A solar cell module is a small, indivisible assembly of solar cells with internal connections and encapsulation, capable of individually providing direct current output. It consists of high-efficiency monocrystalline/polycrystalline solar cells, low-iron ultra-white tempered glass, EVA, TPT, interconnecting strips, busbars, a backsheet, and an aluminum alloy frame. Module types include monocrystalline silicon solar cells, polycrystalline silicon solar cells, and amorphous silicon solar cells. The core component of a solar panel is the solar cell. Generally speaking, the electrical characteristics of the cells used in each panel should be basically consistent; otherwise, a so-called hot spot effect will occur on cells with poor electrical performance or those that are shaded (problematic cells).
To prevent hot spots, a bypass diode should be connected in parallel with each cell. When a cell malfunctions or is shaded, the current generated by other cells exceeding that of the problematic cell will be bypassed by the bypass diode. However, connecting a diode in parallel with every single cell is impractical. Typically, in solar cell modules, 18 cells (for modules with 36 or 54 cells in series) or 24 cells (for modules with 72 cells in series) are connected in series, followed by a diode connected in parallel.
Photovoltaic glass
Because individual solar photovoltaic cells have poor mechanical strength and are easily broken; moisture and corrosive gases in the air will gradually oxidize and corrode the electrodes, making them unable to withstand the harsh conditions of outdoor operation; at the same time, the operating voltage of individual photovoltaic cells is usually low, making it difficult to meet the needs of general electrical equipment. Therefore, solar cells are usually sealed with EVA film between an encapsulation panel and a backsheet, forming an indivisible photovoltaic module with encapsulation and internal connections, capable of providing DC power output independently. Several photovoltaic modules, inverters, and other electrical accessories constitute a photovoltaic power generation system.
Encapsulating film (EVA)
The encapsulating film for solar cells is located in the middle of the solar cell module, wrapping around the solar cell and bonding it to the glass and backsheet. The main functions of the encapsulating film include: providing structural support for the solar cell circuitry, maximizing light coupling between the cell and solar radiation, physically isolating the cell and circuitry, and conducting heat generated by the cell. Therefore, encapsulating film products need to possess characteristics such as high moisture barrier properties, high visible light transmittance, high volume resistivity, weather resistance, and anti-PID (Potential Inhibition of Specific Effects) properties.
battery cells
Silicon solar cells are typical two-terminal devices, with two terminals located on the light-receiving and back-lighting sides of the silicon wafer, respectively. Their primary function is power generation. The mainstream solar cells on the market are crystalline silicon solar cells and thin-film solar cells, each with its own advantages and disadvantages. Crystalline silicon solar cells have relatively low equipment costs, but high consumable and cell costs. However, they also have high photoelectric conversion efficiency and are well-suited for outdoor sunlight power generation. Thin-film solar cells have relatively high equipment costs, but very low consumable and cell costs. Their photoelectric conversion efficiency is only slightly more than half that of crystalline silicon solar cells, but they perform exceptionally well in low-light conditions, generating electricity even under ordinary artificial light.
The principle of photovoltaic power generation: When a photon shines on a metal, its energy can be completely absorbed by an electron in the metal. If the energy absorbed by the electron is large enough, it can overcome the Coulomb force inside the metal atom and escape from the metal surface, becoming a photoelectron. Silicon atoms have four outer electrons. If atoms with five outer electrons, such as phosphorus atoms, are added to pure silicon, it becomes an N-type semiconductor; if atoms with three outer electrons, such as boron atoms, are added, it forms a P-type semiconductor. When P-type and N-type atoms are combined, a potential difference is formed at the interface, forming a solar cell. When sunlight shines on the PN junction, current flows from the P-type side to the N-type side, forming a current.
Back panel
A solar backsheet is a photovoltaic encapsulation material located on the back of a solar cell module. In outdoor environments, it primarily protects the solar cell module from environmental factors such as light, humidity, and heat, resisting the erosion of the encapsulation film and cells, thus providing weather-resistant insulation. Because the backsheet is the outermost layer on the back of the photovoltaic module and is in direct contact with the external environment, it must possess excellent resistance to high and low temperatures, ultraviolet radiation, environmental aging, moisture barrier properties, and electrical insulation to meet the 25-year lifespan of the solar cell module. With the photovoltaic industry's increasing demands for power generation efficiency, some high-performance solar backsheet products also feature high light reflectivity to improve the photoelectric conversion efficiency of the solar module.
Photovoltaic inverter
In solar photovoltaic (PV) power generation, the electricity generated by the photovoltaic array is direct current (DC), while many loads require alternating current (AC). DC power supply systems have significant limitations; they are not convenient for voltage conversion, and their application range is limited. Except for special electrical loads, inverters are needed to convert DC to AC. The photovoltaic inverter is the heart of a solar PV power generation system. It converts the DC power generated by the PV system into the AC power required for daily life using power electronic conversion technology, and is one of the most important core components of a PV power plant.
