Single-axis tracker and north-south tilt

[jackattack]

Hello,

When modeling trackers I often want to be able to adjust the slope of the tracker to reflect a north or south-facing slope by adjusting the Axis Tilt in the Near Shadings module. However I have noticed when creating models and then running simulations, that the software does not distinguish between a "flat" array (zero degree axis tilt) and a +1 or -1 degree axis tilt - meaning the production is the same for all three of these scenarios, although in the real world we know production would be different, even by a little bit. Production only changes when you hit +/-2 degrees axis tilt.

We have been asked by many clients to model systems with less than 2 degrees tilt, because they want to see how those slopes will affect production. It would be good to be able to do this in Near Shadings with precision. You can do this in the Orientation module (if you are not using Near Shadings), however it is my understanding that using Near Shadings is always going to be more accurate than just Orientation.

Please let me know if this is something you can change or if I'm missing a hidden parameter that could change this. Also, in the US we tend to use percentages to measure slopes rather than degrees - if it's possible to make that unit change in future versions, that would be great! Currently the civil engineer gives me a slope in percentage and I have to convert it to degrees for PVsyst.

Thanks.

[André Mermoud]

I don't understand your affirmation.

It is quite possible to define a tracking system with axis tilt = -1° or +1°, event in the 3D tool. There is no restriction here.

I know that architects are often using percentages for the tilt. They also use to take the North as azimuth reference.

However in most solar applications this is expressed in terms of degrees. It would be very confusing to work in two different units for a such fundamental parameter in PVsyst.

[jackattack]

Mr. Mermoud,

Thanks for your reply. You are right that you can model it in the 3D tool, but in the report there is no difference in production between 0-degrees, -1-degrees, and +1 degrees, when we would expect even some small difference. Additionally, the "Axis Tilt" on the first page shows 0-degrees, not 1-degree. I have attached a couple images of reports, the +1-degree images indicate that although I used a +1-degree tilt in the model, it was still simulated as a 0-degree tilt. The +2-degree simulation shows that the simulation was done with the correct tilt, with a corresponding change in production.

[Bruno Wittmer]

You have to make sure, that the axis tilt is the same in the 'Orientation' Dialog as for the trackers in the 3D scene definition.

PVsyst will crosscheck those two values and give an error message, if they do not match, but only differences larger than 1° are considered errors.

The report will show you the value defined in the 'Orientation' Dialog, and this is also the value used in the simulation.

So you should change the axis Tilt to 1° also in the 'Orientation', to get the expected result.