PVSyst vs PVSol

[Berliner]

Hello guys, I am a newbie. I am a Masters student of solar technology from Berlin. I am currently interning in Martifer solar.

Well as a part of my work here at Martifer, I am comparing the functionality of PVSyst and PVSol.

While I was designing a system, a very small one. Just as a trial run. A 2.64kW system using 12X 220W Schott Poly panels.

When I was sizing the inverter, I learnt that PVSyst recommends to undersize the inverter. Minimum 80% of the PVoutput. Whereas PVSol suggests I oversize it.

What do you guys recommend or how do you generally size the inverter?

Thanks in advance!

 

[Earthstore]

It depends on many factors, location, pitch of roof, orientation, split system or one array, there are several design tools that will all give you different answers, and different performance figures too.

Experience seems to be the best way to know what is correct, but you have to start somewhere, but I would suggest roughly that in the center of the UK that slightly undersized would be best, as long as your chosen inverter works well with the total panel voltage too, also one make of inverter may work well in one situation, but a different make could work better in another.

System design is very important to produce the maximum power from you limited roof space, I am sure there are many systems installed worldwide that could be producing more power if they had been designed better.

I hope this helps.

 

[Worcester]

Be careful, undersizing and oversizing are sometimes used the wrong way round! - make sure they are both applying it the saem way - PVSol and Sunny Design for example both use it opposite ways.

Generally Inverters will have a lower continuous output than the peak output from the panels, as shading, orientation, elevation, weather conditions ect mean that a 4kWp (kilowatt PEAK) system will not produce 4kW many times during a year. so the inverter may only need to be sized at say 3.6 kW continuous. Wether you call that undersized or oversized depends upon wether you take PV/Inverter or Inverter/PV

 

[Berliner]

@Earthstore: thanks for your insight. Yeah Im aware of the factors. In order to make the system independent of these factors, I designed my system as a simple ground mounted system with no shading and oriented south . I just wanted to check wat values the PVSYST and PVSOL throw up.
Please correct me if I am wrong, but I was under the impression that, over sizing an inverter is bad because then the Inverter is not working at the maximum efficiency and so power is lot.

 

[Berliner]

@Worcester thanks but they ratio used for sizing in both of them is PV/Inverter

 

[Worcester]

In which case for a fixed array in the UK I would always expect that ratio to be < 1 - i.e. "undersized", so that it is more offten working in its sweet spot of efficiency.

 

[Berliner]

If the PV/Inverter ratio is less than 1, implies the power of the inverter is more than the power of the PV array, in which case the inverter is "oversized" isnt it?

for eg, PV array power= 4kW. if the ratio of PV/inv is say 0.9. Then the inverter power would be 4.44kW. and so its going to miss the sweet spot, right?

 

[SibertSolar]

Yes, I'm sure Worcester meant >1

 

[Gavin A]

you don't say what inverter.

some inverters such as the SB1700 shouldn't be undersized in the same way as eg the 2000HF, as the peak efficiency is lower down the power and voltage range on them, and the 1700 figure actually already relates to the peak temporary output of the inverter, not it's maximum continuous output, whereas the 2000HF will happily run continuously at 2000W AC output all day long, and is most efficient year round with 2500Wp of panels attached.

And IMO your post illustrates nicely why it's important to really understand the how's and why's of the technology, and how to get the best out of it all yourself so you can if needed calculate the best options from the datasheets alone, rather than blindly following what the software says, as the software is only ever as good as the data inputted, and we've regularly found minor glitches with every bit of design software we've used... it's almost inevitable as the software writers struggle to keep up with the rapidly changing specs of the multitude of panels and inverters on the market.

Welcome to the world of solar geekery though.

 

[Worcester]

Sorry yes, brain overload .... The PV Peak Output > Inverter MAX Output therefore > 1 . Too many coffees today

As GavinA says you've got to be VERY careful of the names that manufacturers give to their inverters!

 

[Berliner]

Thanks Gavin! I was not aware of the SB1700's weird efficiency curve until now. I am glad I learnt something new :clap:

 

[Berliner]

I am assuming most of you use PVSol here. When you dont find the module or inverter you are going to use in your system design because it is an obsolete one or it is just not available in the database, I create a new *.mod( module) or a *.wrn (inverter) file by overwriting the values of an existing component in the database window. Isn't there an easier way to import specs for components? I know ABB for instance provides *.wrn files which can be directly loaded into the PVSol database.

 

[Worcester]

ABB of course have just bought Power-One

Yes most use PV*Sol, and a few use PVSyst.
Those that use PV*Sol swear AT it regulalry :banghead:
Those that use PVSyst, swear by it :devil2: (That's just beacuse they have to justify there reasons for being different and will resist anyone telling them anything else :jester: )

 

[Berliner]

Haha, I ve been swearing at PVSol too. I find PVSyst much better just cuz it lets you play around with so many parameter. And its the 'official' simulation tool here

 

[Ian-LS]

Well we use neither PV Syst or PV Sol......I rarely swear at google sketch up just at myself for doing something stupid with sunny design or our own shading analysis