Will my solar system give me direct electricity if I have only 6 solar panels of 250 watts

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naqibdanish
naqibdanish Registered Users Posts: 2 ✭
in Off Grid Solar & Battery Systems #1
Assume if I have a solar system with 6 panels of 250 wats each, with an MPPT hybrid charge controller. In Afghanistan, our home appliances run on 220V and not 110V. if the total voltage that is generated by the solar system is 190 V, and the total amp is 7 - panels connected in series, that will make 1330 watts (190*7) - assuming that the system generates this much watts, irrespective of weather condition. Can I use 1330 directly from the solar system, or the system will only use my battery backup. I was concerned that since the inverter does not generate enough voltages i.e. 220, so the system might discharge since my solar panel does not generate enough voltages that are 220V. Does the MPPT charge controller have the ability to compensate for the voltage shortages (220-190=30) from the amp and give me the desired energy and leave the battery backup intact?
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #2
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    I think there's a language barrier, or you are using an all-in-one inverter charge controller.

    A charge controller only outputs DC voltage to the battery bank. An inverter outputs AC voltage that it is designed for, I hope you bought a 220 volt inverter.

    An inverter should always "...generate enough voltages i.e. 220" to run your applications. Inverters are pretty much dependent on your battery bank to start inductive loads (anything with a motor).

    Battery based systems tend to use about double the perceived wattage when run off the battery bank and may use 30-50% more when run off the solar array, more or less directly. The measured wattage will be less under load and the inverter it's self will use some of the wattage converting DC to AC.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,461 admin
    edited July 2021 #3
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    Welcome to the forum Naqibadanish,

    Solar Panels are not really "solar batteries"... You don't have a 12 volt battery that will supply 0-100 Amps until the battery is discharged...

    A "12 volt" solar panel will output from something like 15 volts (full sun, hot day, under load) to 30 volts (sub freezing day, no load). "Typical 220 VAC loads" and such just do not like that wide of voltage range.

    The current output of a solar panel is equal to the amount of sun hitting that panel at any moment of the day... A 190 Watt panel rated at Vmp=30 volts will output:
    • 190W/30V= 6.3 Amps @ ~24-30 VDC under full 12pm noon sun on a cool/clear day
    The problem is that that "perfect" solar energy is not always happening... On a (relatively) clear day, you could see anything from 95 Watts to 240 Watts typical... And obviously zero Watts at sun rise and sun set.

    That is where Batteries come to play... You have a "large" solar array that can support your energy needs AND recharge the battery bank during the day, and use power from the battery bank when the sun is not available (nights, bad weather, etc.). Batteries are expensive, large, and relatively easy to ruin (over discharging, over charging, running very hot, etc.).

    And you mentioned an AC inverter... It can take your DC battery voltage (or even directly from solar panels in some models) and take the DC voltage/current and converter it to 220 VAC @ 50/60 Hz very easily...

    The issue is that the solar panels and battery bank need to be large enough (enough energy storage) to be able to keep the batteries charged and your appliances running.

    Can it be done... Yes, very easily (if not cheaply). Because solar power (especially with batteries, charge controller, AC inverter, etc.) is relatively expensive--The loads you want to run should be the most efficient loads you can purchase (i.e., LED lights vs Filament lights, laptop computer vs desktop computer, small water pump that runs for hours into a tank vs a large water pump that feeds your plumbing directly, etc.)... 

    There are a few loads that can be run directly from solar panels (no batteries). Pumping water to a storage tank can be one of those... There are pumps with internal electronics that take solar energy from the solar panels and pump a "little" water in morning and evening, and pump more water during the day... A very good use of solar and a good way to keep the costs down.

    https://forum.solar-electric.com/discussion/comment/191136#Comment_191136
    Some discussions about VFD (Variable Frequency Drives)... Basically a variable frequency inverter with (typically) three phase output. Used to soft start motors (handy for 3 phase well pumps, or pumps with well head starting capacitor) and can also turn an AC motor into a variable speed motor (very handy for pumping applications).

    WELL PUMP and Inverter QUESTION
    Wind/solar for large scale pumping etc (out of my depth!)
    could use knowledge - using Gould jet pump - transfering from 230vAC to ? DC (new link/thread 10/27/2012)
    Help required to design off grid system (information on possibilities to connect "standard VFDs direct to solar panels) (new link 1/13/2013)

    And from a new poster, link to solar VFD (looks interesting):

    VeichiElectric said:
    u really should read this article about solar pumps:
    https://www.veichi.org/solutions/water-supply/pump-vfd-or-vsd-for-constant-pressure-water-supply-system.html (updated link -BB 1/1/2019)
    In your case I wonder if a solar PV inverter would help or not.

    -Bill

    1/7/2017:
    Dave Angelini said:
    Grundfos has been doing solar water pumping for 30 years in the Americas and over the seas 
    http://us.grundfos.com/about-us/news-and-press/news/Pumped-by-the-Sun.html
    They have some really nice plant tours down in the Fresno area of California.
    The pump motor has a VFD (variable frequency drive) is really just a version of the AC inverter 220 VAC @ 50 Hz... Instead, the VFD will vary the voltage and frequency based on pump loads and amount of sun. And these types of systems can scale from relatively small (less than 1,000 Watts to over 4,000 Watts (or larger?).

    With solar/electricity/engineering, almost anything can be done. However, costs are a big issue... And you may want something that is "off the shelf" (already designed and mfg with support) instead of designing your own system from the ground up.

    Best place to start--Tell us more about your electrical needs (appliances/devices, how much energy per day, etc.) and we can help start with some paper designs and see what works best for your.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • naqibdanish
    naqibdanish Registered Users Posts: 2 ✭
    #4
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    Thank you for your comments and clarification.
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