Two panels on one enphase?

[shastaron]

Not to highjack the thread but is there a practical application to this for us Off-grid? Since we have to store at DC is there any benefit?

[solartek]

Absolutely if I did this I would for sure do it by the book. I also like the idea of being able to work into a bigger system instead of jumping into spending a ton right out of the box.

Is the Envoy - Energy Management Unit with one year data service a required device?

The EMU is not required. You just won't get all the fancy data logging.

[BB.]

Without the EMU (and a required Internet connection / subscription back to the hosting website?)--I don't believe you will get any information at all... Have 20 units setup and one fails--you would probably never see it with plain monitoring (5% loss of power)... Weather variability would probably swamp putting a kWHr meter on the array output.

In California, I believe for the larger installations (over 5-10kW?), phone home energy logging is required for the rebates.

Regarding off-grid systems... I would guess that you could hook up a TSW inverter + battery bank system, and have the Enphase back drive the TSW inverter to charge the batteries (or share the load).

This has been done with larger installations (one around 10kW or so--Solar Guppy's lab/home--as I recall). Should work with the smaller setups too.

However, there are drawbacks... 1. No "off the shelf" regulation of GT inverter power backfed through TSW inverter/charging the battery--could overcharge/damage/worse the battery bank.

2. Enphase does not seem to offer off-grid monitoring solutions (need real bi-directional Internet acess). Also, for a small system I would wonder if the "EMU" would be a significant power hog (if it worked off-net).

3. Given that you can wire up a regular MPPT Solar Charge Controller to any reasonable size of panels and charge the battery bank directly--why do it for Off-Grid applications?

-Bill

[shastaron]

That makes sense. I couldn't see how it would help off-grid but just wanted to check. Still is a neat concept for grid tie.

[gvoffgrid]

I've been thinking about trying an EnPhase unit on my off-grid installation. I should probably talk to them first, but my thinking is this ...

I just built an 8X8 chicken coup with perfect southern exposure, with a perfectly pitched roof. I plan to run AC power to it. It seems like a cool idea to plop some panels on the roof and tie into the (off)grid, if possible.

The shed is some distance from the rest of the solar system, batteries, etc., and the supplemental panel installation and wiring would be far easier at the shed than at or near the existing array (AC vs DC installation).

My house could easily absorb the power from one EnPhase unit (on one leg). With an EnPhase inverter tied in to my (off)grid, would the existing inverter simply draw less current from my battery bank/charge controller? Please excuse my ignorance of how a grid-tie inverter works, but how does the grid-tie inverter ensure that any loads draw power from it vice the grid (in my case, a Trace/Xantrex SW554?

DDDD

[niel]

now don't get me wrong here as i'm sure there would be a point at which an enphase would work in conjunction with a large offgrid load, but what that point would be is unknown to me. it isn't how large of an inverter (or generator for those that have wondered) you have as much as how large of an ac load you have to absorb the higher voltage introduced by the enphase inverter. loads absorb this ac power and not inverters or generators. would i believe that you would be using that many kilowatts at the time and everytime (daylight) the enphase is to always be engaged? not likely. either expand your present system to allow for the new loads and run the appropriate wire to the coup or get yourself another system to handle the coup.

[gvoffgrid]

now don't get me wrong here as i'm sure there would be a point at which an enphase would work in conjunction with a large offgrid load, but what that point would be is unknown to me. it isn't how large of an inverter (or generator for those that have wondered) you have as much as how large of an ac load you have to absorb the higher voltage introduced by the enphase inverter. loads absorb this ac power and not inverters or generators. would i believe that you would be using that many kilowatts at the time and everytime (daylight) the enphase is to always be engaged? not likely. either expand your present system to allow for the new loads and run the appropriate wire to the coup or get yourself another system to handle the coup.

Thank you for your response. Definitely food for thought. I guess I need to learn how grid-tie inverters work.

However, in the model I'm exploring, if the house loads amounted to less than the capacity of the enphase system, I would think it would simply be underutilized, much like the solar panels are underutilized once the battery bank is charged. This is not the most efficient model to be sure, but neither are most solar off-grid systems (lacking an infinitely large battery).

[niel]

you aren't using the utility grid system as a battery, but are using batteries as batteries. sending the enphase power into the inverter ac system will not store any power, which you have acknowledged, that you can reap back making this underutillization of power at the time a throwing away of the power you could be sending to more batteries that can utilize it when it's needed and not so dependent upon the time the power is used. also underutillized power from the enphase will cause a rise in the ac voltage levels and one must be aware of this as higher voltages can damage things plugged into it. you just won't have the grid there that would load down and be large enough to absorb the rise in voltage the enphase would introduce.