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A comprehensive introduction of solar photovoltaic power generation
What is solar photovoltaic power generation?
Solar photovoltaic power generation refers to the use of solar radiation directly into electrical power generation. Solar photovoltaic power generation is the mainstream of today’s solar power generation, so now people often say solar power is photovoltaic power generation.
The principle of photovoltaic power generation - how does a photovoltaic cell generate electricity?
In 1839, the French scientist Becquerel found that under sunlight irradiation with special electrical properties of the semiconductor can produce free charge. These free charges are directed to move and accumulate, thus generating electricity when its ends are closed. This phenomenon is known as the “photovoltaic effect”, or PV effect for short
A photovoltaic cell is the most basic unit of solar photovoltaic power generation, and it is a semiconductor device with the characteristics of light and electricity conversion. The photovoltaic effect occurs in the presence of light, and the accumulation of a heterogeneous charge at both ends of the cell converts light energy into direct current energy.
The unique electrical characteristics of photovoltaic cells are achieved by doping certain elements (e.g., phosphorus or boron, etc.) into crystalline silicon, such as crystalline silicon photovoltaic cells, which creates a permanent imbalance in the molecular charge of the material, forming a semiconductor material with special electrical properties.
Main components of a photovoltaic power system
A complete solar photovoltaic power generation system usually consists of photovoltaic modules, inverters, convergence boxes and other major equipment.
Photovoltaic Module
As the core component of a PV power plant, their role is to convert sunlight into electricity. These modules consist of multiple PV cells, each of which is a tiny power generation unit. When sunlight hits a PV cell, photons interact with the silicon material inside the cell to generate an electric current.
These currents are pooled and converted, eventually becoming electricity that can be utilized. There are currently three types of modules on the market: monocrystalline silicon modules, polycrystalline silicon modules and amorphous silicon modules.
Inverter
The inverter is the key equipment in a solar photovoltaic power generation system, and it’s important to find a reliable inverter manufacturer. Its role is to convert the DC current generated by PV modules into AC current. The inverter not only realizes the conversion of current, but also ensures that the quality of the output AC power is up to standard through filtering, voltage stabilization and other processing.
Solar inverters can be divided into the following three categories: stand-alone inverters, grid-connected inverters, and battery backup inverters.
Confluence box
In solar photovoltaic power generation system, in order to reduce photovoltaic system wiring and improve system reliability, it is necessary to use an AC convergence box between the inverter and the grid-connected cabinet.
Users can determine the model of the AC converter box according to the input current designed for the grid-connected cabinet and the output current of the grid-connected inverter. The internal configuration of PV AC convergence box has input circuit breaker, output circuit breaker and AC lightning protector.
Main functions: converge the output current of multiple inverters, protect the inverters from the hazards of the AC grid-connected side/loads, serve as the inverter output disconnection point, improve the safety of the system, and protect the safety of the installation and maintenance personnel.
Classification of photovoltaic power generation systems
- Stand-alone PV
Stand-alone PV is also called off-grid PV. Independent photovoltaic power plants include village power supply systems in remote areas, solar household power systems, communication signal power supply, cathodic protection, solar street lamps and other kinds of solar photovoltaic power generation systems with batteries that can be operated independently.
- Grid-connected PV
Grid-connected photovoltaic power generation is the solar module generated by the DC power through the grid-connected inverter converted to meet the requirements of the utility grid AC power directly into the public power grid.
- Distributed PV
Distributed photovoltaic power generation system, also known as decentralized power generation or distributed energy supply, refers to the configuration of a smaller photovoltaic power supply system at the user site or close to the site of electricity consumption to meet the needs of specific users, or to support the economic operation of the existing distribution grid.
How does PV power enter the grid?
Directly into the grid
The power generated by PV plants with a capacity of less than 8 kW is converted into AC power by a single-phase inverter and then directly fed into the 220 V power grid.
Entering the grid after boosting
The power generated by small collective PV plants with capacity of 8kW~400kW enters the 0.4kV grid after being transformed into AC power by three-phase inverters.
Most of the power generated by medium-sized PV plants with capacity of 400kW~20MW enters the 10-35kV grid. The electricity generated from large-scale PV power plants of more than 20 MW generally enters the grid of 66 kV and above.
In the above three cases, it is necessary to raise the power to the corresponding grid voltage through the step-up transformer, and the AC power after the step-up will flow to the substation through the grid, and then complete the process of “on-line”, which can be used by thousands of households.
Why is photovoltaic power a green and low-carbon energy source?
Solar photovoltaic power generation has significant energy, environmental protection and economic benefits, is one of the highest quality green energy. In China under average sunshine conditions to install 1 kilowatt photovoltaic power generation system, this can generate 1200 kw in a year. And this can reduce the use of coal (standard coal) of about 400 kilograms, reduce carbon dioxide emissions of about 1 ton.
According to the World Wide Fund for Nature (WWF) research results: from the reduction of carbon dioxide effect. Installation of 1 square meter of photovoltaic power generation system is equivalent to planting 100 square meters. The current development of renewable energy such as solar photovoltaic power generation is one of the effective means to fundamentally solve the haze, acid rain and other environmental problems.
Earth’s surface to receive solar radiation to meet the global energy demand of 10,000 times, according to preliminary statistics, and with the solar photovoltaic power generation of technological advances and large-scale application of its power generation costs will be further reduced. It’ll become a more competitive way of supplying energy, and gradually from the complementary energy to alternative energy and become the future dominant energy source.
Conclusion
In conclusion, the solar photovoltaic power generation system not only represents a clean and renewable energy solution, but also a key way to realize energy diversification and reduce greenhouse gas emissions. With the continuous advancement of technology and cost reduction, solar PV power generation is gradually becoming an important part of the global energy market.
In the future, with the development of energy storage technology and smart grids, PV power generation will play an even more important role in the energy transition, bringing a brighter and more sustainable future for human society.
