What is the difference between off-grid and connected photovoltaic systems
Commonly, off-grid photovoltaic power plants store solar power in batteries, and then convert them to 220V household voltage through inverters.Grid-connected refers to the connection to the power grid. The grid-connected pv power station doesn’t have electric energy storage device, which is directly converted into the voltage required by the national grid through the inverter and supply for household use primarily ,and the rest can be sold to the state.At present, the national policy supports solar photovoltaic power generation. As long as the household photovoltaic power station generates electricity, there will be state subsidies. However, if it is connected to the grid, it should first apply to the local state grid department.
Grid connection is to connect to the public grid, which means the solar power generation are connected to the household power grid and public power grid. This is a power generation system that can only operate depending on the existing power grid. It is mainly composed of solar panels and inverters. The solar panels are directly converted into 220V AC by the inverter and supply power to household appliances. When the power generation capacity of solar energy exceeds that of household appliances, the surplus power will be transmitted to the public grid; when the power generation capacity of Taiyang energy can not meet the needs of household appliances, it will be automatically supplemented from the grid. And this whole process is intelligent control, do not need manual operation.
As the photovoltaic power generation system does not need to use batteries, it also saves a lot of costs. In particular, the new grid connection policy issued by the state has made it clear that the household photovoltaic power station can be connected to the grid free of charge, and the surplus power can be sold to the power company.From the long-term perspective of investment, the cost can be recovered in about 6-10 years according to the 25 year service life of the household photovoltaic power station, and the remaining ten years are earned.Therefore, if you want to save electricity costs and convenient power supply, you should choose grid connected solar power generation system, which is also the mainstream way at present.
However, the disadvantages of the grid is the PV power can nor run when the public power grid is cut off. But if the grid connected inverter is replaced by the intelligent micro grid inverter (hybrid inverter of grid connected and off grid), the power station can operate normally.
So, how can we store the electricity generated during the day and use it at night? In the daytime, the controller stores the power generated by photovoltaic in the battery, and at night the controller releases the power stored in the battery for lighting..
Off grid photovoltaic power station, also known as independent photovoltaic power station, is a power generation system independent of the power grid. It mainly consists of solar panels, energy storage batteries, charge and discharge controllers, inverters and other components.The electricity from the solar panel flows directly into the battery and is stored. When the electric appliances need to be supplied, the DC current in the battery is converted into 220V AC through the inverter, which is a repeated cycle of charging and discharging process.This kind of power generation system is widely used because it is not restricted by the region. It can be installed and used as long as there is sunlight. Therefore, it is very suitable for remote areas without power grid, isolated islands, fishing boats, outdoor breeding bases, etc., and can also be used as emergency power generation equipment in areas with frequent power failure.
The battery of this system accounts take 30-50% of the prime cost, which has 3-5 years to use, and then it has to be replaced. From an economical consideration, it is difficult to promote the system in a wide range, so it is not suitable for the use of convenient places but it has strong practicability for families in areas without power grid or frequent blackouts.In particular, in order to solve the lighting problem of power failure, DC energy-saving lamp can be used, which is very practical.