Hydroelectric power is electricity generated by water turbines that convert potential energy in falling water to mechanical energy.
Hydropower turbines are driven by water. The main source of energy is gravity and the height at which the water falls down into the turbine. The product of the water’s mass, the gravity factor (g = 9.81), and the head, which is defined as the difference between the dam level and the tailwater level, yields the stored water’s potential energy.
Hydropower can be generated from uncontrolled river flows, dams with limited storage capacity above natural flow, or water drawn from reservoirs that can store input for many years.
The power potential of one cubic meter of water is related to the distance between the dam and the turbine. The reservoir level dips somewhat when water is discharged, affecting electricity generation.
The way tailwater is moved away from the turbine, allowing new water to enter, has an effect on electricity output. The turbine is built to give the best possible water flow. Reduced or increased water intake may reduce power generation per unit of water.
The key economic question in hydropower production is the temporal pattern of water usage in the reservoir given the output capacity for each time period. If there is enough storage capacity, water used today can be reused tomorrow. As a result, most hydropower analysis is dynamic.
Dams and Diversions
A dam is used to store water that is subsequently used to create electricity. For example, the dam’s reservoir aids in the concentration of water flowing from a river. It can also be used to boost the river’s level and create falling water.
Dams are divided into several categories. Depending on the ground conditions, their structure changes. Gravity dams, for example, are constructed on the ground. Others lean against the riverbanks if they’re strong enough. Dams used in hydropower plants are schematically represented.
Dams must be regularly monitored because unintended failure is a risk. Between 1959 and 1987, 30 major dams collapsed, killing around 18,000 people. Despite the fact that dams are constantly monitored and maintained, 0.6 percent of all dams have failed.
Dams are not necessary to generate electricity. Diversion or run-of-the-river is the term for this. The aim is to use a penstock to divert part of the water from fast-flowing rivers to a turbine. In areas like Niagara Falls, diversion is used.
A water wheel on a floating platform might power the Amazon River, the world’s largest river system. On the scale of what our forebears could harness, the amount of energy that can be harnessed is little. It would only generate about 650MW of electricity.
Head and Flow
The height of the waterfalls as well as the flow rate of the water. The potential energy per unit of time arising from a flow of water falling from a large height is the power that can be recovered.
The entire efficiency of generating electricity from water flow is around 85%. The yield factor between reservoir potential energy and power output is in the range of 75–80 percent, depending on the site and technology, due to flow losses before the water reaches the turbine blades. This is significantly more than any fossil-fuel power plant could provide.
The same quantity of power can be generated by many types of hydroelectric facilities. It can be supplied by a high head reservoir with a limited flow, such as those found in the mountains, or a low head reservoir with a large flow, such as those found in rivers.
A high head is defined as a height difference of more than 100 meters between the low and high altitude regions of a mountain. A difference of less than 10m is referred to as a low head. A medium-sized head is roughly in the middle. The divisions between classes are rarely as obvious in reality.
The penstock, or pipe that conveys the flow, must endure high pressures when the head is high. The pressure rises by one atmosphere every ten meters due to the high density of water. A 1000m head at the outflow level equals an increased pressure of 100 atm.
Water turbines are the modern equivalents of traditional waterwheels. They convert potential energy generated by the difference in elevation between an upstream water reservoir and the turbine-exit water level (the tailrace) into work. Hydroelectric plants presently use the majority of water turbines to generate energy.
Impulse turbines, which are utilized for high water heads and low flow rates, are the most common type of water turbine. Reaction turbines, which are employed for heads of less than 450 meters and moderate to high flow rates, come in a wide range of designs. They are available with horizontal or vertical shafts.
An impulse turbine converts potential energy, or the head of water, into kinetic energy by discharging water through a precisely designed nozzle. To collect water energy and convert it to usable work, the jet is launched into the air and directed onto curved buckets attached to the runner’s perimeter.
Modern impulse turbines are based on an idea established by American engineer Lester Allen Pelton in 1889. The efficiency can reach 91 percent when running at 60–80 percent of full load.
The power of a wheel can be increased by using many jets. Two-jet setups are popular for horizontal shafts. A single shaft can sometimes have two independent runners driving a single electric generator. Four or more separate jets can be found in vertical-shaft units.
If the turbine’s electric load changes, it must immediately adjust its power output to meet the demand. The water flow rate must be regulated to keep the generator speed constant. A hydraulic servomotor controls the flow rate through each nozzle via a centrally situated, precisely shaped spear or needle that moves forward or backward.
The velocity of the water leaving the nozzle is nearly consistent regardless of the aperture thanks to a well-designed needle. It’s not a good idea to reduce water flow suddenly to match a decrease in load.
