The Enphase Energy Management System

[RegGuheert]

This article says the AC Batteries will launch in "early 2016" in Australia where some customers pay "more than four times as much as the feed-in tariff" for their electricity. Clearly such a situation would greatly hinder Enphase's business opportunities in Australia. The obvious implication is that it is much better to NOT let your PV-generated electricity flow back into the grid under such a rate structure, but instead should try to use it all yourself.

[DaveEV]

Here in San Diego I have over a 2-1 ratio between peak and offpeak rates from May-October. But the winter months theres only a 10% difference. Peak rates are between 12-6pm, so the value would be charging batteries from solar before 12pm and discharging them before 6pm.

However, utility rates will be changing, perhaps substantially as more solar comes online and storage will give you a lot of flexibility to adapt to future rate changes.

[RegGuheert]

As expected, Enphase announced on their blog that they will start selling their AC Battery product in Australia.

They have also announced that they are launching the Enyoy-S. I suspect this announcement is related to the changes seen at their Enlighten website the other day. I suppose the new Enlighten website was needed to allow the new Envoy-S to talk to their servers.

The Envoy-S is certainly a requirement for introduction of both the AC Battery AND the S275 microinverter. I expect we will learn more about all of these new products in the near future.

It seems clear that the S275 will have no problem with market acceptance (barring some product durability problem). Customers will appreciate the enhanced efficiency and additional power capability and utilities will likely find that having four-quadrant-capable power converters scattered around their grid will have extremely high value.

The question is whether customers connected to grids such as Hawaii and parts of Australia with high penetration of PV will embrace the AC Battery. I expect they will as the utilities use their pricing policies to become more closed to PV energy being distributed on their network. One thing is for sure: more PV penetration means additional expense to add solar to the grid. I do think this is something that many who are holding out on installing solar are not counting on.

[RegGuheert]

Enphase has now provided datasheets for the released portions of their Energy Management System including the Envoy-S and the AC Combiner Box.

Enphase has not yet released the AC Battery so there is no datasheet, but they did update the brochure. This new brochure has some interesting "specifications":

Higher performance
• 96% round-trip efficiency for the battery
• 2 cycles per day delivers twice the value for a faster payback period

If the battery has 96% round-trip efficiency and the new S280 Microinverter has 97% one-way efficiency, then the overall round-trip efficiency for the AC Battery comes to 90% (ACout/ACin). This should be slightly higher than the Tesla PowerWall AC/AC efficiency.

How do you get 2 cycles/day? Assuming TOU metering, it seems that you would tend to have one main charge cycle each day with multiple discharge periods, one just before and one just after the main charge cycle.

Greater reliability
• Lithium iron phosphate chemistry from Eliiy Power for long cycle life
• 10 year warranty
• No single point of failure

10-year warranty is nice! I wonder what the details are.

Safer
• Our prismatic cells from Eliiy Power are highly stable over time
• Safety certified by TUV Rheinland
• No high voltage DC in system
• Most usable capacity with greater than 95% depth of discharge

95% DOD is very high. Is it really warranted to do that twice each day for 10 years? I doubt it.

It will be interesting to learn more details about this battery system.

[wwhitney]

So has Enphase said anything about the possibility of using the Enphase Energy Management System to provide an AC-coupled battery backup during grid outages? Is there a provision for a dump load?

Cheers, Wayne

[JimSouCal]

So has Enphase said anything about the possibility of using the Enphase Energy Management System to provide an AC-coupled battery backup during grid outages? Is there a provision for a dump load?

Cheers, Wayne

i asked a sales engineer yesterday. All he would say is they know there is a demand and they are working on it. The new inverters are expected to Bo in distribution channels in October. I just got pricing today.

[RegGuheert]

So has Enphase said anything about the possibility of using the Enphase Energy Management System to provide an AC-coupled battery backup during grid outages?

Actually, they have. Here is what Enphase CEO Paul Nahi said recently:

“Does backup have that much utility? I think backup is being way overblown as a capability. If you really need backup, the problem is, 7kWh, 20kWh isn’t gonna do it. If you really want backup, you get a generator. There are companies that provide natural gas or diesel generators that are very inexpensive, and can truly keep you backed up indefinitely. That’s not to say there isn’t a market for battery backup [but] it’s going to be relatively small.

