Solar cells (solar chips, photovoltaic cells) are optoelectronic semiconductor sheets that use sunlight to directly generate electricity. As long as it is illuminated by light that meets certain lighting conditions, it can instantly produce voltage and generate current if there is a loop. In physics, it is called solar photovoltaic (photovoltaic, abbreviated PV), or photovoltaic for short. Solar cells are devices that directly convert light energy into electrical energy by photoelectric effect or photochemical effect. Crystalline silicon solar cells that work with the photoelectric effect are the most widespread, while thin-film cells that work with the photochemical effect are still in their infancy.
Principle
Sunlight shines on the p-n junction of the semiconductor, forming new paires hole-electron. Under the action of the integrated electric field of the p-n junction, the photogenerated holes move towards. the p region and the photogenerated holes flow towards the p region. Electrons flow to area n and when the circuit is turned on, a current is generated. This is how photovoltaic solar cells work.
There are two solar power generation methods: one is the light-heat-electricity conversion method and the other is the direct light-electricity conversion method.
Light-heat-electricity conversion
The light-heat-electricity conversion method uses thermal energy generated by solar radiation to produce electricity. Generally, a solar collector converts the absorbed thermal energy. The steam from the working fluid then drives the steam turbine to produce electricity. The first process is a light-heat conversion process;the second process is a heat-to-electricity conversion process, which is the same as ordinary thermal power generation. The disadvantages of solar thermal energy production are low efficiency and high cost. Its investment is estimated to be at least 5 to 10 times more expensive than that of ordinary thermal power plants. A 1,000 MW solar thermal power plant requires an investment of 2.0 to 2.5 billion US dollars, and the average investment for 1 kW is 2,000 to 2,500 US dollars. Therefore, it can only be used on a small scale for special occasions, and large-scale use is not economically profitable and cannot compete with ordinary thermal or nuclear power plants.
Direct conversion of light into electricity
Energy production by solar cells is based on the photoelectric properties of specific materials. Black bodies (likesun) emit electromagnetic waves of different wavelengths (corresponding to different frequencies), such as infrared, ultraviolet, visible light, etc. When these rays shine on different conductors or semiconductors, the photons interact with free electrons in the conductor or semiconductor to produce an electric current. The shorter the wavelength and the higher the frequency of the ray, the higher its energy. For example, the energy of ultraviolet rays is much higher than that of infrared rays. However, not all wavelengths of ray energy can be converted into electrical energy. It should be noted that the photoelectric effect has nothing to do with the intensity of the ray only when the frequency reaches or exceeds the threshold that can produce the photoelectric effect. current can be generated. The maximum wavelength of light that can produce an effect pphotoelectric in a semiconductor is linked to the bandgap width of the semiconductor. For example, the band gap of crystalline silicon is approximately 1.155 eV at room temperature. Therefore, light has a wavelength less than 1100 nm. is necessary to produce a photoelectric effect in crystalline silicon. Power generation by solar cells is a renewable and environmentally friendly way to produce electricity. During the electricity generation process, no greenhouse gases such as carbon dioxide are produced and no pollution is caused to the environment. According to the production material, it is divided into semi-silicon-based conductor batteries, CdTe thin-film batteries, CIGS thin-film batteries, dye-sensitized thin-film batteries, organic material batteries, etc. Silicon batteries are divided into single crystal batterieslines, polycrystalline batteries and amorphous silicon thin film batteries. The most important parameter for solar cells is conversion efficiency. Among the laboratory-developed silicon-based solar cells, the efficiency of monocrystalline silicon cells is 25.0%, the efficiency of polycrystalline silicon cells is 20.4%, the efficiency of thin-film cells CIGS. Solar cells reach 19.6% and CdTe efficiency. The efficiency of thin film cells reaches 16.7%, and the efficiency of thin film cells made of amorphous silicon (amorphous silicon) is 10.1%.
Solar cell is a photoelectric component which can convert energy. Its basic structure is the use of P-type and it is formed by joining N-type semiconductors. The basic material of semiconductors is "silicon", which is non-conductive, but if different impurities are mixed in the semi-conductor, it can be transformed into P-type and N-type semiconductors, and the P-type semiconductor then has a hole (the P-type semiconductor has one less negatively charged electron, which can be considered like an extra positive charge), and the potential difference between the N-type semiconductor and the N-type semiconductor has an extra free electron to generate current, So when the sun shines, the light energy changes silicon atoms. The electrons are excited, resulting in convection of electrons and holes. These electrons and holes are affected by the built-in potential and are attracted to N-type and P-type semiconductors respectively, and gather at both ends. At this point, if the exterior is connected with electrodes, a loop is formed. This is the principle of energy production by solar cells.
To put it simply, the principle of photovolt solar energy productionAic is to use solar cells to absorb sunlight with a wavelength of 0.4 μm to 1.1 μm (for silicon crystals) and directly convert the light energy into electrical energy. to go out. .
Since the electricity generated by solar cells is direct current, if you need to power household appliances or various electrical devices, you need to install a DC/AC converter and convert it to alternating current to power. to households or industries. Use electricity.
Development of solar cell charging Solar cells are used in consumer goods, and most of them have charging problems. In the past, nickel-metal hydride or nickel-cadmium dry batteries were generally used for charging, but nickel. -Metal hydride dry batteries cannot withstand high temperatures, and nickel-c batteriesadmium cannot withstand high temperatures. Dry batteries have environmental pollution problems. Supercapacitors are developing rapidly, with large capacities, shrinking areas and low prices. Therefore, some solar products have begun to use supercapacitors as charging objects, thereby improving many solar charging problems:
Charging is relatively slow and fast. ,
More than 5 times longer lifespan,
wide charging temperature range,
reduces solar battery usage (can be charged at low voltage).
