Any computer programs for these calculations?

alyaz
alyaz Solar Expert Posts: 114 ✭✭✭
in Solar Beginners Corner #1
Has anyone stumbled across a program for inputting battery bank capacity, panel specs, geographical location, length of runs, etc... that does the math?

I found one for 'Unirac' systems, but can't find anything for calculating / inputting different hardware to find out the best size controller, best way to wire panels, etc...

I appreciate this is probably a pretty simple exercise once you understand all the variables, but in the mean time, a program or app would be nice to have...

:blush:
3.3 kW solar.  3 Midnite Solar controllers; 5 lightening suppressors.  Magnum’s inverter; auto gen start, BMK.  Davidson 2 v FLA’s - 24v bank.  Perkins diesel gen.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Any computer programs for these calculations?

    No, it is not simple. Not even when you understand what you're doing and have done it dozens of times. There's so much to it that mistakes are easily made. To put it all into one program would be daunting, and possibly make it more confusing. I find it easier to break it down into subsections of the whole system. That allows you to make the necessary adjustments for "ideal" sizing vs. commercially available equipment as you go.

    For instance the battery bank specifications This is the first thing you need to determine, and it has to be based on anticipated load requirements. That will inevitably work out to some size other than what's available, so you round up. In other words your needs may be for 297 Amp hours. There are no batteries that size. You go up to the next available configuration (probably 320 L16's).

    Then you can figure out how much panel you need and what charge controller to go with it. Again you calculate for the battery bank charge requirements and round up to the nearest available size. You have some tolerance here, as you can run 5% to 13% of the battery capacity in terms of peak charge current. If you've considered your depth of discharge properly in the first step then the replacement of Amp hours should take care of itself at this stage.

    And always there is wire sizing. This includes the need to run Voltage drop calculations (using tools such as are available on line - look under the FAQ section here) and check for current-handling ability (particularly on high current DC lines).

    You can run PV Watts http://www.nrel.gov/rredc/pvwatts/ to get some idea of the power potential in your area using different configurations and angles.

    Different companies have their own string sizing tools for matching panel configurations to charge controllers/GT inverters.

    There's always more than one solution to the same situation. Determining which one is right for you can involve a number of intangible factors which can't be included on a spreadsheet. If one were to try and lock it in to a program inevitably some factor or option would be left out and that might be just the thing for someone, somewhere. Solar is very site-specific.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #3
    Re: Any computer programs for these calculations?

    there's also voltage drop calculations to do too. if you delve into the one in my signature line that can be lengthy to read and understand how it works, but it is fairly accurate and takes many real world things into consideration. i gave the formulas and data while another put this into a spreadsheet as i am not that acquainted with pcs to do that. if i was i'd have laid it out better.

    if memory serves me, the old user bad apple had an all encompassing program that i did not dive into to try and it may still be on the forum somewhere. i believe it was multi-windowed and complex. i'm not sure just how much was covered by the program or how accurate it was. i believe he gave a link to it and i have no idea what would happen today if one tried to download it.

    if all of this were simple i can say that there would be a much smaller forum here as there would be less to discuss.
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