The Enphase Energy Management System

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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.
 
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.
 
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.
 
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":
Enphase AC Battery Brochure said:
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.
Enphase AC Battery Brochure said:
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.
Enphase AC Battery Brochure said:
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.
 
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
 
wwhitney said:
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.
 
wwhitney said:
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:
Paul Nahi said:
“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.
 
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..

RegGuheert said:
wwhitney said:
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:
Paul Nahi said:
“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 said:
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.

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

index_img01.jpg

Eliiy Power said:
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:
Eliiy Power said:
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.
 
Enphase enters development and supply agreement with Eliiy Power
The AC Battery will be rolled out to the Australian market later this year before being introduced in the U.S. and select markets in Europe in 2016. A modular battery built using Eliiy’s lithium-based technology, a typical system provides 1.2 kWh or energy storage and 275/550 W power output.
I wonder when "2016" is - I know that a lot were hoping to see it hit the market already since they announced the product a year ago already.
 
drees said:
Enphase enters development and supply agreement with Eliiy Power
...A modular battery built using Eliiy’s lithium-based technology, a typical system provides 1.2 kWh or energy storage and 275/550 W power output.
While it is a recent article, it's clear they are using the old data from the original press release. We now know the S275 does not exist, only the S280 (and S230), so the AC Battery will offer 280/560 W power output options and I suspect, as mentioned, a bit more capacity for the battery. We'll see.
 
http://storage.pv-tech.org/news/enphase-names-battery-price-for-imminent-solar-plus-storage-push-in-austral

Ouch - AUD$1150 / kWh (USD$838 / kWh).
 
drees said:
http://storage.pv-tech.org/news/enphase-names-battery-price-for-imminent-solar-plus-storage-push-in-austral

Ouch - AUD$1150 / kWh (USD$838 / kWh).
If someone can safely after market set it up to allow me to use as a back up and still harvest PV energy, I'll be in... Otherwise, no...
 
drees said:
I wonder when "2016" is - I know that a lot were hoping to see it hit the market already since they announced the product a year ago already.
This link from for residents of Australia and New Zealand to sign up for monthly email updates on the AC Battery indicates it will not be available until "Winter 2016," which means June 2016 at the earliest for them.

I suppose they will evaluate how things are going over there for a while before introducing it elsewhere.
drees said:
Ouch - AUD$1150 / kWh (USD$838 / kWh).
Let me make a couple of assumptions to try to get at the cost of the non-inverter portion:

- 560-W version is being priced.
- Inverter portion of the price is US$0.50/W or US$280.
- AC Battery includes 10 smaller-capacity versions of the Eliiy cells shown on their website giving 1.2 kWh total storage (see edit below).

That would put the unit price at US$1006. The non-inverter portion of the system would then have a price of US$726, or about US$605/kWh. Some of this price is packaging and some is warranty. It also includes wiring and fusing for the battery (just four solar wires with M4 connectors and a fuse, perhaps). I wonder if there is anything else. Assumedly Enphase could just require two Engage positions for the 560-W unit, but I don't know how the system would know they are both connected to the same battery. Perhaps the Envoy can cause only one battery-connected S280 to charge and/or discharge at a time and see if any others are affected. But that seems a bit too indirect. There needs to be some knowledge of the battery characteristics in there somewhere.

This brings up another question: Is the new S280 only powered by the DC side like the M250? If so, then it seems a prolonged period without AC would cause the Li-Ion bettery to become drained below the operating threshold for the inverter, which would completely brick the unit.

Edit: The video in this link confirms that the capacity will be 1.2 kWh, so I have adjusted the calculations accordingly.
 
It seems that Enphase has added a new page for their energy storage solutions which includes a link to a preliminary datasheet for the Australian version of the AC Battery.

