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drees
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Re: The Enphase Energy Management System

Tue Nov 04, 2014 1:50 am

RegGuheert wrote:Will owners of S275 microinverters be able to go to their Envoys and turn on a new "Snow Melt" mode?

The S275 will be mounted in the battery module in your garage sitting in between the batteries and the grid - not your solar panels and grid.
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RegGuheert
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Re: The Enphase Energy Management System

Tue Nov 04, 2014 2:09 am

drees wrote:
RegGuheert wrote:Will owners of S275 microinverters be able to go to their Envoys and turn on a new "Snow Melt" mode?

The S275 will be mounted in the battery module in your garage sitting in between the batteries and the grid - not your solar panels and grid.
Actually, they will be used in BOTH places. But, by far, most of them will be installed with PV panels since the grid battery market has yet to develop. Here is a picture of the S275 microinverter:

Image

According to this article in GreenTechSolar, the main thrust of these new bi-directional microinverters is to provide power-factor control for the grid:
GreenTechSolar wrote: Paul Nahi, Enphase's CEO, said the firm's fifth-generation microinverter is its "most technologically advanced microinverter -- this was not even possible to do when we started the company."

He noted that the 275-watt, 97 percent CEC efficiency microinverter "needed to address the complexity of the grid" with reactive power control, volt/VAR and ride-through.
For reference, here is a paper which discusses the details of microinverter VAR control in much more detail. While it focuses on VAR control schemes at nighttime, it also references other papers on the topic. It does appear that the discussion is relevant to the latest Enphase architecture. Also, CalTech has written a much more technical paper which is less inverter-focused and more grid-issue focused.

But VAR control will prove to be a contentious issue, since it mostly benefits the utilities as the fraction of solar increases at the expense of the owner of the PV installation. As such, there should be compensation provided by the utility for this valuable capability. Can anyone say "even more complicated rate structures in CA"?

Unfortunately, it seems that my desire for snow melting is not on the radar...
RegGuheert
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2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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drees
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Re: The Enphase Energy Management System

Tue Nov 04, 2014 11:11 pm

RegGuheert wrote:Actually, they will be used in BOTH places.

I stand corrected. :-)

I am excited about the 97% efficiency number (though the new IG inverters are nearly there at 96.5%) and the 275W rating. High efficiency will be critical for an energy management system and by next year I suspect 300W panels will be fairly common even for residential installs.

The GTM article notes Enphase's battery supplier ELIIY Power and has this to say which I found interesting:

According to Belur, after an extensive global search for the right battery chemistry and vendor, Enphase sourced ELIIY Power's lithium-iron-phosphate battery, a chemistry known for its safe operation which is also used by battery vendor A123. Nahi said that ELIIY is "extremely cost-competitive in this space." Belur noted that with all due respect, he is very surprised by the high prices being quoted for batteries from companies like Tesla or SolarCity.
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Re: The Enphase Energy Management System

Wed Nov 05, 2014 6:05 am

I have to say that I really like Enphase's market approach here. Some more thoughts:

- Surprising, but Logical!: Obviously, I didn't see this one coming. (Perhaps QueenBee did?) That said, it's a logical next step enabled by the miracle that is modern power electronics. Just like a "Brushless DC Motor" is really an AC synchronous motor with an electronic commutator to allow connection to a DC power source, we need to get used to the idea that an "AC battery" is reall a DC battery with an electronic interface to the power grid.

- Leverages Strengths, Minimizes Development Costs: Enphase has come up with an approach which leverages their strength in microinverters and at the same time will support their position in the overall PV market. This approach minimizes their development costs and risks and should allow them to slowly and steadily ramp up this product as the market grows. It will be interesting to see Enphase try to convince their customers to purchase batteries after telling them for years that batteries were liabilities.

- Emerging Market: The market for chemical batteries for grid storage is in its very early stages. Utilities have wanted to do this for many decades, but cost and reliability concerns have limited grid storage primarily to pumped hydro (which is currently growing rapidly worldwide).

