A hydropower plant uses water to generate electricity. Hydroelectric is a renewable source of energy that produces electricity by using a dam or diversion structure to change the natural flow of a river or other water bodies.
Hydroelectric power is electricity generated by generators driven by the movement of water. Hydroelectric power plants typically consist of dams built to shut off the water from rivers, form reservoirs, or collect water that is pushed into the dam. As the water drains, the pressure along the block directs the downpipe towards the turbine. This turns a turbine, which in turn turns a generator that produces hydroelectric power. There are many types of hydropower plants, which we will look at later.
Our dependence on traditional and other resources such as coal, oil, and natural gas puts pressure on our planet, but we live damaging the environment and polluting the air. To get energy from these fossil fuels, they must be burned. When burned, it releases greenhouse gases such as N2O, CH4, CO2, and H2O. Greenhouse gases emit and absorb radiation.
Of the greenhouse gases mentioned, CO2 is the most common. It accounts for more than 80% of all greenhouse gases. The problem with high CO2 is that it absorbs and emits infrared radiation. This leads to an increase in the temperature of the Earth’s surface and the atmosphere closest to the surface, causing many potential problems.
As the Earth’s temperature rises, the ice caps begin to melt and release huge amounts of water into the ocean, raising sea levels. As a result, millions of people living in sea level areas are displaced. In the current environmental conditions, the need for renewable energy sources is starting to increase. Energy is considered renewable if it comes from an infinite source.
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Detailed Description
Hydropower accounted for 16.6% of global electricity and 70% of all renewable energy in 2015. It is projected to grow at about 3.1% per year over the next 25 years.
The relatively low cost of hydroelectric power makes it an inexpensive source of renewable electricity. Unlike coal or gas power plants, hydropower plants do not consume water. A typical electricity cost for a hydropower plant larger than 10 MW is 35 cents per kWh. With the help of dams and reservoirs, this is also an elastic source. The energy generated by hydroelectric power plants increases and decreases very quickly (in seconds) to accommodate changing energy requirements. The project does not generate any direct waste during the construction of the hydroelectric power plant.
Historically, hydroelectric power has been used to the water, plow, and pump crops. However, in the 19th century, its use spread to the smaller scale electricity production of that era.
This is because hydropower requires only the vertical movement of water. The reason for choosing hydropower over other forms of renewable energy is the amount used per year compared to the rest. According to various statistics, hydroelectric power consumption in 2017 was 4,065 TWh (terawatt-hour), while the cumulative energy consumption of other renewable energy sources was about 2,200 TWh. Also, comparing the use of hydroelectric power with the existing biofuel (fossil fuel) utilization, it can be seen that only hydroelectric power can completely replace biofuel as a renewable energy source.
Types of Turbines Used in Hydropower Plant
There are three main types of hydro turbines: reaction turbines, gravity turbines, and impulse turbines. The type of turbine for a hydropower plant is selected based on head and flow requirements. Some other factors are considered when choosing a turbine, such as a cost, efficiency, and turbine depth.
- Impulse turbines.
- Gravity turbines
- Reaction turbines
Impulse Turbines:
Impulse turbines typically use the speed of water to traverse a flow path and discharge it at atmospheric pressure. Water drips into every bucket in the hallway. The lower part of the turbine is not sucked. Water enters the rotor and then flows from the bottom of the turbine casing. Impulse turbines are generally suitable for low flow, high head applications. Impulse turbines are available in three main types: cross-flow turbines, Turgo turbines, and Pelton wheel turbines.
Gravity Turbines:
Gravity turbines are a perpetual kinetic energy concept that involves converting the kinetic energy of Earth’s gravity into electricity. The technology is still in its infancy and is undergoing significant improvements with new patents and advancements.
Reaction Turbines:
Reaction turbines are the most well-known type of hydro turbine. Reaction turbines generate electricity through the interaction of flowing water and pressure. Instead of hitting the flow paths one at a time, you place them directly into the water passing through the paddles. Compared to impulse turbines, reaction turbines are typically used in high-pressure head and high flow positions.
