New energy technology paper on new energy power generation technology 1
Starting from the global energy situation, this paper introduces the application of energy power generation technology in China, and finds that China's new energy power generation has important strategic significance for modernization. Two new energy power generation technologies, wind power generation system and fuel cell power generation system, are further introduced. Wind power generation is the most mature technology, the most large-scale development conditions and commercial prospects in non-water renewable energy power generation, and it is also the focus of recent development. Fuel cell is a device that directly converts chemical energy into electrical energy. It has high energy conversion efficiency and hardly emits oxides of nitrogen and sulfur.
Keywords: new energy; Wind energy; Fuel cell; Power generation technology
China Library Classification Number: F206 Document Identification Number: A
Energy shortage has become a bottleneck restricting the economic development of all countries. How to develop advanced and safe new energy utilization technologies and how to improve energy utilization rate has also become a topic of concern to all countries in the world. The EU put forward the 20-20-20 plan for the first time: by 2020, renewable energy will account for 20% of the EU's total energy consumption. From June 5438 to February 2007, former US President George H.W. Bush also signed the Energy Independence and Security Act (EISA), thus vigorously promoting the use of new energy and energy-saving plans. In addition, from the perspective of environmental protection, in order to protect the earth on which human beings depend, developing new energy is also the only way.
First, the current situation of energy and power generation technology in China
In 20 1 1 year, China's new energy power generation continued to maintain a rapid development trend, and the grid-connected installed capacity continued to grow, and the power generation continued to increase. By the end of 20 1 1, the installed capacity of new energy in China reached 70 million kilowatts, ranking first in the world, and the installed capacity of new energy connected to the grid reached 54.09 kilowatts, up 47.4% year-on-year, accounting for about 5. 1% of the total installed capacity of power generation. Among them, the grid-connected capacity of wind power accounts for about 85.5% of the total installed capacity of grid-connected new energy; The installed capacity of grid-connected solar photovoltaic accounts for about 4.4% of the total installed capacity of grid-connected new energy; The installed capacity of new energy such as biomass accounts for about 10. 1% of the total installed capacity of grid-connected new energy.
20 1 1 year China's new energy generation is about101600 million kW? H, a year-on-year increase of 29.9%, accounting for about 2.2% of the total power generation. Among them, wind power generation accounts for about 72.0% of the total new energy power generation; Solar photovoltaic power generation accounts for about 0.9%; Biomass and other new energy sources account for about 27. 1%. 20 1 1 year, China's new energy generation will be 320g/(kW? H) calculation, which is equivalent to saving 324 1000 tce and reducing CO2 emission by 90.3 million t. ..
Electric energy is the foundation of national life and production. No matter from the perspective of energy or the power system itself, it is of great practical and strategic significance to study new energy power generation technology for China's modernization and people's life.
Second, wind power generation technology
Wind energy resources mainly include land resources and sea resources. Wind power generation is the most mature technology, the most large-scale development conditions and commercial prospects in non-water renewable energy generation, and it is also the key direction of new energy development at present.
1. Development status
In recent years, China's wind power industry has made great progress, which is inseparable from China's rich wind energy resources. According to relevant data, at the height of 10 meter above the ground, the theoretical reserve of wind energy resources in China is about 4.3 billion kilowatts, and the technical development capacity is about 300 million kilowatts. It is estimated that it may double when it is 50 meters above the ground. The offshore resources are high 10 meter, and the economic recoverable amount is about 750 million kilowatts, which is 50 Mi Yue1500 million kilowatts. Judging from the total installed capacity of grid-connected wind farms in China, by the end of 2006, about 9/kloc-0 wind farms have been built in China, with a total installed capacity of about 2.6 million kilowatts, an increase of 654.38+0.34 million kilowatts compared with 2005, with a growth rate of 654.38+0.05%. According to the national long-term plan, wind power generation will reach 150,000 kilowatts in 20 15 years and 30 million kilowatts in 2020. However, compared with developed countries, China's development scale is still very small, and its development speed is also very slow. The important factors that restrict the development of wind power in China include technology and system. In terms of technology, the manufacturing level of wind turbines is low, the performance testing equipment and technology of wind turbines are relatively backward, and there is a lack of corresponding certification bodies; In terms of system, the operation and maintenance level and system of wind farms are obviously different from those of foreign wind farms and domestic thermal power production, and there is a lack of detailed records and analysis of problems and failures in the operation process.
