Abstract
Every optical system for sunlight concentration requires following the sun in its movement. The sun tracking method is essentially chosen on the base of collection geometry and optical system configuration. A simple, useful, and original technique to realise sun tracking is proposed. It is based on a double guiding system using two complementary procedures. A passive tracking device performs a preliminary collector orientation. Then an active tracking system realises its fine positioning and adjustments exploiting an optical pointing sensor. The core of this active tracking device is the sun finder. Pointing sensors for fibre-coupled, CPV (Concentrating Photo voltaic), and linear collectors are presented, illustrating in detail the working principle and practical use. All sensors were optically characterised in laboratory, under controlled and reproducible conditions. Some field tests completed the experimentation evaluating the sensors performance in outdoor working conditions.
Highlights
Tracking the movement of the sun is a strategy to enhance the performance of solar photovoltaic plants
Using plane Photo voltaic (PV) panels, the required pointing precision is of the order of few angular degrees; it is sufficient to drive the motors dedicated to orient the PV panels, using a software taking into account sun’s ephemerides during the arc of the year [1,2,3,4,5,6]
To improve the pointing precision, we suggest the use of a device including two sections, with different Field Of View apertures (FOV), corresponding to different accuracies
Summary
Tracking the movement of the sun is a strategy to enhance the performance of solar photovoltaic plants. Maintaining aligned the optical system with the sun’s position requires an angular precision higher than the tenth of degree This accuracy is not realisable using a passive driving device due to problems connected to the plant orientation, difficulties in keeping a high mechanical stability, wind action, and the precision required by the type of concentrator in use. For these reasons, it is not sufficient to use only the alignment technique based on the ephemerides; so the solar plants usually employ an additional device devoted to supply to the moving system the information necessary to correct the concentrators’ orientation in order to keep them aligned in the sun’s direction. Sun finders equipped with an optical system are utilised as astronomical pointing devices [15]
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