One thing that jumps out at me is that I see NO MENTION of the use of Engage cabling system. The datasheet makes no mention of Engage and the page includes the following verbiage:
Enphase Website said:
Step One: Install mounting bracket on studs.
Step Two: Connect with standard AC wiring.
Step Three: Hang and secure AC battery to mounting bracket.
The picture associated with "Step Two" looks nothing like Engage and more like standard wiring in conduit. My impression is that they have been performing cost-take-out on the AC battery and they realized that there is little need for the on-roof ruggedization which Engage provides. I suspect they have also eliminated the MC4 connectors for similar reasons. In fact, I wonder if the inverters are packaged in a very different manner to their roof-mounted counterparts, even if the electronics are extremely similar. The other benefit of elimination of Engage cables is that an electrician can wire up the AC Battery using only what is already on his/her truck. Also, the wiring gauge is not limited to 12 AWG, allowing larger wires to be used, if desired in order to reduce wiring losses.

Just for reference, I will take this opportunity to pull my per-kWh calculation for energy stored in the AC Battery from another thread
RegGuheert said:
For $1000, you get a battery which is guaranteed to cycle twice per day for 10 years. In other words, you will pay $1000/(365 days/year * 10 years * 2 cycles/day * 1.2kWh/cycle * 0.9 kWh/kWh) = $0.127/kWh for energy stored in the AC Battery. This number assumes there is no cost for additional PV and/or installation and that no other equipment is required to be purchased to connect the AC Batteries (not valid, since, at a minimum, Engage cable and breakers are required).
The US$0.127/kWh result does not include Engage in the calculation and the 90% round-trip efficiency (0.96*0.97*0.97) still seems correct, so that calculation should still apply.

No doubt the utilities are well-aware of the fact that consumer-level storage is coming. As such, I expect them to raise the price of grid-tied solutions so that they are a bit below that of a battery-based system. Perhaps 5 to 8 cents/kWh.

So that would leave the homeowner with a couple of risk factors to balance:
- Purchase the AC Battery with the warranty-based assurance that it will provide electricity for about $0.13/kWh for 10 years and trust that Enphase will be around to honor that warranty.
OR
- Stick with the utilities pay somewhat less now knowing that they will "alter the arrangement" repeatedly during that same 10-year period.

Unfortunately the problem with the utilities in CA is that they make their pricing schemes so complicated that very few homeowners are likely to have sufficient data to determine what the actual costs will be in their specific case. This fact in itself will likely drive some homeowners toward battery-based solutions rather than sticking with the utilities.
 
RegGuheert said:
...Unfortunately the problem with the utilities in CA is that they make their pricing schemes so complicated that very few homeowners are likely to have sufficient data to determine what the actual costs will be in their specific case. This fact in itself will likely drive some homeowners toward battery-based solutions rather than sticking with the utilities.
That, and... In a not so rational way, we'd like to be able to make and store our "own" energy...
 
It is interesting that there appears to be a S230 inverter bolted to the inside of the enclosure. I have to imagine that they are using a standard inverter with perhaps custom pigtails internally to a wiring block for external hookup using off-the-shelf parts.

I also find it interesting that they quote "round trip cell efficiency" instead of the round trip efficiency of the entire system. 90% does appear to be a reasonable estimate.

I don't see how one can really get two cycles a day out of the system, unless there are multiple peak power periods in the day.

Now with solar becoming so prevalent, you can definitely see two peaks in grid demand here in California - one around 9am and one around 7pm. So perhaps you might charge the battery from solar during the day for the evening peak and then charge the battery from the grid during the night for the morning peak?

Also, at 90% RTT efficiency, there is no financial reason to use the system in the winter here - the spread between peak and off-peak is only about 90% - $0.21758 peak and $0.18742 off-peak or 86%.

If you use 1.0 kWh from the grid to charge off-peak and only get 0.9 kWh out peak, you make just short of a penny. You would have to use the system as some sort of aggregated grid resource to really make any decent return on it (perhaps tying your system in to work with OhmConnect? I'm not sure how their points system is scored because it seems to vary with each event, but it appears that you can get paid at least $0.20-0.30 / kWh for avoided or exporting energy usage during "Ohm Hours". The problem is these events don't occur all that regularly...
 
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