Midnight Solar AC Coupled Sunny Island Systems Introduced

David and Laura
David and Laura Solar Expert Posts: 139 ✭
in Solar Product Reviews & Opinions #1
It looks like Midnight Solar is coming to market with an AC Coupled system based around the Sunny Island inverter:

http://www.midnitesolar.com/pdfs/mnsma_frontBack_web.pdf
http://www.midnitesolar.com/pdfs/midnite_smaAC_homePower_web.pdf

There's lots of interesting information about how they have AC Coupled quite a few different inverters (Outback, XW, Magnum, Enphase, etc) in this presentation:

http://www.midnitesolar.com/pdfs/acCoupling.pdf

This has value for people who have grid-tied systems and want to be able to use their solar generation capability even when the grid is out, however, our interest in SMA's Sunny Island is because our site is need to have a small micro-grid deployed in the next year. (Three >1000 foot separated buildings, long cable runs to where the solar will be, etc)

We've been investigating SMA's products, but it's unfortunate that the European models fit our needs far closer than the North American models (and cost less, too!). Too bad that it's not easy to import them for use in completely off-grid deployments...
House: 2x SMA SI 6048 w 24x 2V DEKA Unigy II; 2x SMA SB 3000TL-US w 24x Sharp ND-H235Q2
Cabin: 1x Magnum MS4024 w 24x 2V DEKA Unigy II; 1x Morningstar TS-MPPT-60 w 6x Sharp ND-H235Q2; 1x 200 Watt Harris microhydro
Intertie: 1x SMA WB 3800; 1x Lambda GEN-600 DC Supply; 2x PSL pQube
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Comments

  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #2
    Re: Midnight Solar AC Coupled Sunny Island Systems Introduced
    David & Laura wrote: »
    We've been investigating SMA's products, but it's unfortunate that the European models fit our needs far closer than the North American models (and cost less, too!). Too bad that it's not easy to import them for use in completely off-grid deployments...

    That is consistent with Midnight's comments about the SI and SB combination being the hardest to make NEC compliant, even using the US models. But apparently their very full custom E-panel takes care of most if not all of those problems. Even if you could easily import the European models for off-grid use, some off-gridders may still be visited by an AHJ some time. :-)
    SMA SB 3000, old BP panels.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #3
    Re: Midnight Solar AC Coupled Sunny Island Systems Introduced
    inetdog wrote: »
    That is consistent with Midnight's comments about the SI and SB combination being the hardest to make NEC compliant, even using the US models.
    What are the problems? Is it that pesky 120% rule in the protected loads panel?
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #4
    Re: Midnight Solar AC Coupled Sunny Island Systems Introduced
    ggunn wrote: »
    What are the problems? Is it that pesky 120% rule in the protected loads panel?

    I would like to know too, but from the looks of the panel picture, it is more along the lines of needing umpteen disconnects, ground fault detectors and overcurrent protectors to meet NEC.
    SMA SB 3000, old BP panels.
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  • SolaRevolution
    SolaRevolution Solar Expert Posts: 410 ✭✭
    #5
    Re: Midnight Solar AC Coupled Sunny Island Systems Introduced

    This wolud be very helpful for ease of installation. The Midnite acCoupling pdf includes a picture of one of my Sunny Island systems with a Midnite Nottagutter. The Nottagutter was very helpful but still not as convenient as their new gear looks.

    Unfortunately there is still no provision for regulated (multi-stage) battery charging for non Sunny Island systems. I'm still looking for that large diversion load.
    Midnite does have a provision for cutting off part or all of the connected GT inverters during grid failure. It seems that this could be configured to provide muliple tiers (especiallsy with micro inverters) for battery charging with a fairly small one for "finish amps".

    -Alex
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #6
    Re: Midnight Solar AC Coupled Sunny Island Systems Introduced

    Actually we do have a scheme for dropping a string or two. It is really pretty straight forward we just chose not to put it in the manual. I would point out that the 3 stage charging of a AC coupled battery during a grid down condition is really not that important as it is a rare occasion. There may be room for a large 5K or 10K AC diversion load but thats going to make lots of heat and be cumbersome. If I where truly truly focused on having true 3 stage charging while AC coupled I would do one of two things:

    1-Switch to a battery based grid tie inverter system

    2-Use a PWM diversion controller off the DC battery to limit voltage

    Ryan
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  • SolaRevolution
    SolaRevolution Solar Expert Posts: 410 ✭✭
    #7
    Re: Midnight Solar AC Coupled Sunny Island Systems Introduced
    halfcrazy wrote: »
    2-Use a PWM diversion controller off the DC battery to limit voltage

    Hi Ryan,

    Can you control 6000 watts of PV with a single diversion controller/load. (6000 x 1.25 = 7500 Watt rated)

    -Alex
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