Another type of impulse turbine is the turgo. The jet hits the runner from one side at an oblique angle before continuing in a single path and discharging on the other. This turbine was designed for medium-sized units with high heads.
The reaction of increased water flows in the runner while the pressure drops generate forces that drive the rotor in a response turbine. The emerging jet propels the rotor in the opposite direction in a revolving lawn sprinkler, showing the reaction principle.
Due to the variety of possible runner types, reaction turbines can be used for a far larger range of heads and flow rates than impulse turbines. A spiral intake casing with control gates to manage the flow of water is common in reaction turbines.
At the intake, some of the water’s potential energy may be converted to kinetic energy as the flow increases. Following that, the rotor extracts the water energy.
Cost of Hydropower
The cost of electricity varies greatly around the United States. The average cost of one kilowatt-hour of electricity—the amount of energy required to run a 1,000-watt device for one hour—ranged from approximately six cents in certain states to 25 cents in Hawaii in 2010.
A number of factors determine the cost of energy in any given state, but one of the most important is the amount of electricity generated by hydropower. Idaho, for example, has the lowest electricity rates in the country, and hydropower accounts for nearly all of the state’s electricity generation.
Hydropower is a low-cost energy source, possibly the cheapest currently available. Because hydropower accounts for a large amount of their energy, Idaho, and Paraguay enjoy low electricity rates in neighboring South American countries like Chile and Uruguay. Hydropower can be used to generate renewable energy.
Hydropower is cost-effective for several reasons. When fossil fuels like oil, coal, or natural gas are burned for heat and light, they are depleted forever. More minerals must be gathered in order to continue creating electricity from these minerals. The costs of labor for obtaining these resources are enormous.
Hydroelectric turbines, on the other hand, are constantly supplied with water. No one needs to discover a new water source once one day’s flow has been converted to electricity. Carrying water from one site to another is also not required. Hydropower saves money by eliminating the need to dig up and transport fuel over long distances, as well as a significant portion of the cost connected with electricity generation.
The low cost of production of hydropower is due to its dependability. Despite the fact that river water levels vary depending on rainfall and the time of year, the volume and speed of river water are normally sufficient to create a reliable supply of electricity.
Hydroelectricity supply is rarely disrupted from one day to the next, let alone month to month or year to year, except in extreme droughts or when emergency maintenance is required. Because the amount of energy generated is known, the cost of a hydroelectric facility is predictable.
Hydropower often has this level of supply and pricing constancy. Most other sources of energy, on the other hand, lack this benefit for technological and economic reasons. Oil, for example, is subject to sudden price spikes as the world’s available supply fluctuates—and as oil companies and governments react to political events in oil-producing countries.
Hydroelectric power is a step forward from other renewable energy sources. It is difficult to store solar energy for later use. Another example is wind power: when there isn’t enough wind, wind turbines sit idle, causing electricity to become scarce and expensive. Hydroelectric power is also far cheaper than solar power.
Hydropower is frequently referred to as “green energy” because it does not emit hazardous pollutants like SO2 and NOx, nor does it emit a global pollutant like CO2.
However, there are environmental issues with hydropower, the major environmental issue is the exploitation of hydropower sites in general. Reservoirs are frequently built intentionally by flooding previous natural ecosystems or populated regions.
Water is also drained from lakes and watercourses and transported over long distances by tunnels, and pipelines from reservoirs to turbines are typically visible, but they can even enter inside mountains via tunnels. Hydropower systems, as a result, “devour” the natural environment.
There may be environmental hazards as a result of the change in reservoir level and the volume of water flowing downstream. Changes in reservoir levels, as well as the volume of water flowing downriver, could pose problems for aquatic life. Shifting microclimates in natural river and lake regions may also pose problems for agriculture.
The environment is a major source of worry in today’s society. Cars and trucks emit greenhouse gases into the atmosphere, which contribute to climate change. Industrial waste pollutes the world’s seas and rivers.
The combustion of fuel to generate electricity, heat, and other types of power accounts for more than 80% of carbon dioxide emissions. Energy consumption has wreaked havoc on the environment. Global climate change is mostly caused by carbon dioxide.
The extraction of fossil fuels from the earth has the potential to have severe environmental impacts. Coal mining may devastate mountaintops, and heavy equipment used to bring oil and natural gas to the surface can leave scars on the ground. The usage of energy contributes greatly to the pollution of the air and water.
Pros and Cons of Hydropower Energy
For a long time, hydropower has been the most extensively utilized renewable energy source of electricity, and it, like any other energy source, has advantages and downsides.