All types of reaction turbines have a diffuser under a flow path called a “draft pipe (or bleed pipe)” through which the water is drained. When the divider pipe slows the flow rate, a suction force is created below the flow path, which increases the effective height.
Relative Efficiencies of Turbines
A turbine operating at a specific speed produces a specific flow. If the river does not have enough flow to meet this demand, the turbine will begin to discharge and its performance will decrease rapidly. Then you need to close it or change its internal appearance. This process is called regulation. Variable turbines can increase or decrease the inlet flow by moving the inlet blades or impeller blades. Other turbines absorb less flow, inevitably reducing their efficiency.
Therefore, when comparing different types of turbines, the key factors are their relative efficiency and flow reduction effect at design time. For example, Kaplan and Pelton’s turbines are very efficient even when operating below the design flow rate of a hydropower plant. In contrast, cross flow and Francis turbines are less efficient when operating at less than half of normal flow.
Some Advantages of Hydroelectricity
1) Flexibility:
This type of energy is a flexible source of electricity. It can be raised or lowered very quickly with the help of hydropower to meet changing energy requirements. It only takes a few minutes to start a turbine in a hydropower plant. It takes 6090 seconds from cold start to full charge. This is much shorter than a steam power plant or gas turbine. Even if there is excess power generation, the amount of power generation can be quickly reduced. Therefore, other than emptying the pool or meeting downstream demand, the HPP’s limited capacity is usually not used to generate main power.
2) Low Cost:
The main advantage of conventional hydrostatic reservoir dams is that they store water in the form of high-quality clean energy for subsequent transportation at a low cost. The average electricity price for a hydropower plant with a capacity of 10 MW or more is 35 cents per kWh. If hydroelectric power is used as a peak current to meet demand, it is more valuable than basic power than intermittent power.
The economic life of hydroelectric power plants is very long, and some power plants can be used for 50-100 years. The system is automated, so operating labor costs are low and there are only a few people on-site during normal operations.
If the dam is used multiple times, adding a hydropower plant at a relatively low cost of construction can be a useful source of income to offset the cost of operating the dam. However, some evidence shows that, in most countries, without adequate risk management measures, large dam construction costs are too high and construction times are too long, resulting in risk adjustment. This shows that you cannot profit later.
3) Suitable for Industrial Applications:
Many hydroelectric projects provide electricity to the public grid, but some provide services to specific industrial companies. For example, dedicated hydroelectric projects are typically built to provide the large amounts of electricity needed for aluminum electrolysis plants.
4) Reduced CO2 Emissions:
Hydroelectric power plants do not consume fuel and hence they do not generate CO2. Carbon dioxide is first generated during project construction. The reservoir emits some methane each year, but the life cycle of greenhouse gases emitted from hydroelectric power is typically the lowest. In 2011, hydroelectric power displaced 3 billion tonnes of carbon dioxide compared to equivalent fossil fuel production. Wind energy is second. The third place is a nuclear power and the fourth place is solar power.
Hydropower has little impact on greenhouse gas emissions, especially in temperate countries. The impact of greenhouse gas emissions can be observed in tropical regions because power plants and reservoirs produce more methane in tropical regions than in tropical regions.
These power plants emit fewer greenhouse gases than solar and other power plants that must run on fossil fuels. Like other non-fossil fuels, hydroelectric power does not emit nitrogen oxides, sulfur dioxide, or other particles.
5) Safe:
Hydropower is safer than other fossil fuels and nuclear power. Contains no fuel except water.
Disadvantages of Hydroelectricity
(a) Ecosystem damage and loss of land:
Large reservoirs connected to traditional hydroelectric power plants can flood large areas upstream of dams and destroy biologically valuable and useful lowland, grassland, wetlands, and valley forests. The construction of large dams usually involves the movement of people and wildlife. However, dams can impede the flow of rivers and damage local ecosystems. Habitat fragmentation due to reservoirs often exacerbates land loss.
