10.78kW Enphase system and XW6048

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  • jaggedbenjaggedben Solar Expert Posts: 230 ✭✭
    Re: 10.78kW Enphase system and XW6048
    stephendv wrote: »
    Isn't it possible to reconfigure the frequency on the enphase units?


    I think that is possible, but I believe you need Enphase to do it for you, and since this would not be a configuration they support, good luck with that.
  • jaggedbenjaggedben Solar Expert Posts: 230 ✭✭
    Re: 10.78kW Enphase system and XW6048
    Very true. This is the standard AC-coupled micro grid behavior. I'm trying to find an inverter (Sunny Island?) that will allow linearly raising frequency with excess AC-coupled power (load is too small).

    As I said, the Sunny Island will do that, but only with SMA's own Sunny Boys.
    The idea being that even though the inverters are all set the same, tolerances will cause sequential inverters to go off-line and come back on-line.

    That just doesn't sound like a good idea to me, if you can get it work at all. Do you really want to rely on unknown tiny differences within tolerance between Enphases to prevent your Sunny Island or batteries from blowing up? This tolerance is not even on the spec sheet for the Enphases. I would scratch this idea. Either it is going to be 'all on/all off' with the Enphases or it is not going to happen.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: 10.78kW Enphase system and XW6048
    jaggedben wrote: »
    As I said, the Sunny Island will do that, but only with SMA's own Sunny Boys.



    That just doesn't sound like a good idea to me, if you can get it work at all. Do you really want to rely on unknown tiny differences within tolerance between Enphases to prevent your Sunny Island or batteries from blowing up? This tolerance is not even on the spec sheet for the Enphases. I would scratch this idea. Either it is going to be 'all on/all off' with the Enphases or it is not going to happen.
    That sounds like a bad idea to me. If the loads exceed the threshold by just a little bit, the Enphases all turn on, then they swamp the loads so they turn off. It sounds like you could get into an oscillation situation with a lot of power slamming off and on. That doesn't sound good.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    I've read, somewhere online, the Enphase tolerance was +-2.5%. When spread across 44 units the chances are very good they will not all cycle at the same time. Temperature variations will add to that as well.

    So the question:
    Can the Sunny Island(s) respond quickly enough to load changes with frequency shifting and if some of the Enphase inverters can cycle off/on quickly enough to control the power supply at a somewhat stable amount.

    When stated in those terms, the answer doesn't look positive.

    Time to look for a used SI and do some testing.
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: 10.78kW Enphase system and XW6048

    Even using a sunny island + sunny boy SMA always recommend that the combined output of the sunny boys must be less than the power of the sunny island.

    I think that the problem of too much power on the AC side will not be solved by frequency shifting. The frequency shift only starts when the battery is fairly full, so the SI has to regulate how much current goes to the battery. But if you have 10kW surplus on the AC side, and a partially charged battery, with only a 5kW SI between the two, then I think you risk overloading the charger, and watching an expensive fire and smoke display. The frequency shift wouldn't kick in, because the SI would see an uncharged battery.

    You could always give the SMA tech support team a call, they've been very helpful with my annoying questions in the past. You could try the chaps in Germany directly as they all speak english and have the most experience with the kit.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 10.78kW Enphase system and XW6048

    From post #7 of this thread:
    If you intend to use the XW as a "synch base" for the Enphase units and thus increase your over-all capacity be prepared for headaches.

    :roll:
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    As much as I don't want to admit it, it is looking as if I'll end up with something like 2 Sunny Island 5048 units. They would handle the full output of the PV array.

    I am still exploring other options. And I want to get at least a year on the array before full conversion to AC-coupled. Initially it will be GT only, still have to prove normal operation prior to making changes.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: 10.78kW Enphase system and XW6048
    stephendv wrote: »
    Even using a sunny island + sunny boy SMA always recommend that the combined output of the sunny boys must be less than the power of the sunny island.
    If memory serves, the maximum passthrough current for a Sunny Island is 56A at 120V, which is 6720 Watts. The SI is a 5000 Watt device.
  • Dr. StrangeloveDr. Strangelove Solar Expert Posts: 49
    Re: 10.78kW Enphase system and XW6048
    As much as I don't want to admit it, it is looking as if I'll end up with something like 2 Sunny Island 5048 units. They would handle the full output of the PV array.

    Yeah, me too. A Xantrax solution would have been preferable but their "one size fits all" approach isn't going to work - oh, and pick up 2000AH of batteries while you're at it.

    Good luck with the Enphase units - you might want to ask them "why" it isn't a supported topology. Most likely because they simply haven't tested it. Nobody seems too keen to document their frequency shift power control specs - it's like some kind of giant secret. If you can get Enphase to work with you, I'd recommend that you set the FSPC "gain" (slope factor) to several different levels spread out across all your micro inverters. This will have the effect of spreading the control loop feedback pole frequency, dampening it and making a more stable system.

