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Thread: Calculating the requirements for an off-grid solar power system

  1. #1
    Member
    Join Date
    Apr 2012
    Location
    Granada Spain - Off grid 1200 metres
    Posts
    60

    Default Calculating the requirements for an off-grid solar power system

    I have just spend the last 2 days trying to make a calculator for designing off grid solar systems.

    Here it is:
    http://crazycalculations.com/solar_power/

    Although I live off grid I am a total non expert on the mathematics of solar power systems. I have trusted in the fact that Sunking knows what he is talking about and I have used two of his tutorials for inspiration.

    http://www.solarpaneltalk.com/showth...ghlight=design
    http://www.solarpaneltalk.com/showth...p-Why-Tutorial

    Hopefully I have not made any mistakes.

    One area which concerns me is that SUNKING states.

    "To figure the daily load, go back to the original load number before the fudge factor—that is, 6000 watt hours."

    That means that when we calculate battery requirements we don't use the fudge factor????
    Is that correct?

    The main reason why I have spent the time making this calculator is because in another thread everyone told me that my system has massively undersized batteries. This is surprising because I am happy with my system.
    Using the calculator it is possible to explain why I am reasonably happy. It is because I have a very big difference between maxmum power partytime and times of batten down the hatches minimalism. Also I have shut down my freezer for the winter and put the food in another house.
    The default settings for the calculator are the ones from my house.

    I have thought about adding more functionality such as a
    Pay back time calculator.

    Anyway I would appreciate it if anyone has any feedback and I hope it may be useful for other people.
    If there are any concrete suggestions for improvement I would probably follow them up.

  2. #2
    Administrator
    Join Date
    Feb 2011
    Location
    Annapolis Md
    Posts
    6,216

    Default

    Quote Originally Posted by cortijo View Post
    I have just spend the last 2 days trying to make a calculator for designing off grid solar systems.

    Here it is:
    http://crazycalculations.com/solar_power/



    "To figure the daily load, go back to the original load number before the fudge factor—that is, 6000 watt hours."

    That means that when we calculate battery requirements we don't use the fudge factor????
    Is that correct?
    that is correct. The fudge factor takes into account losses for inverters charging etc not battery sizing.
    There is a calculator on there in the top thread that takes into account more than the basics you outlined.
    Rich
    WWW.solarsaves.net

    NABCEP certified Technical Sales Professional

    http://www.solarpaneltalk.com/showth...Battery-Design

    http://www.calculator.net/voltage-drop-calculator.html (Voltage drop Calculator among others)

    www.gaisma.com

  3. #3
    Solar Fanatic
    Join Date
    Feb 2010
    Posts
    13,600

    Default

    Here is the easy rundown.
    MSEE, PE

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