Hydroelectric power generation, as a renewable, pollution-free and clean energy source, has long been valued by people. Nowadays, large and medium-sized hydropower stations are widely used and relatively mature renewable energy technologies worldwide. For example, the Three Gorges hydropower station in China is the largest hydropower station in the world. However, large and medium-sized hydropower stations have many negative impacts on the environment, such as dams blocking the smooth flow of natural rivers, blocking the discharge of sediment, and changing the ecosystem environment; The construction of hydropower stations also requires extensive inundation of land, resulting in a large number of immigrants.
As a new energy source, small hydropower has a much smaller impact on the ecological environment, and therefore is increasingly being valued by people. Small hydropower stations, like large and medium-sized hydropower stations, are both hydroelectric power plants. The commonly referred to “small hydropower” refers to hydropower stations or hydroelectric power plants and power systems with very small installed capacity, and their installed capacity varies depending on the national conditions of each country.
In China, “small hydropower” refers to hydropower stations and supporting local power grids with an installed capacity of 25MW or less, which are funded and operated by local, collective, or individual entities. Small hydropower belongs to non carbon clean energy, which does not have the problem of resource depletion and does not cause pollution to the environment. It is an indispensable component of China’s implementation of sustainable development strategy.
Developing renewable energy such as small hydropower according to local conditions and transforming hydropower resources into high-quality electricity has played an important role in ensuring national economic and social development, improving the quality of life of the people, solving the problem of electricity consumption in areas without electricity and power shortage, promoting river governance, ecological improvement, environmental protection, and local socio-economic development.
China has abundant reserves of small hydropower resources, with a theoretical estimated reserve of 150 million kW and a potential installed capacity of over 70000 MW for development. It is an inevitable choice to vigorously develop small hydropower to improve energy structure in the context of low-carbon environmental protection, energy conservation and emission reduction, and sustainable development. According to the plan of the Ministry of Water Resources, by 2020, China will build 10 small hydropower provinces with an installed capacity of over 5 million kW, 100 large small hydropower bases with an installed capacity of over 200000 kW, and 300 small hydropower counties with an installed capacity of over 100000 kW. By 2023, as planned by the Ministry of Water Resources, small hydropower generation will not only achieve the 2020 goal, but also have greater development on this basis.
A hydroelectric power station is a power generation system that converts water energy into electricity through a water turbine, and the water turbine generator set is the core device for achieving energy conversion in small hydropower systems. The energy conversion process of a hydroelectric generator set is divided into two stages.
The first stage converts the potential energy of water into the mechanical energy of the water turbine. Water flow has different potential energy at different altitudes and terrains. When the water flow from a higher position impacts the turbine at a lower position, the potential energy generated by the water level change is converted into the mechanical energy of the turbine.
In the second stage, the mechanical energy of the water turbine is first converted into electrical energy, which is then transmitted to the electrical equipment through the transmission lines of the power grid. After being impacted by water flow, the water turbine drives the coaxial connected generator to rotate. The rotating generator rotor drives the excitation magnetic field to rotate, and the stator winding of the generator cuts the excitation magnetic field lines to generate induced electromotive force. On the one hand, it outputs electrical energy, and on the other hand, it generates an electromagnetic braking torque in the opposite direction of rotation on the rotor. The water flow continuously impacts the water turbine device, and the rotational torque obtained by the water turbine from the water flow overcomes the electromagnetic braking torque generated in the generator rotor. When the two reach equilibrium, the water turbine unit will operate at a constant speed to stably generate electricity and complete energy conversion.
A hydroelectric generator set is an important energy conversion device that converts the potential energy of water into electrical energy. It generally consists of a water turbine, generator, speed controller, excitation system, cooling system, and power plant control equipment. A brief introduction to the types and functions of the main equipment in a typical hydroelectric generator set is as follows:
1) Water turbine. There are two commonly used types of water turbines: impulse and reactive.
2) Generator. Most generators use electrically excited synchronous generators.
3) Excitation system. Due to the fact that generators are generally electrically excited synchronous generators, it is necessary to control the DC excitation system to achieve voltage regulation, active and reactive power regulation of electrical energy, in order to improve the quality of output electrical energy.
4) Speed regulation and control device (including speed regulator and oil pressure device). The governor is used to regulate the speed of the water turbine, so that the frequency of the output electrical energy meets the power supply requirements.
5) Cooling system. Small hydro generators mainly use air cooling, using a ventilation system to help dissipate heat and cool the surface of the generator’s stator, rotor, and iron core.
6) Braking device. Hydraulic generators with rated capacity exceeding a certain value are equipped with braking devices.
7) Power plant control equipment. Most power station control equipment adopts computer digital control to achieve functions such as grid connection, frequency regulation, voltage regulation, power factor regulation, protection, and communication of hydroelectric power generation.
Small hydropower can be divided into diversion type, dam type, and hybrid type based on the method of concentrated head. Most small hydropower stations in China are relatively economical diversion type small hydropower stations.
The characteristics of small hydroelectric power generation are small station construction scale, simple engineering, easy procurement of equipment, and basically self use, without transmitting electricity to places far away from the station; The small hydroelectric power grid has a small capacity, and the power generation capacity is also small. The rejection of small hydroelectric power has strong local and mass characteristics.
As a clean energy source, small hydropower has contributed to the construction of socialist new energy villages in China. We believe that the combination of small hydropower and energy storage technology will make the development of small hydropower more eye-catching in the future!
Post time: Dec-11-2023