Hydroelectric projects can damage aquatic ecosystems before and after plants. Hydroelectric power plants have changed the environment downstream. The water flowing from the turbine is usually free of suspended sediments that can cause erosion and dike failure. Turbine doors often open temporarily and are observed quickly.
(b) Water loss due to Evaporation:
A 2011 National Renewable Energy Institute study found that US hydroelectric power plants generate between 5.39 and 68.14 cubic meters of hydropower per megawatt-hour (1,425-18,000 US gallons) per megawatt-hour. The average was 17.00 m3/MWh (4491 US gal/MWh). Therefore, the cooling tower is used for the loss of power generation technology including solar power at 2.98 cu at 3.27 m3/MWh (865 US gal/MWh). m/MWh (786 gal/MWh) of the CSP tank. Multiple uses of the reservoir (water supply, recreational, flood protection, etc.) result in evaporation of all reservoirs due to hydroelectricity.
(c) Siltation and flow shortage:
When water flows, it can carry particles heavier than itself downstream. This has detrimental effects on dams and subsequent power plants, especially rivers and silos. Silt reduces its ability to fill reservoirs and contain flooding. Apply horizontal pressure to the top of the dam. During floods, some sediments may become sandy, unusable, or flattened.
Changes in river flow are related to the energy generated by the dam. Low river flow reduces the amount of bottled water in the reservoir and the amount of water available for hydroelectric power generation. Regions that rely heavily on hydroelectric power due to reduced river flow may experience energy shortages.
Climate change may increase the risk of traffic congestion. A US study of the Colorado River found that moderate climate change could reduce river flow by 40%. For example, a 2 degree Celsius increase in temperature can reduce rainfall by 10%. Brazil is particularly vulnerable because of its high dependence on hydropower. By the turn of the century, overall energy production could be reduced by 7% per year due to rising temperatures, reduced runoff, and changing rainfall conditions.
(d) Emissions of Methane Gas:
Smaller positive effects were found in the tropics, as sediments from tropical power plants were found to produce large amounts of methane. This is because plant material in flooded areas decomposes in an anaerobic environment to form methane (greenhouse gas). The World Commission on Dams reports that the reservoir is larger than the generating capacity. In the reservoir, the surrounding forest was not cleared until the water had accumulated in the greenhouse. The gas discharged from the tank may be higher than the conventional tank.
Greenhouse gas emissions from reservoirs in America and Northern Europe typically account for 2-8% of general electricity production from fossil fuels. New methods of underwater logging in underwater forests could mitigate the impact of forest decline.
(e) Relocation Issue:
For hydropower plants, the dam needs a place, and people living in the planned reservoir area are relocated. In 2000, the World Dam Commission estimated that between 400 and 80 million people worldwide were evacuated from dams.
Types of Hydropower Plant
Currently, hydropower, solar power, solar power, wind power, waves, heat pumps, and many other types of renewable energy sources are being used. There are tons of renewable energy sources, but choosing the type of energy to use is just as important as using them. There are several factors to consider when choosing a renewable energy type, including environmental impact, cost, efficiency, and energy source.
In fact, hydro and coal-fired power plants generate electricity in the same way. In a reciprocal context, the energy source is used to rotate a propeller component called a turbine. The turbine rotates the electrical shaft of the generator. Coal-fired power plants use steam to turn turbine blades. Hydroelectric power plants use wastewater to drive turbines.
Hydropower is a renewable energy source that accounts for about one-sixth of the world’s electricity. Less polluting than steam engines. In some countries, such as Quebec or Norway, maximum power is obtained in this way.
Dams store large amounts of water in reservoirs. The water intake is at the bottom of the dam. Gravity pushes water through the pressure pipe into the dam. At the end of the pressure line, the turbine propeller rotates to release the water. The turbine shaft rotates and the generator generates electrical energy. Power cords connect to generators that provide electricity to homes and mines. The water continues to flow over the engine and through the propellers into the river next to the dam.
