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All You Want To Know About Solar Photovoltaic Is Here.
- May 08, 2018 -

Solar photovoltaic technology is a forward-looking technology that can directly convert the sun's light energy into electric energy and make full use of it. Its broad application prospects make the world work hard for development, innovation and application for the world. This period will introduce the principles of solar power generation, solar cells, solar cell modules, photovoltaic controllers, photovoltaic inverters and so on.

1.The principle of solar power generation

Solar cells are devices that respond to light and convert light energy into electricity. There are many kinds of materials that can produce photovoltaic effect, such as monocrystalline silicon, polycrystalline silicon, amorphous silicon, gallium arsenide, selenium, indium, copper and so on. Their power generation principles are basically the same. Now we take crystal as an example to describe the process of optical power generation. P type crystalline silicon can obtain N type silicon by doping phosphorus and form P-N junction.

When the light is irradiated on the surface of a solar cell, a part of the photon is absorbed by the silicon material; the energy of the photon is transferred to the silicon atom, which makes the electrons move over and become a free electron to form a potential difference on both sides of the P-N junction. When the external circuit is connected, the current will flow through the external circuit under the action of the voltage. A certain output power. The essence of this process is the process of converting photon energy into electrical energy.

2. The process of making solar cells

Silicon is one of the most abundant materials on our planet. Since scientists discovered the semiconductor characteristics of crystalline silicon in nineteenth Century, it has changed almost everything, even human thinking. At the end of the twentieth Century, "Silicon" was seen everywhere in our lives. Crystalline silicon solar cells were the fastest growing industries in the past 15 years. The process of production can be roughly divided into five steps:

A. purification process

B. pull rod process

C. slicing process

D. battery process

E. encapsulation process.

3. Application of solar cell

In the 60s of last century, scientists had applied solar cells to space technology, communication satellite power supply. At the end of last century, in the process of self introspection, it was becoming more and more friendly to such clean and direct energy forms as photovoltaic power, not only in space applications, but also in many fields. Such as solar courtyard lamp, solar power generation system, independent system of village power supply, photovoltaic water pump (drinking water or irrigation), communication power, cathodic protection of oil pipeline, power supply of optical cable communication pump station, seawater desalination system, urban middle road mark, highway signpost and so on. Advanced countries such as Europe and the United States incorporate photovoltaic power generation into urban power system and natural village power supply system in remote areas. The combination of solar cells and building systems has become the trend of industrialization. Solar photovoltaic glass curtain wall elements have been used more and more, with several projects in Shanghai and Beijing entering the substantive operation, this way will replace the ordinary glass curtain wall, it has the characteristics of small reflected light intensity, good insulation performance and so on!

4. Solar cell components

Solar cell modules (PV modules) are made up of a number of solar panels connected in series and connected in parallel. In one component, the standard number of solar cells is 36 (10cmx10cm), which means that a solar cell component can generate about a voltage of about 17V, which can be effectively charged for a battery with a rated voltage of 12V. At present, the output power of PV modules is as high as several hundred watts.

After packaging the solar cell into components, it can provide enough mechanical strength, anti vibration and impact resistance; it has good sealing, anti-corrosion, wind protection, hail prevention, moisture proof, good electrical insulation, and anti ultraviolet radiation. The potential quality problems may occur in the edge seal and the junction box on the back of the component.

According to the needs of PV installation, when a single component is not satisfied with high voltage and current in the application field, multiple components can be assembled in series and in parallel into a "solar cell square", also called a "photovoltaic array", to obtain the required voltage and current, and the power can be combined according to the actual demand. Determine.

5. Solar photovoltaic controller

The photovoltaic charging controller can be divided into five types: parallel photovoltaic controller, series type photovoltaic controller, pulse width modulation type photovoltaic controller, intelligent photovoltaic controller and maximum power tracking type photovoltaic controller.

a. Parallel photovoltaic controller

When the battery is full, use the electronic component to divert the output of the photovoltaic array into the internal parallel resistor or the power module, and then consume it in the form of heat. Parallel photovoltaic controllers are generally used in small and low power systems, such as voltages within 12V, 20A and systems. This kind of controller is reliable, without mechanical components such as relays.

b, series photovoltaic controller

The charging process is controlled by mechanical relay and the photovoltaic array is cut off at night. It is generally used in higher power systems, and the capacity of the relay determines the power level of the charging controller. It is relatively easy to fabricate a series photovoltaic controller with a continuous current of over 45A.

c. Pulse width modulation type photovoltaic controller

It switches the PV array input with PWM pulse mode. When the battery tends to be full, the frequency and time of the pulse are shortened. According to the study of the American National Laboratory of santia, this charging process forms a more complete charging state, which can increase the total cycle life of the battery in the photovoltaic system.

d. Intelligent photovoltaic controller

Based on MCU (such as the MCS51 series of Intel company or PIC series of Microchip company), the running parameters of the PV power system are collected at high speed, and the single or multipath photovoltaic arrays are cut off and connected by the software program according to certain control rules. For medium and large photovoltaic power systems, distance control can also be carried out through the RS232 interface of MCU and MODEM modem.

e, maximum power tracking controller

The power of the solar cell voltage V and current I is multiplied to get the power P, and then judge whether the output power of the solar cell at this time is maximum, if it does not run at the maximum power point, the pulse width is adjusted, the modulation output duty ratio is D, the charging current is changed, the time sampling is carried out again, and the judgment of whether the duty ratio is changed is made. Through this optimization process, the solar cell can always be operated at the maximum power point to make full use of the output energy of the solar array. At the same time, PWN modulation is used to make the charging current a pulse current, so as to reduce the polarization of the battery and improve the charging efficiency.