PV grid-connected system and PV off-grid system, only a word difference, but the price difference of thousands, why is there such a big difference?
Speaking of PV off-grid system, mainly by the PV off-grid system consists of modules, solar controller / inverter, battery pack, load, etc.. Its practical application is extremely wide, widely used in transportation, military, aerospace and other fields, almost everywhere, some may question why I have not seen it? The application of PV off-grid system is as small as rechargeable battery, street light, reaching aerospace, transportation and so on. Take our daily life, the roadside solar street lights, is a small off-grid system, daytime through photovoltaic power generation, battery storage daytime photovoltaic panels generated by the electricity, night through the storage of electricity stored electricity lighting.
And for off-grid systems in the battery, there are several of the most important: the most important, the most expensive, the most easily broken. Off-grid systems are not connected to the grid, so they need batteries to store electricity, so naturally the battery is the most important part of the system. At present, there are lead-acid batteries and lithium batteries, which account for 30%-50% of the cost of the power generation system in off-grid systems. Of course, "no one is perfect, no gold is perfect", the service life of the battery has been criticized, which is also a major technical barrier in the industry today. From the point of view of the market off-grid system used batteries, lead-acid batteries are generally in about 3 years, lithium battery life in 6, 7 years, with the emergence of high-efficiency battery technology life will become longer.
The grid-connected PV system consists of modules, grid-connected inverters, brackets and other related system accessories. As the grid-connected system needs to be connected to the grid, it needs to be equipped with two-way meters, and the electricity generated by the grid-connected system is AC electricity, which can be used directly for household loads, and the excess electricity can also be sold into the grid.
It is not difficult to find that both off-grid system and grid-connected system are composed of core part components, inverters. But what are the differences between off-grid inverters and grid-connected inverters?
The main points to look at are: composition, cost, and efficiency.
First of all, the grid-connected inverter is generally a two-stage structure of boost and inverter, while the off-grid inverter generally has a four-stage structure, including controller, boost, inverter, and isolation.
Then look at the price off-grid inverter cost is about two times more than the grid-connected inverter. Off-grid system inverter it is costly. It mainly depends on the overload capacity is a hard indicator. Off-grid inverter output connected to the load, and there are many loads are inductive loads, the starting power is 3-5 times the rated power, overload capacity, which requires higher power and quality of components, naturally the cost is more expensive. The front section of the PV grid-connected inverter is connected to the module, and the rear output is connected to the grid, which is different from it.
The third look at the efficiency. The same power, off-grid inverter overload capacity than the grid-connected inverter to more than 30% higher.
With the maturity of photovoltaic technology, the price of products down, around the off-grid and grid-connected applications will also be more and more, I believe that in the near future there will be more people benefit from it.
