Expert introduction: Solar panels

The principle of solar cells: Sunlight shines on the semiconductor pn junction, forming new hole-electron pairs. Under the action of the pn junction electric field, holes flow from the n region to the p region, and electrons flow from the p region to the n region. When the circuit is connected, current is formed. This is the working principle of solar cells with the photoelectric effect. There are two ways to generate solar power: one is the light-heat-electricity conversion method, and the other is the light-electricity direct conversion method.

Light-heat-electricity conversion

(1) Photothermal-electrical conversion method uses the heat energy generated by solar radiation to generate electricity. Generally, the solar collector converts the absorbed heat energy into steam, which then drives the steam turbine to generate electricity. The former process is the photothermal conversion process; the latter process is the heat-electrical conversion process, which is the same as ordinary thermal power generation. The disadvantages of solar thermal power generation are low efficiency and high cost. It is estimated that its investment is at least 5 to 10 times more expensive than that of ordinary thermal power plants. A 1000MW solar thermal power plant requires an investment of 2 to 2.5 billion US dollars, and the average investment of 1kW is 2,000 to 2,500 US dollars. Therefore, it can only be used on a small scale in special occasions, and large-scale use is not economically viable and cannot compete with ordinary thermal power plants or nuclear power plants.

Direct optical-to-electrical conversion

2) Direct light-to-electricity conversion This method uses the photoelectric effect to directly convert solar radiation energy into electrical energy. The basic device for light-to-electricity conversion is a solar cell. A solar cell is a device that directly converts solar energy into electrical energy due to the photovoltaic effect. It is a semiconductor photodiode. When sunlight shines on the photodiode, the photodiode will convert the solar energy into electrical energy and generate current. When many cells are connected in series or in parallel, they can become a solar cell array with relatively large output power. Solar cells are a promising new power source with three advantages: permanence, cleanliness and flexibility. Solar cells have a long life. As long as the sun exists, solar cells can be invested once and used for a long time. Compared with thermal power generation and nuclear power generation, solar cells will not cause environmental pollution. Solar cells can be large, medium and small, ranging from medium-sized power stations with millions of kilowatts to solar cell groups for only one household, which is unmatched by other power sources.

Solar panel

Classification: Crystalline silicon solar panels: polycrystalline silicon solar cells, monocrystalline silicon solar cells.

Amorphous silicon panels: thin-film solar cells, organic solar cells.

Chemical dye solar cell panel: dye-sensitized solar cell.

Solar panels

The solar power generation system consists of a solar cell group, a solar controller, and a battery (group). If the output power is AC 220V or 110V, an inverter is also required. The functions of each part are:

1. Solar panels: Solar panels are the core and most valuable part of a solar power generation system. They convert solar energy into electrical energy, either by storing it in a battery or by driving a load. The quality and cost of solar panels will directly determine the quality and cost of the entire system.

(II) Solar controller: The function of the solar controller is to control the working state of the entire system and protect the battery from overcharge and over discharge. In places with large temperature differences, a qualified controller should also have the function of temperature compensation. Other additional functions such as light-controlled switch and time-controlled switch should be optional for the controller.

(III) Battery: Generally, it is a lead-acid battery, which is generally available in 12V and 24V. In small and micro systems, nickel-metal hydride batteries, nickel-cadmium batteries or lithium batteries can also be used. Its function is to store the electrical energy generated by the solar panel when there is light, and release it when needed.

(IV) Inverter: In many occasions, AC220V, AC110V AC power is required. Since the direct output of solar energy is generally DC12V, DC24V, DC48V. In order to provide power to AC220V appliances, the DC power generated by the solar power generation system needs to be converted into AC power, so a DC-AC inverter is needed. In some occasions, when multiple voltage loads are required, a DC-DC inverter is also needed, such as converting 24VDC power into 5VDC power (note, not a simple voltage reduction).

The production process of crystalline silicon solar cells:

Crystalline silicon solar cells

"Silicon" is one of the most abundant materials on our planet. Since scientists discovered the semiconductor properties of crystalline silicon in the 19th century, it has changed almost everything, even human thinking. At the end of the 20th century, "silicon" can be seen everywhere in our lives and its role. Crystalline silicon solar cells have been the fastest to be industrialized in the past 15 years. The production process can be roughly divided into five steps: a. Purification process b. Rod drawing process c. Slicing process d. Battery manufacturing process e. Packaging process

