Research On Two-axis Sun-tracker Based On The Solar Trajectory

With the growing of energy problem worldwide, solar energy is becoming morewidely used as a clean and non-polluting energy. Quality testing for the mostimportant use of solar thermal products such as solar collectors is particularlyimportant. The vehicle sun-tracker is the key component of the mobile thermalperformance testing system for solar thermal products. It has a greatsignificance to improve the detection efficiency.A numerical control two-axis automatic sun-tracker based on the solar trajectorywas designed for solar collector testing system on the existing study of sun tracking. Itcan realize real-time sun tracking.Firstly, the status of energy utilization in our country and the current situation ofsolar thermal products’ quality were described. Existing sun-tracking devices wereanalyzed comparatively from their principle to implementation. The tracking programbased on solar trajectory was selected for the system. On this basis, the calculationof the sun position was given, especially, the controversial algorithms for timedifference were researched，the optimal algorithm which was not far off astronomicalalmanac was selected by comparing time difference data of one year.The hardware of the tracking system was designed using the intermittent controlmode and two-axis rotating model，size of the system was decided by the carryingvehicle’s space. Servo motors’ rotation of the two axes was controlled by industrialcontrol computer to achieve the two-axis tracking. The software program for eachmodule was wrote in Labview-based language and debugged. The system realized thefunctions including manual adjustment and automatic tracking based on the position ofthe sun calculated by the computer using the geographical latitude, longitude and time.Two-axis tracking system designed was used for tracking test in real environment.Its tracking accuracy was analyzed. It was showed that the two-axis suntracker designed can test environmental conditions automatically, its variousfunctions met the project’ requirements. Tracking accuracy of the system wasdetermined to be less than±2°.The vehicle two-axis sun tracker has been integrated in the mobile thermalperformance testing system for solar thermal products. It’s convenient to use.Energy absorption rate of flat panel solar collectors are increased. Testing requirementswere met.