To fully understand the operation of a hydropower plant, several types of energy transfer must be considered. There are three main types of hydroelectric power plants. Reservoir, hydro accumulator, and rumor.
1) Impoundment Hydroelectric Power Plant:
Of the three types of hydropower plants, the most used type for collecting hydraulic power is impoundment. The system uses dams to store river water in reservoirs. During the operation of this HPP, the water from the reservoir is discharged into a canal. Water hits the turbine and rotates. The turbine is connected to the generator. The generator works due to the movement of the turbine shaft. Electricity generated by generators (located in power plants) is transmitted to the community through transmission lines and networks. Notable examples of impoundment hydroelectric power plants include the Hoover Dam (Colorado River, USA) and the Three Gorges Dam (Yangtze River, China).
A turbine is not simply placed in the center of a river or dam. so that the turbine can rotate easily. The reason is that the river’s water flow doesn’t have enough energy (both kinetic and potential) to rotate the turbine fast enough and consequently not enough energy to be delivered to the generator. Hence, the impoundment system has a hydraulic head with a vertical height difference between the water level in the upper reservoir and the water level in the lower reservoir. This provides much more kinetic and potential energy to the water flowing into the turbine. This is due to the change in altitude and the increase in the turbine rotation speed. This increased power consumption provides more power to the generator output. As a result, more hydropower is generated.
2) Pumped Storage Hydroelectric Power Plant
Pumped water storage dams are extensions of impoundment and run-of-river hydropower systems. They are generally much smaller in terms of power generation compared to other types of hydropower plants.
Pumped storage is to add a pumping method. Through this, the water discharged from the lower storage tank can be returned to the upper storage tank and reused during times of high power demand. During off-peak periods, the power plant reverses the rotation of the turbine so that when electricity demand increases, the water discharged from the lower reservoir can be pumped back through the penstock to the upper reservoir for reuse.
3) Run-of-River (Diversion) Hydropower Plant
The run-of-rive hydropower system is a well-known method of hydropower. This is a system that uses the natural flow of water to turn a turbine. This turbine is connected to a generator that produces hydroelectric power. Because they do not have significant height differences, they lack the potential energy of ordinary plants. The construction of a derivative plant requires a constant flow rate. Without a reservoir, water is sometimes diverted downwards through pressure reduction. The water, guided through the conduit, passes through a generator room where the water flow turns turbines identical to those of the reservoir. These turbines provide mechanical energy to the generator, which converts the generator into electrical energy. As before, this energy is delivered via power lines to where it is needed.
The Efficiency of the Hydropower Plant
Today, hydropower is the most efficient way to generate electricity on a large scale. The flow of energy can be converted and controlled. The conversion process absorbs CE and converts it directly into electrical energy. There are no inefficient thermodynamic intermediate processes, no heat losses, or no chemicals. To extract 100% of the kinetic energy from flowing water, the flow must be stopped so that the overall efficiency is never 100%.
Future of Hydropower
Hydropower uses PE in rivers and currently provides 17.5% of the world’s electricity (Norway 99%, Sweden 40%, Switzerland 55%, Canada 57%, and the United States 7%). Except in some countries, hydroelectric power is often used for peak loads because it is easy to start and stop. In developed countries, this is not a major option for the future. Most of these countries have evolved because there are critical locations (eg environmental factors) where gravity may or may not be accessible. Growth through 2030 is projected mainly in China and Latin America.
Final Thought
Hydropower is the cheapest form of electricity. It is increasing every day worldwide. The conversion efficiency of a hydropower plant largely depends on the type of turbine used.
For large mechanisms, the conversion efficiency can reach 95%. Small power plants with a capacity of less than 5 MW have efficiencies between 80% and 85%. However, it is difficult to obtain energy at low flow rates.