nwdiver
Well-Known Member
That's pure speculation at this point... any backup system with Enphase would NEED to be AC coupled. The power wall at it currently exists is DC coupled.
SolarEdge’s StorEdge™ DC coupled storage solution allows home owners to maximize self
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That's pure speculation at this point... any backup system with Enphase would NEED to be AC coupled. The power wall at it currently exists is DC coupled.
Alright, so either a new Powerwall with built-in conversion or a AC-DC converter would have to be employed.
Ampster
Active Member
I don't know what skimpy is but I have a 4k PV system with Enphase inverters. I chose to add a 48V hybrid inverter that was expensive but I got a deal on 15kWhr of lithium LiFePo prismatics ($3000 or $200/per KWh) that I configured as a 48V pack. I had to buy a separate battery management system and a charger. As mentioned earlier in this thread I can only rationalize it as a hobby. The Powerwall with the SolarEdge inverter is a better value but you would have to abandon the Enphase inverters and connect the PV panels in a string configuration. There would also be the cost of Solar Edge Optimizers.
Skimpy meaning 2.6 KWh (Suniva panels). I've since added a heat pump and tankless electric water heater (ditching a gas furnace and water heater in the process), so I have expansion on the mind (to say nothing of the energy demands that an eventual EV will require). To take advantage of a Powerwall battery backup, the parallel microinverter configuration I have with Enphase would have to be dumped and the single SolarEdge inverter would take its place. This loss of redundancy takes away one of the key benefits of this system, it seems (one panel failure not disrupting the output of the remainder), not that I've had occasion to use this feature since installation 2 years ago, but from what I understand this multiple inverter configuration also maximizes output so I'm not sure I'd want to get rid of it. There must be a more elegant way to add battery backup (something along the lines of your LifePo pack), but I take it requires incorporating what you described as a hybrid inverter between the solar array's microinverter and battery, and the product SolarEdge is introducing here is no such beast. I'm in no rush to add battery backup, but it's been at the back of mind as something to add in the future. Much research to do, but the next thing I'm likely to do is add generation capacity. Thanks for the exposition.
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Ampster
Active Member
From what I understand from this Forum and Solar Edge website, the optimizers do the same MPPT thing on the DC string as the Enphase inverters. Apparently they also do individual panel reporting. I don't know if they facilitate adding capacity like the Enphase inverters do or if you have follow string sizing rules.
If you are thinking about adding capacity you could consider leaving the Enphase system intact and adding capacity with the Solar Edge. The two systems would be coupled on the AC side.
If you are thinking about adding capacity you could consider leaving the Enphase system intact and adding capacity with the Solar Edge. The two systems would be coupled on the AC side.
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Enphase is poorly positioned for batteries. With AC coming off the roof, doing a AC-DC conversion will lose an extra ~10% efficiency compared to a solaredge solution. A good all DC solution looks to be about 90% efficient round trip through the powerwall. Enphase will be about 80%.
That would be a fair compromise, I think, especially since the system isn't even paid for!
Interesting, nothing like postpurchase regret. I also saw Solar Edge's own microverter comparison, which seems to underscore your point: Comparison to Microinverters
It's easy to see the cost savings here with more affordable scalability.
I'm not sure which scalability you're talking about, but I am interested to see how much inverter they will put if you want 2 or 3 PowerWalls strung together.
Well, scalability in terms of increasing generating capacity at minimal cost and with better efficiency courtesy of having one inverter in conjunction with one power optimizer per panel versus the seemingly more rickety Enphase solution of one microinverter per panel. Since my system is underpowered, I'm still in the contemplation stage over here such that I'm not giving full weight to the notion of the Powerwall just yet. 
Apologies for generating (pun intended?) any undue confusion.
Apologies for generating (pun intended?) any undue confusion.The inverter controls wattage from the powerwall, so the size probably depends on the output desired. If three powerwalls are going to be running at the full 5000w spec each, that will obviously need a big inverter.
I don't expect a three powerwall setup will require a 15,000w inverter, but maybe so. I'm curious how charging multiple powerwalls will be done too.
Ampster
Active Member
Yes, ultimately the load in kWs will determine how much capacity you would need. 5000 Watts is probably peak for the Powerwall. If the usable capacity of the Powerwal is 7500 Watthours even at a load of 2500Watts it would only last for 3 hours.
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Well...true if you are connected to the grid. I'm not going to be. So for me, off grid is key and I'd like the inverter to support that, seems that without the ability to store the owner of a system has no ...pricing/buying power. Once they can make a sell or keep decision then they have more power and can effectively negotiate.
Ampster
Active Member
A 350v system will still save you money on wire size. I also believe that it MAY be more efficient going from Solar to batteries and from batteries to AC because of the higher voltage.
Why not just have the modules and a battery back up with a charge controller take out every single microinverter for every device in the home and make simple dc power supplies to every single component in the home?
Because there is no standard DC voltage level. And running low voltage DC any real distance results in high losses.
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