Hydroelectricity
What is the principle of hydroelectric power generation?
When the gravitational potential energy of water is converted into kinetic energy, the water flushes the turbine, and the turbine starts to rotate. If we connect the generator to the turbine, the generator can start generating electricity. If we raise the water level to flush the turbine, the generator will start to generate electricity. When using a water turbine, it can be found that the speed of the water turbine increases. Therefore, it can be seen that the greater the water level difference, the greater the kinetic energy obtained by the water turbine, and the higher the electrical energy that can be converted. This is the basic principle of hydropower generation. The energy conversion process is: the gravitational potential energy of the upstream water is converted into the energy of the water flow. Kinetic energy, when the water flow passes through the hydraulic turbine, the kinetic energy is transferred to the steam turbine. The hydraulic turbine drives the generator to rotate and converts the kinetic energy into electrical energy. Therefore, it is the process of converting mechanical energy into electrical energy. Due to the different natural conditions of the hydropower station, the capacity and speed of the hydraulic generator set vary within the range. Very large. Usually small hydroelectric generators and high-speed hydroelectric generators driven by impact turbines mostly adopt horizontal structures, while large and medium-sized speed generators mostly adopt vertical structures. Since most hydropower stations are located far away from cities, It is usually necessary to supply power to the load through a long transmission line. Therefore, the power system places higher requirements on the operational stability of the hydroelectric generator: the motor parameters need to be carefully selected; the rotational inertia of the rotor is required to be relatively large. Therefore, the hydraulic turbine The appearance of the generator is different from that of the steam turbine generator. Its rotor has a large diameter and a short length. The hydraulic generator set requires a short time to start and connect to the grid, and its operation and scheduling are flexible. In addition to general power generation, it is especially suitable as a regulator. Peak units and emergency backup units.
What is the principle of hydroelectric power generation?
The basic principle of hydropower is to use the water level difference to generate electricity with a hydroelectric generator. That is, the potential energy of the water is converted into the mechanical energy of the hydraulic wheel, and then the mechanical energy is used to drive the generator to obtain electricity. Scientists take advantage of the natural conditions of the water level difference, effectively utilize fluid engineering and mechanical physics, and carefully combine them to achieve the highest power generation capacity, so that people can use cheap and pollution-free electricity.
Advantages: Water energy is an inexhaustible, renewable and clean energy source. However, in order to effectively utilize natural water energy, it is necessary to artificially build hydraulic structures that can concentrate the water drop and regulate the flow, such as dams, diversion pipes, culverts, etc. Therefore, the project investment is large and the construction period is long. However, hydropower has high efficiency, low power generation cost, quick start-up of the unit, and easy adjustment. Due to the use of natural water flow, it is greatly affected by natural conditions. Hydropower is often an important part of the comprehensive utilization of water resources, and forms a comprehensive utilization system of water resources together with shipping, breeding, irrigation, flood control and tourism.
Disadvantages:
1. Due to terrain restrictions, it is impossible to build a large capacity. The single unit capacity is about 300MW.
2. The factory construction period is long and the construction cost is high.
3. Because it is located in a natural river or lake area, it is susceptible to feng shui disasters and affects other water conservancy projects. Electricity output is easily affected by weather conditions such as drought and rain.
4. It is not easy to increase the capacity after the factory is built.
5. Ecological damage: Intensified water erosion below the dam, changes in rivers and impacts on animals and plants, etc.
6. Dam construction, resettlement, etc. are required, and infrastructure construction investment is large.
7. The fertile alluvial soil downstream is reduced due to erosion.
What is the basic principle of hydroelectric power?
The basic principle of power generation is to use the kinetic energy of flowing water to drive the rotation of turbine blades.
Usually, a large dam is built in the middle of a river to harness this energy. There is a new invention that uses water and electricity on a small scale to power portable equipment.
Robert Kamarichka, an inventor from Ontario, Canada, came up with the idea of installing a small hydroelectric engine on the sole of a shoe. He believes these microturbines could provide enough power for any portable device.
When the user walks, the conductive liquid contained in the heel bladder generates pressure, prompting the liquid to flow through the conduit and enter the hydropower generation module. As the user continues to walk, the heel of the shoe is lifted and the bladder is subjected to downward pressure.
The flow of liquid drives the rotor and shaft to rotate, generating electrical energy.
What are the advantages and disadvantages of thermal power generation and hydropower generation?
The advantages of thermal power generation are that it is easier to select a plant site, requires less land, requires less investment, and has a short construction period.
