Detailed description of the difference between grid-connected photovoltaic power generation system and off-grid photovoltaic power generation system

Detailed description of the difference between grid-connected photovoltaic power generation system and off-grid photovoltaic power generation system

       Today, I will give you a popular science. If you install a solar photovoltaic power station in your home, should it be on-grid or off-grid? Do you need batteries?

       To put it simply, the off-grid photovoltaic power station is to store solar power in a battery, and then convert it into a household 220V voltage through an inverter. The name of the grid-connected power station can also be roughly understood. It refers to the connection to the mains. The grid-connected photovoltaic power station 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 for household use , The household’s unused electricity can be sold to the country. At present, national policy support is vigorously supporting solar photovoltaic power generation. As long as household photovoltaic power plants generate electricity, there will be state subsidies. However, if you are connected to the grid, you must first apply to the local State Grid Department.

1. Grid-connected photovoltaic power station

Grid-connected means that it must be connected to the public power grid, that is, solar power generation, home power grid, and public power grid are linked together. This is a power generation system that must rely on the existing power grid to operate. It is mainly composed of solar panels and inverters. The solar panels are directly converted into 220V AC power by the inverter and supply power to the household appliances. When the power generated by the solar energy exceeds the power used by the household appliances, the excess electricity is sent to the public Grid; when solar power can't meet the use of household appliances, it will automatically be replenished from the grid. And this whole process is intelligently controlled and does not require manual operation.

Since this photovoltaic power generation system does not require the use of batteries, it greatly saves costs. In particular, the country’s new grid-connected policy has clearly stated that household photovoltaic power stations can be connected to the grid for free, and excess electricity can be sold to power companies. From a long-term perspective of investment, based on the 25-year service life of a household photovoltaic power station, the cost can be recovered in about 6-10 years, and the remaining ten years will be earned. Therefore, if you want to save electricity bills and provide convenient power supply, you can choose a grid-connected solar power system, which is also the current mainstream method. There is a more detailed introduction about costs and benefits in this WeChat public account (Home Photovoltaic Power Generation).

However, grid connection also has its shortcomings, that is, photovoltaic power generation cannot operate when the public grid is out of power. However, if the grid-connected inverter is replaced with a smart micro-grid inverter (a hybrid inverter for 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? This requires the addition of a controller and a battery. During the day, the controller stores the electricity generated by the photovoltaic in the battery, and at night the controller releases the electricity stored in the battery for lighting.

2. Off-grid photovoltaic power generation system power station

This is also called an independent photovoltaic power station. It is a power generation system that does not rely on the grid and operates independently. It mainly consists of solar panels, energy storage batteries, charge and discharge controllers, inverters and other components. The electricity generated by the solar panel flows directly into the battery and is stored. When it is necessary to supply power to the appliance, the DC current in the battery is converted into 220V AC power through the inverter, which is a repeated cycle of charging and discharging process. This kind of power generation system is not restricted by region and is widely used. It 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. Emergency power generation equipment in the region.

This kind of system must be equipped with batteries, and it occupies 30-50% of the cost of the power generation system. Moreover, the service life of the battery is generally 3-5 years, and it must be replaced afterwards, which increases the cost of use. In terms of economy, it is difficult to be widely promoted and used, so it is not suitable for use in places where electricity is convenient.

But for households in areas without power grids or areas with frequent power outages, it has strong practicability. Especially in order to solve the lighting problem during power outage, DC energy-saving lamps can be used, which is very practical. Therefore, the off-grid power generation system is specially designed for use in areas without power grids or areas with frequent power outages.

To put it simply: Grid-connected does not require batteries, off-grid batteries are required.