jackattack

Marco, I have to disagree - it is not impossible - several studies have shown a statistical method to account for all of the factors that you mention, notably the BEW/DNV study, and NREL studies. It is not perfect, but neither is the TMY. It's a best guess. And, System Advisor Model already provides snow loss calculations using the TMY2 dataset which includes snow depths. I agree that is the responsibility of the user to provide the data to run the snow losses, but I would simply ask PVsyst to embed one of the statistical models within their program to make things simpler and easier. The same is true for soiling losses. Obviously snow depths can vary considerably from year to year - from my hometown in Minneapolis, Minnesota, we see snowfall vary as much as +/-30% year to year. But, being able to include a typical estimate is still better than nothing!

Thank you Andre for your response. I agree it is a very complicated formula and may vary in accuracy. I think partial coverage is the biggest issue as well. The paper by BEW and DNV a few years ago provided what I think is the best existing formula, at least as far as I have seen. I believe NREL has issued some papers as well. I wuld be happy to send you those papers if you're not familiar with them. It would require specific inputs from the user but could be feasible.

I agree that that is the correct place to add in snow losses, however I think PVsyst is in a position to help calculate these losses using established formulas added into the software.

I would be very interested to finally see snow losses calculated in PVsyst, either through the link with Meteonorm (the TMY2 dataset contains snow depth info I believe) or allowing import of snow data by users, and having the software calculate losses. This functionality exists in System Advisor Model but it would be good to see it here to make sure PVsyst remains the premier modeling software. BEW and others have provided formulas for calculating losses that could be included in PVsyst. As we work more in northern climates, this becomes a liability for us. I would be open to hearing how you or other members calculate for snow losses currently. Thanks!

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.

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.

The forum itself has a bug in the search function that needs resolution as it seems impossible to search for anything. No matter what terms I search for, it tells me the following: