Solar power generation principle and technical application

1. Principle of solar power generation:

 

(I) How do solar cells work?

 

The working principle of crystalline silicon n/p-type solar cells: When p-type semiconductors and n-type semiconductors are tightly combined and connected into one piece, a p-n junction is formed at the interface between the two. When the photovoltaic cell is irradiated by sunlight, positive and negative charges accumulate on both sides of the p-n junction, generating a photoelectric voltage and forming a built-in electric field. This is the "photovoltaic effect". Theoretically, at this time, if electrodes are drawn out on both sides of the built-in electric field and connected to an appropriate load, a current will be formed and power will be obtained on the load. Solar cell modules are solid devices that use the electronic properties of semiconductor materials to achieve P-V conversion.

 

(II) Basic components of solar energy systems

 

As shown in the figure above, the solar power generation system consists of solar cell modules, solar controllers, and batteries (groups). If the output power is AC 220V or 110V, an inverter is also required.

 

(III) The functions of each part are

 

Solar panels: Solar panels are the core part of the solar power generation system and the most valuable part of the solar power generation system. Its function is to convert the sun's radiation into electrical energy, or to store it in the battery, or to drive the load to work.

 

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

 

Battery: Generally a lead-acid battery, 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 then release it when needed.

 

Inverter: The direct output of solar energy is generally 12VDC, 24VDC, and 48VDC. In order to provide power to 220VAC appliances, the DC power generated by the solar power generation system needs to be converted into AC power, so a DC-AC inverter is required. Efficiency is one of the important criteria when purchasing an inverter. The higher the efficiency, the less power loss will be incurred in the process of converting the direct current generated by the photovoltaic module into alternating current. It can be said that the quality of the inverter determines the benefits of the power generation system, and it is the core of the solar power generation system.

 

(IV) The main factors to be considered in the design of solar power generation system:

 

Where is the solar power generation system used? What is the sunlight radiation in the area?

 

How large is the load power of the system?

 

What is the output voltage and frequency of the system, DC or AC?

 

How many hours does the system need to work every day?

 

If there is rainy weather without sunlight, how many days does the system need to supply power continuously?

 

What is the load condition, resistive, capacitive or inductive, and how large is the starting current?

 

II. Application of solar power generation technology:

 

The solar photovoltaic power generation system is a power generation and power conversion system composed of photovoltaic panels, controllers, and power storage and conversion links. With the rapid development of the global photovoltaic industry, many photovoltaic power generation related technologies have been greatly developed, from the production of solar panels to the design of power electronic converters. For a photovoltaic power generation system, solar cell technology, maximum power point tracking (MPPT) technology of photovoltaic arrays, concentrator technology, islanding effect detection technology, etc. are all important technologies involved in the operation of the system.