Photovoltaic power generation is based on the principle of photovoltaic effect, using solar cells to directly convert sunlight energy into electrical energy. Whether it is used independently or connected to the grid, the photovoltaic power generation system is mainly composed of three parts: solar panels (modules), controllers and inverters. They are mainly composed of electronic components and do not involve mechanical parts. Therefore, photovoltaic power generation equipment is extremely refined, reliable, stable, long-lasting, and easy to install and maintain. In theory, photovoltaic power generation technology can be used in any occasion that requires power, from spacecraft to household power, from megawatt-level power stations to toys, photovoltaic power sources are everywhere. The most basic element of solar photovoltaic power generation is solar cells (sheets), including single crystal silicon, polycrystalline silicon, amorphous silicon and thin film batteries. At present, single crystal and polycrystalline batteries are used the most, and amorphous batteries are used for some small systems and computer auxiliary power supplies. The efficiency of domestic crystalline silicon batteries is about 10 to 13%, and the efficiency of similar foreign products is about 12 to 14%. A solar panel composed of one or more solar cells is called a photovoltaic module. At present, photovoltaic power generation products are mainly used in three aspects: one is to provide power for places without electricity, mainly for the life and production of residents in the vast areas without electricity, as well as microwave relay power supply, communication power supply, etc. In addition, it also includes some mobile power supplies and backup power supplies; the second is solar daily electronic products, such as various solar chargers, solar street lights and solar lawn lights; the third is grid-connected power generation, which has been widely promoted and implemented in developed countries. my country's grid-connected power generation is in its infancy. At present, photovoltaic power generation products are mainly used in three aspects:

One is to provide power for places without electricity, mainly to provide electricity for the life and production of residents in the vast areas without electricity, as well as microwave relay power supply, etc. In addition, it also includes some mobile power supplies and backup power supplies

The second is solar daily electronic products, such as various solar chargers, solar street lights and various solar lawn lamps, etc.

The third is grid-connected power generation, which has been widely promoted and implemented in developed countries. my country has not yet started grid-connected power generation, but part of the electricity used in the 2008 Beijing "Green Olympics" will be provided by solar power and wind power.

The most basic element of solar photovoltaic power generation is solar cells (sheets), which include single crystal silicon, polycrystalline silicon, amorphous silicon and thin film cells. At present, single crystal and polycrystalline cells are used the most, and amorphous cells are used for some small systems and computer auxiliary power supplies. The efficiency of domestic crystalline silicon cells is about 10-13%, while the efficiency of similar foreign products is about 12-14%. A solar panel composed of one or more solar cells is called a photovoltaic module. In 2002, the global output of solar cells and photovoltaic modules was about 600MW, of which Japan accounted for 45%, the United States 25%, and Europe about 22%. Japan is the fastest growing country in the photovoltaic industry, surpassing the United States in less than 10 years. In 2001, there were 4 Japanese companies among the world's top 10 solar cell manufacturers, namely Sharp, Kyoto Ceramics, Sanyo and Mitsubishi. Most developed countries in Europe and the United States have formulated "sunshine plans" and taken measures to encourage residents to install solar power generation systems, such as partial grants, interest-free loans and "seed funds", and purchase excess solar power in residents' homes at prices several times higher than ordinary electricity prices.

Solar tracking control system is an indispensable supporting equipment that can effectively improve the power generation efficiency of solar panels: Due to the rotation of the earth, relative to a solar photovoltaic power generation system at a fixed location, the angle of the sun's light changes all the time in spring, summer, autumn and winter, and every day when the sun rises and sets. Only by effectively ensuring that the solar panels can always face the sun can the power generation efficiency reach the best state. At present, the common solar tracking control systems in the world need to calculate the angle of the sun at different times of each day of the year based on the longitude and latitude of the installation point, and store the sun's position at each time of the year in the PLC, single-chip microcomputer or computer software, that is, to achieve tracking by calculating the sun's position.

It uses computer data theory, which requires data and settings of the earth's longitude and latitude regions. Once installed, it is inconvenient to move or disassemble. Each time it is moved, the data must be reset and the parameters must be adjusted. The principles, circuits, technologies, and equipment are complex, and non-professionals cannot operate them casually. A solar photovoltaic power generation company in Hebei has exclusively developed an intelligent solar tracking system that is world-leading, low-cost, easy to use, does not require calculation of solar position data in various places, has no software, and can accurately track the sun on mobile devices anytime and anywhere. This system is the first solar space positioning tracker in China that does not require computer software at all. It has an international leading level and is not restricted by geographical and external conditions. It can be used normally in an ambient temperature range of -50℃ to 70℃; the tracking accuracy can reach ±0.001°, maximizing the accuracy of solar tracking, perfectly achieving timely tracking, and maximizing the utilization rate of solar energy. It can be widely used in various types of equipment where solar tracking is required. The automatic solar tracker is affordable, stable in performance, reasonable in structure, accurate in tracking, and easy to use. The solar power generation system equipped with an intelligent sun tracker can be installed on high-speed cars, trains, communication emergency vehicles, special military vehicles, warships or ships. No matter where the system is traveling, how it turns or makes a turn, the intelligent sun tracker can ensure that the required tracking part of the equipment is facing the sun.

