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Thread: can you help with a shopping list for a solar generator?

  1. #1

    Default can you help with a shopping list for a solar generator?

    hi,
    I have need of a solar generator,I am giving my self a headache with this simple project,I have studied all the wiring...easy enough,but how many watts for the solar panel,what size inverter,battery?
    I need this to charge up two laptops in the evenings( one 13 mac book air+one hp 17inch),plus 2 smart phones (galaxy s3's) and use a small hand held cd player.
    occasionally I will turn on the petrol generator usually at night and would like to boost up the battery if it needs it.
    The unit will be stationary on a varandah,I dont want to unplug anything when boosting with the AC POWER supply,just plug the solar gen into the mains (the generator powers the house,when its on) and charge without disconnecting the panels.
    I would also like some indication how much charge is in the battery.

  2. #2
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    Default

    What you are actually going to build is an off grid solar system with the capability of charging with a generator.
    So to start you need to determine two things.
    Daily use in Watt hours. (Best way is with a Kill a watt meter with each item plugged in for a few days to determine how much each uses each day.
    Second is insolation or sunhours during the worst months of the year you will be there (rainy season) Go here http://www.gaisma.com/en/dir/gm-country.html and find the city closest to where the house is.
    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

    Default

    Quote Originally Posted by Naptown View Post
    What you are actually going to build is an off grid solar system with the capability of charging with a generator.
    So to start you need to determine two things.
    Daily use in Watt hours. (Best way is with a Kill a watt meter with each item plugged in for a few days to determine how much each uses each day.
    Second is insolation or sunhours during the worst months of the year you will be there (rainy season) Go here http://www.gaisma.com/en/dir/gm-country.html and find the city closest to where the house is.
    thank you,I will get back with the info,It's BRUFUT by the way.

  4. #4
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    Quote Originally Posted by gambiasurfgirl View Post
    thank you,I will get back with the info,It's BRUFUT by the way.
    Remember this
    Insolation is 4.98 KWM2 per day in the worst month. actually very good for solar.
    So the calculation would be
    Load (undetermined at this point) x 1.5 (Assuming a MPPT charge controller If using a PWM controller figure load x 2) / 4.98 (hours of insolation)
    Battery size is Load (in Watt hours) x 5 /voltage for 2 day autonomy without having to run the generator.
    So in the example above with a load of say 1000 Watt hours a day it would take using a Mppt charge controller
    Battery size 1000x5= 5000 watt hours = @48V = 100AH @24V =200 AH @12v = 400 AH
    Solar panels would take with MPPT and I strongly suggest you go this way
    1000 x 1.5 =1500/ 4.98 = 300 watts of panels.
    We will talk battery type later on in the conversation.
    Last edited by Naptown; 01-21-2013 at 08:09 PM.
    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

  5. #5
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    Default

    Quote Originally Posted by Naptown View Post
    Load (undetermined at this point) x 1.5 (Assuming a MPPT charge controller If using a PWM controller figure load x 2) / 4.98 (hours of insolation)
    I'm trying to wrap my mind around your formula.

    You used 1000 watt hours for your example because the load was unknown.

    Is the below true?

    If I used 3320 watt hours per day x 1.5 for MMPT / 4.98 = 1000

    Would 3320 watt hours be the correct load to get the 1000 watt hours you used for the rest of your example? I'm trying to solve for x since it was unknown so I can apply the same formula to other setups but I need to make sure I understand your example by filling in the blank.

    I know my particular insolation is different as well as load, etc. but if I understand your example I can plug in my own particular variables to see if my setup is correct or needs adjusting.

    I guess I'm not sure if the 1000 watt hours came BEFORE or AFTER you multiplied by 1.5 and divided by 4.98.

    Thanks for the clarification.

  6. #6
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    Quote Originally Posted by johngalt View Post
    I'm trying to wrap my mind around your formula.
    Try reading this. It will help.
    MSEE, PE

  7. #7
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    Quote Originally Posted by Sunking View Post
    Try reading this. It will help.
    Thanks - The extra details helps it all come together.

  8. #8

    Default 2 laptops and 2 smartphones,oh and a cd player

    trying to keep up with the usage has been really hard,sometimes the batteries are low,sometimes we are using the phones heavily,its not as simple as how many hours a day the tv is on....
    can we keep the suggestion of 1000w ???
    so this means i need :
    solar panels of 300w
    charge controller 20a? (300w/24v =12.5amp)
    battery 200ah (on 24v)
    well since this is not going to be as small as i imagined,perhaps I should be looking at starting with something this size and just upgrade every so often by adding panels and batteries...is such a thing possible? and if so I would probably want the biggest charge controller and inverter i can afford at the outset.

  9. #9
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    Quote Originally Posted by gambiasurfgirl View Post
    adding panels and batteries...is such a thing possible?
    You do not add batteries, you replace them with larger ones.
    MSEE, PE

  10. #10

    Default why

    Quote Originally Posted by Sunking View Post
    You do not add batteries, you replace them with larger ones.
    why do you not buy more?
    I do not know how to calculate at all.
    so if I were to get say 2kw panels, and buy 4 of 'New 500W Car Power Inverter 12V DC to 220V AC' and put these in parallel to get 2 kw needed for the panels,
    then how much battery is needed? should it be one battery or can they be put in series or parallel?

    and what else should one buy? blocking diodes?

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