Large off grid solar system advice

rama
rama Solar Expert Posts: 36 ✭
in Off Grid Solar & Battery Systems #1
Hi all,
Does anyone have any experience with large off-grid PV systems of 10K and above, and using only one central inverter? The question I have is I've looked into a few models but it seems they all require very high input voltage (from battery), like 110VDC minimum. While this is already beyond the normal large off grid systems at 48V, I guess batteries can be connected to such high voltage. But is there a charge controller capable of handling charging 110VDC+ battery bank?

Or is this whole central inverter thing basically not a good idea and I should go with several smaller inverters?

Thanks in advance for any input
Erik
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Comments

  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #2
    Re: Large off grid solar system advice

    I would go with smaller inverters purely for redundancy and failover reasons. Xantrex, SMA Sunny Island, Victron and Studer will all let you build 10kW systems with just 2 large inverters and keep the battery bank at 48V.
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  • blackswan555
    blackswan555 Solar Expert Posts: 246 ✭✭
    #3
    Re: Large off grid solar system advice

    Do you have a link to what you are looking at ? But off grid, This side of the pond ( Europe) is normally 48v max, Grid tie (battery-less) is higher 100v +

    I look after outback systems (3kw per inverter) from 3 > 27 KW (1 >9) inverters if that`s any use to you ?

    Have a good one
    Tim
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  • rama
    rama Solar Expert Posts: 36 ✭
    #4
    Re: Large off grid solar system advice

    Sorry I don't have the photo... it's just a brochure of this 10~400KVA online double conversion phase ups/inverter/frequency converter. I double checked with a few more SI people and no one recommends the use of these giant central inverters. Even if I want to force-link all components to the right voltage, I doubt I'll be able to find a charge controller large enough to charge 190V+ battery bank, not to mention wiring costs.

    Looks like I'll stick to what you and stephendv suggested, much more manageable I think. Thanks for the input!
    blackswan555 wrote: »
    Do you have a link to what you are looking at ? But off grid, This side of the pond ( Europe) is normally 48v max, Grid tie (battery-less) is higher 100v +

    I look after outback systems (3kw per inverter) from 3 > 27 KW (1 >9) inverters if that`s any use to you ?

    Have a good one
    Tim
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  • blackswan555
    blackswan555 Solar Expert Posts: 246 ✭✭
    #5
    Re: Large off grid solar system advice

    http://outbackpower.com/forum/viewtopic.php?f=17&t=3539 is a 12kw system /230v European, You can use the relevant inverter for your country,
    Depending on loads you could install 3 instead of 4 inverters, They would surge to 10 ish KW for a reasonable time, (30 mins) and 14.5 kw ish for a short time, (5 sec) 17kw peak (motor start etc) and if that was not enough, you could always add a 4th (up to 10 total)

    Have a good one
    Tim

    ps I don`t work for Outback, just use their equipment :D
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  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
    #6
    Re: Large off grid solar system advice

    From my point of view Outback's inverters aren't suitable for large installations because their biggest one is only 3kW, so you'd need 3 or 4 as you point out to meet the 10kW requirement - which can add to the cost considerably. They also don't support generator boost or generator support like most other inverters in that class do (which could be a very useful feature for large installations).

    SMA do a 5kW inverter - and it's really the only one worthwhile considering in the sunny island range
    Xantrex do a 6kW version
    Victron do 5 and 8kW versions
    Studer-inno do a 5,6 and 8kW version but they don't seem to have a US presence, mostly EU

    All 48V, all offer generator boost.
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #7
    Re: Large off grid solar system advice

    I would also consider multiple inverters. Beside already mentioned items you can do better load and standby management with multiple inverters.

    For heavy 240 vac loads you can do load managment with an automatic priority control.
    These 240 vac heavy load inverters can be set to standby when loads are inactive. You can also avoid surge voltage droops on regular 120 vac loads that are on other inverters.

    You will also end up with lower low load and standby power drain then with a single high power inverter that has a higher no load power consumption.

    Make sure you can cover any large startup surge requirements, like air conditioner compressor.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
    Re: Large off grid solar system advice

    I agree with the multiple inverter idea. Tailor the inverters to the expected loads, and wire accordingly. You will have some build in redundancy, as well as lower over all efficiency loses.

    T
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