hydropower

Brief introduction

Hydroelectric power uses the potential energy of rivers, lakes, and other rivers and lakes to convert the potential energy contained in it into the kinetic energy of the turbine, and then uses the hydro turbine as the driving force to promote the generator to generate electrical 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 process of converting the potential energy of water into mechanical energy and then into electrical energy. Because the power voltage emitted by the hydroelectric power plant is low, to be transmitted to users at a long distance, the voltage must be increased through the transformer, and then transported to the substation in the user concentration area by the empty rack transmission line, and finally reduced to the voltage suitable for household users and factory power equipment, and transmitted to each factory and home by the distribution line.

principle

How does hydropower work? The whole process of animation shows the whole process, and years of doubts are solved

The basic principle of hydropower generation is to use the water level drop to generate electricity with the hydro turbine generator, that is, to use the potential energy of water to convert into the mechanical energy of the water turbine, and then use the mechanical energy to push the generator to obtain electricity. Scientists have used the natural conditions of the water level drop to effectively use fluid engineering and mechanical physics to achieve the highest power generation and provide people with cheap and pollution-free electricity.

while low-level water is distributed throughout the earth by absorbing sunlight, thereby restoring high-level water sources.

In 1882, the first recorded application of hydroelectric power was in Wisconsin, USA. Today, the scale of hydropower generation ranges from tens of watts used in the countryside of the third world to millions of watts for power supply in large cities.

class

According to the classification of concentrated drops, there are: embankment hydropower plants, diversion hydropower plants, hybrid hydropower plants, tidal hydropower plants and pumped storage power plants.

According to the degree of runoff regulation, there are: unregulated hydropower plants and regulated hydropower plants.

According to the nature of water sources, it is generally called conventional hydropower stations, that is, using natural rivers, lakes and other water sources to generate electricity.

According to the size of the water head used by the hydropower station, it can be divided into high head (more than 70 meters), medium head (15-70 meters) and low head (less than 15 meters) hydropower stations.

According to the installed capacity of hydropower stations, they can be divided into large, medium and small hydropower stations. Generally, the installed capacity of less than 5,000kW is called small hydropower stations, those with an installed capacity of 5,000 to 100,000kW are called medium-sized hydropower stations, and those with an installed capacity of 100,000kW or more are called large hydropower stations or giant hydropower stations.

process

When the unit needs to run to generate electricity, open the main valve (similar to the function of the faucet at home), and then open the guide wing (a small water gate that actually controls the output force) to make the water impact the turbine. If you want to adjust the output of the generator set, you can adjust the opening of the guide wing to increase or decrease the amount of water to achieve it, and the water after power generation returns to the river through the tail channel to supply the downstream water.

advantage

Water

Hydro energy is an inexhaustible, inexhaustible and renewable clean energy source. However, in order to effectively use natural water energy, it is necessary to manually build hydraulic buildings that can concentrate the water drop and regulate the flow, such as dams, diversion pipes and culverts. Therefore, the project investment is large and the construction period is long. However, hydropower generation has high efficiency, low power generation cost, fast unit start-up, 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 together with shipping, aquaculture, irrigation, flood control and tourism, it forms a comprehensive water resources utilization system.

generate electricity

Hydropower is a renewable energy source with a low environmental impact. In addition to providing cheap electricity, it also has the following advantages: flood control, irrigation water, improved river navigation, and improved transportation, electricity supply and economy in the area, especially tourism and aquaculture. The comprehensive development plan of the Tennessee River in the United States is the first large-scale water conservancy project, driving the overall economic development.

shortcoming

General overview

1. Due to terrain limitations, it is not possible to build too large capacity. The capacity of the unit is about 300MW.

2. The construction period of the factory is long and the construction cost is high.

3. Because it is located in natural rivers or lakes, it is susceptible to feng shui disasters, affecting other water conservancy undertakings. Power output is susceptible to weather drought and rain.

4. It is not easy to increase capacity after the factory is built.

5. Ecological damage: intensified erosion of water flow below the dam, changes in rivers and their impact on animals and plants, etc.

6. Damming is needed to immigrate, etc., and the investment in infrastructure construction is large.

7. The fertile alluvial soil downstream is reduced by erosion.

Ecological impact

Huge dams that flood a wide range of upstream areas can destroy biodiversity, productive lowlands, river valley forests, wetlands and grasslands, and reservoirs built for hydropower can cause fragmentation of habitats in surrounding areas and worsen soil erosion.