The disadvantage is that the fuels used in thermal power plants, such as coal and oil, cannot be regenerated. It would be a pity to burn them as fuel. Some pollution will occur during production and the cost of power generation is high. The start-up time of the unit is long, and it takes several hours to more than ten hours for the unit to start from the cold state before it can be connected to the grid to generate electricity.
The advantage of hydropower is that water resources can be regenerated and the production cost is low, only 1/5 to 1/3 of thermal power. There is no pollution, and the unit starts quickly. It only takes a few minutes for the unit to be connected to the grid and generate electricity.
Comprehensive consideration of hydropower, shipping, irrigation, and aquaculture, and building a hydropower hub can improve its economic benefits. The disadvantages of hydropower are that it is difficult to select a plant site. The construction of dams requires very high geological conditions. The construction of reservoirs will submerge a lot of farmland and a large number of immigrants. Large reservoirs will destroy the ecological balance of local areas. It requires a lot of investment and a long construction period.
Regarding the investment and construction cycles of thermal power and hydropower, research and practice in recent years have proven that the theory that traditional thermal power has less investment and shorter construction cycle than hydropower is one-sided. Thermal power requires a large amount of coal and oil. In order to produce coal or oil, mines or oil fields must be built. In order to transport oil or coal, railways or oil pipelines must be built.
If the investment in extracting fuel and building railways or oil pipelines is taken into account, the investment in hydropower is similar to, or even lower than, thermal power. Therefore, prioritizing the development of hydropower is the correct policy.
Countries with developed industries give priority to the development of hydropower. The degree of development and utilization of hydropower resources is very high, reaching more than 90%, and hydropower accounts for a large proportion. Only when all hydropower resources are developed can thermal power be developed. my country has exploitable hydropower resources of up to 3.
7.8 billion kW, ranking first in the world. In the context of increasing energy shortages and growing calls for environmental protection, my country has established the correct policy of giving priority to the development of hydropower, increased investment and development in hydropower, and has become the largest hydropower project market in the world.
According to statistics, there are currently 58 large-scale hydropower stations that have been built or are under construction in our country, of which 19 are with an installed capacity of more than 1,000MW. By the end of 1997, my country's total installed hydropower capacity was 60,000MW, ranking third in the world after the United States and Canada.
At present, my country's hydropower development rate is only 15, which is far lower than the average hydropower development rate of 24 countries in the world. The potential for hydropower development is still huge.
Why can water generate electricity?
Their explanations are too professional. In fact, it is simple: what generates electricity is the kinetic energy generated by water. The electricity is generated through turbines. Stationary water itself cannot generate electricity. It can conduct electricity. hehe! Water is nature's most useful power because it is the easiest to control. Flowing water can be transported through sluices or pipelines, and more importantly, a flow can be divided into reservoirs by dams that can hold large amounts of water and release the required amount when needed. Hydraulic power is often planned as a hydroelectric power plant, usually built on large dams. The best locations are in high mountain areas and narrow valleys with steep sides. Dams built in such valleys can produce reservoirs more than 100 kilometers long. . Large-scale plans may involve more than a simple dam and reservoir. In the Snowy Mountains of Australia, water from the Snowy River is transferred to sixteen power plants through a series of underground channels. Hydropower is also used to store excess energy from other power plants, which can be handled in so-called pumped storage plants, using two separate reservoirs with different water levels. Under normal operation, water from the higher reservoir is used to drive a turbine to generate electricity, while water passing through the turbine is stored in the lower reservoir. Once there is excess electricity, it is used to pump water from the lower reservoir back to the upper reservoir. The demand for electricity is highest during the day, which means that in most power stations, pumping work is usually completed at night. Hydropower generation uses water with potential energy from high places such as rivers and lakes to flow to low places, and converts the potential energy contained in it into the kinetic energy of a water turbine. It uses the flow volume and height difference to turn the water turbine.
