Enphase getting into storage systems...

[kwilcox]

Now that I've spent some time thinking about how it is connected, I can't personally see how it can easily be anything else. Maybe dedicated branch circuit connected to generation/storage system? The interesting point against this is the following bullet which implies GT operation:

• Intelligent system maximizes utility bill savings and battery life

To do this, it also needs to know whole-house usage at any given point in time which pretty much requires something like a CT on the POCO feeder.

edit: and here's how (I should've just read inetdog's post first lol)...

http://enphase.com/eblog/2014/new-enphase-energy-management-system-accelerates-mainstream-solar-adoption/

It looks like I might just have lucked out by choosing an enphase engage based system....

[fun2drive]

I can see real value in a system that does the grid tie to be dropped when utility power fails and allow self contained operation. I read about the SMA Sunny Boy inverters that do this but the lack of power output that would allow running appliances with induction motors would require some buffer like a battery storage to allow that powering up that LRA use.
I really desire an application which would allow a safe seamless change over from grid tie to stand alone and back once utility power. At the moment my only real choice is a generator and automatic transfer switch if utility power goes down...

Interesting idea but I would agree seems to be a limited market for this type of application.

[paulcheung]

I can see the gridtie users hate to see their PV power gone wasted when the grid is down, If the grid is not reliable then you should not have grid tie installaion in the first place! If the grid is reliable and just occasionally down once a week or month for few hours, You have a lot of other opions to power the whole house with a generator or an UPS just to power some critical circuits like computer and modems.

It is just not econmical sensible to has a grid tie system and then spend lot of money use battery backup to save the little power produced by the PV panels.

Yes you can use a something to fool the grid tie inverter to start, but what happen to the buffer resource when the cloud pass by? you don't feel any problem because the grid is buffer all the demand when the grid is up, BUT when it is down, you try to use battery buffer that. see how much money you have to spend to get that done. might as well do it off grid from the first place.

When you on grid tie, you usually don't conserve, use the power as you like and have all the air condition running and other big current drawing eqipments, I just don't see it make any sense at all to mess with the installation.

Cheers

[Sunking]

GTI are current sources, not voltage. They need very low impedance of the grid to operate properly.

[kwilcox]

Nope. AC coupling allows GT arrays to power off-grid/battery based PV systems. The SE Conext is a good example of this. Here's how they do it:

http://solar.schneider-electric.com/wp-content/uploads/2014/04/Conext-XW-AC-Coupling-Application-Note_Rev-B.pdf

Conext actually varies the line frequency to cycle the GT array on/off when the batteries reach full charge.

Here's the Enphase whitepaper on how to do AC coupling with their GT inverters (this forms the basis of their battery system too btw):

http://enphase.com/global/files/Enphase_Application-Note_AC-Coupled-Battery-Based-Systems.pdf

First sentence from above link: "AC Coupling allows use of Enphase Microinverters with off-grid and battery-based photovoltaic systems.".

This is why their storage system is pretty much genius. The batteries form an integral part of the panel/inverter system. The new Envoy S controller controls charge by cycling the inverters using their established powerline control protocol (used today for Enlighten based monitoring/control). End result: deliver just enough energy to minimize the home's grid power requirements. In short, its designed to avoid the need to use the grid as a battery.

The key here is the existing Enphase powerline control protocol which allows the Envoy S to precisely control M2xx GT inverters and their new bi-directional S275 inverters used by the battery system. All this running on Enphase Engage cable. Genius.

Here's some examples based on my current understanding of the system which will be available in 3Q15:

I could, for example, set this system (PV Array/Enphase GT microinverters/Enphase batteries/Envoy S controller) up with a single demand side outlet that is my garage 40 Amp car charger outlet. No POCO interconnect anywhere. If I plug enough batteries into the trunk cable, I can store an entire days worth of power locally then just release it when the car is on the charger.

