The solar cell is the smallest unit of photoelectric conversion, and the size is generally 4~100cm². The working voltage of a single solar cell is about 0.45~0.5V, and the working current is about 20~25mA/cm². Generally, it cannot be used as a power source alone. After the solar battery cells are connected in series and parallel and packaged, they become solar battery modules. The power is generally from a few watts to several tens of watts or hundreds of watts, which is the smallest unit that can be used as a power source alone. The solar cell modules are connected in series and parallel and installed on the bracket to form a solar cell array, which has the output power required by the load (Figure 2-21).
A solar cell can generate a voltage of about 0.45V, which is far lower than the actual voltage required. Therefore, a solar cell module contains a certain number of solar cells, which are connected by wires. The standard number of solar cells on a solar cell module is 36 or 40 (10cm×10cm), which means that a solar cell module can generate about 16V voltage, which can be used to effectively charge a battery with a rated voltage of 12V.
The solar cells connected by wires are sealed to form a physical unit called a solar cell module. The module has certain anti-corrosion, wind, hail, rain and other abilities. Standard solar cell modules are widely used in many fields and systems. When a certain application field requires higher voltage or current, and a single component cannot meet the requirements, multiple components can be connected in series and parallel to form a square array to obtain the required voltage or current.
The reliability of solar cells depends to a large extent on their anti-corrosion, wind-proof, hail-proof, and rain-proof capabilities, and the main potential problems are the sealing of the edges and the junction box on the back of the module.
The solar cell packaging methods mainly include double-sided glass sealing and glass alloy laminated sealing.
Double-sided glass sealing: There are glass plates on both the front and back of the solar cell module, and the solar cells are embedded in a layer of polymer. One of the main problems with this sealing method is the connection between the glass plate and the junction box. This connection has to pass through the edge of the glass plate because it is expensive to punch holes in the glass plate.
Glass alloy laminated and sealed: The front of this component is a glass plate, and the back is a layer of alloy flakes. The alloy flakes are mainly used for moisture-proof and pollution-proof. Solar cells are embedded in a layer of polymer. In this solar cell module, the battery and the junction box can be directly connected by wires.