Then the water turbine is used as the prime mover to drive the generator to generate electricity. Because the power generated by hydroelectric power plants has a low voltage, in order to be transmitted to long-distance users, the voltage must be increased through a transformer, and then transported to the substation in the user concentrated area through an overhead transmission line, and then reduced again to a level suitable for home users. , the voltage of the electrical equipment in the factory is transmitted to various factories and household users through distribution lines. Utilize natural water flow as a resource. Hydroelectric power generation uses dams to store water, which can be used day and night without exhaustion. It is both convenient and economical. Therefore, in the past fifty years, all countries in the world have focused on thermal power and hydraulic power in power generation, and have been striving to develop hydropower resources. Initially, more than 80% of the nation's power generation in the United States was thermal power, but now, hydraulic power accounts for nearly half. This shows the importance of developing hydraulic power. In countries that are short of fuel, such as Switzerland and Italy, it is even more necessary to develop hydropower in large quantities to make up for the shortage. Hydropower can be divided into conventional hydropower and pumped storage hydropower according to its development function and operation mode: Taiwan has 36 conventional hydropower plants with a total installation capacity of 1.57 million kilowatts. They are further divided according to their transportation mode. There are three types, reservoir-type power plants such as Deji, Shimen, Zengwen, Wushe and other reservoirs. Adjustable power plants: such as Longjian, Liwu and other power plants and stream-flow power plants. Due to the rapid increase in electricity consumption in Taiwan in recent years, Taiwan Electric Power Company has actively developed excellent water resources to meet the needs of national economic construction in order to provide sufficient power supply capacity. Therefore, using the principle of water level difference, the Mingtan Tower was developed in the Sun Moon Lake Scenic Area. Pumped storage hydroelectric power generation project. Mingtan Pumped Storage Power Plant is equipped with six 267-kilowatt pumped storage turbine generators. Sun Moon Lake is used as the upper pool, and a lower pool is built in the Shuili River Valley downstream. The approximately 380-meter drop between the upper and lower pools is used for pumping and storage. The method of generating electricity is to use the remaining electricity to pump the water from the lower pool to the upper pool for storage during off-peak power consumption at night, and then release the high-level water stored in the upper pool during the peak power consumption period during the day. Driving generators to generate electricity, hydroelectric power plants build dams and set up transmission lines. The initial cost was higher than that of thermal power plants. However, in the past ten years, the difference has gradually become closer. Thirty years ago, the construction cost of thermal power plants averaged US$1 per kilowatt. 100~150 yuan. So far, this figure has increased to US$150-200 per kilowatt. The construction cost of a hydroelectric power plant is US$180-250 per kilowatt. Although the construction costs are different, if fuel costs and transportation costs are estimated, then The total cost of hydroelectric power generation is lower than that of thermal power plants, which is a great convenience. By the end of 1940, the hydropower plants established by countries around the world to utilize their water resources had approximately 70 million horsepower, but by the end of 1955, this had increased to 121 million horsepower. Within fifteen years, more than 50 million horsepower has been added, an increase of approximately 73%, which is really astonishing.
The method of hydropower generation. Hydropower is to release water with high potential energy in rivers, lakes and other places to low places. The kinetic energy of the water is used to push the turbine, which then drives the generator set to generate electric energy, which is supplied to users through the power transmission and distribution system. Therefore, hydropower generation The basic elements are river flow and height. With the changes in the power system, hydropower generation methods can be divided into the following four types: 1. River-flow power plants build dams on rivers with large slopes to block the flow of river water and introduce The power plant generates electricity, and the amount of electricity generated depends on the natural flow of the river. The flow of electricity is continuous 24 hours a day. Early hydropower plants all used this form to provide the electricity needed by users throughout the day, such as Wulai's Cougeng High Ping'Zhumen and other power plants fall into this category. 2. Adjust pool-type power plants to build small reservoirs at appropriate locations in rivers to regulate the flow during the day and provide power generation for about six hours during peak periods, such as Longjian'Liwu and other power plants. 3. Reservoir-type power plants build large reservoirs at appropriate locations in rivers to regulate the annual flow of the river for daily power generation. Due to the limited flow of rivers in this province, they only provide peak power most of the time. This location It also has the function of storing floodwater and relieving drought. In addition to generating electricity, it also contributes greatly to the supply of water for people's livelihood and irrigation water in the lower reaches of the river
Principle of hydroelectric power station
Hydropower is the use of water power (with water head) drives the hydraulic machinery (water turbine) to rotate, converting water energy into mechanical energy. If another machine (generator) is connected to the water turbine, electricity can be generated as the water turbine rotates, and the mechanical energy is converted into electrical energy. . In a sense, hydropower is the conversion process of water potential energy into mechanical energy and then into electrical energy.
