Development of inexpensive all-weather solar tracking control system for amendable tracking precision

Abstract: To reduce costs and complexity of solar tracking system, a simple solar tracking control system and T-L type sun origination detector are developed by analog circuit and photoelectric conversion principle. The tracking system is composed of bridge circuits and amplification circuits; it has functions of manually adjusted tracking accuracy and manually working. It is used to drive 12V DC gear motor, and it can be used for single-axis tracking, can also be used for dual-axis tracking. The tracking system only requires six common types of electronic components, which costs no more than 10 RMB. In order to reduce external environment impact on tracking performance of the system, a T-L-type orientation detector was designed for the tracking system. The L-type shading plate of the orientation detector was fixed to the L-type clapboard, therefore, the cross-section the shading plate and the clapboard showed a T-shape. Then, the clapboard was fixed to the substrate, and two sides of the clapboard were installed respectively with four photoresistors. Two were used to control movement of east-west direction; the other two were used to control movement of north-south direction. In addition, back of the substrate was installed with two photoresistors. Also, it was paralleled respectively with the two photoresistors which were used to control the movement of east-west direction. One of the photoresistor was used for controlling energy concentrator return orient in a next day; one of the photoresistor was used for balance another photoresistor behind the substrate. When using the system, the orientation detector was installed on a plane which paralleled to energy concentrator so that the orientation detector always synchronized to movement and energy concentrator. To test performance of the tracking system, in this paper, the tracking performance of the system was analyzed by light spot detection experiments. The method of the experiment was that an inverted paper cup was attached to a piece of paper. A hole was drilled at the geometric center of bottom of the paper cup, and then concentric circles with 2 mm interval were drawn on the paper. Then, the paper cup and the orientation detector were fixed to bracket of the dual-axis tracking device. Thereby, observation was made on the light spot which was generated by a small hole in bottom of the paper cup in the sunshine that was located on the first of several concentric circles on the paper. The observation time was the summer solstice at 09:00-16:00 in 2015, 10 min recorded once every spot positions on concentric circles. Intervals of 10 min recorded a position of the light spot on concentric circles. The recorded dates of the light spot, the distance between the hole and the paper was used for a simple calculation, thus, the angle between incident light of the sunlight and normal direction of the paper was calculated. If the calculated angle was larger, the tracking error was greater and vice versa. After the analysis, we discovered that angle error of the system increased as time increased. The value of the angle error decreased first, and then increased. At about 13:00, the error angle has a minimum value of 0.14°; at 09:00 and 16:00, there is a maximum angle error, and its value was 5°and 2.9°, respectively. Theoretically, the angle between the normal direction of the paper and the incident light of sunlight should always be consistent, and angle error does not change with time, but, the results of our experiments were different. After analyzing solar radiation, we discovered that solar radiation along with time increased, the amount of radiation increased first, and then decreased. At about 13:00, solar radiation had a maximum value of 972.9 W/m2; at 09:00, there was a minimum, and its value was 443.6 W/m2. The results showed that the tracking accuracy of the system was related to solar radiation, the higher solar radiation intensity was, the higher tracking accuracy would be. Its minimum tracking precision can reach 0.14° in one day. This tracking system is suitable for the situation for lower tracking accuracy and cost. It will establish the foundation for the popularization of solar tracking control system.