How do I make a dual-tilt system with rows facing east and west? I understand that this system performs worse than a fixed-tilt system facing the equator, but I need to maximize DC capacity in a constrained space.
(credit: Five key considerations for east-west solar design, PV Tech (2018)
Yes you can! Here’s a workaround to model EW dual-tilt in SolarFarmer.
Just make two layout regions on top of each other! with azimuths at 90 (east) and 270 (west), they turn purple as a result see Why is this layout region red or purple?,
- then align and set the offset as you like,
- and finally string them.
Hint: You can use the string inverter feature to automatically string and place as many inverters as needed, or add central inverters individually to manually string modules for finer control. That’s what I did for this example so I could use one inverter per row, but put the west and east facing strings on different MPPT’s.
Here’s an example of a 277kWdc (210kWac) system with 840-qty. CS6U-330M modules in 42 strings of 20 modules/string connected to 7 SMA Sunny Tripower 30kW inverters each with 2 MPPT’s, so the 1st MPPT is for the east string and the 2nd is for the west.
Use 3D to simulate this dual tilt system since the inverter is strung to modules in both layout regions and to capture the terrain. As is typical for EW dual tilt systems, it doesn’t perform as well, but the space is filled up better with more DC. In this example, the site has nearly twice as much DC as a site with only south facing panels. The tilt gain becomes a loss because modules are not tilted toward the the sun half the time, but the PR is 83% and the yield is over 1600[kWh/kWp].
I think I set my tilt too high to allow wide access between the rows, so it might be fun to play around with this system by cloning it and adjusting the tilt. Or use SolarFarmer’s built-in scripting to run a loop of different parameters and aggregate the results to a CSV file. Check out scripting snippets for optimization in the documentation for more details.