A multi-objective assessment of the effect of solar PV array orientation and tilt on energy production and system economics

Abstract

This analysis considers the effect of the placement (azimuth and tilt) of fixed solar PV systems on their total energy production, peak power production, and economic value given local solar radiation, weather, and electricity market prices and rate structures. This analysis details a model that was used to calculate the output of solar PV systems across a range of azimuths and tilts to find the energetically and economically optimal placement. The result of this method, which concludes that the optimal placement can vary with a multitude of conditions, challenges the default due-south placement that is conventional for typical installations. We found that for Austin, TX the optimal azimuth to maximize energy production is about 187–188°, or 7–8° west of south, while the optimal azimuth to maximize economic output based on the value of the solar energy produced is about 200–231° or 20–51° west of south. The differences between due south (which is the conventional orientation) and the optimal placement were on the order of 1–7%. Solar PV arrays that are not constrained on their placement, such as ground mounted arrays, could possibly increase overall production or the value of that production at no additional installation cost by a slight rotation from the traditional orientation of due south. The model is then extended to consider 1020 locations across the United States that have Typical Meteorological Year (TMY) data to provide a spatial view of optimal solar placements across the country. For the rest of the US we found that for most locations the energetically optimal solar PV azimuth is within 10° of south. Considering the temporal value of the solar energy produced from spatially-resolved market conditions derived from local time-of-use rates, the optimal placement shifts to a west-of-south azimuth in attempt to align solar energy production with higher afternoon prices and higher grid stress times. There are some locations particularly on the west coast that have west-of-south energy optimal placements, possibly due to typical morning clouds or fog. Further solar considerations, such as maximum peak alignment also have the potential to influence solar placement. These results have the potential to be significant for solar PV installations: utilities might alter rate structures to encourage solar generation that is more coincident with peak demand, utilities might also use west-of-south solar placements as a hedge against future wholesale electricity price volatility, building codes might encourage buildings to match roof azimuths with local optimal solar PV generation placements, and calculations of the true value of solar in optimal and non-optimal placements can be more accurate.