Hydropower projects affect aquatic ecosystems upstream and downstream of the surrounding area. For example, studies have shown that dams along the Atlantic and Pacific coasts of North America reduce salmon populations that need to spawn upstream because dams prevent these fish from spawning upstream in breeding grounds. Although fish ladders are installed in the largest dams in salmon habitats, this is not avoided. Young salmon are also suffering damage because they have to pass through turbines in power stations as they migrate to the sea. To protect these fish, some parts of the United States transport small salmon downstream by yacht during parts of the year. In exceptional cases, some dams, such as the Marmot Dam, have been removed due to their impact on fish. How to design turbine generators that cause less damage to aquatic life is an active area of research. Some mitigation measures, such as fish ladders, have become a requirement for new project approvals and review of existing projects in some countries.

For example, the construction of large-scale water conservancy projects in the Yangtze River Basin has seriously affected the migration routes and breeding grounds of the Chinese sturgeon, causing its population to decline sharply and be in danger of extinction.

Environmental impact

Environmental Impacts of Hydropower GenerationEnvironmental Impacts of Hydropower GenerationEnvironmental Impacts of Hydropower Generation

1. Geography: Huge reservoirs may cause surface activity and even induce earthquakes. In addition, it will also cause hydrological changes in the basin, such as a decrease in the downstream water level or a decrease in sediment from the upstream. After the completion of the reservoir, due to the large evaporation, the climate is cool and stable, and the rainfall is reduced.

2. Biological aspects: For terrestrial animals, after the completion of the reservoir, a large number of wild animals and plants may be submerged and killed, or even completely extinct. For aquatic animals, after the completion of the reservoir, due to changes in the upstream ecological environment, fish will be affected, resulting in extinction or population reduction.

At the same time, due to the expansion of the upstream water area, the habitat of certain organisms (such as snails) has increased, creating conditions for the spread of some regional diseases such as schistosomiasis.

3. Physical and chemical properties: The water flowing into and out of the reservoir changes in terms of physical and chemical properties such as color and odor, and the density, temperature, and even solubility of each layer of water in the reservoir are different. The water temperature of deep water is low, and the organic matter at the bottom of the sedimentary reservoir cannot be fully oxidized in anaerobic decomposition, and the carbon dioxide content of the water body increases significantly.

classify

According to the nature of water sources, they can be divided into: conventional hydropower stations, that is, using natural rivers, lakes and other water sources to generate electricity.

Pumped storage power stations use the excess electricity at the trough of the power grid load to pump the water from the lower reservoir to the high place for storage, release water to generate electricity when the load of the grid is at its peak, and collect the tail water in the lower reservoir.

According to the means of developing water heads of hydropower stations, it can be divided into:

There are three basic types: dam hydropower station, diversion hydropower station and hybrid hydropower station.

According to the size of the water head used by the hydropower station, it can be divided into:

High head (above 70 meters), medium head (15-70 meters) and low head (less than 15 meters) hydropower station.

According to the size of the installed capacity of hydropower stations, it can be divided into:

Large, medium and small hydropower stations. Generally, small hydropower stations with an installed capacity of less than 5 000 kW, medium-sized hydropower stations with 5 000 to 100,000 kW or more, and large hydropower stations with a capacity of 100,000 kW or more are large or mega hydropower stations.

evolution

In 1878, France built the world's first hydroelectric power station. The first hydroelectric power station in the Americas was built on the Fox River in Appleton, Wisconsin, USA, consisting of two DC generators driven by a waterwheel, with an installed capacity of 25kW, and was generated on September 30, 1882. The first commercial hydroelectric power station in Europe was the Tevoli hydroelectric power station in Italy, built in 1885 with an installed capacity of 65kW. Since the 90s of the 19th century, hydropower has been valued in many countries in North America and Europe, and a number of hydropower stations of tens to thousands of kilowatts have been built using excellent terrain such as turbulent rivers, falling waters, and waterfalls in mountainous areas. In 1895, a large turbine-driven 3750kW hydroelectric power station was built at Niagara Falls on the U.S.-Canada border. After entering the 20th century, due to the development of long-distance transmission technology, hydraulic resources in remote areas were gradually developed and utilized, and power was supplied to cities and power centers. Since the 30s, the speed and scale of hydropower construction have developed faster and greater, and due to the progress of science and technology such as dam building, machinery, and electricity, it has been possible to build various types and scales of hydropower projects under very complex natural conditions. The world's exploitable hydropower resources are about 2.261 billion kW, which are unevenly distributed and the degree of exploitation varies from country to country.

