Why is the photovoltaic off-grid and grid-connected system so different?
The photovoltaic grid-connected system and the photovoltaic off-grid system are only one word difference, but the price is different by thousands. Why is there such a big gap?
Speaking of photovoltaic off-grid systems, mainly by photovoltaic off-grid systems by components,Solar Controller/Inverter, battery pack, load, etc. It is widely used in practical applications, widely used in transportation, military, aerospace and other fields. It can be seen almost everywhere. Some people may wonder why I have not seen it. The application of photovoltaic off-grid system is small enough to charge treasure, street lamp, reach space, Traffic, etc. Take our daily routine, the roadside solar street light is a small off-grid system, which generates electricity during the daytime, the battery stores the daytime photovoltaic panels, and the nighttime electricity storage.
For the battery in the off-grid system, there are several of the most: the most important, the most expensive, the most vulnerable. The off-grid system is not connected to the grid, so a battery is needed to store electricity. Naturally, the battery is the most important part of the system. At present, the battery has a lead-acid battery and a lithium battery. In the off-grid system, it occupies 30%-50% of the cost of the power generation system. Of course, "no one is perfect, gold is not barefoot", the service life of the battery has been criticized, which is also a major technical barrier in the current industry. From the perspective of batteries used in off-grid systems in the market, lead-acid batteries are generally around 3 years old, and lithium batteries last for 6 or 7 years. With the emergence of high-efficiency battery technology, the life expectancy will become longer.
The photovoltaic grid-connected system consists of components, grid-connected inverters, brackets and other related system components. Since the grid-connected system needs to be connected to the grid, it needs to be equipped with a two-way meter. The electricity generated by the grid-connected system is AC, which can be directly used in the home. The load, excess electricity can also be sold to the grid.
It is not difficult to find that both the off-grid system and the grid-connected system are composed of core components and inverters. But what are the differences between off-grid inverters and grid-connected inverters?
Mainly look at the following points: composition, cost, efficiency.
First look at the composition, grid-connected inverters are generally two-stage structure of boost and inverter, while off-grid inverters generally have four levels of structure, including controller, boost, inverter, and isolation.
Look at the price of the off-grid inverter is about twice the cost of the grid-connected inverter. Off-grid system inverters are costly. Mainly depends on the overload capability is a hard indicator. The off-grid inverter output is connected to the load, and many loads are inductive loads. The starting power is 3-5 times of rated power, and the overload capability is strong. This requires higher power and quality for components, and the natural cost is more expensive. . The photovoltaic grid-connected inverter is connected to the front section of the inverter, and the back-end output is connected to the grid.
Third, look at efficiency. With the same power, the off-grid inverter overload capability is 30% higher than the grid-connected inverter.
With the maturity of photovoltaic technology and the decline in product prices, there will be more and more applications around off-grid and grid-connected. It is believed that more people will benefit from it in the near future.
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