Renewable Energy Source
Hydropower is the process of using water to generate electricity. Using water instead of traditional fossil fuel energy sources produces no harmful pollution in the air or water. Hydroelectric power plants do not require the usage of fossil fuels. Its sources will not be empty like fossil fuels. We can use it continuously for generating energy.
Clean Energy Source
Hydroelectric power, as one might expect, is one of several “green” and “clean” alternative energy sources accessible. Hydroelectric energy does not pollute the environment when used to create electricity. Hydroelectric power plants do not produce any toxic or greenhouse gases that pollute the environment. Only the construction of power plants produces the most pollution.
Hydropower is a flexible energy source because hydro facilities may be scaled up and down to meet changing energy demands. Furthermore, hydro turbines take significantly less time to start up than gas turbines or steam plants.
Cost Effective Energy Source
Hydroelectric power is a cost-effective source of energy, despite its hefty initial construction costs. River water is an infinite resource that is immune to price fluctuations. The pricing of fossil fuel-based energy sources such as coal, oil, and natural gas are all affected by economic uncertainty.
Hydroelectric power plants have a 50-100-year average lifespan, showing that they are long-term investments that will benefit many generations to come. They can also be readily modified to meet current technology requirements, and their operating and maintenance costs are much reduced.
Development of Remote Communities
While the majority of the hydroelectric facilities will be used to support public electricity networks, others will be created to serve a specific industrial business sector that employs locals. Dedicated hydropower plants are frequently built to supply large amounts of electricity to aluminum electrolytic plants.
Dams are a popular tourist attraction. They are appropriate for fishing, boating, swimming, and irrigation. Dams also generate lakes, which are used for recreational activities like fishing and boating. The water from the lake is then dumped back into the river.
Hydroelectric generating plants can store large volumes of water for agriculture when rainfall is scarce. Water retention capacity is significant because it protects water levels from depletion and minimizes drought and flood susceptibility.
However, hydroelectric electricity is not without flaws and has some drawbacks too:
The majority of hydropower plants are massive infrastructure projects that entail the construction of a dam, a reservoir, and electricity-generating turbines. While a large hydropower project can often provide low-cost energy for 50 to 100 years after completion, the initial construction costs might be substantial.
This, combined with the fact that suitable reservoir locations are becoming increasingly uncommon, means that the cost of developing large-scale hydropower plants may continue to rise.
Natural water flow disturbances can have a big impact on the ecology and ecosystem of rivers. As there is a dearth of food or when the mating season begins, some fish and other creatures shift. Dam construction could cut off their migration pathways, resulting in a lack of reproduction or fish deaths.
Dams that generate electricity contribute significantly more to global warming than previously assumed. Plant material in flooded areas begins to rot and degrade in an anaerobic atmosphere. As a result, carbon dioxide and methane are released, increasing pollution levels.
Floods Risk in Lower Elevations
If the dam releases powerful water currents, communities downstream are at risk of flooding. In the long run, people’s livelihoods in such regions may be compromised.
One of the primary drawbacks of constructing hydroelectric power plants is the possibility of local droughts. The total cost of energy is influenced by the availability of water, and drought could have an impact on this, preventing people from getting the electricity they need.
It’s tough to find a suitable location with a big year-round water supply, sufficient water volume, and proximity to power lines. It’s also a delicate balancing act between keeping adequate river water-free and damming many rivers for power generation.
Frequently Asked Questions (FAQs)
The majority of hydroelectric power plants need the construction of a dam, which would result in habitat damage and fragmentation. Furthermore, because most hydroelectric projects are physically big, they may result in the flooding of large areas inside a river valley.
Hydroelectric power generation produces no emissions into the atmosphere. Instead of relying on foreign or long-distance domestic energy sources, hydroelectric power makes use of a local resource: flowing water. Transportation costs, pipelines, price changes, and political issues are all eliminated with this local power source. Hydroelectric energy can be adjusted to meet specific energy requirements according to demand because of its flexibility in production.
Although the power generated by water plants produces few emissions, the decomposition of plants in flood zones produces considerable amounts of methane. Hydropower can have major environmental consequences, including fish injury and a negative effect on downstream water quality. Dams remove water required for healthy in-stream ecosystems, altering natural river flows, by diverting water out of water bodies for power.
Hydropower is the most efficient way to generate electricity. It’s quite difficult to make the right estimation about hydropower construction costs. Because its budget is largely affected by the geographical location, availability of water resources, and choice of turbine type.
Micro-hydropower systems are small hydropower plants that have an installed power generation capacity of fewer than 100 kilowatts. Micro-hydro has the potential to be a significant energy source in rural areas.