The role of the solar cell module is to convert solar energy into electrical energy, supply the load to work or charge the battery pack; the role of the controller is to protect the charging and discharging of the battery pack; the battery pack is used to store electric energy; the function of the inverter is to convert the DC power converted to alternating current. At night or in rainy days, when the solar cell components cannot work, the battery pack supplies power to the load. It can be seen that the battery pack plays a very important role in the photovoltaic power generation system.
The working mode of the storage battery can be divided into two types: cycle use and floating charge use. Often in the state of frequent charge and discharge, that is, cyclic use; often in the state of charge, it is used for floating charge, which can make up for the capacity loss of the battery due to self-discharge. VRLA batteries used in photovoltaic power generation systems belong to the recycling method.
In early photovoltaic off-grid power generation systems, open-type lead-acid batteries were generally used as energy storage devices, but open-type lead-acid batteries have disadvantages such as adding acid and water for maintenance, and the acid liquid is easy to pollute the environment, which is not conducive to unattended use and environmental protection. In recent years, valve-regulated sealed lead-acid batteries (VRLA) have become popular because they are sealed without acid leakage and do not corrode equipment and pollute the environment, and are widely used in telecommunications, electric power, railways and other industries. Almost all batteries used in photovoltaic systems are VRLA batteries. There are two main functions of VRLA batteries:
(1) In the case of night or cloudy and inconsistent photovoltaic array production capacity and load power consumption, the battery can store excess energy or provide energy to the load.
(2) Since the working characteristics of solar cell modules are greatly affected by solar irradiance and temperature, the load is often not near the optimal working point. The VRLA battery has a clamping effect on the working voltage of the solar battery, which can ensure that the load is near the optimal working point.
Photovoltaic power generation systems are mostly built in remote mountainous areas, plateaus, and Gobi. The natural environment is very harsh, and the temperature of the working environment varies widely. Therefore, the battery in the photovoltaic power generation system has the following requirements: deep cycle discharge performance, long charge and discharge cycle life; strong overcharge resistance; strong capacity recovery after over discharge; good charge acceptance; VRLA battery technology in static When used in the environment, the electrolyte is not easy to stratify; it has maintenance-free or low-maintenance performance; it should have good high and low temperature charge and discharge characteristics; it can adapt to the use environment in high altitude areas; the consistency of each battery in the battery pack is good.