captured” by the huge turbines inside the hydropower plant. The turning turbine activates a generator to produce electricity. The electricity is then transported via huge transmission lines to homes, businesses, and industries across the country.[1]
Hydropower is a renewable source of energy because it relies on the water cycle. The water cycle is constantly recharging the water in rivers and streams that supply hydropower plants. As long as adequate water supply is maintained, hydropower is a renewable resource that can generate clean electricity indefinitely.[2]
Overall, hydropower relies on the force of falling or fast-moving water to spin a turbine connected to a generator, producing carbon-free electricity in the process.
[1] https://www.energy.gov/eere/water/how-hydropower-works
[2] https://www.eia.gov/energyexplained/hydropower/
Main Components of Hydropower Plants
Hydropower plants rely on four main components to generate electricity: the dam, reservoir, turbine, and generator. Components of a Hydropower Plant and their Functions.
The dam is built to control water flow and create a reservoir. The reservoir stores potential energy in the form of water held at an elevation. Hydroelectric Power Plant Components. When water is released from the reservoir, gravity causes it to flow downhill through the penstock towards the turbine. The moving water rotates the turbine, transforming the potential energy into mechanical energy.
The turbine is connected to the generator shaft. As the turbine spins, it rotates the generator, which converts the mechanical energy into electrical energy. Generators rely on the principles of electromagnetism to generate electricity. The generated electricity is then transported via transmission lines to homes, businesses, and the power grid.
Water Supply
Most hydropower plants rely on river water flow and elevation drop to turn turbines and generate electricity. The kinetic energy of flowing water is converted into mechanical energy by the turbine, which then rotates a generator to produce electricity.
Hydropower plants require a reliable water source with substantial flow and elevation change, typically harnessing the potential energy in water as it flows downstream from higher to lower elevations. According to the U.S. Geological Survey, hydropower represents about 17% of total renewable electricity generation globally, underlining its reliance on sufficient river water supply and flow.[1]
Dams along rivers often regulate and control water flow for optimizing hydropower generation. Storing water in reservoirs behind dams allows electricity to be generated on demand when water is released through the turbines. So most hydropower depends on adequate river water volume and flow rate to drive turbine rotation.[2]
With most hydropower harnessing the potential energy of falling or fast-flowing river water, water supply and flow are the primary reliance of hydropower plants worldwide.
[1] https://www.usgs.gov/special-topics/water-science-school/science/hydroelectric-power-water-use
[2] https://www.energy.gov/eere/water/hydropower-basics
Dams
Dams play a critical role in hydropower plants by creating reservoirs that store water and control its flow. The dam acts as a barrier that impounds rivers and streams, allowing water to collect in the reservoir behind it. This creates a water supply that can be controlled.
Dams provide the hydropower plant with the ability to regulate water flow and release water on demand for electricity generation. The water in the reservoir has potential energy which gets converted to kinetic energy as it travels through the dam’s intake and penstock pipes. The controlled release of water drives the turbines which then generate electricity.
By regulating water flow, dams also provide flood control and water storage benefits. Excess water can be held back during periods of high rainfall and released slowly over time or saved for drier periods. Overall, the dam’s ability to create a reservoir and manage water flow is essential for hydropower generation. <"https://www.hydro.org/waterpower/why-hydro/other-benefits/">Most hydropower installations are multi-purpose, providing services like irrigation, municipal water supplies, and recreation in addition to renewable electricity generation.
Turbines
One of the key components in a hydropower plant is the turbine, which converts the energy of flowing water into rotational mechanical energy (U.S. Department of Energy, https://www.energy.gov/eere/water/types-hydropower-turbines). There are two main types of turbines used in hydropower plants – reaction turbines and impulse turbines.
Reaction turbines, such as propeller and Francis turbines, operate by water flowing through the turbine and causing blades to spin. Propeller turbines are well-suited for low-head, high-flow applications, while Francis turbines are used for a wider range of head and flow combinations (Enel Green Power, https://www.enelgreenpower.com/learning-hub/renewable-energies/hydroelectric-energy/hydroelectric-turbines).
Impulse turbines, like Pelton wheels, operate by water jets striking and turning buckets on the wheel. Pelton turbines are used for high-head, low-flow sites. The kinetic energy of the water jet is converted into rotational energy by the impulse of the water jet on the buckets.
The optimal turbine design depends on the head and flow characteristics of the site. Proper turbine selection and design is critical to maximizing the conversion of hydraulic power into rotational mechanical power.
Generators
The generator is a key component of hydropower plants. Its role is to convert the mechanical power from the spinning turbine into electrical power. Inside the generator, coils of wire rotate around magnets to produce an electric current based on Faraday’s law of electromagnetic induction.
When the turbine spins, it rotates a shaft connected to the generator. This mechanical power from the spinning shaft causes electromagnets in the generator to rotate around coils of copper wire, or vice versa. As the magnetic field crosses the coils, it induces a voltage which generates an electrical current. This alternating current is delivered to a transformer to increase the voltage to the proper level for transmission (How Hydropower Works).
Therefore, the generator acts as the critical link between the kinetic energy of the moving water which spins the turbine, and the electric energy that is delivered to homes and businesses. Without the generator converting mechanical to electrical power, the hydropower plant could not produce usable electricity.
Transmission
Once the electrical power is generated at the hydropower plant, it must be transmitted to the end users like homes, businesses, and industries. Electricity generated from hydropower plants is typically transmitted over long distances via transmission lines and towers.
Transmission lines are necessary because hydropower plants are often located far from population centers. Dams are built in remote areas with optimal water resources, which could be hundreds of miles away from the demand for power. According to the U.S. Energy Information Administration, hydropower plants account for over 40% of all U.S. electricity generation in the Western United States, while population centers are mainly in the east. https://www.eia.gov/energyexplained/hydropower/
The transmission system converts the electricity from low voltages at the power plant to extremely high voltages for efficient long-distance transportation. Step-up substations with transformers increase the voltage from around 13-26kV at the plant to 230kV-765kV for the transmission lines. This minimizes energy losses over long distances. Step-down substations then reduce the voltage again for distribution to end users. Modern transmission systems interconnect grids so electricity can be moved between regions to match supply and demand.
Capacity
According to Statista, as of 2022, China had the largest installed hydropower capacity in the world, totaling 414.8 gigawatts. Brazil and Canada followed with the next highest capacities at 131 and 83.6 gigawatts respectively[1]. In terms of output, China also led with 1,328 terawatt-hours of hydropower generated in 2022. Brazil and Canada again followed behind with 428 and 393 terawatt-hours respectively[2].
While some developed countries like the United States, Canada, and Norway have significant hydropower capacity, most of the top countries for installed capacity and generation are developing nations. Countries like India, Vietnam, Turkey, and Malaysia are rapidly expanding their hydropower sectors to meet rising electricity demand and pursue renewable energy sources. The abundance of untapped hydro resources as well as lower construction costs make hydropower an attractive option for many developing countries.
Conclusion
Hydropower has been crucial as a renewable energy source for decades. Most hydropower plants rely on a combination of water supply, dams, turbines, generators and transmission lines to generate electricity. The main advantage of hydropower is that it harnesses the water cycle driven by the sun, making it a clean and sustainable energy source that does not emit greenhouse gases or other pollutants. While hydropower facilities require substantial infrastructure investments initially, they can operate for many decades and provide inexpensive electricity once built. Hydropower complements other renewable energy sources like wind and solar power as a flexible and reliable back-up energy supply when weather conditions fluctuate. Overall, hydropower will continue playing a vital role in the renewable energy landscape for the foreseeable future.
