0 Preface
Energy is the lifeline of the national economy and plays a decisive role in the sustainable development of society. As a renewable energy source, solar energy has become the most ideal alternative energy source due to its wide distribution, cleanliness, and permanent characteristics. It has received extensive attention and research from various countries in the world, among which solar power generation is the most important research task.
Solar power is mainly divided into two basic forms of photovoltaic power generation and thermal power generation. Thermal power generation is also called Concentrating Solar Power (CSP), which uses the focusing effect of the mirror to collect the heat of the solar energy, provides high-temperature steam through the heat exchange device, and promotes the steam turbine to drive the generator to generate electricity. According to solar energy collection methods, thermal power generation can be divided into three types: trough type, dish type, and tower type.
1 slot, dish, tower thermal power
1.1 Trough Solar Thermal Power System
Trough solar thermal power generation system is a series of parabolic trough concentrator collectors arranged in series or in parallel, trough parabolic reflectors focus the sun on the linear heat collector, heat transfer fluid to produce high temperature and high pressure steam, promote the turbine Drive the generator to generate electricity. The reflector of the trough solar thermal power system mirror is a single parabola, and the condenser form is a line condenser. Trough solar thermal power plant shown in Figure 1.
The trough solar thermal power generation system is relatively compact in structure compared with the dish type and the tower type. The collectors and other devices are generally installed on the ground, and the installation and maintenance are convenient, and the economic benefits are not limited by the production scale. It is currently the most mature solar heat. Power generation technology. According to statistics, as of 2009, solar trough thermal power stations operating worldwide accounted for 88% of all solar thermal power stations, accounting for 97.5% of projects under construction.
As the trough parabolic concentrator collector is a line focus collector, its main disadvantages are large heat dissipation area of ​​the collector, complicated heat transmission pipelines, and large heat loss.
1.2 Dish Solar Thermal Power System
The dish type solar thermal power generation system uses a dish-shaped parabolic mirror to focus sunlight on a collector. The heat transfer medium is heated by a collector and drives the turbine to run, which in turn drives the generator to generate electricity. It is generally installed in the focal point. Stirling generators generate electricity. The reflector mirror surface of the dish type solar thermal power system is a hyperbolic parabolic surface, and the spotlight form is spotlighting. Dish solar thermal power generation device is shown in Figure 2.
Due to spot-spot solar power generation system, spot concentrating, small converging area, high power generation efficiency, up to 29.4%; system footprint is small, manufacturing cost is low, stand-alone capacity is generally 5 ~ 25kW, suitable for establishing Distributed energy system.
Because of its small scale, the disc solar thermal power generation system has high initial investment and low commercialization.
1.3 Tower Solar Thermal Power System
Tower solar thermal power generation system uses a large number of directional reflectors to emit sunlight to a collector mounted on the top of a high tower. The water in the collector is heated to generate water vapor, which drives the steam engine to start the turbine and then drives the generator to generate electricity. The mirror of a tower power generation system is generally a plane mirror. Tower solar thermal power plant is shown in Figure 3.
Tower solar thermal power system reflectors are relatively simple to prepare, with high converging multiples and high thermal conversion rates, enabling high-power generation. However, its cost is high and its reliability needs to be strengthened.
2 Concentrated solar thermal power generation technology development status and trends
2.1 The Development Status of Overseas Solar Thermal Power Generation
In 1950, the Soviet Union designed and manufactured the world's first small-scale experimental device for solar thermal power towers. From the 1980s to the early 1990s, solar thermal power generation entered the peak period of development. According to statistics, the built-in power was more than 500 kW. There are more than 20 solar thermal power stations. In the following 10 years, due to the large investment in the construction of solar thermal power plants and high construction costs, thermal power generation has entered a trough period. In recent years, due to energy crisis and environmental deterioration, solar thermal power generation has attracted people's attention and re-entered a peak period of research.
In 2007, the PS10 solar thermal power tower designed and manufactured in Spain was the first commercial tower solar thermal power plant in Europe with an installed capacity of 11MW and an average annual power generation efficiency of 10.5%. The PS20 solar thermal power station was officially started in 2009 and is expected to be completed in 2013. Completed, to meet the daily needs of 180,000 families to use electricity.
2.2 Development Status of Domestic Solar Thermal Power Generation
China's solar thermal power generation technology started late. It was not until the 1970s that some basic research was started. In recent years, the development of solar thermal power generation technology has achieved certain progress thanks to the support of national policies. However, compared with developed countries, it still exists. A big gap.
In October 2005, the 70kW tower solar thermal power generation system in Nanjing, Jiangsu was successfully connected to the grid; in December 2010, Datang Tianwei 10MW solar thermal power generation pilot demonstration project was started in China's first megawatt solar thermal power station; February 2011, Ordos, Inner Mongolia 50MW trough solar thermal power station completed the demonstration tender, plans to invest 1.6 billion yuan, annual power generation 120 million kW? h. At present, the 1MW solar power tower thermal power project conducted by the Institute of Electrical Engineering of the Chinese Academy of Sciences in Yanqing County, Beijing is under experiment. The disc-type solar thermal power generation demonstration line jointly developed by the China Academy of Building Materials Research Institute and Xi'an Aerospace Power Co., Ltd. has been completed. Lanzhou Dacheng Technology Co., Ltd., Beijing Film Machinery Research Institute, and Ekobo Energy Technology (Shanghai) Co., Ltd. etc. A series of solar thermal power projects are under research and development.
2.3 Development trend of solar thermal power generation
Since the current cost of solar thermal power generation is relatively high compared with the cost of conventional energy generation, whether it can significantly reduce the cost of power generation is the key to its commercialization. With the rapid development of focused solar thermal power generation technology, trough solar thermal power generation has been favored by major energy companies with its mature technology. The main objective of trough thermal power generation technology in the future is to reduce costs, optimize structure, and increase efficiency.
3 Conclusion
In a situation where energy is becoming increasingly scarce and the environment is deteriorating, solar thermal power generation, as a completely clean power generation method, will surely be greatly developed. With the emphasis and strong support of national policies, solar thermal power generation will be widely used with the solution of various technical bottlenecks and the reduction of costs.
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