Basic principles of thermal power plants
Basic principles of thermal power plants
It is a factory that converts the heat energy generated by the combustion of solid, liquid or gas fuels such as coal, oil and natural gas into kinetic energy to produce electric energy. According to the category of fuel, it can be divided into coal-fired thermal power plant, oil-fired thermal power plant and gas-fired thermal power plant. According to function, it can be divided into power plant and thermal power plant. The power plant only produces and supplies electric energy to users; The thermal power plant not only produces and supplies electric energy to users, but also supplies heat energy. According to the service scale, it can be divided into regional thermal power plants, local thermal power plants and train power plants. Regional thermal power plants with large installed capacity are generally built near fuel bases, such as large coal mines. This kind of power plant is also called pithead power plant, and its electric energy is supplied to users through long-distance transmission lines. Turnkey construction of mini CHPs are mostly built in load centers, and fuel needs to be transported in for a long distance. The power produced by them is supplied to more concentrated users.
In 1875, the thermal power plant of Paris North Railway Station in France was built to generate electricity, using a very small DC motor for nearby lighting. This is the first thermal power plant in the world. Subsequently, small thermal power plants were built in the United States, Russia and Britain. In the late 1880s, with the growth of industrial and domestic power consumption, the United States built the first AC power plant in 1886. In 1888, British C.A. Parsons successfully developed the first 75kW steam turbine generator with high and low pressure cylinders and installed it in flowbanks power plant in Britain. In 1891, Parsons manufactured the first generator set with condenser for Cambridge electric lamp company in England, with a capacity of 100kW and greatly improved thermal efficiency. In 1882, China built a thermal power plant with a 12KW DC generator in Shanghai. On July 26 of that year, it officially generated power for power supply and lighting.
The main characteristics of generator for thermal power plants are a short construction period, low project cost, fast investment recovery and flexible site selection compared with hydropower stations with the same capacity. The main disadvantage of thermal power plant is that it pollutes the environment to a certain extent. The environmental protection measures taken mainly include: the use of high-efficiency electrostatic precipitator and desulfurization measures, the comprehensive utilization of fly ash, and the use of circulating cooling to protect water sources.
The hydroelectric power plants form a huge static water potential energy storage, a large amount of water flows through the turbine and rotates the generator to generate electricity. The world's largest hydropower dam, China's Three Gorges Dam, generates up to 22500 megawatts of electricity. This means that the dam can generate enough electricity to power more than 18 million households (based on the average energy consumption rate in the United States). Hydropower stations account for nearly 6.7% of the world's total power generation.
The hydroelectric power plant is the largest renewable energy in the world. With the construction of new hydropower dams and tidal power stations and the improvement of system efficiency, the impact of hydropower generation is becoming greater and greater. Hydrodynamic modeling is also improving and manufacturing tolerances are shrinking, bringing hydro turbine for hydroelectric power plant efficiency close to 100%. The development of gearbox manufacturing, lubricant material science and manufacturing tolerance will continue to improve efficiency, while stronger magnet magnetism, higher wire efficiency and better control system can also improve efficiency. As long as there is water flow and drop, hydropower will become a valuable choice for sustainable energy.
Wind power generation is a kind of renewable clean energy. With the continuous breakthrough in wind power technology in China, all kinds of domestic wind power equipment are becoming larger and larger, the power is becoming higher and higher, and wind farms are becoming more and more common. How does wind power generate electricity and what electricity does it generate? The principle of wind power generation is very simple. The wind turbine is used to convert wind energy into mechanical energy, and then the mechanical energy is converted into electrical energy through the generator!
There are two kinds of common wind turbines, one is a horizontal axis fan, the other is vertical axis fan! Most of the fans we see are horizontal axis, that is, the rotation plane of the three blades is perpendicular to the wind direction. Driven by the wind, the rotating blades drive the shaft, and then drive the generator through the speed increasing mechanism! The vertical axis fan has an advantage over the horizontal axis fan. The horizontal axis fan needs to adjust the blade and wind direction vertically, but the vertical axis fan is omnidirectional. Unless the wind direction comes from above, it does not need to adjust the angle. However, it also has a fatal disadvantage. The wind energy utilization rate of the vertical axis fan is very low, only 40%, and some types of vertical axis fans have no starting ability, Starting device needs to be added!
Great changes are taking place in the global energy market. By the middle of this century, the proportion of electricity in total energy will more than double and climb to 45%, of which the renewable energy dominated by solar photovoltaic will play an important role. At the same time, coal-fired power generation, which currently accounts for a large proportion, will be replaced on a large scale. The reason is very simple, the cost is reduced!
The significant decrease in cost will increase the proportion of solar photovoltaic power generation from 1% in 2016 to 40% in 2050, a full increase of 65 times, and solar photovoltaic is expected to become the only largest power supply source in the world within 20 years. In particular, large-scale photovoltaic power plants are expected to grow exponentially in the next 20 years, which is very different from the prediction of the International Energy Agency (IEA) unchanged from the present .
Biomass and waste account for about two-thirds of the world's major renewable energy production. Biomass is a kind of renewable energy, including anything from agricultural waste to forestry waste. Biomass has been used as fuel for tens of thousands of years; Now, people have found ways to convert biomass into heat and electricity. These methods are used everywhere, from home heating to commercial power plants.
Biomass power plants generate electricity and heat by burning biomass in boilers. The most common types of boilers are hot water boilers and steam boilers. Residues, sawdust, natural gas and other biomass are used in boilers. Add water to the boiler and heat it under pressure to high temperature to produce steam. The steam drives the turbine, which is connected to the generator.