When many people are going to install a photovoltaic system on their roof, they will always struggle with a question: should it be connected to the grid or off-grid, and do I need a battery? Today, I will tell you the difference between the two.
In simple terms:
The off-grid photovoltaic system stores the solar power in the battery, and then converts it into the household 220V/380V voltage through the inverter.
The grid-connected photovoltaic system can also be roughly understood from the name. It refers to the connection with the mains. The grid-connected photovoltaic system has no electric energy storage device, and is directly converted into the voltage required by the national grid through the inverter, and is given priority to households. Use, the electricity that households can't use up can be sold to the state.
At present, the national policy supports and is vigorously supporting solar photovoltaic system. As long as the home photovoltaic system generates electricity, there will be state subsidies. However, if you want to connect to the grid, you must first apply to the local national grid department.
Specific differences:
Grid-connected photovoltaic system
Grid-connected means that it must be connected to the public grid, that is, the solar system, the home grid, and the public grid are linked together. This is a power system that must rely on the existing grid to operate.
It is mainly composed of solar panels and inverters. The output of solar panels is directly converted into 220V/380V AC power by the inverter and supplies power to household appliances. When the power generated by solar energy exceeds the power used by household appliances, the excess electricity will be delivered. To the public grid; and when the solar system can not meet the use of household appliances, it is automatically supplemented from the grid. And this whole process is intelligently controlled and does not require manual operation.
Since this photovoltaic system does not require the use of batteries, the cost is greatly saved. In particular, the new grid-connection policy issued by the state has clearly stated that household photovoltaic systems can be connected to the grid for free, and excess electricity can also be sold to power companies. From the long-term perspective of investment, according to the 25-year service life of the household photovoltaic system, the cost can be recovered in about 5 years, and the remaining 20 years are earned. Therefore, if you want to save electricity expenses and provide convenient power supply, you should choose a grid-connected solar system, which is also the mainstream method at present.
Off-grid photovoltaic system
This is also called an independent photovoltaic system. It is a power generation system that operates independently without relying on the grid. It is mainly composed of solar panels, energy storage batteries, charge and discharge controllers, inverters and other components. The electricity emitted by the solar panel directly flows into the battery and is stored. When it is necessary to supply power to the electrical appliance, the DC current in the battery is converted into 220V AC by the inverter, which is a repetitive cycle of charge and discharge. Since this power system is not restricted by regions, it is widely used and can be installed and used as long as there is sunlight. Therefore, it is very suitable for remote areas without power grids, isolated islands, fishing boats, outdoor breeding bases, etc., and can also be used as frequent power outages. Regional emergency power generation equipment.
This kind of system must be equipped with batteries and occupies 30-50 percent of the cost of the power system. Moreover, the service life of the battery is generally 3-5 years, and it has to be replaced after that, which increases the cost of use. In terms of economy, it is difficult to be popularized and used on a large scale, so it is not suitable for use in places where electricity is convenient.
However, it is very practical for families in areas without power grids or areas with frequent power outages. Especially in order to solve the lighting problem during a power outage, DC energy-saving lamps can be used, which is very practical. Therefore, off-grid power generation systems are specially designed for use in areas without power grids or areas with frequent power outages.