Or, instead of a 40Amp outlet, I could connect the demand side to my main panel, then tie in my TED5000 which is one of the supported Envoy S interconnect components (along with NEST thermostats and a whole bunch of other exciting products). Now it has instantaneous whole house usage available for charging calculations. Excess array production would then be diverted to local storage and be "played back" when array production was insufficient to meet the home's instantaneous demand. Net metering hassles avoided. "demand vs. usage" debate still rages though.

Or, to avoid the "demand vs. usage" debate, I set up a new load center on the system demand side that isn't connected to the POCO. Now I run kitchen/bathroom circuits there. TED5000 (or other) monitors this load center for charging optimization.

The result: partial grid defection and not a single thing the utility can do about it. ...This is also a complete off-grid system minus generator backup btw. There might be a supported generator solution too but I didn't see it.

Sadly, it is the utilities themselves that are driving this innovation by refusing to embrace their potentially lucrative role as an energy storage provider. The last connectivity example above will be my reply to a 2015 rate-case rubber stamp in SE WI.

Again, this is my current understanding of the system which was just announced. If anybody has corrections (like a possible grid-tie requirement which isn't clear at this point) then I'd love to hear it.

edit:

It appears that S series inverters will be required at the panels too. M2xx inverters cannot be controlled by an Envoy S. Bummer.

[paulcheung]

Nope. AC coupling allows GT arrays to power off-grid/battery based PV systems. The SE Conext is a good example of this. Here's how they do it:

http://solar.schneider-electric.com/wp-content/uploads/2014/04/Conext-XW-AC-Coupling-Application-Note_Rev-B.pdf

Conext actually varies the line frequency to cycle the GT array on/off when the batteries reach full charge.

Here's the Enphase whitepaper on how to do AC coupling with their GT inverters (this forms the basis of their battery system too btw):

http://enphase.com/global/files/Enphase_Application-Note_AC-Coupled-Battery-Based-Systems.pdf

First sentence from above link: "AC Coupling allows use of Enphase Microinverters with off-grid and battery-based photovoltaic systems.".

This is why their storage system is pretty much genius. The batteries form an integral part of the panel/inverter system. The new Envoy S controller controls charge by cycling the inverters using their established powerline control protocol (used today for Enlighten based monitoring/control). End result: deliver just enough energy to minimize the home's grid power requirements. In short, its designed to avoid the need to use the grid as a battery.

The key here is the existing Enphase powerline control protocol which allows the Envoy S to precisely control M2xx GT inverters and their new bi-directional S275 inverters used by the battery system. All this running on Enphase Engage cable. Genius.

Here's some examples based on my current understanding of the system which will be available in 3Q15:

I could, for example, set this system (PV Array/Enphase GT microinverters/Enphase batteries/Envoy S controller) up with a single demand side outlet that is my garage 40 Amp car charger outlet. No POCO interconnect anywhere. If I plug enough batteries into the trunk cable, I can store an entire days worth of power locally then just release it when the car is on the charger.

Or, instead of a 40Amp outlet, I could connect the demand side to my main panel, then tie in my TED5000 which is one of the supported Envoy S interconnect components (along with NEST thermostats and a whole bunch of other exciting products). Now it has instantaneous whole house usage available for charging calculations. Excess array production would then be diverted to local storage and be "played back" when array production was insufficient to meet the home's instantaneous demand. Net metering hassles avoided. "demand vs. usage" debate still rages though.

Or, to avoid the "demand vs. usage" debate, I set up a new load center on the system demand side that isn't connected to the POCO. Now I run kitchen/bathroom circuits there. TED5000 (or other) monitors this load center for charging optimization.

The result: partial grid defection and not a single thing the utility can do about it. ...This is also a complete off-grid system minus generator backup btw. There might be a supported generator solution too but I didn't see it.

Sadly, it is the utilities themselves that are driving this innovation by refusing to embrace their potentially lucrative role as an energy storage provider. The last connectivity example above will be my reply to a 2015 rate-case rubber stamp in SE WI.

