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The difference between on-grid and off-grid installation of photovoltaic power stations in homes
- May 09, 2018 -

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First, grid-connected photovoltaic power station


On-grid connection means that it must be connected to the public power grid, that is, solar power generation, home power grids, and public power grids 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. Solar panels are directly converted into 220V AC power through the inverter and used to supply power to household appliances. When the power generated by solar energy exceeds the power used by home appliances, excess power is transferred to the public. Grid; and when solar power generation can not meet the use of household appliances, it will be automatically added from the grid. This entire process is intelligently controlled and does not require manual operation.


Since this type of photovoltaic power generation system does not require the use of a battery, it also greatly saves costs. In particular, the new grid-connected policies that have been issued by the state have made it clear that home photovoltaic power stations can be accessed free of charge 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 family photovoltaic power plant, the cost can be recovered in about 6-10 years, and the remaining 10 years will be earned. Therefore, if you want to save on electricity expenses and the power supply is convenient, then you should choose a grid-connected solar power system. This is the current mainstream approach.


However, grid-connected networks also have the disadvantage that photovoltaic power generation cannot operate when the public power grid is powered off. However, if the grid-connected inverter is replaced by an intelligent micro-grid inverter (a hybrid inverter with a grid and off-grid), the power plant can operate normally.


So, how can we store the electricity generated during the day for use in the evening? This requires the addition of controllers, storage batteries, etc. The daytime controller stores the electricity generated by the photovoltaics in the storage battery, and at night the controller releases the electricity stored in the storage battery for lighting use.


Second, off-grid photovoltaic power station


This is also called an independent photovoltaic power station. It is an independent power generation system that does not depend on the power grid. It mainly consists of solar panels, storage batteries, charge and discharge controllers, and inverters. The electricity from the solar panel flows directly into the battery and is stored. When the power supply to the appliance is required, the DC current in the battery is converted to 220 V AC by the inverter, which is a repeated cycle charging and discharging process. Since this type of power generation system is not restricted by geographical area and is widely used, it can be installed and used only in a place where there is sunlight, so it is very suitable for remote areas without power grids, isolated islands, fishing boats, outdoor breeding bases, etc., as well as frequent power outages. Regional emergency power generation equipment.


This kind of system must be equipped with a battery and occupy 30-50% of the cost of the power generation system. And the battery life is generally in 3-5 years, then have to be replaced later, which is to increase the cost of use. In terms of economy, it is difficult to get a large-scale promotion and use, so it is not suitable for use in electricity-convenient places.


However, it is also very practical for homes with no grid or frequent power outages. In particular, DC energy-saving lamps can be used to solve the problem of lighting during power outages, which is very practical. Therefore, off-grid power generation systems are specifically designed for use in areas with no grid or frequent outages.