Virtual Tracker panel arrangement

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Re: Virtual Tracker panel arrangement

Postby thechad » Mon Jul 07, 2014 2:00 pm

:) absolutely plan to, they (or thier subie) did a fantastic job on the original install.

Yeah, I'll def. give them a call...infact if someone from EM knowledgable in this and my specific install (can provide details) wants to call me feel free to send me a PM.
else feel free to skip over the part where i ask about other installers who know about adding panels inexcess of the inverter capacity if it is in any way inapropriate.

I guess i assumed it was outside the norm and so not something they would do...
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Re: Virtual Tracker panel arrangement

Postby thechad » Fri Jul 11, 2014 1:22 pm

Bugger :(

Got the call and this is not going to work for me.

The Aurora only takes one string of panels and regulations (it seems) prevents me "overprovisioning" panels onto the system (by more and 600W or so). Stupid regulations!

Micro-Inverters (or a new system) appear to be the only solution....sigh :(
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Re: Virtual Tracker panel arrangement

Postby Gordon-Loomberah » Fri Jul 11, 2014 1:33 pm

Yea, I think there is a rule somewhere about a limit to overdriving inverters, but it is no doubt based on having them all facing to the North, and I doubt they have considered the Virtual Tracker idea that doesn't overload the inverter. If your inverter is not too far from the limit already, under those regulations, you probably can't add another string :(
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Re: Virtual Tracker panel arrangement

Postby thechad » Fri Jul 11, 2014 1:37 pm

Exactly.

Silly rule designed to protect silly people.

Oh well, time to move on to another project. Should have thought about this better when I got the system and put a 3kW inverter in and split the panels...even though it would never generate over 2kW...sigh
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Re: Virtual Tracker panel arrangement

Postby Tracker » Fri Jul 11, 2014 6:39 pm

..
Gordon - Just revisiting this update and I wondered if there was a possible better arrangement..
You suggested that pure East and West facing be used..

Do you have an idea of the benefit to pointing the arrays at say North +/- 60deg (as compared to 90deg)
My gut feeling would suggest only a very-small early/late difference, but a generally better daily total..
..
.
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Re: Virtual Tracker panel arrangement

Postby Tracker » Fri Jul 11, 2014 6:46 pm

thechad wrote:Got the call and this is not going to work for me......The Aurora only takes one string of panels and regulations (it seems) prevents me "overprovisioning" panels onto the system (by more and 600W or so). Stupid regulations!...

Who is it that is saying this..

ie.. is it not a case of just doing it.. What or who will complain.. other than the installer, who might advise that it would breach the inverter's guarantee.. Just curious..
..
.
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Re: Virtual Tracker panel arrangement

Postby thechad » Fri Jul 11, 2014 6:51 pm

EM... who installed the original system :)

All for hacking stuff andbending the rules...but this wouldbe a bit brave for me.

I wonder if there is a clear legal issue (warranty or other) or if these rules are more of a "guidance"

Sdit: I wonder if I could "push the envelope" and move one panel from north to west and add 3 more west ?

thoughts
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Re: Virtual Tracker panel arrangement

Postby Gordon-Loomberah » Fri Jul 11, 2014 7:47 pm

Tracker wrote:..
Gordon - Just revisiting this update and I wondered if there was a possible better arrangement..
You suggested that pure East and West facing be used..


That's probably best for summer around latitudes around 30ishS, but

In July 2013 I wrote: So, on the March equinox, point them at the sun at 8:30am, and 8:15am on the Sept equinox.
In the afternoons on the equinoxes,15:25 in Sept and 15:40 in March. A few days either side wont make much difference, but the time should be within +/- 5 mins... but it is easy to buy a cheap clinometer to measure tilt, or use a spirit level and a suitable 30-60-90deg triangle. I'm sure you can work it out ;)


If you face them NE and NW, and don't tilt them up enough, there will be a significant solar noon peak, so you wouldn't be able to run twice the rated capacity of panels into an inverter input (you still need 120degrees between them if you want to run 2X the inverter's input rating of panels). It would generally be better for winter, but worse for summer.
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Virtual tracker

Postby Benny » Mon Aug 11, 2014 8:29 pm

Gordon, what's the basic method to add another set of panels on different orientation to get virtual tracking. Is it just necessary to get the second set to have the same OC/MPPT voltage as the first set ? And when I say "same" how close should it be ? I'm thinking here of an inverter with only single MPPT input so the 2 arrays will really be in parallel.

I have a large thin film system, 3 strings each 500W in parallel, facing NE. Very happy with performance but thinking of adding another array on NW. Much smaller roof there so it needs to be high output/efficiency panels.
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Re: Virtual tracker

Postby Gordon-Loomberah » Mon Aug 11, 2014 9:44 pm

You need to have the Vmp of any parallel strings as close as possible to the existing 3 strings, preferably within a percent or two. If you are using a different type of panel, then you should probably make some allowance for the typical operating temperatures and the temperature coefficients, which gets a bit complicated- best to stick with the same type of panel.
If the arrays are not facing ~120degrees or more apart, then you need to be careful not to exceed the inverter's maximum input current when calculating the max size string(s) you can add.
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