Again, this is my current understanding of the system which was just announced. If anybody has corrections (like a possible grid-tie requirement which isn't clear at this point) then I'd love to hear it.

edit:

It appears that S series inverters will be required at the panels too. M2xx inverters cannot be controlled by an Envoy S. Bummer.

Whole of these points are come back to storage, If you can find any form of storage cost effective, by all mean you will be able to go off grid and won't have to worry anything about the grid down.

With the off grid without generator, the generator's purpose is to keep the battery alive while you have rain or snow for days. if you have other mean to do that, by all means.

The bottom line is cost effective storage when the sun is not shinning on your panels..

[nomadh]

I don't know what AC coupling really means. I think these grid tied systems are missing a HUGE point. Any gt system should be able to make power during the day when the grid is down. It doesn't need to be elegant or perfect And it should be a feature for little extra cost. Its mostly an engineering cost to the company as most of the needed parts are already there. The inverter is already 90% done. Batteries are a PITA. A ridiculously expensive, wearing out when you need them useless when you don't PITA. I think most usual solar buyers would like some power from their system in an emergency if it was just a little more cost and took no maintenance. Almost nobody wants it if it doubles or even triples the price and cost another 50% every 10 years after that.
So I still don't really feel I have an answer to "Is the enphase going to allow off grid solar?" Does ac coupling imply that? It still looks to me enphase only cares about shifting the time it can supply power while on grid. Maybe this new battery pack can be hot rodded? Sort of like how the prius was hot rodded to allow charging from home until Toyota introduced like they were marketing geniuses. Once again I was thinking what stupid company didn't include such an obvious, inexpensive feature like this to begin with.

[russ]

I don't know what AC coupling really means. I think these grid tied systems are missing a HUGE point. Any gt system should be able to make power during the day when the grid is down.

You would also like your Chevy to have all the features and speed of a Ferrari?

[inetdog]

You would also like your Chevy to have all the features and speed of a Ferrari?

...and not cost any more than without those features?

[russ]

...and not cost any more than without those features?

An old boss of mine had a comment for when we were discussing engineering and someone in the meeting said "I wish" or "I hope"

Something like, "Wish in one hand and crap in the other. Come back and tell us which hand fills up first".

[paulcheung]

I don't know what AC coupling really means. I think these grid tied systems are missing a HUGE point. Any gt system should be able to make power during the day when the grid is down. It doesn't need to be elegant or perfect And it should be a feature for little extra cost. Its mostly an engineering cost to the company as most of the needed parts are already there. The inverter is already 90% done. Batteries are a PITA. A ridiculously expensive, wearing out when you need them useless when you don't PITA. I think most usual solar buyers would like some power from their system in an emergency if it was just a little more cost and took no maintenance. Almost nobody wants it if it doubles or even triples the price and cost another 50% every 10 years after that.

It won't happen until someone come up the solution for cost effective storage. the biggest problem is the cost of storage, you need it to stable the power and backup when the source is not be able to provide the power.

[kwilcox]

Well, Enphase certainly hasn't released pricing yet, but the tech is there.

[russ]

Well, Enphase certainly hasn't released pricing yet, but the tech is there.

The tech has been there for a long time - cost effectiveness has not and is a long way out.

[kwilcox]

The Enphase system is unique in that it interfaces with third party home management systems like TED and Nest to control the exact amount of energy provided by PV based systems. Then it meters this energy such that net output to the grid is always zero. No other system that I know of can do this. No other system that I know of can optimize charging when power is flowing backward through the battery inverters either.

So I disagree with your statement that the tech has been around for a long time. I don't have empirical data to cite against your "cost effectiveness has not and is a long way out" statement however. I guess we'll have to wait until Enphase releases pricing for that.

[JCP]

I think I read that Li-on batteries cost about $300 a Kwh. Cars only use 2/3 of the battery capacity to keep them going longer. So, a house would probably require a good 30KWh battery to be helpful (and that only covers a day of consumption or so). Today's cost: $9000. Maybe $3-4000 in a few years if all goes well.

Or maybe Ambri (www.ambri.com) will make their liquid battery happen and make it work. Who knows?