A comprehensive engineering facility that converts water energy into electrical energy. Also known as hydropower plant. It includes a series of hydropower station buildings built to produce electrical energy from water energy and various hydropower station equipment installed. These buildings use the height difference of the natural water flow to form a water head, collect and regulate the flow of the natural water flow, and transport it to the hydraulic turbine. Through the joint operation of the hydraulic turbine and the generator, the concentrated water energy is converted into electrical energy, and then through the transformer and switch Stations and transmission lines input electrical energy into the grid. In addition to the buildings required for power generation, some hydropower stations often have other buildings that serve comprehensive utilization purposes such as flood control, irrigation, shipping, tree crossing, and fish crossing. The complex of these buildings is called a hydropower station hub or water conservancy hub.
Hydropower stations are classified in various ways. According to the nature of the water source utilized by hydropower stations, they can be divided into three categories. ①Conventional hydropower stations: use water sources such as natural rivers and lakes to generate electricity; ②Pumped storage power stations: use the excess electricity during low load periods in the power grid to pump water from lower reservoirs to higher reservoirs for storage until the grid load peaks The water is released to generate electricity, and the tail water is sent to the lower reservoir to meet the needs of power load such as peak shaving of the power grid; ③Tidal power station: Use the tidal energy formed by the rise and fall of sea tides to generate electricity.
Hydropower stations can be divided into two categories according to their utilization methods and regulating capabilities of natural water flow. ①Run-off hydropower station: a hydropower station that has no reservoir or a very small reservoir capacity and has no or very small ability to regulate natural water; ②Storage hydropower station: a hydropower station that has a reservoir with a certain storage capacity and has different regulating capabilities for natural water flow.
In the construction of hydropower station projects, the following classification methods are often used. ①According to the development method of hydropower stations, that is, according to the means of concentrating water heads and the engineering layout of hydropower stations, they can be divided into three basic types: dam-type hydropower stations, diversion-type hydropower stations, and dam-diversion hybrid hydropower stations. This is the most common classification method in engineering construction. ②According to the size of the water head utilized by hydropower stations, they can be divided into high head, medium head and low head hydropower stations. There is no unified regulation on the specific division of water head in the world. In some countries, a hydropower station with a water head below 15m is considered a low-head hydropower station, a hydropower station with a water head of 15-70m is a medium-head hydropower station, a hydropower station with a water head of 71-250m is a high-head hydropower station, and a hydropower station with a water head greater than 250m is a super-high-head hydropower station. China usually calls a hydropower station with a water head greater than 70m a high-head hydropower station, a water head less than 30m a low-head hydropower station, and a water head 30 to 70m a medium-head hydropower station. This classification standard is more suitable for the classification of the main buildings of the hydropower station and the classification scope of the hydroelectric generating units. ③According to the installed capacity of hydropower stations, they can be divided into large, medium and small hydropower stations.
Countries generally classify hydropower stations with an installed capacity of less than 5,000kW as small hydropower stations, 5,000 to 100,000 kW as medium-sized hydropower stations, 100,000 to 1 million kW as large hydropower stations, and those with an installed capacity of more than 1 million kW as giant hydropower stations. China stipulates that hydropower stations are divided into five classes, among which: first class [large (1) hydropower station] with an installed capacity of more than 750,000 kW, second class [large (2) hydropower station] with an installed capacity of 750,000 to 250,000 kW, and second class [large (2) hydropower station] with an installed capacity of 250,000 to 250,000 kW. 25,000 kW is a third-class [medium-sized hydropower station], 25,000 to 0.05 million kW is a fourth-class [small (1) hydropower station], and less than 0.05 million kW is a fifth-class [small (2) hydropower station]; but statistically speaking Below 12,000 kW are used as small hydropower stations.
What are the advantages and disadvantages of hydropower generation?
Hydroelectric power generation
Advantages:
(1) Utilize the potential energy held by water at high altitudes to convert kinetic energy to drive the prime mover.
(2) Use guiding water channels and pressure water pipes to convert the potential energy of water volume into kinetic energy.
(3) The favorable hydraulic location is far from the load center, the distance from electricity is long, and the transmission cost is high.
(4) The efficiency of hydropower generation is as high as over 90.
(5) The cost per unit of output power is the lowest.
(6) The power generation starts quickly and the power generation can be completed within a few minutes.
Disadvantages:
(1) Due to terrain restrictions, it is impossible to build a large capacity. The single unit capacity is about 300MW.
(2) The factory construction period is long and the construction cost is high.
(3) Because it is located in a natural river or lake area, it is susceptible to feng shui disasters and affects other water conservancy projects. Electricity output is easily affected by weather conditions such as drought and rain.
(4) It is not easy to increase the capacity after the factory is built.