Abstract:
Solar energy is one of the major sources of renewable energy. The challenge is to increase the solar energy conversion by improvements in orientation of the solar collector. Current available solutions such as time and date approach, passive materials, auxiliary bifacial solar cells and electrical optical sensors are designed to simply face the highest level of radiation; which in turn may lose track of the sun and follow clouds during cloudy condition. A novel low cost sensor consisting of photodiodes, aluminum housing, electronic amplifiers, low pass filters and a microcontroller was developed to determine the angle of illumination and present innovative control strategies for solar trackers such as stalling during low light conditions, step track during moderate cloudy conditions and continuous tracking during sunny conditions The sensor was successfully constructed and calibrated under controlled laboratory conditions by incorporating a jig consisting of a physics light box, collimated lens and a laser pointer. It was found that the sensor had a wide sensing range of up to ±1.0 radians (±57.3 degrees) and could achieve a respectable angle sensing range of up to ±0.33 radians (±18.9 degrees). When compared with a mathematical model of the position of the sun, the best accuracy of the sensor was found to be ±0.0081 radians (±0.47 degrees). A reduction in the sensors accuracy was detected when it was used outside due to environmental noise such as diffuse irradiation and reflections. The sensor did not meet its accuracy criteria of 0.1 degrees and it cannot be used in concentrated solar tracking applications. The sensor however was used in a low power solar tracker (10W) and produced 8% more energy than the yearly optimal fixed solar panels. It could also successfully detect poor environmental conditions (cloud cover) and has the potential of utilising advanced control strategies mentioned above.