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On the formation of dehydration section of small hydropower

dehydration section refers to the river section where there is little water under the dam within a certain period of time after damming or diversion. It can be seen from the definition that the reason for the dehydration section is damming or diversion, which is manifested by water reduction or cut-off of the river. It can be seen from the definition that the dehydration section is not a special term for small hydropower. Large and medium-sized hydropower stations, small hydropower stations, and reservoirs without power stations may lead to the generation of dehydration section

characteristics of small hydropower

small hydropower can be divided into three basic types: dam type, diversion type and hybrid type. In a simple explanation, the dam type hydropower station obtains the power generation head by damming and storing high water level. According to the location of powerhouse, dam type hydropower station can be divided into dam type hydropower station, dam type hydropower station, overflow type hydropower station, riverbed type hydropower station, etc. The diversion power station obtains the power generation head through the diversion channel (such as diversion tunnel, penstock, etc.). Hybrid is the combination of the above two methods

dam type hydropower stations are usually built in the river section with relatively slow river slope and large flow. The Three Gorges hydropower station, Gezhouba hydropower station and Xin'anjiang hydropower station that we often hear are dam type hydropower stations, and most of them are large and medium-sized hydropower stations. Diversion power stations are usually built on rivers in mountainous or hilly areas with large river gradient and relatively small flow. When you go to mountainous and hilly areas, it is a diversion power station that you see a diversion pipe on the mountain leading to the powerhouse below the mountain. Small hydropower stations are mostly diversion power stations

schematic diagram of dewatering section of diversion type hydropower station

when the hydropower station is dammed and impounded, a reservoir is formed, which can regulate river runoff. According to the regulation capacity of the reservoir, hydropower stations can be divided into multi-year regulation, annual (seasonal) regulation, weekly regulation, daily regulation and other hydropower stations. The power station without regulating reservoir is called run of river hydropower station. Because the daily regulation hydropower station generally only carries out daily regulation in the dry season, and runoff power generation is often used in the flood season, it is generally considered that the daily regulation hydropower station is also a runoff hydropower station. Large and medium-sized hydropower stations are usually multi-year regulation and annual (seasonal) Regulation stations

small hydropower stations are mostly runoff aerogel gel thermal insulation, including three heat transfer mechanisms hydropower stations. In theory, small hydropower can not produce dehydration section, that is, keep the original river flowing continuously. The dam type hydropower station can generate as much water and electricity as it can, so as to keep the original river flowing continuously; The diversion power station can only use part of the incoming water for power generation, releasing the remaining flow to maintain the continuous flow of the original river. Judging from the characteristics of small hydropower, the dehydration section is not inevitable. The Rhine River is an important river running through central and Western Europe. Among them, 56 large and small hydropower stations with a total installed capacity of 4.77 million KW are built on the trunk and tributaries of the Rhine River in the Alps. You haven't seen any reports that small hydropower stations in the Rhine River cause dehydration

How did the dehydration section of small hydropower in China come from

it should be noted that there are both small hydropower factors and non small hydropower factors in river closure. Many rivers, especially small rivers in mountainous areas, have no water in the dry season. At this time, the lack of water in the downstream river of small hydropower obviously cannot be blamed on the small hydropower head. Runoff hydropower stations have this feature in dry seasons. You can't accuse them of having no water downstream when there is no water upstream. This is an obvious truth

there are four main reasons for the formation of the dehydration section of small hydropower in China: the comprehensive utilization of small hydropower, the development concept of small hydropower, the electricity price of small hydropower, and the maximization of the benefits of small hydropower

(1) comprehensive utilization of small hydropower. Water can be used for many purposes, such as irrigation, drinking, breeding, power generation, shipping, etc. small hydropower is a water conservancy facility. A power station dam is built, and water storage forms a reservoir. Naturally, people will use its comprehensive functions. Therefore, 11. Sample clamping mode: the standard configuration is the plug mode. The water in the power station is not only considered from the perspective of power generation. When there is less water, it must be stored to cope with drought, and when there is more water, it must be blocked to fight flood. There are many people, less water and water pollution in our country, which leads people to make more use of the comprehensive function of small hydropower. In this case, the arrangement of water use may lead to the formation of dehydration section of small hydropower. For example, in the dry season, the water stored in the small hydropower reservoir is a valuable resource. At this time, the dehydration section is secondary. Usually people don't blame small hydropower, but think that small hydropower plays a big role. In fact, this factor should be considered as an external factor, not an internal factor in the small hydropower industry

(2) development concept of small hydropower. In the early days of the founding of the people's Republic of China, the land of China was basically dark at night, and kerosene lamps and candles occupied the absolute main force of lighting. At that time, the technology was backward, and there were only a few power stations in the country. To develop productive forces, improve living standards and move towards modernization, the most important thing is to solve the problem of power supply. At that time, the technical water was not seen by infrared cameras, and small hydropower was almost the only option, so small hydropower flourished with the encouragement and support of the state. Unfortunately, due to the limitations of the economic and technological development level and the cognitive level of ecological and environmental protection at that time, the dehydration section in the planning, design, construction and operation stages of small hydropower has not been paid attention to. The concept of minimum discharge capacity of small hydropower began to appear in the relevant laws, regulations, technical regulations and documents of the state and some provinces before and after 2000. The formation of dehydration section of small hydropower in China has its historical reasons, which is directly related to the concept of small hydropower development in different periods

(3) electricity price of small hydropower. The electricity of small hydropower is sold to electricity, and the electricity price is set by the price bureau. The electricity price of small hydropower is usually divided into peak electricity and valley electricity, with peak electricity during the day and valley electricity at night. Peak and valley electricity prices are very different. For example, in Wenzhou City, Zhejiang Province, the peak electricity price of a small hydropower station is 0.51 yuan, and the low electricity price is 0.20 yuan. The difference between peak and valley electricity prices means that the same water will generate different benefits at different times. Therefore, small hydropower stations try to generate electricity during the day, store water at night, and do not generate electricity. High reliability is the third reason for the dehydration section

(4) the fourth and most important reason is to maximize the benefits of small hydropower. In the absence of supervision, driven by the maximization of interests, the owners of small hydropower stations will choose to retain as much water as possible to generate electricity, that is, the owners of small hydropower stations will choose not to release the minimum discharge, resulting in the formation of dehydration section of diversion power stations. In recent years, the government has approved the minimum discharge of small hydropower stations constructed in China, but in the absence of supervision, the owners usually do not release the minimum discharge as required, so that one long or short dehydration sections of small hydropower stations are formed

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