In addition to solar cells, batteries, controllers and inverters are the main components of photovoltaic power generation systems. The technical conditions are as follows:
Battery is a key component in photovoltaic power generation system. At present, there is no special battery for photovoltaic system in China, but conventional lead-acid batteries are used. The main types are: 1) fixed lead-acid batteries, which are mostly used in large photovoltaic power stations and communication systems, and need regular maintenance (such as adding water) when using; 2) The industrial sealed battery is mainly used for industrial photovoltaic systems such as communication and military. It requires no maintenance and is easy to install, but it is expensive and has a short service life; 3) Small sealed batteries, most of which are 6V and 12V combined batteries, have shorter service life but are more expensive, and are commonly used in household photovoltaic systems; 4) The starting batteries for automobiles and motorcycles are the cheapest, but they have the shortest service life, are troublesome to install, require water addition and regular maintenance, and have acid fog pollution. The capacity design of the battery is very important. The capacity design must be based on the climatic conditions and load conditions of the place of use, otherwise problems will occur.
There are many types of controllers used in photovoltaic systems, such as 2-point controller, multi-channel sequential controller, intelligent controller, high-power tracking charging controller, etc. At present, most of the controllers used in China are simple designed controllers, and intelligent controllers are only used in communication systems and large photovoltaic power plants. Compared with foreign controllers, the main gap in China is that domestic controllers are prone to failure due to device quality, non-polar reverse connection protection, short circuit, overcurrent and other problems; Low degree of specialized production, no temperature compensation, no battery load state control, rarely using pulse width regulation or maximum power tracking mode of control.
DC/AC inverter is also a key component in photovoltaic system. Because its function is AC/DC conversion, the most important indicators of this component are reliability and conversion efficiency. At present, China is at the same level as foreign countries in small power inverter, but it needs to be further improved in large power inverter.
At present, the largest optoelectronic market in China is still in the field of communications, including microwave relay stations, satellite communication ground stations, satellite TV receiving differential transmission systems, program-controlled telephone exchanges, military communication stations, etc. The current market share is about 50. Through the efforts during the “Ninth Five Year Plan” period, as well as the demonstration and promotion of various domestic and international cooperation projects, the application field of photovoltaic power generation for power supply in remote and remote areas has been further expanded. Including independent photovoltaic power stations and household photovoltaic power supply systems, its market share has risen from about 20 to more than 30. Some of these projects have been completed, while others are being implemented, such as the national “Ninth Five Year Plan” science and technology breakthrough project, the “Radio and TV Village to Village” project, the “Construction of Photovoltaic Power Station in Tibet’s County without Water and Electricity Resources” project, the “China Bright Project”, the “GEF/World Bank China Photovoltaic Market Promotion Plan”, the “UNDP China Photovoltaic Project”, the “Japan NEDO China Photovoltaic Project”, and the “Netherlands China Photovoltaic Cooperation Project”. In addition, the projects of “Implementing the Development of Household Optoelectronic Systems in Gansu Province, China” and “Applying Optoelectronic Technologies and Products in Rural Electrification Construction in Northwest China” jointly carried out by China and the United States have completed the supporting installation of 320 sets of 20Wp household optoelectronic systems in Gansu in 1998, and a total of 340 sets of household wind/light complementary power supply systems were installed in Inner Mongolia in 2000. The implementation and completion of these projects have promoted the large-scale promotion and application of photovoltaic power generation in China and greatly promoted the development of rural electrification in China. During the Ninth Five Year Plan period, more than 40 county, township and village level photovoltaic power stations with a total installed capacity of more than 600 kilowatts were built, about 150000 sets of household photovoltaic power supply systems were promoted and applied, and photovoltaic power generation systems with a total power of more than 50 kilowatts were established in about 20 rural schools.
In particular, it is worth mentioning the construction of photovoltaic power stations in the counties without hydropower resources and electricity in Tibet and the Tibet Ali Photovoltaic Plan, which began to be implemented this year. The former was started in 1989. After 10 years of efforts, it was completed in 1999. Seven county-level photovoltaic power stations were built, including Ando, Bangor, Nima, Shuanghu, Geji, Gaize and Cuoqin, with a total installed capacity of 425KWp. All the photovoltaic power stations in the seven electricity free counties in Tibet are located in the Qiangtang Plateau in northern Tibet above 4500 meters above sea level, known as “the roof of the roof of the world”. The Tibet Ali Photovoltaic Plan was implemented in 2001 and completed within three years. It is planned to build 38 township level photovoltaic power stations and promote 11000 sets of household photovoltaic lighting systems in Ali.
Grid connected photovoltaic power generation technology is the trend of photovoltaic power generation in the world today. It is a major technical step for photovoltaic technology to enter the stage of large-scale power generation and become one of the components of the power industry. It has accounted for 18% of the total in the international photovoltaic product market. During the “Ninth Five Year Plan” period, under the arrangement of the Ministry of Science and Technology of the People’s Republic of China, a 5KW photovoltaic grid connection demonstration system was successfully built, and beneficial experience was gained.
Small wind/light complementary power supply system began to be popularized and applied on a large scale during the Ninth Five Year Plan period. In Inner Mongolia, there are a large number of farmers and herdsmen who have installed micro wind turbines to supplement the configuration of solar cells, which makes the system settings more reasonable and improves the quality of power supply. According to the plan of the Ministry of Science and Technology of the People’s Republic of China, two small demonstration power stations were built in Tibet during the “Ninth Five Year Plan” period, namely, the 4KW wind/light complementary power station in Nase Township, Naqu Prefecture, and the 2KW wind/light complementary power station in Ali Science and Education Training Center.
In terms of system engineering, due to the constraints of technology, economy and other factors, many application fields with market potential, such as large-scale (>100KW) photovoltaic or wind light diesel complementary power station system, photovoltaic seawater desalination system, solar water pump drip irrigation project, solar electric locomotive, photovoltaic hydrogen generation system and large-scale photovoltaic grid connected power generation, have not really started.
China is rich in solar energy resources and has a huge potential market. After more than 20 years of hard work, it has laid a good foundation for greater development and large-scale application of solar photovoltaic power generation. However, in order to achieve the goal of full commercialization and further expand the market, it is also necessary to strive to remove market barriers that restrict development, mainly in production costs, construction specifications, funds, policies and market development.
Production cost: China’s solar cell module manufacturers have small production scale, backward infrastructure and production equipment, and the overall level of product quality is lower than that of foreign products. The production cost of PV modules is about 20% higher than that of foreign countries. High cost is the key reason that restricts the rapid development of photovoltaic power generation market.
Construction specifications and technical standards: There are no uniform design and construction specifications for photovoltaic power plants and systems at home and abroad, which will not guarantee the construction quality of photovoltaic power plants and systems, and also affect the further promotion of photovoltaic power generation. Photovoltaic power generation system.