Principles of photovoltaic power generation

principle

The main principle of photovoltaic power generation is the photoelectric effect of semiconductors. When a photon shines on a metal, its energy can be absorbed by an electron in the metal. The energy absorbed by the electron is large enough to overcome the internal gravity of the metal to do work, escape from the metal surface and become a photoelectron. Silicon atoms have 4 outer electrons. If pure silicon is doped with 5 outer electrons such as phosphorus atoms, it becomes an N-type semiconductor; if pure silicon is doped with 3 outer electrons, such as Boron atoms form a P-type semiconductor. When the P-type and N-type are combined together, the contact surface will form a potential difference and become a solar cell. When sunlight hits the PN junction, the current flows from the P-type side to the N-type side, forming a current.

The photoelectric effect is a phenomenon in which light causes a potential difference between different parts of a non-uniform semiconductor or a combination of a semiconductor and a metal. At the beginning, it is the process of converting photons (light waves) into electrons and light energy into electric energy; secondly, it is the process of forming voltage.

Photovoltaic power generation principle diagram

After ingot casting, ingot breaking, slicing and other procedures, polysilicon is made into silicon wafers to be processed. Doping and diffusing a small amount of boron and phosphorus on the silicon wafer form a PN junction. Then screen printing is used to print the finely prepared silver paste on the silicon wafer to make grid lines. After sintering, the back electrode is made at the same time, and a layer of anti-reflection coating is applied to the surface with grid lines. So far made. The battery slices are arranged and combined into a battery assembly to form a large circuit board. Generally, the aluminum frame is wrapped around the module, the front is covered with glass, and the electrode is installed on the back. 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 needs to be installed. After power generation, it can be stored in batteries, or it can be fed into the public grid. In the cost of the power generation system, battery components account for about 50%, and current converters, installation fees, other auxiliary components and other costs account for the other 50%.

advantage

Regardless of the world or China, conventional energy is very limited. China's primary energy reserves are far below the world average, only about 10% of the world's total reserves. Solar energy is an inexhaustible and inexhaustible renewable energy source for human beings. It has sufficient cleanliness, safety, relative universality, real long life and maintenance-free, resource sufficiency and potential economy, etc. Advantages, have an important position in the long-term energy strategy.

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

① No risk of exhaustion;

②Safe and reliable, no noise, no pollution discharge, clean (no pollution);

③The advantages of building roofs can be used without being restricted by the geographical distribution of resources; for example, areas without electricity and areas with complex terrain;

④On-site power generation and power supply can be achieved without consuming fuel and erecting transmission lines;

⑤High energy quality;

⑥Users are easy to accept emotionally;

⑦The construction period is short, and the time it takes to obtain energy is short.

shortcoming

However, the production of solar panels has the characteristics of high pollution and high energy consumption. Under the current conditions, the production of solar panels for domestic use is still the past, but a large number of exports are equivalent to polluting China and benefiting the world. According to statistics, It is necessary to burn more than 40 kilograms of coal to produce a 1m×1.5m solar panel, but even China’s relatively inefficient thermal power plants can use this coal to produce 130 kWh of electricity (generally, a 1mx1.6m solar panel generates electricity per year. Above 250 kWh)-This is enough for a 2.2-watt light-emitting diode (LED) bulb to emit light for 30 years based on 12 hours of work per day.

① The irradiated energy distribution density is small, that is, it takes up a huge area;

②The energy obtained is related to weather conditions such as four seasons, day and night, overcast and sunny.

③Compared with thermal power generation, generators will cost more.

④ The photovoltaic panel manufacturing process is not environmentally friendly.