Popular science: What is the difference between an off-grid inverter and a grid-connected inverter?

Off-grid inverters are used in off-grid power generation systems. Off-grid power generation systems are not connected to the mains, and form a set of systems by themselves. Grid-connected inverters are used in grid-connected power generation systems, which rely on city power.

First, grid-connected photovoltaic power stations

Grid-connected means that the power grid must be connected to the public grid, that is, solar power generation, household power grid, and public power grid. This is a power system that must rely on the existing power grid to operate. It mainly composed of solar panels and inverters, solar panels generate 220V ac power directly converted by the inverter and supply power to household appliances. When solar power exceeds the power used by household appliances, the surplus electricity is transferred to the public power grid. When solar power can\'t produce enough electricity for household appliances, it is automatically replenished from the grid. The whole process is intelligently controlled and does not require manual operation.

Since the photovoltaic system does not require a battery, the cost is greatly reduced. In particular, the new state policy on grid-connected electricity has made it clear that domestic photovoltaic power stations can be connected to the grid for free, and that surplus electricity can be sold to power companies. From the long-term perspective of investment, according to the service life of a family photovoltaic power station for 25 years, the cost can be recovered within 6-10 years, and the remaining ten years will be earned. So, if you want to save on electricity costs and have a convenient power supply, you can choose to have a connected solar system, which is the mainstream way.

However, the disadvantages of grid connection are that when the public power grid is cut off, the photovoltaic power generation cannot operate. But if the grid-connected inverter is replaced by an intelligent micro-grid inverter (a hybrid grid-connected and off-grid inverter), the power station can operate normally.

So, how can you store electricity generated during the day and use it at night? This requires adding controllers and batteries, etc. During the day, the controller stores the photovoltaic power in the battery, and at night the controller releases the battery power for lighting.

Second, off-grid pv power station

This is also called independent photovoltaic power station, don\'t rely on the power grid and independent operation of the power system, mainly include solar panels, storage battery, charge and discharge controller, inverter and other parts. The electricity from the solar panel flows directly into the battery and is stored. When it needs to be supplied to the electric device, the DC current in the battery is converted to the alternating current of 220V by the inverter. This is a repeated cycle charge and discharge process.

This kind of power generation system is widely used because it is not restricted by the region. As long as it has sunlight, it can be installed and used, so it is very suitable for remote non grid area, isolated island, fishing boat, outdoor breeding base and so on. It can also be used as an emergency power generation equipment in the area of power outage.

Such systems are required to have batteries and account for 30-50% of the cost of generating a system. In addition, the service life of the battery is generally 3-5 years, after which it has to be replaced, which increases the service cost. In terms of economy, it is difficult to be widely used, so it is not suitable for convenient use of electricity.

But for families without power grids or frequent power outages, they are also very practical. In particular, in order to solve the lighting problem of power failure, DC energy saving lamps can be used, which is very practical. Therefore, the off grid power generation system is specially designed for locations without power grids or frequent power outages.

Simply put: connecting to the grid does not batteries while off-grid needs.

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