The solar cell and the battery constitute the power supply unit of the system, so the battery performance directly affects the system operating characteristics.(1) Battery unit: Due to technical and material reasons, the power generation of a single battery is very limited. A practical solar cell is a battery system in which a single battery is composed of a series and a parallel, which is called a battery assembly (array). A single cell is a silicon crystal diode that, under the conditions of a semiconductor material, is irradiated onto a PN junction of a homogeneous semiconductor material of two different conductivity types, P-type and N-type, under certain conditions. Solar radiation is absorbed by the semiconductor material, producing non-equilibrium carriers, electrons and holes, in the conduction and valence bands. Similar to the P-N junction barrier region, there is a strong built-in electrostatic field, so that the current density J, the short-circuit current Isc, and the open circuit voltage Uoc can be formed under illumination. If the electrodes are drawn on both sides of the built-in electric field and connected to the load, theoretically the circuit formed by the PN junction, the connecting circuit and the load, then the "photogenerated current" flows, and the solar cell module realizes the power to the load. P output.
(2) Electrical energy storage unit: The direct current generated by the solar battery first enters the storage of the battery, and the characteristics of the battery affect the working efficiency and characteristics of the system. Battery technology is very mature, but its capacity is affected by the end of electricity demand, sunshine time (power generation time). Therefore, the battery watt hour capacity and ampere-hour capacity are determined by the predetermined continuous daylight-free time.