Multiple Orientations - Low Production?

[defreight]

Hey guys,

I have recently modeled my companie's projects in PVsyst to get a more accurate production estimate for O&M. The .7 derate used in PVWatts by previous employees looks good when comparing production, but is not good when trying to diagnose if a system is actually producing like it should.

Nevertheless, all went well until I modeled a project we just actually got PTO and onto the grid. It is a commercial standing seam roof. Here are some key details.

Pitch : 5deg

Azimuth: 167 & 357 deg (or as PVsyst likes, -13 and 167 deg)

South facing roof:

76 strings of 11 Canadian Solar CS6X-310P

North facing roof:

93 strings of 11 Canadian Solar CS6X-310P

DC System Size = 576.29 kW

Inverter: Solectria Renewables SGI 500kW 480 VAC

Problem:

All my other simulations took only a few seconds to complete, but this simulation takes about 7-10 minutes to run. Upon completion, the report shows a tremendous amount of losses. Some of the notable ones are:

Ohmic Wire Losses: 29.5 %

Mixed Orientation Mismatch: 5.5%

Inverter Loss during operation (efficiency): 14.5%

The mixed orientation mismatch seems like a reasonable number but the other two? I defined a 1.5% and 1% loss in power due to wire losses in the detailed losses section and I had that set for every project I modeled over the past week.

I seemed to have stumped the other engineer on staff with this as well so any advice is appreciated. I have uploaded the files as well, but I am not sure which ones you need.

-Alex

P.S. I had included the meteo file in the zip but it was just over the maximum size. This project was modeled using the Boston meteo file.

FTE 330.zip

[André Mermoud]

We discovered indeed an error in the simulation of systems with Mixed Orientations in the versions 6.33 and 6.34.

This will be corrected in the next version 6.35, to be released very soon.