2. Impact on power system
Wind turbines are driven by wind, and the random fluctuation and intermittence of wind determine that the electric energy output of wind turbines is also fluctuating and intermittent. Therefore, the large-scale access of wind farms will bring power fluctuations, increase the burden on the power grid, and affect the quality and stability of power supply.
Influence of (1) on power quality. The period of wind speed fluctuation caused by airflow movement is usually several seconds to several minutes. This short-period wind speed fluctuation and the operating characteristics of the wind turbine itself may affect the power quality of the power grid. First of all, it will affect the frequency: the fluctuation of active power of wind power will cause the fluctuation of electromagnetic power. Due to the inertia of the generator rotor, it is difficult for the regulating system to keep up with the instantaneous change of electromagnetic power, resulting in power imbalance and changing the generator speed and system frequency. In addition, wind power will also affect the voltage: the fluctuation of the output power of grid-connected wind turbines will lead to voltage fluctuation, and the frequency range of its output power is within the range of voltage flicker (25Hz), so it will cause voltage flicker, and finally it will produce harmonic voltage and harmonic current.
(2) Influence on power grid stability. For weak electricity network, the fluctuation of wind power will lead to instantaneous voltage drop and frequent disconnection of wind turbines. After the fault is cleared, the increase of generator magnetization and slip will consume a lot of reactive power, making it difficult to restore the grid voltage.
(3) The influence on frequency modulation and peak shaving ability. The fluctuation period of wind speed caused by the long-term and seasonal movement of airflow is usually several hours, even days or months, which will increase the burden of frequency modulation and peak shaving in existing power grids. The low period of load curve often corresponds to the peak period of wind power output, and the grid-connected generation of wind farms increases the peak-valley difference of equivalent load of power grid, which greatly increases the burden of frequency modulation and peak regulation of power grid.
Third, solar photovoltaic cell power generation technology
1. 1 solar photovoltaic cell
Solar photovoltaic power generation, also referred to as solar photovoltaic power generation, is considered to be the fastest developing and most promising renewable new energy technology in the world in the future. The basic principle of solar photovoltaic cells is to use the "photovoltaic effect" of semiconductors to directly convert solar energy into electric energy. Materials that can generate electricity by photovoltaic effect are called photovoltaic materials. Devices that directly convert solar energy into electric energy through photovoltaic effect are called solar photovoltaic cells or photovoltaic cells. Photovoltaic cell is the core component of solar photovoltaic power generation.
1839, French physicist becquerel discovered that the voltage of a photovoltaic cell consisting of two pieces of metal immersed in electrolyte rises when it receives sunlight. In his published paper, he called this phenomenon "PhotovohaicEffect". "Photovoltaic effect" is a phenomenon that the distribution and concentration of current-conducting carriers in heterogeneous semiconductors or semiconductor-metal mixed materials change under the action of light, thus generating potential difference between different parts. 194 1 year, orr discovered the photovoltaic effect on silicon materials, which laid the foundation for the wide application of semiconductor silicon in solar photovoltaic power generation. From 65438 to 0954, Bell Laboratories scientists Darryl Chapin and Pirson successfully developed the world's first practical monocrystalline silicon photovoltaic cell. In the same year, Vekker discovered that gallium arsenide has photovoltaic effect, and deposited cadmium sulfide thin film on glass to make the world's first thin film photovoltaic cell. Dafeng 20 MW photovoltaic power station, which was put into operation in February of 20 10, is the largest thin-film photovoltaic power station in China, with an annual power generation of 23 million kw h.
The working principle of solar photovoltaic cells is shown in figure 1.
A PN junction is made by doping impurities in a semiconductor to form a balanced built-in electric field. Under the action of the built-in electric field, excess carriers generated by external excitation are separated, thus forming an external voltage. Under illumination, electrons in the semiconductor absorb photon energy, jump from valence band to conduction band, form electron-hole pairs and become carriers. The lowest energy required to generate carriers is the band gap Eg of the semiconductor, and solar cells made of materials with smaller band gaps can form larger current.
The first generation photovoltaic cell based on monocrystalline silicon is the mainstream of solar photovoltaic cell market at present, and its photoelectric conversion rate has reached 24. 7%. The photoelectric conversion efficiency of the second generation photovoltaic cells based on thin film technology has reached 16.5% ~ 18.8%. Thin-film photovoltaic cells have a good development prospect because they greatly reduce the consumption of semiconductor materials. It should be pointed out that in the photoelectric conversion process of photovoltaic cells, photovoltaic materials do not undergo any chemical changes and mechanical wear, so solar photovoltaic cells are an ideal clean energy source without noise, odor and pollution. In 2006, the total output of solar cells in China reached 400 MW for the first time, thus surpassing the United States to become the third largest producer and the fastest growing country in the world.
