Fronius String Efficency Calculator

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Fronius String Efficency Calculator

Postby Card Shark » Tue Nov 06, 2018 1:51 pm

Could somebody please point me to a resource that compares string configuration efficiency? Had a Symo 5.0.3 installed with 17 X Sunpower SPR P19 320 in a 9/8 string configuration that appears to be performing under spec. Have visited https://fronius.solarconfigurator.de/so ... ator/quick which lists acceptable configurations but not the optimum. Also https://www3.fronius.com/froniusdownload/tool.html however it does not list my inverter as an option.
Last edited by Card Shark on Tue Nov 06, 2018 2:21 pm, edited 1 time in total.
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Re: Fronius String Efficency Calculator

Postby Gordon-Loomberah » Tue Nov 06, 2018 2:12 pm

What is Voc for those panels?

There appears to be a wide range of configurations for optimal efficiency, but I'm a bit concerned about Voc for that string of 9 exceeding 600V.

Other than the Voc issue, I doubt your underperforming is due to the panel config. Any shading issues?
You will see reduced output in hot weather (got to 39C here today), could that be an issue there?
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Re: Fronius String Efficency Calculator

Postby Card Shark » Tue Nov 06, 2018 2:21 pm

No shading issues Gordon. They are SPR P19 - 320 with a Voc of 42.6.
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Re: Fronius String Efficency Calculator

Postby Gordon-Loomberah » Tue Nov 06, 2018 2:30 pm

OK on the string voltage then, some of those SPR panels have Voc >60V @25C.

What about temperature?

What is the underperformance issue? Low overall output or low peak relative to rating?
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Re: Fronius String Efficency Calculator

Postby Card Shark » Tue Nov 06, 2018 2:59 pm

Lower peak relative to rating. 5.44 System facing almost true north. Flat mounted on a level 0 degree roof so expecting about 7% loss. Output max to date 4.7 kw. Panel temp coef - 0.29% C
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Re: Fronius String Efficency Calculator

Postby Gordon-Loomberah » Tue Nov 06, 2018 3:35 pm

4.7/5.44 = 86%. I don't know your latitude, but most would be quite happy with that max output with flat panels at this time of year. It should increase as the sun gets higher, but heat will cut it back, however, I'm sure you will see 5kW before too long.

hmm, flat mounted on a flat roof- could be facing north, south, east or west ... but mostly straight up ;)
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Re: Fronius String Efficency Calculator

Postby Card Shark » Tue Nov 06, 2018 6:21 pm

Fair call Gordon, thank you! Lat 28. Last install near by was with a tilt kit. Learnt quickly in an older house NOT a fun thing to sit through on a beach location every strong southerly.

Origin installer got the string setup completely wrong last system. Thought here we go again.
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