1. Current status of domestic solar cell equipment market

my country started its research on solar cells in 1958. In the late 1980s, China introduced a number of solar cell production lines, which increased my country's solar cell production capacity from several hundred kilowatts in three small factories to 4.5MW in six factories. This capacity lasted until 2002, when the output was only about 2MW. The rapid expansion of the European market, especially the German market, and the extraordinary development of Wuxi Suntech Power Co., Ltd. have brought unprecedented development opportunities and demonstration effects to our photovoltaic industry.

2. Current status of domestic solar cell equipment technology

In terms of battery and component production equipment, before 2002, most of the equipment for the four backbone solar cell production lines in China was imported, and some domestic equipment originally used for semiconductor lines was used sporadically by manufacturers, and its performance, reliability and practicality could not be guaranteed.

Since 2002, through cooperation with first-class enterprises and introduction of advanced process technology, after many technological upgrades, key equipment of domestic solar cell and module production lines such as 8〃 diffusion furnace (for 6〃 or 156mm×156mm solar cell square wafers), plasma etcher, low-temperature drying furnace, high-temperature sintering furnace, cleaning machine, laminator, etc. have been widely used in domestic production lines to replace imported equipment. In particular, the hot wall production PECVD equipment, one of the most critical equipment for cell manufacturing, which was successfully developed in 2004, has basically enabled my country to have the ability to supply complete lines of solar cell manufacturing equipment except for fully automatic screen printing machines.

Five of the eight key equipment for solar cell and module production, namely diffusion furnaces, plasma etching machines, drying/sintering furnaces, cleaning machines, and laminating machines (for module production), have basically reached international standards, and their cost-effectiveness is very obvious. They have occupied the vast majority of the domestic market and successfully prevented the entry of imported equipment in batches. This year, they have begun to attract the attention of European, American and Southeast Asian merchants, and have begun to export a small amount.

PECVD production capacity and process level are close to the world's advanced level, and have begun to be used by more and more domestic users, but there is still a gap in the degree of automation (automatic loading and unloading of wafers).

The other two key equipment, the fully automatic screen printing machine and the automatic sorting machine, have not made any breakthroughs in core technology, and their overall level is far behind that of foreign countries. Almost all domestic production lines use expensive imported equipment.

Although the technical performance of single crystal furnaces in material growth equipment is not up to the international advanced level, it is not that far behind and has an advantage in performance-price ratio. Taking advantage of the rare opportunity of silicon material shortage, it has been able to form mass production, occupy the domestic market and export a small amount.

my country has abundant solar energy resources. The average annual daily radiation in most areas is above 4 kWh per square meter. The theoretical reserves reach 1.7 trillion tons of standard coal per year. The potential for the development and utilization of solar energy resources is very broad. From the distribution of the total annual solar radiation in the country, the Qinghai-Tibet Plateau, Northwest China, North China, most of Northeast China, Yunnan, Guangdong, Hainan and other low-latitude areas are all rich or relatively rich in solar energy resources.

The application space of my country's solar power generation industry is also very broad. First, my country has a desert area of ​​more than 1 million square kilometers, mainly distributed in the northwest region with rich light resources. If the desert is used to install a grid-connected solar power generation system, it can provide a very considerable amount of electricity. Second, solar cell modules can not only be used as energy equipment, but also as roofing and wall materials, which not only saves energy and building materials, but also has good economic benefits. Third, there are still many residents in remote areas of my country who have not yet used electricity. If they rely solely on the construction of power grids for power supply, the cost is high, the construction period is long, and it is not economical. Solar power generation does not require the construction of transmission lines, and the construction period is short, which can effectively solve the problem of electricity use in remote areas.

The Chinese government has also given full support to the solar energy industry. In January 2006, the "Renewable Energy Law of the People's Republic of China" was officially implemented. This law made provisions in resource survey and development planning, industrial guidance and technical support, promotion and application, price management and cost sharing, economic incentives and supervision measures, legal responsibilities, etc. Subsequently, the state successively issued the "Interim Measures for the Management of Special Funds for Renewable Energy Development" and "Interim Measures for the Management of Special Funds for Renewable Energy Building Applications" and other implementation details to support the development of renewable energy, making the state's support policies in the field of renewable energy increasingly clear. This series of laws and policies undoubtedly strongly support the development of my country's solar power generation industry.

In the past 20 years, my country's solar power generation industry has long maintained a global market share of about 1%. After 2005, the industry has developed by leaps and bounds. Companies such as Wuxi Suntech, Tianwei Yingli, Xinguang Silicon, LDK Solar, Xinjiang New Energy, Changzhou Trina, and Tianjin Kyocera have entered the growth stage, with production scales expanding, technical levels improving, and corporate competitiveness increasing. In addition, companies in Zhejiang, Baoding, Sichuan and other places have begun production or trial runs of polycrystalline silicon solar cells, and the market has formed a situation where monocrystalline silicon and polycrystalline silicon are the two main battery products. At present, my country's non-polycrystalline silicon thin-film battery industry is also showing a rapid development momentum. Many domestic companies have begun or plan to invest in non-polycrystalline silicon thin-film battery projects through cooperation with foreign companies.