1.2 solar photovoltaic power station
Solar photovoltaic power station is to package several photoelectric conversion devices, that is, photovoltaic cells, into photovoltaic cell modules, and then combine several modules into a photovoltaic array with certain power according to needs, and then match them with energy storage and measurement and control devices to form a solar photovoltaic power station.
Solar photovoltaic cells have great flexibility, which can be used not only to build sporadic power stations, but also to form a solar photovoltaic power generation system for small and scattered power users. This independent solar photovoltaic power generation system is called off-grid solar photovoltaic power generation system.
Due to the change of day and night sunshine and the influence of weather, off-grid photovoltaic power generation system usually needs to be combined with other power sources, such as diesel generator sets and batteries, which increases the investment and maintenance costs of power stations. Off-grid photovoltaic power generation systems are often built in remote mountainous areas and desert areas far away from the power grid to supply power to independent regional users. The 20 kW photovoltaic power station in Tsuole, Tibet is an off-grid photovoltaic power station built earlier in China, with a total investment of 2.9 million yuan, which was officially put into operation in February 1994.
The system of off-grid solar photovoltaic power station is shown in Figure 2.
The power generation system of the power station consists of solar photovoltaic cell array, storage battery, DC controller, DC- AC inverter, AC power distribution cabinet and standby power supply system (including diesel generator set and rectifier charging cabinet). Its working principle is that the solar photovoltaic cell array supplies power to the battery pack through the DC control cabinet, and the upper and lower limit voltages of the battery pack are set as required, and the DC control cabinet automatically controls the charging. The battery pack supplies power to the DC- AC inverter through the DC control cabinet, converts DC into three-phase AC through the inverter, and then supplies power to users through the AC distribution cabinet in a three-phase four-wire system. When the battery voltage drops to the lower limit voltage, the DC control cabinet will automatically cut off its output circuit, so that the DC- AC inverter will stop working, so as not to cause excessive discharge of the battery. Diesel generator set is the backup power supply of power station. When necessary, the standby power supply charges the battery through the rectifier charging cabinet, or directly supplies power to users through the AC distribution cabinet when the photovoltaic power generation system fails to stop. DC- AC inverter and diesel generator set can't supply power to users at the same time, so it is necessary to set interlocking devices in AC distribution cabinet to ensure the uniqueness of power supply.
When the capacity of solar photovoltaic power station reaches a certain scale, it can also be connected to the power grid, which is called grid-connected photovoltaic power station. At this time, if the local load is insufficient, the surplus electric energy can be transmitted to the power grid. When the local solar power generation is insufficient, the power grid provides power to users. Therefore, the grid-connected photovoltaic power station does not need to use energy storage devices, which reduces the system investment and maintenance costs. At the same time, due to the mutual assistance with the power grid, the utilization rate of power generation equipment and the safety and reliability of power supply are improved, which is the inevitable trend of the large-scale development of solar power generation technology. The first grid-connected photovoltaic power station in China is the Tibet Yangbajing Renewable Energy Base 100 kW high-voltage grid-connected photovoltaic power station, which was completed and put into operation in 2006. At the end of 20 10, Dunhuang 2 × 10 MW photovoltaic power generation project, the first photovoltaic power generation project in China, was completed and put into operation.
Four. Conclusion and prospect
Based on the global and China energy situation, this paper analyzes that new energy power generation technology is an urgent and practical research topic at present, and then introduces the characteristics of wind power generation system and fuel cell power generation system and their development status in China. New energy not only refers to wind energy and fuel cells, but also includes biomass energy, ocean energy, geothermal energy and photovoltaic cells. New energy power generation technology has great development potential in China and even the world. On the stage of mankind tomorrow, new energy will replace fossil fuels and play an important role.
References:
[1] Xu Dehong. Introduction to new energy power electronics [D]. Hangzhou: Zhejiang University, 2009.
[2] Hao Wei, Shu Juan and Zhang Granule. Overview of new energy power generation technology [C]. The fifth postgraduate academic exchange meeting of North China Electric Power University in 2007.
Shi Tao. Modeling and Simulation of Fuel Cell Power Generation System [D]. Nanjing: Southeast University, 2007: May 6, 63-64.
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