Author Topic: Calculation on Sizing New Array for Classic 200  (Read 148 times)

dRdoS7

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Calculation on Sizing New Array for Classic 200
« on: August 22, 2018, 09:52:08 PM »
Hi,

I have had a Classic 200 since 2012, connected to 3kW (12 x 250w as 4S, 3P) North facing (we live in Oz - no, not with Dorothy) on a 25 deg pitch roof. Been working fine. Well actually the Classic went back to the USA last year (maybe it was missing it's family) for repair.

Finance Dept. has approved an new lot of panels.  :)

I am going to place them as 1kW East, 1kW West, 1kW North, and 1kW North tilted up @ 10/15 deg. (all on 25 deg pitch roofs). This is to get sun earlier in the morning/later in the afternoon, and winter. Plus, that's the only roof areas I have left.

I have a 200Ah NiFe battery bank. This consists of 40 cells switching between 35 or 40 to the inverter, depending on total bank voltage. The inverter has an alarm at 58.2V, and a max of 61V. While nominally 48V, it is actually higher, but not really 60V either (although I have the Classic set at that so the Battery Volt gauge on the LA doesn't go off scale). Classic is connected to the 40 cells, and Bulk is set at 67V. That will be lower with the new inverter as it can run (Bulk) at 64V. and I will use only 38 cells (probably those 2 will be paralleled to 2 of the 38 - hate to lose any capacity).

I am buying a new inverter, which has an MPPT controller, and I will transfer the "old" 3kW array to it (set as 6S, 2P).

My plan is/was to buy 16 x 250w panels, but if I can, 16 x 285w (or even 300w).

I've used the Classic Sizing Tool, for the 250w case, but it doesn't have a half-way between 48V & 60V. At 48V the array shows as 1.1 required & "Excessive", at 60V it shows as 0.8 required & "OK". Really the total array wouldn't be as high as 4000w due to them all pointing in different directions, and/or angles.

I'd like to calculate (using an excel spreadsheet) the actual (possible maximum) that the arrays can output to the Classic using the direction & tilt of each. That way I can compare the 3 sizes and make sure I can't hurt the Classic.

I can create a spreadsheet, but I don't have any idea how to calculate the output of an array depending on the direction and tilt. (IE. actual output = panel watts x sun angle x location x tilt x direction)

Any help would be much appreciated.

Thanks,

dRdoS7

mike90045

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Re: Calculation on Sizing New Array for Classic 200
« Reply #1 on: August 22, 2018, 10:19:18 PM »
I'd say that the panels, split evenly on 3 planes, would not overpower the controller at any given time.  Even at array noon, since they are all off axis, you won't get full power.   I'm guessing at any given time, you will see <65% of total array nameplate.

But then again, I'm not the mfg, so their word overrides mine
http://tinyurl.com/LMR-Solar

Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV

dRdoS7

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Re: Calculation on Sizing New Array for Classic 200
« Reply #2 on: August 22, 2018, 11:30:54 PM »
Hi,

I'd say that the panels, split evenly on 3 planes, would not overpower the controller at any given time.  Even at array noon, since they are all off axis, you won't get full power.   I'm guessing at any given time, you will see <65% of total array nameplate.

But then again, I'm not the mfg, so their word overrides mine

Yes, I'm guessing too, that's why I want to calc. it up to the largest possible panels. I know the limits, more or less.

dRdoS7

ClassicCrazy

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Re: Calculation on Sizing New Array for Classic 200
« Reply #3 on: August 22, 2018, 11:36:30 PM »
When I was at the energy fair there was someone who had some software that would do all those calculations . It cost some money but there was a two week free trial I believe which would be enough time to do the design.
But I don't remember the name of the software company - maybe you can search it out .
Here are some free design softwares - maybe one can help you out .
https://photovoltaic-software.com/free.php
Larry
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

dRdoS7

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Re: Calculation on Sizing New Array for Classic 200
« Reply #4 on: August 23, 2018, 03:08:28 AM »
Hi,

When I was at the energy fair there was someone who had some software that would do all those calculations . It cost some money but there was a two week free trial I believe which would be enough time to do the design.
But I don't remember the name of the software company - maybe you can search it out .
Here are some free design softwares - maybe one can help you out .
https://photovoltaic-software.com/free.php
Larry

Thanks for that, I found a link to PVSyst there which has a 1 month eval period (should be enough, even for me :) ). I'm downloading it ATM.

The other thought I had, which was prompted by mike90045, is just reduce the Vmp in the Classic Sizing Tool to 75% (incase 65% is too low).

