Optimal Bi-Annual Tilt Angles and Optimal Tilt Transition Timing for Fixed Tilt Arrays in the United States

Abstract

As global dependency on renewable energy grows, it is imperative to utilize every Photovoltaic (PV) panel in the most efficient way possible. An important consideration for increasing PV panel energy production is to carefully select the tilt angle relative to the ground of the installed panel. Tracking arrays resolve this issue by dynamically tracking the sun throughout the course of the day, but tracking technology includes additional capital costs and is not affordable for residential systems. The goals of this study are to explore the use of a bi-annual fixed tilt array, where the tilt angle of the fixed array is changed at two times in the year to better capture the seasonal variation in solar irradiation. The goal of this study is to use optimization techniques to resolve the ideal tilt angles as well as the optimal time to change between these two angles for every state in the continental United States. Biannual arrays are then compared to fixed tilt and 1D tracking arrays while examining local weather variations and their effect on the optimal PV tilt angle and solar PV production. In general, PV panels with a fixed tilt in states at higher latitudes collect 90% of the energy that a 1D tracking array would collect, whereas bi-annual tilt angle array produce on average 97% of the energy that a 1D tracking array collects, making the bi-annual tilt method nearly as effective as 1D tracking at these latitudes. Fixed tilt arrays in the southern United States collect on average 85% of the energy that a 1D tracking array would collect, whereas bi-annual tilt arrays in the southern United States produce at maximum 90% of the energy that a 1D tracking array produces. Nearly all states optimize energy production when the tilt angle is changed during the month of March and the month of August. This paper also examines the relationship between summer and winter temperatures and cloud cover, and their effect on optimal tilt and overall PV performance.