A detailed introduction to photovoltaic power generation technology

Solar energy has become the focus of people's attention due to its unique advantages. The abundant solar radiation energy is an important energy source, which is inexhaustible, pollution-free and cheap, and can be freely used.

1. What is solar power generation

Photovoltaic power generation is a technology that directly converts light energy into electrical energy by using the photogenerated volt effect at the semiconductor interface. It is mainly composed of three parts: solar panels (components), controllers and inverters, and the main components are composed of electronic components.

Solar battery can be encapsulated and protected in series to form large-area solar cell modules, and then combined with power controllers and other components to form photovoltaic power generation devices.

2. The principle of solar power generation technology

The main principle of photovoltaic power generation is the photoelectric effect of semiconductors. When a photon hits a metal, its energy can be absorbed by an electron in the metal. The energy absorbed by the electrons is large enough to overcome the Coulomb force inside the metal atom to do work, escape from the metal surface, and become photoelectrons.

A silicon atom has 4 outer electrons, and if an atom with 5 outer electrons, such as a phosphorus atom, is incorporated into pure silicon, it becomes an N-type semiconductor. If an atom with three outer electrons, such as boron atoms, is doped into pure silicon, a P-type semiconductor is formed.

When the P-type and N-type are combined, the contact surface forms a potential difference and becomes a solar cell. When sunlight hits the P-N junction, an electric current flows from the P-type side to the N-type side, forming an electric current.

The photoelectric effect is an important and magical phenomenon in physics. Under the irradiation of electromagnetic waves above a certain frequency, the electrons inside some substances absorb energy and escape to form an electric current, that is, photogenerated electricity. Polysilicon is made into silicon wafers to be processed after going through processes such as ingots and slicing.

When a small amount of boron, phosphorus, etc. is doped and diffused on the silicon wafer, a P-N junction is formed. Then, screen printing is used to print the finely prepared silver paste on the silicon wafer to make a grid line, which is sintered and made into a back electrode at the same time, and a layer of anti-reflective coating is applied to the surface of the grid line, and the cell is thus made.

The cells are arranged and combined to form a large circuit board. Generally, the photovoltaic module is surrounded by an aluminum frame, covered with glass on the front side, and electrodes are installed on the reverse side. With battery components and other auxiliary equipment, a power generation system can be formed.

In order to convert direct current to alternating current, a current converter is required. Once generated, it can be stored in batteries or fed into the public grid. Battery components account for about 50% of the cost of the power generation system, while current converters, installation costs, other auxiliary components, and other expenses account for the other 50%.

3. Advantages and disadvantages found in the process of new energy utilization

● Merit

From the perspective of the world and China, the storage capacity of traditional chemical energy is very limited. Solar energy is an inexhaustible renewable energy source for human beings, which has the advantages of complete cleanliness, absolute safety, relative extensiveness, long life and maintenance-free, resource adequacy and potential economy, and has an important position in the long-term energy strategy.

Compared with the commonly used thermal power generation system, the advantages of photovoltaic power generation are mainly reflected in:

• There is no danger of depletion.
• Safe and reliable, no noise, no pollution emissions.
• It is not limited by the geographical distribution of resources, and the advantages of building roofs can be used. For example, areas without electricity, as well as areas with difficult terrain.
• There is no need to consume fuel and build transmission lines to generate electricity on site.
• High energy quality.
• The construction period is short, and the time taken to obtain energy is short.

● Shortcoming

• The production of solar panels is characterized by high pollution and high energy consumption.
• The irradiation energy distribution density is small and occupies a huge area.
• The energy obtained is related to meteorological conditions such as the four seasons, day and night, and cloudy and sunny weather.
• Generators will be more expensive than thermal power generation.
• The photovoltaic panel manufacturing process is not environmentally friendly.

4. What are the classifications of the system

① Independent PV power generation system

It is also called off-grid photovoltaic power generation. It is mainly composed of solar modules, controllers, and batteries. To power AC loads, an AC inverter also needs to be configured.

Independent photovoltaic power stations include village power supply systems in remote areas, solar home energy storage, communication signal power supplies, cathodic protection, solar street lights and other photovoltaic power generation systems with 12v 100ah lithium ion batteries that can operate independently.

② Grid connected PV power generation system

The direct current generated by solar modules is converted into alternating current that meets the requirements of the mains grid through a grid-connected inverter and then directly connected to the public grid. It can be divided into grid-connected power generation systems with and without batteries.

Grid-tied generation systems with 12 volt 200ah lithium battery are dispatchable and can be integrated into or off the grid as needed. It also has the function of backup power supply, which can provide emergency power when the power grid is out of power for any reason. Photovoltaic grid-connected power generation systems with batteries are often installed in residential buildings.

Grid-tied power generation systems without batteries do not have the functions of dispatchability and backup power, and are generally installed on larger systems. Grid-connected photovoltaic power generation has a centralized large-scale grid-connected photovoltaic power station, the main feature of which is that the generated energy is directly transmitted to the power grid, and the power grid is uniformly allocated to supply power to users.

However, this type of power station has a large investment, a long construction period and a large area. Distributed small-scale grid-connected photovoltaics, especially building integrated photovoltaic power generation, are the mainstream of grid-connected photovoltaic power generation due to the advantages of small investment, fast construction, small floor area, and strong policy support.

③ Distributed PV power generation system

Distributed power generation or distributed energy supply, refers to the configuration of a smaller photovoltaic power supply system at the user's site or near the power consumption site. To meet the needs of specific users, support the economical operation of existing distribution networks, or both.

The basic equipment of the distributed photovoltaic power generation system includes photovoltaic cell modules, photovoltaic array brackets, DC combiner boxes, DC distribution cabinets, grid-connected inverters, AC distribution cabinets, and other equipment, in addition to power supply system monitoring devices and environmental monitoring devices.

Its mode of operation is that under the condition of solar radiation, the solar module array of the photovoltaic power generation system will convert the output of solar energy into the DC distribution cabinet through the DC combiner box, and the inverter connected to the grid will be inverted into alternating current to supply the load of the building itself, and the excess or insufficient power will be adjusted by connecting the power grid.

5. Conclusion

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