EDIT: That didn't help, so instead, I reduced the number of Parallel Strings to 75%, ie from 4 to 3. That works, but is it valid? I'll see if PVSyst gives the same outcome.

dRdoS7
« Last Edit: August 23, 2018, 03:18:35 AM by dRdoS7 »

mike90045

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Re: Calculation on Sizing New Array for Classic 200
« Reply #5 on: August 23, 2018, 11:09:02 AM »
With  3 differently aimed arrays (virtual tracking), you can never max out all 3 at once
3Kw @ 48V is only 62A, I figure you will be 20% below that much of the time
http://tinyurl.com/LMR-Solar

Classic 200| 2Kw PV, 160Voc | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph )| Listeroid 6/1, st5 gen head | XW6048 inverter/chgr | midnight ePanel & 4 SPDs | 48V, 800A NiFe battery bank | MS-TS-MPPT60 w/3Kw PV

Vic

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Re: Calculation on Sizing New Array for Classic 200
« Reply #6 on: August 23, 2018, 12:55:56 PM »
dRd...,

Have you tried running each array,  individually,  on the NREL's PV Watts (?):

https://pvwatts.nrel.gov/

A street is asked for to get started with PV Watts,   but,   a near-city seems to work ...

FWIW,   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

Vic

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Re: Calculation on Sizing New Array for Classic 200
« Reply #7 on: August 23, 2018, 04:29:20 PM »
In checking further,    looks like PV Watts "worldwide" coverage misses Oz  by a great distance   ...    sorry for the error.

Good luck,   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

dRdoS7

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Re: Calculation on Sizing New Array for Classic 200
« Reply #8 on: August 23, 2018, 11:05:37 PM »
dRd...,

Have you tried running each array,  individually,  on the NREL's PV Watts (?):

https://pvwatts.nrel.gov/

A street is asked for to get started with PV Watts,   but,   a near-city seems to work ...

FWIW,   Vic

Yes PVWatts works OK, but it doesn't answer my question.

I'll see if PVSyst gives the same outcome.

PVSyst is way too complicated (it wants to design a complete system), but it does have a tool to allow creation of 2 different arrays at a time, and shows the max at solar noon (2.145kW from East & West arrays @ 1.2kW each). Actually seems more than I would have thought. Slightly more from the 2 North facing (2.282kW). So that's 4.427kW from 4 x 1.2kW. It's not exactly the answer, as I want to do something like the Classic Tool, but with data for separate arrays (and not only 48 or 60V battery).

I think I'll stop worrying about this, put it up, if it's too much for the Classic in summer, I'll isolated one array (or put it to the Hot water service, or run the ACs more). What could possibly go wrong!

Thanks,

dRdoS7
« Last Edit: August 23, 2018, 11:27:55 PM by dRdoS7 »

ClassicCrazy

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Re: Calculation on Sizing New Array for Classic 200
« Reply #9 on: August 24, 2018, 12:13:11 AM »
I believe the Classic will limit the current to it's maximum allowable amount even if it has more input than rated. It is over voltage that is what would kill it.  Someone can correct me if I am wrong about that.

Larry
« Last Edit: August 24, 2018, 12:14:56 AM by ClassicCrazy »
system one
Classic 150 , 5s4p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system two
Classic 150 ,5s 135 watt Kyocero , 16s Calb 100AH LiFePO4 , Outback VFX 3648 inverter
system three
Midnite KID MPPT 24 DC in to  12 volt AGM batterie

dRdoS7

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Re: Calculation on Sizing New Array for Classic 200
« Reply #10 on: August 24, 2018, 12:46:32 AM »
Hi,

Here's the results from Classic Sizing Tool (1 @ 48v & 1 @ 60V).

dRdoS7
« Last Edit: August 24, 2018, 12:50:09 AM by dRdoS7 »

KyleM

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Re: Calculation on Sizing New Array for Classic 200
« Reply #11 on: August 24, 2018, 02:43:29 PM »
I believe the Classic will limit the current to it's maximum allowable amount even if it has more input than rated. It is over voltage that is what would kill it.  Someone can correct me if I am wrong about that.

Larry

Larry as usually you are 100% correct.  The Classic will limit the outgoing current no matter how much you put to it.

Now I am comfortable pushing the current limit 10% over max in any set up. I will even go as high as 15% over on applications that are mobile. Boats RVs etc.
 
The physics of solar dictate you will almost never see that perfect day where the Sun hits everything perfectly and you make the power that the system is rated for. Even IF you manage to come close it will only be for a few minutes a day since the Earth will rotate away from the Sun. 

dRdoS7  As long as your voltage is not going to wander over the limit of the Classic you should be fine at 1.2 even 1.3 on the chart.

DISCLAIMER- running over current on your Classic will make it work harder and create more heat. It can also cut into the life of the Classic.  Depending on the levels it can also void your warranty.
Be careful out there.

-Kyle