The photovoltaic off-grid power generation system is ma […]
The photovoltaic off-grid power generation system is mainly composed of six parts: solar modules, brackets, solar controllers, off-grid inverters, batteries and distribution boxes. After the solar cell module is connected to the solar controller, it first meets the user's load, and then stores the remaining electric energy in the storage battery for night and rainy use. When the battery is out of power, most inverters can also support commercial power input (or diesel generator) as a supplementary energy source to supply power to the load.
The design of photovoltaic off-grid systems is different from the design of grid-connected power generation systems. It needs to consider the user's load size, daily power consumption, local weather conditions and other factors. It is relatively complicated to choose different design schemes according to the actual needs of customers. In order to ensure the reliable operation of the off-grid system, it is necessary to do a preliminary customer demand survey. The design of photovoltaic off-grid system mainly includes inverter selection, module capacity design and battery capacity design.
1. Inverter selection: determine the inverter power according to the size and type of user load
The selection of inverter power is generally not less than the total power of the load, but considering the service life of the inverter and subsequent expansion, it is recommended to reserve a certain margin for the inverter power, generally 1.2~1.5 of the load power Times. In addition, if the load includes motor inductive loads similar to refrigerators, air conditioners, water pumps, range hoods, etc. (the starting power of the motor is 3 to 5 times the rated power). The starting power of the load should be considered, that is, the starting power of the load should be less than the maximum impact power of the inverter. The following is the calculation formula for inverter power selection for design reference.
2. Component capacity determination: Determine the component capacity according to the user's daily power consumption and light intensity
Part of the electricity generated by the photovoltaic module during the day is supplied to the load, while the rest is used to charge the battery. At night or in the case of insufficient solar radiation, the electrical energy stored in the battery will be released to the load for use. It can be seen that the electricity consumed by the load comes from the electricity generated by the photovoltaic module during the day without commercial electricity/or diesel engine as supplementary energy. Taking into account the different light intensity in different regions and different seasons, in order to ensure the reliable operation of the system, the capacity design of photovoltaic panels should also meet the needs of the worst light season. The following is the calculation formula for the capacity of photovoltaic panels:
3. Determination of battery capacity: determine the battery capacity according to night power consumption or backup time
The battery of the photovoltaic off-grid system is mainly used for energy storage to ensure that the load can still work normally when the solar radiation is insufficient. For photovoltaic off-grid systems with important loads, the battery capacity design needs to consider the maximum rainy day in the area. Ordinary photovoltaic off-grid systems do not require high-load power supplies. Considering the cost of the system, the use of the load can be adjusted according to the actual light intensity instead of rain.