    You might be able to make a Windy Boy work with your 360V EV battery pack too.

    Andrew
  • Dr. StrangeloveDr. Strangelove Solar Expert Posts: 49
    Re: 10.78kW Enphase system and XW6048
    ggunn wrote: »
    If memory serves, the maximum passthrough current for a Sunny Island is 56A at 120V, which is 6720 Watts. The SI is a 5000 Watt device.

    SI's are 120VAC devices in the US, so for a split phase 240VAC installation, you'd need 2, for 13kW total. It's the same 56A relay for the 5048U or the 4248U (5kW or 4.2kW).
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: 10.78kW Enphase system and XW6048
    SI's are 120VAC devices in the US, so for a split phase 240VAC installation, you'd need 2, for 13kW total. It's the same 56A relay for the 5048U or the 4248U (5kW or 4.2kW).

    Exactamundo........
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    I read about the "Distributed Intelligent Load Controllers" with great interest. Link for datasheet: http://www.windandsun.co.uk/Data%20Sheets/Sunny%20Island/Distributed%20Load%20Controllers.pdf

    Excerpt from the datasheet:
    "A DILC will disconnect its load immediately if the system frequency or voltage fall below their threshold values. When the system frequency and voltage achieve the required conditions for the load to be switched on, it begins a time-out and then switches on the load. The timeout period will be a random value within a pre-set range."

    Looks like there might be a way to make it work. Either directly or indirectly it could control the Enphase units in groups or individually depending on the need. Having trouble finding the cost.

    Anyone know of something like this available in the US?
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: 10.78kW Enphase system and XW6048

    Nice idea!

    Now if you had a linear frequency shift like with the SI, you could use a handful of those DILCs and install a group of enphases behind each one. Say 5 DILCs each with 2kW worth of enphases behind it. Then set each one to open at a slightly higher frequency than the previous one, so that power is reduced/added in 2kW steps.

    Regarding the XW vs SI costs, since this is for backup purposes in case of power failure, couldn't you just operate with half the array connected when the grid goes down? Do you absolutely need split phase?
  • stephendvstephendv Solar Expert Posts: 1,571 ✭✭
    Re: 10.78kW Enphase system and XW6048

    On that same site under their Prices -> SMA inverters section, they list the price.... 260 USD EACH!
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: 10.78kW Enphase system and XW6048

    In the US, many GT systems are 120/240 VAC split phase (really 240 VAC and a neutral voltage monitor) or 208 VAC minimum Grid Voltage...

    There are not a lot of 120 VAC GT inverters here--especially as you go up in size.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: 10.78kW Enphase system and XW6048
    BB. wrote: »
    In the US, many GT systems are 120/240 VAC split phase (really 240 VAC and a neutral voltage monitor) or 208 VAC minimum Grid Voltage...

    There are not a lot of 120 VAC GT inverters here--especially as you go up in size.

    -Bill
    I think SMA still makes the 700W 120VAC inverter. I call it the Sunny Baby. ;^)
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: 10.78kW Enphase system and XW6048
    ggunn wrote: »
    I think SMA still makes the 700W 120VAC inverter. I call it the Sunny Baby. ;^)

    SB700 specifications: http://lib.store.yahoo.net/lib/wind-sun/SB700specs.pdf
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048
    stephendv wrote: »
    On that same site under their Prices -> SMA inverters section, they list the price.... 260 USD EACH!
    Ahh.. there it is! Thank you. I was busy looking for DILC or distributed.... and didn't see it. $260!! and that's before shipping!

    I'll keep looking for something less expensive. I wonder if they give a volume discount? It would be good to keep the number of panels per DILC low. Should give better stability.
  • jaggedbenjaggedben Solar Expert Posts: 230 ✭✭
    Re: 10.78kW Enphase system and XW6048

    This is sort of 'by the way'...

    The fact that there is 10kW of Enphase isn't really an issue the way I see it. You obviously have multiple branch circuits there, and it should certainly be feasible to connect only part of the Enphase array to a Sunny Island or what-have-you, and leave the rest to only function regularly as GT inverters if that were needed to avoid overloading your off-grid setup.

    It makes sense to size the amount of Enphases appropriately for this system, indeed it may be necessary to make it a small amount of power to avoid too much 'oscillation' and 'power slamming' as described by ggunn a few posts ago. This is all still assuming that you can find an inverter that has programmable parameters to make this work at all... I think the issue is really the software.
  • jaggedbenjaggedben Solar Expert Posts: 230 ✭✭
    Re: 10.78kW Enphase system and XW6048
    jaggedben wrote: »
    There would be two modes in a grid-down situation:

    1) Loads (including battery charging) exceed capacity of Enphases, frequency shifts to in range, Enphases turn on.
    2) Loads (including battery charging) don't exceed capacity of Enphases, frequency shifts out of range, Enphases turn off.
    ggunn wrote:
    That sounds like a bad idea to me. If the loads exceed the threshold by just a little bit, the Enphases all turn on, then they swamp the loads so they turn off. It sounds like you could get into an oscillation situation with a lot of power slamming off and on. That doesn't sound good.

