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PV Array Sizing Tool


Chris Hobson
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I have been designing systems and discovered that clients can change the goalposts sometimes more than once a day. I was using the Midnight solar sizing tool and ended up tired of re-entering panel specs. So I designed my own.

The yellow fields are for the user to alter. There is a drop down list of inverters and if your inverter is not on the list you can go to the inverter sheet and add your own specs. The same with panels there is a open column to add your specific panels. Canadian solar 260W and probably 265W are set to disappear from our shores so I will remove them from the list and add others.

Having set you inverter  then you can set minimum and maximum temperature. Remember these are panel temperatures and although panel minimum and ambient minimum will be the same panel maximum is likely to be 20-30°C higher than ambient temp. Minimum temperatures are important as panels voltages INCREASE with lower temperatures. I know several folk who exceed their SCC's Vmaxbut if you want to do it by the book this spreadsheet will help you. When your panels Vmp is below the MPPT minimum you are warned with pink text as this may or may not be a problem.

You can then play around with number of panels per string and number of strings to find a combination that works for your inverter. 

PV String Tool.xlsx

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2 hours ago, Chris Hobson said:

I have it on good authority that is is not particularly user-friendly. I'll try fix it in version 2.

Maybe because before one figures out where to go to enter custom values they are subjected to other module figures I guess for information. But for now it does the job. I eargerly await the update - lol

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On 2017/09/15 at 1:25 PM, Chris Hobson said:

I have been designing systems and discovered that clients can change the goalposts sometimes more than once a day. I was using the Midnight solar sizing tool and ended up tired of re-entering panel specs. So I designed my own.

The yellow fields are for the user to alter. There is a drop down list of inverters and if your inverter is not on the list you can go to the inverter sheet and add your own specs. The same with panels there is a open column to add your specific panels. Canadian solar 260W and probably 265W are set to disappear from our shores so I will remove them from the list and add others.

Having set you inverter  then you can set minimum and maximum temperature. Remember these are panel temperatures and although panel minimum and ambient minimum will be the same panel maximum is likely to be 20-30°C higher than ambient temp. Minimum temperatures are important as panels voltages INCREASE with lower temperatures. I know several folk who exceed their SCC's Vmaxbut if you want to do it by the book this spreadsheet will help you. When your panels Vmp is below the MPPT minimum you are warned with pink text as this may or may not be a problem.

You can then play around with number of panels per string and number of strings to find a combination that works for your inverter. 

PV String Tool.xlsx 17.46 kB · 137 downloads

I downloaded your tool yesterday. Thanks for the nice tool.  I just have a question regarding the entry MPPT I max.  I notice that you have N/A for the Axpert inverters? What is the reason for that?

I have a Mecer SOL-I-AX_5NB inverter  -  (Axpert MKS II 5K  with PVmax 450Vdc).  I notice on the sticker on the side that it states under the heading Solar charger Mode that the Maximim input current   = 18A.   Do I have to put it into the spreadsheet or is the current limited by the inverter to 18Amps  hence the N/A?

18Amps seem ridiculously low as 2 strings  will exceed that. Does that mean I can only connect a single string to the inverter? I was hoping to use  2 strings of 5 (or 6) x 405W. My roof area is limited so I have to go for the higher wattage panels.  Any suggestions will be appreciated.

Axpert Label.jpg

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