Industrial lens: what is the difference between off-grid and grid-connected photovoltaic systems

Industrial lens: what is the difference between off-grid and grid-connected photovoltaic systems

In simple terms, an off-grid photovoltaic power station stores solar power into a battery and then converts it into a 220V voltage for home use through an inverter. The grid-connected power station can also be roughly understood from the name. It means that it is connected to the city electricity. The grid-connected photovoltaic power station has no electrical energy storage device. It is directly converted into the voltage required by the national grid through the inverter, and it is given priority for household use , The unused electricity of the family can be sold to the country. At present, national policy support is vigorously supporting solar photovoltaic power generation. As long as home photovoltaic power stations generate electricity, there will be state subsidies. However, to connect to the grid, you must first apply to the local State Grid Department.

First, grid-connected photovoltaic power stations

Grid connection 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 a solar panel and an inverter. The solar panel emits 220V AC power directly through the inverter and supplies power to the home appliances. When the solar power generation exceeds the power used by the home appliances, the excess power is sent to the public Grid; and when the amount of solar power cannot meet the use of household appliances, it is automatically replenished from the grid. The entire process is intelligently controlled and does not require manual operation.

Since this photovoltaic power generation system does not require the use of a battery, it also greatly saves costs. In particular, the country's new grid-connected policy has clearly stated that home photovoltaic power stations can be connected to the network for free, and excess electricity can also be sold to power companies. From the long-term perspective of investment, based on the 25-year service life of the home photovoltaic power plant, the cost can be recovered in about 6-10 years, and the remaining ten years are earned. Therefore, if you want to save electricity costs and convenient power supply, choose a grid-connected solar power generation system, which is also the current mainstream method. There is a more detailed introduction to costs and benefits in home photovoltaic power generation.

However, grid connection also has its disadvantages, that is, when the public power grid is cut off, photovoltaic power generation cannot be operated. However, if the grid-connected inverter is replaced by an intelligent microgrid inverter (a grid-connected and off-grid hybrid inverter), the power station can operate normally.

So, how can you store the electricity generated during the day and use it at night? This requires adding a controller and a battery. During the day, the controller stores the electricity generated by photovoltaics in the battery. At night, the controller releases the electricity stored in the battery for supply. Lighting used.

Second, off-grid photovoltaic power stations

This is also called an independent photovoltaic power station, which is a power generation system that operates independently without relying on the power grid. It mainly consists of solar panels, energy storage batteries, charge and discharge controllers, and inverters. The electricity generated by the solar panel directly flows into the battery and is stored. When power is needed to power the appliance, the DC current in the battery passes through the inverter and is converted into 220V AC power. This is a repeated cycle of charging and discharging. This type of power generation system is widely used because it is not limited by area. It can be installed and used as long as there is sunlight. It is very suitable for remote areas without power grids, isolated islands, fishing boats, outdoor breeding bases, etc. Regional emergency power generation equipment.

This system requires 30-50% of the cost of the power generation system because it must be equipped with a battery. In addition, the service life of the battery is generally 3-5 years, and it must be replaced afterwards, which increases the use cost. In terms of economy, it is difficult to get a wide range of popularization and use, 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 practicality. In particular, in order to solve the lighting problem during a power outage, a DC energy-saving lamp can be used, which is very practical. Therefore, off-grid power generation systems are specifically designed for use in places without grid or in areas with frequent power outages.