Solar LED lighting systems have different scales and application forms. The system scale spans a large range, ranging from 0.3~2W lawn lights to hundreds of watts of solar LED high-pole lights. Its application forms are also diverse, and can be widely used in many fields such as household, transportation, communication, space and so on. Although solar LED lighting systems vary in size, their composition and working principles are basically the same. The solar LED lighting system is composed of a square array of solar cells, a solar battery, a controller (some controllers integrate the function of an LED driver, or separate the controller and the LED driver), and an LED light source. The block diagram of the solar LED lighting system is shown in Figure 1.
(1) Solar cell modules. Solar cells are mainly divided into: crystalline silicon batteries (including monocrystalline silicon Monoc-Si, polycrystalline silicon Mult-Si, ribbon/Sheetc-Si), amorphous silicon batteries (a-Si), non-silicon batteries (including steel silver selenide CIS, cadmium nitrate CdTe).
The most important thing in the solar LED lighting system is the solar cell, because it is the core module that collects sunlight. Due to technical and material reasons, the power generation capacity of a single solar cell is very limited. The solar cell in practical use is a solar cell module composed of a single solar cell in series and parallel. In recent years, the price of raw materials for crystalline silicon cells, which is the mainstream technology of solar cells, has continued to rise, resulting in a substantial increase in the cost of crystalline silicon cells, which makes the cost advantages of amorphous silicon cells more obvious. In addition, thin-film batteries (which greatly save the use of raw materials, thereby greatly reducing costs) have become the development direction of solar cells, but their technical requirements are very high. Amorphous silicon thin-film solar cells, as the most mature thin-film solar cells at present, are currently the most promising varieties of thin-film solar cells.
(2) Battery. The battery is an energy storage device in the solar LED lighting system, which converts the direct current power converted from solar radiant energy into chemical energy and stores it for load application. Since the input energy of the solar LED lighting system is extremely unstable, it is generally necessary to configure a battery to make the load work normally. The electrical energy generated by the solar cell is stored in the battery in the form of chemical energy. When the load needs power, the battery converts the chemical energy into electrical energy and supplies it to the load. The characteristics of the battery directly affect the efficiency, reliability and price of the solar LED lighting system. The selection of battery capacity generally follows the following principles: First of all, on the premise of being able to meet the power consumption of the load, store as much electric energy as possible from the solar cell modules during the day, and at the same time be able to store the electric energy required by the load during a predetermined continuous cloudy and rainy day.
The battery capacity is affected by the power consumption of the end load and the sunshine time (generation time). Therefore, the battery watt-hour capacity is determined by the predetermined load demand power and the continuous non-sunshine time. The performance of the battery directly affects the working characteristics of the solar LED lighting system. At present, the valve-regulated sealed lead-acid battery, the deep-discharge liquid-absorbing lead-acid battery, and the solar-specific gel battery are commonly used in the solar LED lighting system.