Question: In the photovoltaic off-grid system, batteries account for a large proportion, and the cost is similar to that of solar modules, but their lifespan is much shorter than that of modules. Lead-acid batteries only last 3-5 years, and lithium batteries last 8-10 years, but they are expensive. BMS management system is required, which increases costs. Can photovoltaic off-grid power stations be used directly without batteries?
Answer: Except for some special applications such as photovoltaic lighting systems, off-grid systems must be equipped with batteries. The task of the battery is to store energy, ensure the stability of the system power, and ensure the power consumption of the load at night or in rainy days.
First, the time is inconsistent
In the photovoltaic off-grid system, the input is a component for power generation, and the output is connected to the load. Photovoltaics generate electricity during the day, only when there is sunlight, and the power generation is often the highest at noon, but at noon, the demand for electricity is not high. Many households use off-grid power stations at night, so what to do with the electricity generated during the day? Store energy first, and this power storage device is the battery. Wait until the peak of electricity consumption, such as seven or eight o'clock in the evening, and then release the electricity.
Second, the power is inconsistent
Photovoltaic power generation is affected by radiation and is extremely unstable. When a cloud comes, the power will immediately decrease, and the load is not stable. Like air conditioners and refrigerators, the starting power is very large, and the normal operating power is less. If the photovoltaic directly carries the load, It will cause the system to be unstable, and the voltage will fluctuate. The battery is a power balancing device. When the photovoltaic power is greater than the load power, the controller sends the excess energy to the battery pack for storage. When the photovoltaic power cannot meet the load demand, the controller sends the battery's electric energy to the load.
The photovoltaic pumping system is a special off-grid power station that uses solar energy to pump water. The pumping inverter is a special inverter that includes the function of a frequency converter. The frequency can be changed according to the intensity of solar energy. When the solar radiation is high, the output frequency If the solar radiation is low, the output frequency will be low and the pumping volume will be small. The photovoltaic water pumping system needs to build a water tower, and pump water into the water tower when the sun is shining. Users need water from the water tower. , this water tower is actually the role of replacing the battery.