System size scaling in LB photovoltaics?

Hello Djordje and all,

I’m playing with your Ladybug Photovoltaics Surface component. It’s very clean–nice work! It seems there might be something awry in the scaling of the output: I’m modeling a 4000sf system (~380m2) and it’s reporting a nominal system size of 0.6kW, though I would expect more like 60kW. For reference, through the pvwatts web interface, the default size (4kW) is explained as roughly a 25m2 system. I suspect this has to do with my rhino model being in units=feet, and I’ve looked into the code a bit; could there be a bug in the use of the unitAreaConversionFactor?

Here’s a screenshot of my output, if it helps to explain what I’m looking at:

Thanks for your thoughts!


Hi Nick,

From your screenshot I can see that you are having an issue with a vertical PVsurface (tilt angle equals 90 degrees). This was a bug and it has been fixed. To benefit from this fix, your Ladybug_ladybug component must be equal or newer than 11th of March 2016. (Ladybug version 0.0.62). Download the newest one from here.

As for the issue you’re having with the final output, would you be so kind to attach both your .gh and .3dm files please? Thank you.

I saw the thread on that bug. I dodged it by inclining the plane 1° off vertical). I’ve spun the plane around and gotten proportional results: output increases ~75% as the plane is tilted towards optimal. But, good point - I’ll pull down your recent updates.

Here are my geometry and script files - thanks for taking a look! the script is a bit ungainly, but I scribbled where your components are, nice and big, and there are only three simple inputs from other modules.

shading and Gen study (591 KB)
geom to share for PVWatts-ladybug.3dm (2.92 MB)

Hi Nick,

It is always beneficial to attach your .gh and .3dm files, no matter how the disposition of your components looks like.

The problem was your moduleEfficiency_ input of the “Photovoltaics module” component.
Always input the PV module efficiency in percent, not as a fraction.

Btw. I replaced your Ladybug_ladybug component with the newest one.

Check the attached file below. (1.1 MB)

Rookie mistake on my part - thanks for taking a look, and for the update!