Optimizing 2-axis time-position tracking photovoltaic arrays under varying sky conditions
Two-axis tracking photovoltaic (PV) arrays are 25 to 40% more efficient than fixed PV arrays in collecting solar radiation. They are typically installed in locations with consistently clear skies. But in recent years there has been a rapid increase in the number of these tracking arrays installed in cloudier locations. Commercial 2-axis tracking arrays may be categorized as follows: light-sensing trackers that use irradiance sensors to track the sun, and time-position trackers that use an astronomical algorithm based on the sun’s apparent position. Both types efficiently collect solar radiation under clear, sunny skies, but their performance declines during cloudy intervals. In the case of light-sensing PV trackers, the irradiance sensors may fail to track the sun when the sky is cloudy. Although time-position 2-axis PV trackers continue to track the sun when it is obscured by clouds, more irradiance could be collected if the PV array did not track the sun. The ability to modify the standard tracking angles in response to changing cloud cover allows the PV array to capture more of the total available irradiance, thereby increasing the amount of electricity produced. In this talk, we share our research in finding the optimal tilt angle of a 2-axis time-position tracking PV array so that its efficiency is maximized under varying sky conditions.