Composition of photovoltaic power generation system
The photovoltaic power generation system is mainly composed of photovoltaic components, controllers, inverters, batteries and other accessories (the grid-connected does not require batteries). According to whether it relies on the public grid, it is divided into off-grid and grid-connected. The off-grid system operates independently and does not need to rely on the grid. The off-grid photovoltaic system is equipped with a battery with energy storage function, which can ensure the stability of the system power, and can supply electricity to the load when the photovoltaic system does not generate power at night or when the power generation is insufficient in rainy days.
Regardless of the form, the working principle is that photovoltaic modules convert light energy into direct current, which is transformed into alternating current under the action of the inverter, and finally realizes the function of electricity and Internet access.
1. Photovoltaic modules
Photovoltaic modules are the core part of the entire power generation system. They are composed of photovoltaic modules or photovoltaic modules of different specifications cut by a laser cutting machine or a steel wire cutting machine. Since the current and voltage of the monolithic photovoltaic cells are very small, it is necessary to connect in series to obtain high voltage, then parallel to obtain high current, output through a diode (to prevent current return), and then encapsulate in a stainless steel, aluminum or other non-metal On the frame, install the upper glass and the back plate on the back, fill it with nitrogen, and seal it. Combine photovoltaic modules in series and parallel to form a square array of photovoltaic modules, also called photovoltaic array.
Working principle: Sunlight shines on the semiconductor pn junction to form a new hole-electron pair. Under the action of the pn junction electric field, holes flow from the p-zone to the n-zone, and electrons from the n-zone to the p-zone. Form an electric current. Its function is to convert solar energy into electric energy, and send it to the storage battery for storage, or to drive the load to work.
①Single crystal silicon: photoelectric conversion rate ≈18%, up to 24%, which is the highest conversion rate of all photovoltaic modules. It is generally encapsulated with toughened glass and waterproof resin, which is durable and has a service life of up to 25 years.
②Polycrystalline silicon: The photoelectric conversion rate is ≈14%, which is similar to the production process of monocrystalline silicon. The difference of polycrystalline silicon is that the photoelectric conversion rate is lower, the price is lower, and the lifespan is shorter. However, the polycrystalline silicon material is easy to manufacture, saves power consumption, and has low production costs. , So it has been vigorously developed.
③Amorphous silicon: The photoelectric conversion rate is ≈10%, which is completely different from the production method of monocrystalline silicon and polycrystalline silicon. It is a thin-film solar cell. The process is greatly simplified. The silicon material consumption is low and the power consumption is lower. The main advantage is that it can generate electricity in low light conditions.