The solar automatic tracking concentrating photovoltaic power generation system controlled by a single-chip microcomputer has the characteristics of high tracking accuracy, large tracking range, and easy real-time control. The system uses a refraction condenser to condense a larger area of sunlight in a smaller area to form a focal spot or focal zone, and place the solar cell on this focal spot or focal zone. This focusing method increases the light energy density of sunlight by more than 400 times, increases the conversion efficiency of solar cells, and can obtain large currents on a small-area monocrystalline silicon wafer. The photovoltaic power generation system is mainly composed of a concentrating cell array, azimuth and elevation drivers, trackers, controllers, brackets, etc., as shown in Figure 1.
Among them, the concentrating cell array is composed of several concentrating cells in series and parallel. For crystalline silicon solar cells, generally low-magnification condensing, proper consideration of heat dissipation conditions is enough. If the concentrating magnification is increased to more than tens of times, the photoelectric conversion efficiency of the concentrating solar cell should generally be greater than 20%, and it must be resistant to high-magnification solar radiation, especially the photoelectric conversion performance at higher temperatures must be guaranteed. Therefore, some special considerations must be made in the selection of semiconductor materials, battery structure and grid line design. At this time, ordinary crystalline silicon solar cells cannot bear it, and special materials and battery structures must be used to manufacture concentrating solar cells.
The solar concentrator uses a Fresnel lens, which is made by using the principle of light refraction at the interface of different media, which has the same function as a general spherical lens. It is the main component of the concentrating battery module, which has the characteristics of small size, light weight, convenient processing, and high light transmittance. A Fresnel lens with a large diameter can be made very thin, which can greatly reduce the quality of the lens compared with a spherical lens. On the one hand, it focuses the sunlight, on the other hand, it also protects the battery components. It is a part of the battery module cover. The radiator of the battery module is located in the shadow of the battery cover (normal tracking state) and is not exposed to direct sunlight, so it is easy to dissipate heat, so that the battery temperature is low and the efficiency is high.
The key technology of the photovoltaic power generation system is to accurately track the sun to ensure that the sun’s rays are parallel to the central axis of the lens during the tracking process, and then through the effect of high-concentration light, the energy of the light spot falling on the photovoltaic cell is very strong, and a large current can be obtained on a small area of monocrystalline silicon wafer. The greater the concentration ratio of the condenser, the higher the tracking accuracy requirements. When the concentration ratio is 400, the tracking accuracy requirements are less than 0.20°. In general, the higher the tracking accuracy, the more complex the structure and the higher the cost, even higher than the total cost of photovoltaic cells in photovoltaic power generation systems.
The basic structure of the tracking system is shown in Figure 2, which is mainly composed of a single chip microcomputer, a sensor, and a stepping motor. Its basic principle is: when the sun shines on the sensor, the sensor signal given by the position deviation between the battery array and the sun (that is, when the array plane is not perpendicular to the sun) is amplified by the preamplifier and the voltage follower is stored in the single-chip microcomputer; after a certain processing by the single-chip microcomputer, the stepping motor is controlled to rotate, so that the concentrator moves with the movement of the sun, so as to achieve the purpose of tracking.