Solar cells performance parameters:

1. Open circuit voltage

Open circuit voltage UOC: the output voltage value of the solar cell when the solar cell is placed under AM1.5 spectrum conditions and 100 mW/cm2 light intensity, and the two ends are open.

2. Short circuit current

Short circuit current ISC: the current value flowing through the two ends of the solar cell when the output end is short-circuited under AM1.5 spectrum conditions and 100 mW/cm2 light intensity.

3. Maximum output power

The operating voltage and current of the solar cell vary with the load resistance. The volt-ampere characteristic curve of the solar cell is obtained by making a curve of the operating voltage and current values corresponding to different resistance values. If the selected load resistance value can maximize the product of the output voltage and current, the maximum output power can be obtained, which is represented by the symbol Pm. The operating voltage and operating current at this time are called the optimal operating voltage and the optimal operating current, which are represented by the symbols Um and Im respectively.

4. Fill factor

Another important parameter of solar cells is the fill factor FF (fill factor), which is the ratio of the maximum output power to the product of the open circuit voltage and the short circuit current.

FF: It is an important indicator to measure the output characteristics of solar cells. It represents the maximum power that a solar cell can output when it is carrying the optimal load. The larger its value, the greater the output power of the solar cell. The value of FF is always less than 1. The series and parallel resistances have a great influence on the fill factor. The larger the series resistance, the more the short circuit current decreases, and the more the fill factor decreases; the smaller the parallel resistance, the larger its divided current, resulting in the more the open circuit voltage decreases, and the more the fill factor decreases.

5. Conversion efficiency

The conversion efficiency of a solar cell refers to the maximum energy conversion efficiency when the optimal load resistance is connected to the external circuit, which is equal to the ratio of the output power of the solar cell to the energy incident on the surface of the solar cell. The photoelectric conversion efficiency of a solar cell is an important parameter to measure the quality and technical level of the cell. It is related to the structure, junction characteristics, material properties, operating temperature, radiation damage of radioactive particles and environmental changes of the cell.

Solar cells power calculation

The solar AC power generation system is composed of solar panels, charging controllers, inverters and batteries; the solar DC power generation system does not include inverters. In order for the solar power generation system to provide sufficient power for the load, it is necessary to reasonably select various components according to the power of the electrical appliances.

The following is an example of a 100W output power, used for 6 hours a day, to introduce the calculation method:

First, the watt-hours consumed per day (including the loss of the inverter) should be calculated:

If the conversion efficiency of the inverter is 90%, then when the output power is 100W, the actual required output power should be 100W/90%≈111W; if it is used for 5 hours a day, the power consumption is 111W×5h=555Wh.

Calculate the solar panel:

Based on the effective sunshine time of 6 hours per day, and considering the charging efficiency and the loss during the charging process, the output power of the solar panel should be 555Wh/6h/70%=130W. 70% of it is the actual power used by the solar panel during the charging process.