New publication from the SUNLAB: Solar Energy
Led by PhD candidate Erin Tonita, SUNLAB researchers have published a new paper in Solar Energy, describing the optimal row spacing of tracked, south-facing fixed-tilt, and east-west vertical photovoltaic (PV) systems as a function of latitude up to 75°N.
Traditional guidelines for determining the layout of PV arrays were historically developed for monofacial fixed-tilt systems at low-to-moderate latitudes. As the PV market progresses toward bifacial technologies, tracked systems, higher latitudes, and land-constrained areas, updated flexible and representational guidelines are required. Old approaches, like the winter solstice rule where row spacing is selected to eliminate direct inter-row shading on December 21 at solar noon, are insufficient to capture the nuance of deployment planning, where practical and economical constraints vary widely both geographically and temporally.
Using their 3D view-factor PV system model, DUET, SUNLAB researchers optimized row spacing for tracked, fixed-tilt, and vertical arrays with both bifacial and monofacial technologies from 17-75°N with acceptable inter-row shading losses of 5-15%. Results were generalized for an arbitrary collector area by presenting the ground coverage ratio (GCR – i.e., the ratio between PV collector length and row pitch). Formulae for calculating the appropriate GCR of a PV deployment between 17-75°N are provided in the article.
GCR varies widely between 0.15-0.68 for fixed-tilt systems compared to 0.17-0.32 for HSAT systems, both with a strong latitude-dependence. Similarly, the optimal tilt of fixed-tilt arrays varies widely from 7° above latitude-tilt to 60° below latitude-tilt, depending on the latitude and GCR. Vertical systems are less sensitive to latitude, with GCR varying from 0.10-0.16 between 17-75°N. In all cases, it was demonstrated that tracked and fixed-tilt PV arrays should have similar GCRs >55°N. Less than 55°N, tracked systems are more sensitive to row-to-row shading losses.
SUNLAB authors additionally found that it is reasonable to approximate the row spacing of bifacial arrays as equivalent to monofacial arrays, with bifacial modules of 96% bifaciality requiring GCRs lower by 0.03 on average than monofacial modules.
Overall, this research provides updated representational and flexible guidelines for PV system design that better suit the expanding PV sector.
Click here for the full article.
E. M. Tonita, A. C. J. Russell, C. E. Valdivia, and K. Hinzer, Optimal ground coverage ratios for tracked, fixed-tilt, and vertical photovoltaic systems for latitudes up to 75°N, Sol. Energy 258, 8-15 (2023). DOI: 10.1016/j.solener.2023.04.038
In the media:
New guidelines for inter-row spacing of PV power plants, pv magazine, July 6, 2023
Graphical abstract