China is the country with the richest hydropower resources in the world, with a developable capacity of about 378 million kW. The first hydropower station in Chinese mainland was the Shilongba Hydropower Station (see color map) built on the Mantis River in Yunnan Province, which was built in July 1910 and generated electricity in 1912, with an installed capacity of 480kW at that time, and later rebuilt and expanded in stages, eventually reaching 6000kW. Before the founding of the People's Republic of China in 1949, there were 42 hydropower stations built and partially built across the country, with a total installed capacity of 360,000 kW, and the annual power generation was 1.2 billion kW·h (excluding Taiwan). After 1950, hydropower construction has developed greatly, with a single hydropower station with an installed capacity of more than 250,000 kW as large, between 25,000~250,000 kW as medium, and below 25,000 kW as small. The largest of them is the Three Gorges Dam on the Yangtze River. A large number of medium-sized hydropower stations have been built on some rivers, some of which are also connected in series as cascades. In addition, a large number of small hydropower stations have been built on some small and medium-sized rivers and ditches. By the end of 1987, the installed capacity of hydropower in China was 30.19 million kW (excluding small hydropower stations below 500kW), and the total installed capacity of small hydropower stations was 11.1 million kW (including small hydropower stations below 500kW, see small hydropower). On August 25, 2010, the largest single investment project in Yunnan Province, Huaneng Xiaowan Hydropower Station Unit 4 (installed capacity of 700,000 kilowatts), was officially put into operation for power generation, becoming a landmark unit with an installed capacity of more than 200 million kilowatts in China, and our country's total installed capacity of hydropower jumped to the first place in the world.

China is one of the countries with the richest water resources in the world, with a developable installed capacity of 542 million kilowatts of hydroenergy resources and an economic developed installed capacity of 402 million kilowatts, and the development potential is still very large.

prospect

In some countries with abundant hydraulic resources but low development (including China), the development of hydropower will be prioritized according to local conditions in the future. In countries and regions where the degree of exploitation of hydropower resources has been high or hydraulic resources are poor, it is imperative to expand and transform existing hydropower stations, and the number of pumped storage power stations built in conjunction with the construction of nuclear power plants will increase. In addition to focusing on the construction of large-scale backbone power stations in China, small and medium-sized hydropower stations will receive further attention due to their short construction period, quick effect and low impact on the environment. With the reform of the electricity price system, the economic benefits of hydropower generation can be more appropriately reflected and evaluated, which is conducive to absorbing investment and accelerating hydropower construction. In the preliminary work of hydropower construction, new survey technologies such as remote sensing, telemetry, geophysical exploration, computer, and computer-aided design will be developed and popularized. Floods, sediment, reservoir migration, environmental protection and other issues will be handled more properly; the automation and telemobilization of hydropower stations will also be further improved and promoted; The development of long-distance, ultra-high voltage, superconducting materials and other transmission technologies will help accelerate the development of abundant hydropower resources in western China and transmit electricity to the eastern coastal areas.

With the implementation of the national "energy conservation and emission reduction" policy, energy substitution emission reduction has become China's practical choice, hydropower has become the first choice for renewable energy, and hydropower enterprises with cost advantages at this stage will enter the fast lane of rapid development. Therefore, domestic excellent hydropower companies pay more and more attention to the research of the industrial market, especially the in-depth study of the industry development environment and industrial buyers. Because of this, a large number of excellent domestic hydropower companies have risen rapidly and gradually become leaders in China's hydropower industry!

The former world's largest hydroelectric turbine rotor was processed in the Three Gorges Dam area and loaded and shipped to the Jinsha River Xiangjiaba Hydropower Station. So far, the Three Gorges Dam area has the ability to process the world's largest hydropower unit rotors.

Xiangjiaba Hydropower Station, located in the lower reaches of the Jinsha River, is the fourth largest power station in the world, with a single unit capacity of 812,000 kilowatts, surpassing the Three Gorges to become the world's largest hydropower unit. The runner that started yesterday, with a maximum diameter of 10.5 meters, a height of 4.7 meters and a weight of 406 tons, is the core component of Unit 3 of Xiangjiaba Power Station, and its size, weight, technical content and manufacturing difficulty are the largest in the world today.

