The photovoltaic power generation system mainly consists of photovoltaic modules, controllers, inverters, batteries and other accessories (grid connection does not require batteries). According to whether it relies on the public power grid, it is divided into off-grid and grid-connected systems. The off-grid system operates independently and does not need to rely on the power 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 power to the load when the photovoltaic system does not generate electricity at night or the power generation is insufficient on rainy days.
Regardless of the form, the working principle is that photovoltaic components convert light energy into direct current, and the direct current is converted into alternating current under the action of the inverter, ultimately realizing the functions of electricity consumption and Internet access.
1. Photovoltaic modules
Photovoltaic modules are the core part of the entire power generation system. They are composed of photovoltaic module sheets or photovoltaic modules of different specifications cut by laser cutting machines or steel wire cutting machines. Since the current and voltage of a single photovoltaic cell are very small, it must be connected in series to obtain high voltage, and then connected in parallel to obtain high current, output through a diode (to prevent current return), and then packaged in a stainless steel, aluminum or other non-metallic On the frame, install the upper glass and back panel, fill with nitrogen, and seal. Combining photovoltaic modules in series and parallel forms a square array of photovoltaic modules, also called a photovoltaic array.
Working principle: Sunlight shines on the p-n junction of the semiconductor to form new hole-electron pairs. Under the action of the electric field of the p-n junction, holes flow from the p region to the n region, and electrons flow from the n region to the p region. After the circuit is connected, Create an electric current. Its function is to convert solar energy into electrical energy and send it to the battery for storage or to promote load work.
Component type:
① Monocrystalline silicon: Photoelectric conversion rate ≈ 18%, up to 24%, which is the highest conversion rate among all photovoltaic modules. It is generally encapsulated with tempered glass and waterproof resin. It is strong and durable, and its service life is generally up to 25 years.
②Polycrystalline silicon: The photoelectric conversion rate is ≈14%, which is similar to the production process of monocrystalline silicon. The difference between polycrystalline silicon is that the photoelectric conversion rate is lower, the price is lower, and the life is shorter. However, polycrystalline silicon materials are easy to manufacture, save power consumption, and have low production costs. , so it has been vigorously developed.
③Amorphous silicon: The photoelectric conversion rate is ≈10%. It is completely different from the production methods of monocrystalline silicon and polycrystalline silicon. It is a thin-film solar cell. The process is greatly simplified, the silicon material consumption is very small, and the power consumption is lower. Its The main advantage is that it can generate electricity in low light conditions.
2. Charger Controller (used in off-grid systems)
The photovoltaic controller is an automatic control device that can automatically prevent the battery from overcharging and over-discharging. Using a high-speed CPU microprocessor and a high-precision A/D analog-to-digital converter, it is a microcomputer data collection and monitoring control system that can quickly collect the current working status of the photovoltaic system in real time, obtain the working information of the PV station at any time, and provide detailed Accumulating historical data of PV stations provides an accurate and sufficient basis for evaluating the rationality of PV system design and testing the reliability of system component quality. It also has a serial communication data transmission function that can centralize multiple photovoltaic system substations. management and remote control.
3.Inverter
An off-grid inverter is the heart of a stand-alone power system, and its core function is to convert stored direct current (DC) into alternating current (AC) that can be used by a home or business. This conversion allows the electricity generated by solar panels or wind turbines, for example, to be used directly in the power supply, or stored in a battery for later use.
There are various types of off-grid inverters, mainly pure sine wave inverters and modified wave inverters. The current quality of the pure sine wave inverter is closest to the mains power supply, which is suitable for the supply of electrical appliances with high current quality requirements, while the modified wave inverter is lower cost and suitable for occasions with low current quality requirements. When choosing an off-grid inverter, you need to consider factors such as power size, output waveform, efficiency, and protection function.
The advantages of pure sine wave inverter are mainly reflected in the following aspects:
1. Higher stability. The output waveform of a pure sine wave inverter is more stable and pure, which can better protect the electrical equipment and make it last longer.
2. Low noise. Due to the accurate output waveform, the operation noise of pure sine wave inverter is also lower than that of ordinary inverters.
3. Be more adaptable. Pure sine wave inverters are able to accommodate a wider range of loads and can support the use of all electrical equipment.
4. Battery
The battery is a device that stores electricity in a photovoltaic power generation system. Currently, there are four types of lead-acid maintenance-free batteries, ordinary lead-acid batteries, gel batteries and alkaline nickel-cadmium batteries. The widely used ones are lead-acid batteries and gel batteries, etc.
Working principle: During the day, sunlight shines on the photovoltaic modules, generates DC voltage, converts the light energy into electrical energy, and then transmits it to the controller. After the overcharge protection of the controller, the electricity from the photovoltaic modules is transferred to the battery for storage.