How Do Hydropower Plants Generate Electricity?
Conventional sources of energy are the energy that is naturally available in nature. They are present in a minimal amount in the world, and will one day perish if it is not sustainably used. Natural gas, coal, oil, thermal power plants, hydroelectricity, and hydropower plants are some of the examples of conventional sources of energy. Among these sources, hydroelectricity is considered to be clean and an efficient source of energy for long term use.
The most significant disadvantage of conventional sources of energy is that they tend to pollute the environment. They are also very limited and finite in terms of quantity available for extraction. The only exception is hydroelectricity. India has a high potential to produce electricity with hydropower plants. Only 15% of the total open source is being used right now. Therefore, you need to get a proper grasp on what is hydroelectricity and on what is hydropower plant.
Hydroelectricity
Let's start by answering the question of what is hydroelectricity. When electrical current is generated from the kinetic energy of flowing water, we call it hydroelectricity. It could be a water turbine driven electric generator in a dam, a generator driven by a water wheel in a water stream, or even an air-driven electric generator in which air is compressed to drive the generator by the action of ocean waves.
Advantages of Hydroelectricity:
It is a clean and non-polluting source of energy.
No fuel is required. Water is the source of energy, and it does not consume water.
Dams are constructed near rivers. As the water level rises, the kinetic energy of water gets changed to potential energy.
Disadvantages of Hydroelectricity:
Highly expensive.
Large areas of human habitation and agricultural fields are submerged.
Dams can be made in limited areas.
Uses of Hydroelectricity:
To generate and supply clean energy.
Hydroelectricity is stored during low usage and used when demand increases.
Hydropower Plant
Let's try to understand what is hydropower plant. When water is at a height, it has potential energy stored in it. When this water flows down, its potential energy is first converted to kinetic energy and then to mechanical energy with the help of turbines. With the use of a generator, the mechanical energy is transformed into electrical energy. Hydropower is essential only next to thermal power. Hydropower plants meet nearly 20% of the total power of the world.
Advantages of Hydropower Plants:
Rainwater is stored in the dam. Thus, it is considered to be a renewable source of energy.
The construction of dams helps in providing irrigation of the local farmers; it also helps in controlling floods.
This method of electricity generation does not produce any pollution.
Their operational cost is very low.
The Disadvantage of Hydropower Plants:
Hydropower plants require high capital with a low rate of return.
Dams can only be built at specific locations.
A Large area of agriculture is submerged underwater.
Uses of Hydropower Plants:
Since the generation of electricity in hydropower plants is very quick, they can provide essential back-up power during major electricity outages.
Hydropower is used to control flood, help in irrigation, and water supply.
Hydropower plays a major role in reducing greenhouse gas emissions.
Working Principle of Hydropower Plant
Now that you have a thorough understanding of what is hydroelectricity, and on what is hydropower plant, we will soon see how is hydroelectricity produced in the plants. We use the gravitational force of the water to produce electricity.
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The first thing that we need is a high-rise dam to stop the flow of water and accumulate it in one place. When all the water is gathered, a lot of potential energy is stored in the water. Next, the sluice gates are opened up, and the water is made to flow with high pressure. When water flows, the potential energy gets converted into kinetic energy. When the running water hits the blades of a turbine, the kinetic energy of the water is converted into mechanical energy. This turbine is in turn connected to a generator. As the turbine rotates rapidly, the generator generates electricity in the powerhouse. The used water will flow out into the river, and the water level in the dam decreases. This level will increase once again with the help of natural rainwater. Therefore, it is a natural resource that will never get exhausted.
World Distribution of Hydropower
The most crucial and widely used renewable source of energy is hydroelectricity which is produced in hydropower plants. Hydropower plants meet only 20% of the total power of the world. When it comes to the production of hydroelectricity, China is the largest producer, followed by the United States, Brazil, and Canada. Around 66% of the economically feasible hydropower is yet to be tapped. Untapped resources are still present in Central Africa, China, India, and Latin America.
Hydropower remains the dominant electricity source across North and Central America.
South America was the second-fastest-growing region, adding 4,855 MW in installed hydropower capacity in 2018.
Hydropower is increasingly recognised in Europe for its flexible services to maintain secure, affordable and sustainable energy supply
East Asia and the Pacific again saw the highest annual increase in hydropower installed capacity in 2018.
FAQs on Hydroelectricity and Hydropower Plant Explained
1. What is hydroelectricity and how does a hydropower plant generate it?
Hydroelectricity is the electricity produced from the energy of moving water. A hydropower plant is the facility designed to capture this energy. The core principle involves building a dam on a river to create a large reservoir of water at a significant height. This stored water possesses gravitational potential energy. When released, it flows downwards through a channel called a penstock, converting its potential energy into kinetic energy. This fast-flowing water strikes the blades of a turbine, causing it to spin and transforming the kinetic energy into mechanical energy. Finally, the turbine is connected to a generator, which converts this mechanical energy into usable electrical energy.
2. What are the main components of a typical hydroelectric power plant and their functions?
A conventional hydroelectric power plant consists of several key components working in sequence:
Dam and Reservoir: The dam is a large barrier that obstructs the flow of a river, creating a reservoir behind it. Its primary function is to store water and raise its level to create a 'head' or height, which is the source of the potential energy.
