[RE-wrenches] Two strings of Different Orientation

[Glenn Burt]

How about a nice Power-One Aurora inverter with two MPP string inputs?
http://www.power-one.com/renewable-energy/grid-tie-solar-inverters.php


-Glenn Burt

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Peter
Parrish
Sent: Thursday, May 20, 2010 11:58 AM
To: 'RE-wrenches'
Subject: [RE-wrenches] Two strings of Different Orientation

Abut once a year we encounter this problem and each time I reach out to
folks for guidance. Up until last year, I don't believe that there was a
readily accessible tool that accurately simulated the behavior of "two
strings of modules with different orientations". PVSyst is too expensive and
hard to master to solve this problem once a year. So here I go again,

I have a roof with an 18 deg pitch and nearly N-S axis (actually 355-175 deg
true). We want to put eight modules on each side of the roof. We can tilt
the modules on each side of the roof 15 or 25 degrees (or any angle in
between, if desired), producing a more southerly (but not equal) orientation
for each sub-array. The results are as follows:

Before (as is)
Sub-array1: pitch 18 deg, azimuth 85 deg
Sub-array2: pitch 18 deg, azimuth 265 deg

After/Case #1 (15 degree tilt-kit)
Sub-array1: pitch 23 deg, azimuth 126 deg (54 deg east of south)
Sub-array2: pitch 23 deg, azimuth 224 deg (44 deg west of south)

After/Case #2 (25 degree tilt-kit)
Sub-array1: pitch 30 deg, azimuth 141 deg (39 deg east of south)
Sub-array2: pitch 30 deg, azimuth 209 deg (29 deg west of south)

My question: Can either Case #1 or Case #2 be wired to a single inverter as
two parallel strings of eight modules each?

Has anyone seen a PVSyst or similar took simulate this two-string
situtation? Does anyone believe that the Fronius IG inverters have special
algorithms that accommodate this lack of idential orientation (their White
Paper notwithstanding)?

We have until Monday to figure this out. Any help would be appreciated.

- Peter

                                                    
Peter T. Parrish, Ph.D., President
California Solar Engineering, Inc.
820 Cynthia Ave., Los Angeles, CA 90065
CA Lic. 854779, NABCEP Cert. 031806-26
peter.parrish at calsolareng.com  
Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885

 


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