Study On A Tracking Control System For Tower Heliostats

With the rapid development of economy, the energy shortage and the consequent pollutionproblems have getting increasingly serious, people pay more and more attention to the developmentand utilization of new energy. As an ideal renewable energy, the use of the solar energy has gettingmore attention, countries all over the world are working on the development of solar energy. Atpresent, because the utilization efficiency of solar energy is low, it is hard for us to popularize thesolar energy technology. Once we can track the sun more precisely, the receiving rate of thermalenergy receiver can be greatly improved, meanwhile, the utilization efficiency of solar energy willbe increased and the popularity of energy technology will be easy. In this way, the current energyshortage is solved and it has no pollution to the environment. In this paper, the sun trackingtechnology is systematic studied.The method of the sun tracking has two kinds, photoelectric tracking and trajectory trackingwhich depending on the movement of the sun. After the analytic comparison, two kinds of methodare combined to fulfill the purpose of tracking the sun precisely. When the intensity of sun lightmeets the requirement of photoelectric tracking, the system works in the way of photoelectrictracking, or else in the way of trajectory tracking which depending on the movement of the sun. Ifthe sun is suddenly sheltered by the clouds in the sunny day, the system can automatically switchfrom photoelectric tracking to trajectory tracking which depending on the movement of the sun;while the intensity of the sun reach the requirement of trajectory tracking again, it can switch totrajectory tracking, so the system can automatically track the sun all-weather.In this paper, theoretical analysis and calculation are done, which is about the solar hour angleand declination angle, the solar altitude angles and azimuth, and the high order angle and azimuth ofheliostat. The photo-sensor based on the measurement of the position of sun is designed, which hashigh precision and well stability. In order to meet the requirement of the control system, C8051F020is selected as the CPU. Considering the features of the single-chip computer and the functionswhich want to achieve, the peripheral circuits of the single-chip computer and relevant software aredesigned. All of the important devices in the system and their functions are described in detail.Relevant interface circuit is designed, mainly including solar intensity detecting module, clock anddisplay module, data storage module, motor driving module and so on. According to therequirements of the design function, the main program module, sun angle calculation module, solarintensity detecting module, clock module and other modules are designed. Because of effective combination of the software and hardware, the tracking control system can achieve higher accuracyand better stability.The hardware and software experiments show that the design of the tower heliostat trackingcontroller's hardware and software are practicable. It has these advantages such as simple structure,designed rationally, running smoothly, high tracking precision and so on. Therefore the system cantrack the sun with high precision and all-weather, and the utilization efficiency of the solar energy isimproved, it also lays the foundation for the popularization of the solar energy.