Intake and Penstock: The intake gates control the flow of water from the reservoir into the penstock, which is a large pipe or tunnel. The penstock carries the water down to the turbine, building up speed and pressure.
Turbine: This is a device with a series of blades. The force of the falling water pushes against the blades, causing the turbine to rotate at high speed. It is the component that converts the water's kinetic energy into rotational mechanical energy.
Generator: Connected to the turbine by a shaft, the generator uses the turbine's rotation to spin a series of large electromagnets past stationary coils of copper wire. This process of electromagnetic induction generates electricity.
3. What is the fundamental difference between hydroelectricity and a hydropower plant?
The difference is between the product and the process. Hydroelectricity is the end product—the electrical energy generated from the force of moving water. In contrast, a hydropower plant (or hydroelectric power station) is the entire infrastructure—the dam, reservoir, turbines, and generators—that facilitates the process of converting water's potential energy into that electricity. Essentially, the plant is the factory, and hydroelectricity is the good it produces.
4. What are the main types of hydropower plants based on their operation?
Hydropower plants are primarily classified into three main types based on how they utilise water:
Impoundment (Reservoir) Type: This is the most common type. It uses a large dam to store river water in a reservoir. Electricity is generated by releasing water from the reservoir through a turbine, which activates a generator.
Diversion (Run-of-River) Type: This type channels a portion of a river's flow through a canal or penstock to a turbine. It typically requires minimal or no water storage in a large reservoir, making it less disruptive to the river's flow and often smaller in scale.
Pumped Storage Type: This plant works like a battery. It stores energy by pumping water from a lower reservoir to an upper reservoir during times of low electricity demand (e.g., at night). During periods of high demand, the water is released back down to the lower reservoir, passing through a turbine to generate electricity.
5. What are the main advantages and disadvantages of using hydropower for electricity generation?
Hydropower has significant benefits but also comes with notable drawbacks.
Advantages:
Renewable: It is powered by the Earth's water cycle, which is a continuous and renewable process.
Low Operating Costs: Once the plant is built, operational costs are relatively low as the fuel (flowing water) is free.
High Reliability: Hydropower is a highly reliable and consistent energy source compared to intermittent sources like solar or wind.
Disadvantages:
High Initial Investment: Building a dam and power plant requires a massive upfront capital investment and a long construction period.
Environmental Impact: The creation of a reservoir floods large areas of land, disrupting ecosystems, displacing communities, and potentially blocking fish migration.
Geographical Dependence: Suitable sites with sufficient water flow and elevation change are limited to specific geographical locations.
6. Why is hydroelectricity considered a 'clean' and 'renewable' source of energy?
Hydroelectricity is considered clean because the generation process itself does not burn fossil fuels or release greenhouse gases like carbon dioxide and sulphur dioxide into the atmosphere, which are major contributors to acid rain and climate change. It is considered renewable because it relies on the water cycle, which is constantly replenished by solar energy causing evaporation and subsequent rainfall. As long as rain and snow feed the rivers, the 'fuel' for hydropower is naturally and continuously available, unlike finite resources like coal, oil, or natural gas.
7. How does the construction of a large hydropower dam impact the local environment and ecosystem?
While hydropower generates clean energy, the construction of a large dam has significant environmental consequences. Creating a reservoir involves flooding vast areas of land, which can destroy forests, wildlife habitats, and agricultural land, as well as displace human communities. The dam acts as a barrier, disrupting the natural flow of the river, which can alter downstream ecosystems, affect water temperature, and block the migratory paths of fish like salmon. Furthermore, the decomposition of submerged organic matter in the reservoir can release methane, a potent greenhouse gas, partially offsetting its 'clean' energy benefit.
8. Compare the primary energy conversion process in a hydropower plant with that of a thermal power plant.
The fundamental difference lies in the initial source of energy used to turn the turbine. In a hydropower plant, the conversion starts with the gravitational potential energy of water stored at a height. This is directly converted into kinetic energy and then mechanical energy to spin the turbine. In a thermal power plant (using coal, for example), the process begins with the chemical energy stored in the fossil fuel. This fuel is burned to convert water into high-pressure steam (thermal energy), and it is the kinetic energy of this steam that is used to spin the turbine. Both plants ultimately use a turbine and generator, but the initial energy source and the method to create motion are entirely different.
9. What are some real-world examples of major hydroelectric power plants in India?
India is home to several large-scale hydroelectric power plants that are crucial to its energy grid. Some prominent examples include:
Tehri Dam, Uttarakhand: Located on the Bhagirathi River, it is the tallest dam in India and one of the tallest in the world, with a significant power generation capacity.
Bhakra-Nangal Dam, Himachal Pradesh/Punjab: A concrete gravity dam on the Sutlej River, it is one of India's earliest and most iconic multi-purpose river valley projects, vital for both irrigation and power.
Srisailam Dam, Andhra Pradesh/Telangana: Constructed across the Krishna River, it has the second-largest capacity for hydroelectric power generation in the country.
Koyna Hydroelectric Project, Maharashtra: It is a complex project with four dams and is the largest completed hydroelectric power plant in India.