In 2012, global hydropower generation increased by 4.3%, higher than the historical average, and all net growth came from China, accounting for 100% of the annual net growth of global hydropower, setting a record for the largest annual increase in a single country in the data sheet. According to domestic statistics, in 2012, the new installed capacity of hydropower in China was 15.51 million kilowatts. By the end of 2012, the installed capacity of hydropower generation reached 248.9 million kilowatts (including pumped storage 20.31 million kilowatts), accounting for 21.7% of the country's installed power capacity, and the hydropower generation capacity was 864.1 billion kWh, an increase of 29.3% year-on-year, accounting for 17.4% of the national power generation, an increase of 3.2 percentage points over the previous year, and in 2012, the average utilization hours of hydropower power generation equipment of 6,000 kilowatts and above were 3,555 hours, an increase of 536 hours year-on-year.

In 2012, China's hydropower consumption reached 194.8 million tons of oil equivalent, an increase of 22.8 from the previous year (2011) of 158.2 million tons of oil equivalent; In 2012, China's hydropower consumption was 194.8 million tons of oil equivalent, accounting for 23.4% of the global hydropower consumption of 831.1 million tons of oil equivalent, making it the world's largest producer/consumer of hydropower and the second largest producer/consumer of hydropower. 206 of the consumption (94.5 million tonnes of oil equivalent).

technology

Research on the science and technology of engineering construction, production and operation of water energy conversion into electricity. The water energy used by hydropower generation is mainly potential energy stored in water bodies. To convert water into electricity, different types of hydropower stations need to be built. It is an engineering measure consisting of a series of buildings and equipment. The building is mainly used to concentrate the drop of natural water flow, form a water head, and use the reservoir to collect and regulate the flow of natural water flow. The basic equipment is a hydro turbine generator set. When the water flow enters the turbine through the hydropower station diversion building, the turbine is driven by the water flow to rotate, so that the water energy is converted into mechanical energy. The water turbine drives the generator to generate electricity, and the mechanical energy is converted into electrical energy, which is then sent to the user through the substation and transmission and distribution equipment. Water energy is a renewable energy source in nature, which is repeatedly regenerated with the hydrological cycle. Water energy and fossil fuels are both resource primary energy sources, which are called secondary energy sources when converted into electrical energy. Hydropower construction is a power construction that completes primary energy development and secondary energy production at the same time, without consuming fuel during operation, and the operation management fee and power generation cost are much lower than that of coal-fired power stations. Hydropower does not undergo chemical changes in the process of converting water energy into electricity, does not excrete harmful substances, and has little impact on the environment, so hydropower is a clean energy source.

Research content

Review

The vast majority of hydropower stations built in the world are conventional hydropower stations built using the natural drop and flow rate of rivers. This kind of hydropower station is divided into two types: runoff type and water storage type according to the utilization mode and regulation capacity of natural water flow. According to the development method, it can be divided into dam-type hydropower station, diversion hydropower station and dam-diversion hybrid hydropower station. Pumped storage power station is a hydropower station that has developed rapidly since the 60s of the 20th century. However, tidal power stations have not yet been developed and utilized on a large scale due to their high cost. Other forms of hydropower, such as using wave energy to generate electricity, are still in the experimental research stage. (See Hydropower Station)

In order to realize different types of hydropower development, it is necessary to use the knowledge of hydrology, geology, hydraulic buildings, hydraulic machinery, electrical installations, water conservancy survey, water conservancy planning, water conservancy engineering construction, water conservancy management, water conservancy economics and power grid operation to study the following aspects.

planning

Hydropower generation is an integral part of the comprehensive development, management and utilization system of water resources. Therefore, when planning hydropower projects, it is necessary to comprehensively consider the needs of power generation, flood control, irrigation, navigation, driftwood, water supply, aquaculture, tourism and other aspects from the full use of water resources and the comprehensive planning of rivers, and make overall plans to fully meet the requirements of all relevant parties as much as possible to achieve the greatest national economic benefits. Hydraulic resources are one of the power sources, and when planning power, they should also be planned according to energy conditions. In areas with abundant hydraulic resources, priority should be given to the development of hydropower and make full use of renewable energy to save valuable coal, oil and other resources. Hydropower generation and thermal power generation are the two main power generation modes today, and in the power system with both methods, their respective characteristics should be given full play to obtain the best economic benefits of the system. Generally, thermal power generation should bear the stable part of the power system load (or base load part), so that it can operate under efficient working conditions as much as possible, which can save system fuel consumption and is conducive to safe and economical operation. Due to the flexibility of start-up and shutdown, hydropower generation is suitable for bearing the load changes of the power system, including peak load and accident backup. Hydropower is also suitable for power systems for tasks such as frequency regulation and phase modulation.