How do solar panels convert solar energy into electrical energy?
The photoelectric conversion efficiency of solar cells increases as the temperature increases.
From a physical point of view, increasing temperature affects carrier mobility (i.e.say electrons and holes) in solar cells. As the temperature increases, carrier mobility increases, allowing more carriers to be transferred from inside the solar cell to the outside, thereby increasing the current density. Therefore, as the temperature increases, the photoelectric conversion efficiency of solar cells increases.
From a chemical point of view, increasing temperature affects the band structure of semiconductor materials in solar cells. The energy band structure of a semiconductor determines the energy state of electrons and holes. As the temperature increases, the energy band structure of the semiconductor changes, allowing more electrons and holes to move from the valence band to the conduction band, thereby increasing the current density.
Therefore, as the temperature increases, the effiPhotoelectric conversion efficiency of solar cells will also increase. Temperature also affects how efficiently solar cells absorb light. As temperatures rise, the semiconductor materials in solar cells absorb more photons, creating more electrons and holes. These electrons and holes can further participate in the photoelectric conversion process, thereby improving the photoelectric conversion efficiency of the solar cell.
Application fields of solar cells:
1. Home and Commercial Applications: The application of solar cells in homes and businesses has become increasingly common. . Homes and businesses can use solar cells to power their homes, reducing their reliance on traditional electricity. Additionally, some commercial facilities, such as shopping mallsCommercial, office buildings, etc., have also started using solar cells to provide electricity to reduce energy costs.
2. Industrial Application: Solar cells are also widely used in industrial fields. For example, some factories and power plants have started using solar cells to provide part of their electricity to reduce their dependence on traditional energy sources. Additionally, solar cells can also be used to power workstations for field operations, oil drilling, mining, and other locations.
3. Agricultural applications: Solar cells are increasingly used in agriculture. Farmers can use solar cells to power irrigation systems, greenhouses, pumping stations and more. In addition, the cellssolar can be used to power agricultural machinery, tractors, harvesters, etc.
4. Environmental and environmental protection: The use of solar cells helps reduce environmental pollution and protect the ecology. Traditional energy consumption results in large amounts of carbon emissions and other pollution, which can be reduced through the use of solar cells. In addition, solar cells can also be used to supply electricity to environmental protection facilities, such as waste treatment plants, sewage treatment plants, etc.
The basic principle of direct solar photoelectric conversion is to use the photoelectric effect to directly convert solar radiation energy into electrical energy. As shown in the figure, this is a simplified circuit for measuring thephotocurrent
Solar energy The principle of the battery is that sunlight shines on the p-n junction of the semiconductor to form new hole-electron pairs. Under the action of the electric field of the p-n junction, the holes flow from the n region to the p region, and. electrons flow from region p to region n. Once the circuit is turned on, create an electric current. This is how photovoltaic solar cells work.
1. Solar power generation methods There are two solar power generation methods, one is light-heat-electricity conversion method and the other is direct light-electricity conversion method.
(1) Light—The thermal-electric conversion method generates electricity using thermal energy generated by solar radiation. Generally, a solar collector converts the absorbed thermal energy into steam as the working fluid, then entersdrives a steam turbine to produce electricity. The first process is a light-heat conversion process; the second process is a heat-electricity conversion process, which is the same as ordinary thermal power generation. The disadvantages of solar thermal power generation are that its efficiency is very low and its cost is high. Its investment is estimated to be at least higher than that of ordinary thermal power generation. The power plant is 5-10 times more expensive. A 1,000 MW solar thermal power plant requires an investment of 2 to 2.5 billion US dollars. the average investment for 1 kW is 2,000-2,500 US dollars. Therefore, it can only be used on a small scale on special occasions, and large-scale use is not economically profitable and cannot compete with ordinary thermal or nuclear power plants.
(2) Methode direct conversion of light into electricity This method uses the photoelectric effect to directly convert the energy of solar radiation into electrical energy. The basic device for converting light into electricity is the solar cell. A solar cell is a device that directly converts solar energy into electrical energy through the photovoltaic effect. When the sun shines on the photodiode, the photodiode converts light energy from the sun into electrical energy, producing current. When many batteries are connected in series or parallel, a solar cell array with relatively large output power can be formed. Solar cells are a promising new energy source with three major advantages: Solar cells have a long lifespan and can be invested once and used for a long time as long as the sun exists, they aredifferent from the production of thermal energy; and nuclear energy production. In comparison, solar cells will not cause environmental pollution; Solar cells can be used in both large, medium and small sizes, ranging from a medium-sized power plant with a million kilowatts to a solar battery for a household. uniquely, which is unmatched by other power sources.
Battery board raw materials: glass, EVA, battery sheets, aluminum alloy shells, tin-plated copper sheets, brackets made of stainless steel, batteries, etc.
| (1) The left side of the power supply is the positive pole, the right side is the negative pole; the ammeter is positive up and negative down (2) B (3) 6.25×10 13 |
| (1) Electrons are emitted by the cathode, B is the cathode (2) Same as the firstquestion (3) q=It=10×10 -6 ×1 C=10 -5 C. And n= , so it contains 6.25×10 13 photoelectrons |
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