    Sure...and I think I should amend my previous post to this:

    There would be two modes in a grid-down situation:

    1) When batteries are low, frequency shifts to in-range, Enphases turn on.
    2) When batteries are charged and load no longer exceeds capacity of Enphases, frequency shifts out of range, Enphases turn off.

    To prevent constant on/off the Enphases should only turn on if you know the battery charging load is going to keep them on for a while. The amount of Enphases you connect to this part of the system depends on the amount of batteries and critical loads you decide to support.

    The point is to use the PV array to charge the batteries to support critical loads if the grid is down for a while. As one normally would with a Outback or a Xantrex or an SI system with a DC PV array designed for that purpose. The guy happens to have already purchased a huge Enphase array - we're calling that water under the bridge - and he wants to find a work around to do what other systems are actually designed to do...
  • sub3marathonmansub3marathonman Solar Expert Posts: 300 ✭✭✭
    Re: 10.78kW Enphase system and XW6048
    I attached a jpg of what I wanted to do with the XW6048, XW MPPT and the 360VDC battery. One of my Engineers called it "mission creep". I guess it is... I'll start with the straight GT micro inverters and continue from there.

    Beyond "mission creep" it is more "Rube Goldbergish." :D It also seems to be a case where somebody doesn't want to make a decision. With the XW inverter, you can have it both ways, with and without the grid, so there really isn't a need for the Enphase microinverters. With the Enphase microinverters there can be no power during the time the grid is down, but you don't have to make a massive investment in batteries.

    If you want to use the Enphase microinverters and still have back up power to your house while the grid is down, the site http://www.priups.com/ should be worth reading. You can use the Prius as a battery bank/generator while the grid is down. And with a completely electric car you would be limited by the battery capacity of the car, instead of the fuel tank of the Prius. But you can get a lot more out of a Prius during power outages, since you can't recharge the completely electric car. Unless of course you've got an XW inverter, which brings you full circle back to the initial dilemma.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048
    jaggedben wrote: »
    To prevent constant on/off the Enphases should only turn on if you know the battery charging load is going to keep them on for a while. The amount of Enphases you connect to this part of the system depends on the amount of batteries and critical loads you decide to support.

    If I run 5kW to an XW and the rest of the micros to the Grid, the system would work. But you still need big batteries to stand up to the cycling of the inverters when the grid is down. What if I could individually turn off the micros connected to the XW? Would that allow a safe decrease in battery size?
    If you want to use the Enphase microinverters and still have back up power to your house while the grid is down, the site http://www.priups.com/ should be worth reading..
    I started by looking at using a UPS and found the PriUPS site. It is great reading. And he is right about the data center UPS' being cheap on Ebay. I saw a 20kVA ups with no batteries for less than $2000. Trouble is most of them are 90% efficient. Too big of a hit to use continuously.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048

    i don't know what good that would do as the enphase system could only add power, and only grid power at that, when the sun shines so you will not get around the need for the batteries unless you will be forbidding an outage from occurring at any time other than a bright and sunny early summer afternoon. we would all like an alternative to having to store power in batteries, but there really aren't any alternatives. if a generator won't do then batteries and inverters are the alternative we are given.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: 10.78kW Enphase system and XW6048
    jaggedben wrote: »
    Sure...and I think I should amend my previous post to this:

    There would be two modes in a grid-down situation:

    1) When batteries are low, frequency shifts to in-range, Enphases turn on.
    2) When batteries are charged and load no longer exceeds capacity of Enphases, frequency shifts out of range, Enphases turn off.

    To prevent constant on/off the Enphases should only turn on if you know the battery charging load is going to keep them on for a while. The amount of Enphases you connect to this part of the system depends on the amount of batteries and critical loads you decide to support.

    Not that I have totally thought out the design, but one thing that the Sunny Island has is a pair of independently programmable relays that can be linked to any number of parameters, one of which is the state of charge of the batteries. You can program a relay to flip one way when the batteries are at any desired SOC and the other way at any other SOC you want.
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048
    niel wrote: »
    i don't know what good that would do as the enphase system could only add power, and only grid power at that, when the sun shines so you will not get around the need for the batteries unless you will be forbidding an outage from occurring at any time other than a bright and sunny early summer afternoon. we would all like an alternative to having to store power in batteries, but there really aren't any alternatives. if a generator won't do then batteries and inverters are the alternative we are given.

