large off grid systems

mahendra
mahendra Solar Expert Posts: 188 ✭✭✭
in Off Grid Solar & Battery Systems #1
hi,Why do off grid solar manufacturers and installers design and install off grid systems when off grid inverters are manufactured to operate only at 48v .Hoe does the maximum operating amps/watts(100 @ 4800w) for the batteries fit in there.How do those systems work in the long run.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: large off grid systems

    Off grid inverters come in three system Voltages typically: 12, 24, and 48.
    Basic comparison of them: http://forum.solar-electric.com/showthread.php?15989-Battery-System-Voltages-and-equivalent-power

    Most off-grid systems are not large because large installs are usually near a grid anyway. The whole industry started out with provided "portable power" (such as for camping) and the notion of running entire full-power households off grid did not exist then. As it is, very high Voltage DC circuits present some challenges to engineering and so most of the time you will not see anyone making/selling/using systems above 48 Volts.

    The average household has a 48kW main service these days (240 VAC * 200 Amps). Normally it is under-utilized. The biggest electric draws would be for anything using it to heat (water, stove, space). On 48 Volt inverter system that same power would require 1000 Amps continuously available. Even without matching Watt hour capacity that much battery power presents its own set of problems: space, weight, maintenance, and charging.

    Probably the largest system of any forum member here is that of Chris Olsen's, whose whole house is electric and off grid. He has not only solar panels but large wind turbines as well, and still needs generator power from time to time.

    That's why for most off-grid system the first step is to reduce the power needs as much as possible.
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  • Photowhit
    Photowhit Solar Expert Posts: 6,006 ✭✭✭✭✭
    #3
    Re: large off grid systems
    mahendra wrote: »
    ...when off grid inverters are manufactured to operate only at 48v .Hoe does the maximum operating amps/watts(100 @ 4800w) for the batteries fit in there....

    I can't recall the other company, but there are higher voltage inverters, Here's a link to ExelTech's modular system that goes up to 106 volt battery storage;

    http://exeltech.com/products/inverters/inverters-above-2k-watt-mx-xo/

    .
    mahendra wrote: »
    ...How do those systems work in the long run.

    This is too vague a question to respond to in a meaningful way.
    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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  • H2SO4_guy
    H2SO4_guy Solar Expert Posts: 213 ✭✭✭
    #4
    Re: large off grid systems

    Exeltech makes inverters that can run on 108 VDC. They are available in a mainframe where you can just add 1000 watt cards to increase the capacity as needed. Up to 20 KW can be installed AND THEN you can add 20 KW more for single phase 220 VAC, AND THEN you can add 20 KW more for three phase power. Pretty cool stuff. Currently there is a 108 VDC 600 watt inverter on evil-bay. I sure did want a setup with 108 VDC, but settled on 48 VDC and 12 VDC, but I couldn't help myself and got some 24 VDC 125 watt pure sign wave inverters by Exeltech for $35 each including shipping. Higher voltage means more KWH of battery in less strings but presents more challenges to charge them. The standard Midnite Classic will charge up to 72 VDC Battery packs, but you need the 250 volt unit to charge 108 volts I think.
    12K asst panels charging through Midnite Classic 150's, powering Exeltechs and Outback VFX-3648 inverter at 12 and 48 volts.  2080 AH @ 48 VDC of Panasonic Stationary batteries (2 strings of 1040 AH each) purchased for slightly over scrap, installed August 2013.  Outback PSX-240X for 220 volt duties.  No genny usage since 2014. 
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #5
    Re: large off grid systems

    the standard classic 150, 200, and 250 can charge batteries between 12v and 93v unless they've revised this. the classic 250mks can charge batteries between 12v and 150v. current ratings change with each one of them for 96a, 79a, 62a, and 40a max respectively.
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  • nu2solar
    nu2solar Solar Expert Posts: 28 ✭
    #6
    Re: large off grid systems
    mahendra wrote: »
    hi,Why do off grid solar manufacturers and installers design and install off grid systems when off grid inverters are manufactured to operate only at 48v .Hoe does the maximum operating amps/watts(100 @ 4800w) for the batteries fit in there.How do those systems work in the long run.

    My husband and I have been completely off grid for five years and live with modern conveniences. We have a 12 volt system and it works very well. We just finished installing new panels this month:)
    http://mikeandlisaworld.blogspot.com/2013/04/chapter-142our-new-solar-panels-being.html
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #7
    Re: large off grid systems

    lisa,
    what size pipe did mike go with and how did he arrive at that? i am thinking of using one long straight pipe with 4 pvs mounted landscape (nothing inbetween, but possibly one support dead center if need be). did mike also allow them to be adjustable or did he design for one angle only for extra strength?
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  • nu2solar
    nu2solar Solar Expert Posts: 28 ✭
    #8
    Re: large off grid systems
    niel wrote: »
    lisa,
    what size pipe did mike go with and how did he arrive at that? i am thinking of using one long straight pipe with 4 pvs mounted landscape (nothing inbetween, but possibly one support dead center if need be). did mike also allow them to be adjustable or did he design for one angle only for extra strength?

    The main pipe that goes into the ground is 3 inches and the cross pipe is 2 1/2 inches a quarter inch thick.
    We have a two position adjustment. One for spring and one for winter. Mike drilled those holes in after we got the poles mounted.
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