Characteristics of independent solar cell system

Independent is a system that is not connected to the public grid of the power company. The photoelectric conversion efficiency of solar cells is affected by the temperature, solar light intensity and battery voltage fluctuation of the battery itself, which will change in one day. The spectrum and light intensity of the sun's radiation on the ground are affected by the atmospheric thickness (i.e. atmospheric quality), geographical location, local climate and meteorology, terrain and features, and their energy changes in one day There are great changes in month and year, and even there are great differences in the total annual radiation between years. The cycle of solar irradiation and radiant energy change in various regions of the earth is 24 hours a day, and the power generation of solar cells in a certain region also changes periodically for 24 hours, which is the same as that of solar radiation in the region. In addition, the change of weather will affect the power generation of solar cell modules. If there are several consecutive rainy days, solar cell modules can hardly generate electricity, so the power generation of solar cells is a variable.

The storage battery works in the floating charge state, and its voltage changes with the change of square burst power generation and load power consumption. The energy provided by the battery is also affected by the ambient temperature. The solar cell charge discharge controller is made of electronic components, which also needs energy consumption, and the performance and quality of the components used are also related to the energy consumption, thus affecting the charging efficiency. The power consumption of the load also depends on the purpose. There are fixed equipment power consumption, such as communication relay stations, unmanned weather stations, etc., while the power consumption of some equipment, such as lighthouses, beacon lights, civil lighting and domestic power consumption, often changes.

For the independent photovoltaic system, photovoltaic power generation is the only power source. In this case, it can be roughly divided into three loads: day, night and day even night. For loads used only in the daytime, most of them can be directly powered by the photovoltaic system, which reduces the loss caused by battery charging and discharging, and the capacity of the equipped photovoltaic system can be appropriately reduced. For all loads used at night, the capacity of photovoltaic system shall be increased accordingly. The capacity required for the load used day and night is between the two. In addition, it can be divided into balanced load, seasonal load and random load according to the service time of the whole year. There are many factors affecting the operation of photovoltaic system, and the relationship is very complex. In the actual situation, it should be handled according to the site conditions and operation conditions.

Due to the randomness of solar radiation, it is impossible to determine the exact amount of solar radiation in each period on the array behind the installation of photovoltaic system, which can only be used as a reference according to the historical data recorded by the meteorological observatory. However, usually, meteorological stations provide solar radiation on the horizontal plane, which needs to be converted into radiation on the inclined square array. For a general photovoltaic system, it is only necessary to calculate the monthly average solar irradiation on the inclined plane, and the instantaneous solar radiation flux does not need to be considered. The designer's task is to design the solar cell application system not only to pay attention to economic benefits, but also to ensure the high reliability of the system under the environmental conditions of the solar cell (i.e. the geographical location of the site, solar radiation energy, climate, meteorology, terrain and contradiction).