    If I measure the power being used and the power being produced I could use panels directly connected to the house loads while the XW/SI inverter provides a power sink/source as the micros sequentially cycle on or off. The AC cycling would be greatly minimized. Smaller AC cycling should allow a smaller battery.

    Next I am looking at purchasing and installing a Home power monitoring system to specifically answer the questions of "How much power is needed overnight"? and "How much at once"? I was assuming I needed an XW6048. Maybe I can use something smaller.
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: 10.78kW Enphase system and XW6048

    Let us know what home power monitoring system you select and how you like it.

    Yes--knowing as much as you can about your loads can save you a bunch of money for off-grid (and even grid tied) systems.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048
    BB. wrote: »
    Let us know what home power monitoring system you select and how you like it.

    Yes--knowing as much as you can about your loads can save you a bunch of money for off-grid (and even grid tied) systems.

    -Bill

    Having trouble deciding between ea$y and DIY for the power monitoring. Thank you!!!! I just realized that I can monitor the power of both the house consumption and the pv array!!

    BB thinking to himself; Yes, I know that!!

    I heard you thinking! Why not use that to control how many PV panels are active? I can calculate the difference between consumption & generation, add or remove panels as needed!! No need to rely on the central inverter doing frequency shifting based on battery voltage. Another question is how much to spend? Too much and it's cheaper to get the batteries. It is great talking to the forum members here!!
  • BB.BB. Super Moderators, Administrators Posts: 32,007 admin
    Re: 10.78kW Enphase system and XW6048

    Interesting... In general, you have to decide if you need to know the direction of power flow or not (the "cheap" pickups/systems only measure power, they do not know the direction of AC power flow--to/from grid).

    And, assuming you can interface to your system (and there are a few people who do interface to their home monitoring systems)--You need to have it react fairly quickly... It appears that the Grid Tie inverters/solar charge controllers have a time constant of around 1 to several seconds. And some units apparently test themselves out by running at full power (XW in GT mode, and/or solar charge controllers during solar PV "scans" to determine Imp/Vmp)...

    It is a very complex system... And it may be fairly expensive/complex to figure out how to make a hybrid/hybrid system work well at reduced power levels (balancing loads against solar gt, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RK_Solar_HopefulRK_Solar_Hopeful Solar Expert Posts: 69 ✭✭✭✭
    Re: 10.78kW Enphase system and XW6048
    BB. wrote: »
    Interesting... In general, you have to decide if you need to know the direction of power flow or not (the "cheap" pickups/systems only measure power, they do not know the direction of AC power flow--to/from grid).

    And, assuming you can interface to your system (and there are a few people who do interface to their home monitoring systems)--You need to have it react fairly quickly... It appears that the Grid Tie inverters/solar charge controllers have a time constant of around 1 to several seconds. And some units apparently test themselves out by running at full power (XW in GT mode, and/or solar charge controllers during solar PV "scans" to determine Imp/Vmp)...

    It is a very complex system... And it may be fairly expensive/complex to figure out how to make a hybrid/hybrid system work well at reduced power levels (balancing loads against solar gt, etc.).

    -Bill

    I don't know if a pre-packaged power measurement system would work. Needs more research. How fast do they update? How fast do I need to turn off/on the micro inverters? Sounds like custom work and/or DIY. I NEED more information!!!

    I was thinking of measuring PV array output & House consumption. Get the data into a controller, probably a PC at first. Decide what to do, turn on or off a micro. Repeat endlessly.

    Found an electronic relay, Solid State Relay, that might work. Have to test the Enphase to check if it will sync up through the SSR. The SSR turns on with 3VDC, turns off with 1VDC. So a low power device can control it. Start small and work up in quantity and complexity.

    The controller may turn out to be an issue. Investigating DIY with Arduino versus buying the controller & IO boards.
  • jaggedbenjaggedben Solar Expert Posts: 230 ✭✭
    Re: 10.78kW Enphase system and XW6048
    Found an electronic relay, Solid State Relay, that might work. Have to test the Enphase to check if it will sync up through the SSR ...

    er...Maybe I'm not understanding what you're thinking, but I have a bunch of questions. For example, I wouldn't put that SSR on a roof. Nor could it be spliced into the Engage cable.

    Note also that the Enphases have a 5 minute wait time after grid power is applied. That's just another reason why I think attempting to turn them on and off individually is kind of quixotic; you're not going to be able to respond immediately to all kinds of loads. I still think you really should be thinking about configuring appropriately sized groups of the Enphases to 'bulk' loads that can start slowly and stay on for a while. Those loads would begin with battery charging and then perhaps go on to include other stuff you might have, such as a well pump or water heater (aka 'dump loads').
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