The Classification and Application of Independent Photovoltaic Power Generation System
An independent photovoltaic power generation system is also called an off-grid photovoltaic power generation system. Typically, the independent photovoltaic power generation system is mainly composed of solar arrays, solar controllers, and storage batteries. When there is sunlight, the photovoltaic power generation array provides power to the load and charges the battery. In other cases, the battery provides power to the load.
Besides, to supply power to the AC load, an AC inverter are also needed. Independent photovoltaic power generation systems can be divided into two categories: DC photovoltaic power generation systems and AC photovoltaic power generation systems.
DC Photovoltaic Power Generation Systems
1. No-battery DC photovoltaic power generation system
The characteristic of the no-battery DC photovoltaic power generation system is that the electrical load is a DC load. Hence, there is no restriction for the load usage time, and the load is mainly used during the daytime. The solar cell is directly connected to the electrical load. When there is sunlight, it generates electricity for the load to work, and when there is no sunlight, it stops working. The system does not need a solar controller and there is no battery storage device. The advantage of the no-battery DC photovoltaic power generation system is eliminating the energy loss and improving the solar energy utilization efficiency. The most typical application of this kind of system is the solar photovoltaic water pump.
2. DC photovoltaic power generation system with battery
A DC photovoltaic power generation system with a battery consists of solar cells, solar controller, storage battery and DC load. When there is sunlight, the solar cell converts solar energy into electrical energy for the load to use, and stores electrical energy to the battery at the same time. At night or in cloudy and rainy days, the battery supplies power to the load. This kind of system is widely used, ranging from solar lawn lights and garden lights, to mobile communication base stations, microwave transfer stations far away from the power grid, and rural power supply in remote areas. When the system capacity and load power are large, solar cell arrays and battery packs are required.
AC Photovoltaic Power Generation Systems
1. AC and AC-DC hybrid photovoltaic power generation system
Compared with the DC photovoltaic power generation system, the AC photovoltaic power generation system and AC-DC hybrid photovoltaic power generation system both include AC inverter, which is used to convert the DC power into the AC power and provide power for the AC load. The AC-DC hybrid photovoltaic power generation system can supply power to both DC loads and AC loads.
2. Mains complementary photovoltaic power generation system
The mains complementary photovoltaic power generation system is mainly based on solar photovoltaic power generation, supplemented by ordinary 220V AC power supplementary power. In such a photovoltaic power generation system, the capacity of solar cells and storage batteries can be designed to be smaller. Basically, when there is sunlight during the daytime, the electricity generated is used on that day, and when there is rainy day, it is supplemented by mains electricity. According to the record, in most areas of China, more than two-thirds of the days are sunny. This form not only reduces the one-time investment of the solar photovoltaic power generation system, but also has significant energy saving and emission reduction effects. It is a suitable way to popularize and promote the solar photovoltaic power generation.
So where is the mains complementary photovoltaic power generation system used? For example, in the renovation of street lamps in an urban area, huge investment costs will be needed if all ordinary street lamps are replaced by solar street lamps. Therefore, it is difficult to achieve. However, if the ordinary street lamps are modified, the original mains power supply lines and lamp poles stay the same, the energy-saving light source lamps and lanterns are replaced, and the mains complementary photovoltaic power generation form is used, it constitutes a mains complementary solar photovoltaic street light, the investment is reduced by more than half, and the energy saving effect is remarkable.