A solar cell is a device that responds to light and converts light energy into electricity. There are many kinds of materials that can produce photovoltaic effect, such as: single crystal silicon, polycrystalline silicon, amorphous silicon, gallium arsenide, selenium indium copper, and the like. Their power generation principles are basically the same. Now, crystalline silicon is taken as an example to describe the photovoltaic power generation process. P-type crystalline silicon is doped with phosphorus to obtain N-type silicon to form a PN junction.
When the light illuminates the surface of the solar cell, part of the photons are absorbed by the silicon material; the energy of the photons is transferred to the silicon atoms, causing the electrons to move away, and the free electrons accumulate on both sides of the PN junction to form a potential difference when the external circuit is turned on. At this time, under the action of this voltage, a current will flow through the external circuit to generate a certain output power. The essence of this process is the process of converting photon energy into electrical energy.
First, solar power generation Solar power generation has two ways, one is the light-heat-electric conversion method, and the other is the light-electric direct conversion method.
(1) The light-thermal-electrical conversion method generates electricity by utilizing the thermal energy generated by solar radiation, which is generally converted into solar panels by solar collectors.
The steam is replaced by a working fluid, and then the steam turbine is driven to generate electricity. The former process is the light-to-heat conversion process; the latter process is the thermo-electric conversion process, which is the same as ordinary thermal power generation. The disadvantage of solar thermal power generation is that it is very inefficient and costly. It is estimated that its investment is at least 5 to 10 times more expensive than ordinary thermal power stations. A 1000 MW solar thermal power station requires an investment of 2 to 2.5 billion US dollars, and an average investment of 1 kW is 2,000 to 2,500 US dollars. Therefore, it is suitable for small-scale special occasions, and large-scale utilization is economically uneconomical and cannot compete with ordinary thermal power plants or nuclear power plants.
(2) Light-to-electric direct conversion method This method uses the photoelectric effect to directly convert solar radiation energy into electrical energy. The basic device for light-to-electrical conversion is solar cells. A solar cell is a device that converts solar energy directly into electrical energy due to the photovoltaic effect. It is a semiconductor photodiode. When the sun shines on the photodiode, the photodiode turns the solar light into electrical energy. Current. When many batteries are connected in series or in parallel, they can become a square of solar cells with relatively large output power. Solar cells are a promising new type of power source with three advantages of permanentness, cleanliness and flexibility. Solar cells have a long life. As long as the sun exists, solar cells can be used for long-term investment; with thermal power generation and nuclear power generation. In contrast, solar cells do not cause environmental pollution; solar cells can be large and small, ranging from large to medium-sized power plants of up to one million kilowatts, to solar cells that are only available to one household, which is unmatched by other power sources.
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