building

The buildings of the hydropower station include: the water-retaining buildings required for the formation of the reservoir, such as dams, sluices, etc.; Drainage buildings that discharge excess water, such as spillways, overflow dams, drainage holes, etc.; water inlet for power generation; water diversion buildings of hydropower stations from the water inlet to the turbine; Flat water buildings (see pressure regulating room, front pool), hydropower station plants, tailwaters, hydropower station boost switch stations, etc. are set up to stabilize the flow and pressure changes of water diversion buildings. The performance, applicable conditions, forms of structure and structure, design, calculation and construction technology of these buildings should be carefully studied.

equipment

Water turbines and hydro turbine generators are basic equipment. In order to ensure safe and economical operation, the plant is also equipped with corresponding mechanical and electrical equipment, such as hydraulic turbine governors, hydraulic devices, excitation equipment, low-voltage switches, automatic operation and protection systems, etc. In the step-up switch station of hydropower station, step-up transformers, high-voltage distribution switching devices, transformers, lightning arresters, etc. are mainly set up to receive and distribute electrical energy. The final power is delivered to the user through transmission lines and step-down substations. These devices are required to be safe, reliable, economical and efficient. For this reason, the design, construction, and installation must be carefully studied.

Operation management In addition to its own conditions such as waterway parameters and reservoir characteristics, the operation of hydropower station is closely related to grid dispatch, and the hydropower station reservoir should be kept at a high water level as much as possible, reduce wastewater, and maximize the power generation of the hydropower station or minimize the fuel consumption of the power system to achieve the highest economic benefits of the power grid. For hydropower stations and reservoirs with flood control or other water use tasks, flood control scheduling and water supply should be carried out on time, flood control and reservoir capacity should be reasonably arranged, and the basic requirements of relevant departments should be comprehensively met, and the optimal operation mode of the reservoir should be established. When there is a group of reservoirs in the power grid, the mutual compensation benefits of the reservoir group should be fully considered. (See Hydropower Station Operation Scheduling)

Benefit evaluation

The financial income obtained from hydropower generation supplying power to the power grid and users is its direct economic benefits, but there are also indirect and social benefits of non-financial income. Some countries in Europe and the United States implement a variety of electricity price systems, such as calculating electricity prices at different times of the day and different seasons of the year, different electricity prices for emergency power supply in case of accidents, and charging electricity prices according to kilowatt capacity. For a long time, China has implemented a single electricity price based on electricity, but hydropower can also undertake the peak shaving, frequency regulation, phase modulation, and accident (rotation) backup of the power grid in addition to generating electricity, bringing economic benefits to the operation of the entire power grid. In addition to providing water for power generation, hydropower stations and reservoirs also give full play to comprehensive utilization benefits. Therefore, when carrying out hydropower construction, it is necessary to consider the overall situation of the national economy, clarify the economic benefits, and conduct national economic evaluation.

peculiarity

(1) Energy renewability. Since water flow is constantly circulating according to a certain hydrological cycle, it is uninterrupted, so hydraulic resources are a renewable energy source. Therefore, the energy supply of hydropower is only the difference between wet and dry years, and there will be no energy depletion problem. However, in particularly dry years, the normal power supply of hydropower stations may be disrupted due to insufficient energy supply, greatly reducing output.

hydropower

(2) Low power generation cost. Hydropower simply uses the energy carried by the water flow without consuming other power resources. Moreover, the water used by the previous power station can still be used by the next level power station. In addition, because the equipment of hydropower stations is relatively simple, their maintenance and maintenance costs are much lower than those of thermal power plants of the same capacity. Including fuel consumption, the annual operating cost of thermal power plants is about 10 to 15 times that of hydropower stations of the same capacity. As a result, hydropower is less expensive and can provide cheap electricity.

(3) Efficient and flexible. The hydro turbine generator set of the main power equipment of hydropower generation is not only highly efficient, but also flexible in starting and operating. It can be quickly put into operation from a standstill state in a few minutes; Complete the task of increasing or decreasing the load in seconds, adapting to the needs of changing power loads, and without causing energy loss. Therefore, the use of hydropower to undertake the tasks of peak shaving, frequency regulation, load backup and accident backup of the power system can improve the economic benefits of the whole system.