[JimSouCal]

As per below, if this vein runs through the company, I'd submit the CEO isn't looking at the tea leaves accurately. I see this as unfortunate for a company seemingly keyed into marketing and buyer behavior.

Perhaps internally, as I mentioned from the sales engineering side that I spoke to prior, there is some thought on an official use of the battery to provide an AC wave and voltage to the array, and allow for solar harvest during grid outage...

Locally (LADWP), we've had several outages, one during the last super bowl, so much that I have received 4 direct mailers from those generator companies Nahi refers to... Perhaps he misses the selling poing of having a solar array cool the fridge and other managed load items during occasional outages...

Nighttime items like LED lights go a long way on batteries... Load shedding goes a long way to make batteries last...

Anyway, I will very likely proceed with the install of my array using the new inverters (s280) and Envoy S. My understanding is there is a safe reliable engineering to get the system backed up and producing during down grid times... Moreover, if anyone has engineering expertise in that end, I'd welcome the contact..

So has Enphase said anything about the possibility of using the Enphase Energy Management System to provide an AC-coupled battery backup during grid outages?

Actually, they have. Here is what Enphase CEO Paul Nahi said recently:

“Does backup have that much utility? I think backup is being way overblown as a capability. If you really need backup, the problem is, 7kWh, 20kWh isn’t gonna do it. If you really want backup, you get a generator. There are companies that provide natural gas or diesel generators that are very inexpensive, and can truly keep you backed up indefinitely. That’s not to say there isn’t a market for battery backup [but] it’s going to be relatively small.

[DaveEV]

As per below, if this vein runs through the company, I'd submit the CEO isn't looking at the tea leaves accurately. I see this as unfortunate for a company seemingly keyed into marketing and buyer behavior.

I agree. Having some amount of off-grid capability is an important selling feature if you're going to have storage.

Locally (LADWP), we've had several outages

I've had 2 outages in the last month lasting 30-90 minutes. Would have been nice to have some backup!

[RegGuheert]

Here is some additional information about the battery technology directly from the manufacturer:

Battery Cell Specifications

Nominal capacity: 50 Ah
Nominal voltage: 3.2 V
Weight: 1.5 kg
Size: W 170.5 x D 43.5 x H 111.9 mm
Energy density: 106 Wh/kg
Operating temperature: -20 to 60C (guaranteed operating temperature: 0 to 45C)
Cathode material: Lithium iron phosphate
Anode material: Carbon

This data makes me wonder whether Enphase' AC Battery will store 1.6k Wh of energy rather than the 1.2 kWh originally indicated. The reason is that each of these cells stores 160 Wh of energy and ten cells in series gives you an overall battery output voltage ranging from 28 V to 36 V, which fits perfectly with the S280's "Peak power tracking voltage" range of 27 V to 37 V. Ten cells would weigh about 33 lbs. Add in 15 lbs. for two S280s, a BMS, wiring and connectors and another 10 lbs. for packaging and you are right around 60 lbs for the unit, which should be manageable.

So, the question becomes: Is a ratio of 1.6 kWh/560 W proper for the intended purpose of time-shifting, or is that too much energy storage? For my system, I would need about 18 of these (~10 kW) to keep nearly all of my extra production off the grid, which would equate to 28.8 kWh of batteries. That seems to be a bit much storage without the ability to provide backup (though about right for backup), so perhaps they really are going with the smaller cells. Perhaps sizing the AC battery for time-shifting is similar to sizing microinverters to modules: handling the 100% case is overkill and you make out fine handling the 70% case. I suppose with the battery it depends on the regulations where you live.

The cycle life claimed for this battery is very impressive:

What’s more, they offer an extended lifespan: even if charged and recharged repeatedly for 10 years (approx. 12,000 times), they will retain 80.1%* of their electricity storage capacity.

*Estimated value assuming 23ºC room temperature and three full charge and recharge cycles per day (depth of discharge (DOD) = 100%).

Hopefully those numbers are real and include the effects of calendar life as well and not just the cycling.