- Very Low Barriers for Entry: Enphase's offering minimizes the barriers to entry by reducing the cost, risk and difficulty of adding grid storage to any installation. They also allow an incremental approach to adding AC batteries. This should give Enphase access to a large base of early adopters who already own and (mostly) trust Enphase microinverters for their PV systems. It will be trivial to "dip your toe into the water" of grid storage technologies with this product. (The exception here could be related to regulatory issues that utilities may try to put into place to restrict the installation of these devices.)

- Low Cost: As drees has pointed out, cost is the key issue that Enphase must focus on in order to grow this market. And even then, it will likely be limited to areas with steep TOU rate structures. That is likely to be a steadily-growing market as energy becomes a more and more expensive commodity and/or net metering becomes less available.

- Future Support for Grid Failures? If Enphase wants to create a much larger market for this product, they will need to come up with an offering that will provide power in the case of grid interruption. While I do not expect to see such a capability for at least a few years, such an offering would directly compete with traditional battery-based inverters and eventually even home backup generators (when combined with controllable microinverter-based PV).

- Batteries and Microinverters on Similar Growth Path: I expect Li-ion battery capacity to grow at a steady rate, just as we see happening with PV module and microinverter power ratings. That should allow the AC battery to steadily improve as all three technologies mature together.

- Safety is Critical: Safety will be a critical issue for this product. That has always been a hallmark of microinverters, but the addition of Li-ion batteries to the mix changes the equation significantly. If there is even a single house fire caused by one of these AC batteries, the market for this product could quickly disappear. Because of this, I will be a bit surprised if these units actually come in a plastic package.

- Reliability is Critical: Reliability will also be critical to the success of this unit. Obviously, the battery is the main concern here. But I will point out that even with the hardware design for the microinverter being shared with the PV version, it does NOT follow that the microinverter will be as reliable in the battery as it is on the rooftop. This is because on the rooftop the PV module has distinct limits on the amount of current and voltage that it can deliver. In the battery application, the inverter now faces very low-impedance sources on BOTH the AC and the DC sides. Drawing power from the AC side also adds new forms of stress to the inverter that Enphase inverters have not previously faced. These facts can make it more challenging to keep all the components in their safe operating areas. I expect the firmware for the battery application will take a few iterations to iron out. Overall, I do not expect the AC Battery to be as reliable as the microinverters on the roof. Clearly, neither does Enphase, given that the warranty period is only 40% as long.

- Will EVs Compete? My first thought was that Enphase's main competition in this space might come from EVs. My reasoning was that as EV battery capacity and reliability improves, EVs should be able to provide more-and-more grid-interactive capabilities. And personally, I do not relish the idea of purchasing and servicing batteries for BOTH the car and the house. But the EV may not be able to fill the role that Enphase is targeting since the EV will often not be at home when the PV is producing and will also need to charge when the PV is NOT producing. As such, Enphase should be able to provide capabilities that EVs cannot touch.

Overall, I do not expect these things to fly off the shelves anytime soon. But Enphase's approach allows them to deliver a product into the market with a minimum amount of development and manufacturing costs, which should allow them to withstand a very slow market ramp-up and learn as the units get deployed. It will be interesting to watch.
RegGuheert
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Enphase Inverter Measured MTBF: M190, M215, M250, S280

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Re: The Enphase Energy Management System

Wed Nov 05, 2014 8:28 am

A very interesting thing to be sure - a neatly packaged "bolt-on" battery storage unit!

My only let-down is the capacity. 1.2kWh. Unless there is a mechanism to allow the Enphase equipment to operate in island mode when the grid is not available, I'd need quite a few of those to make it through a typical power outage scenario without resorting to generator power.

So what would really be needed is the intelligence to selectively disable the output of some or all of the solar panels to try and match the actual building load, using the batteries to deliver/absorb the difference. With a system like that I'd only need about 5 of these battery units to make it through a typical winter evening assuming the panels operated during the day to make it up.
=Smidge=

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Re: The Enphase Energy Management System

Thu Nov 06, 2014 12:11 am

Smidge204 wrote:My only let-down is the capacity. 1.2kWh. Unless there is a mechanism to allow the Enphase equipment to operate in island mode when the grid is not available, I'd need quite a few of those to make it through a typical power outage scenario without resorting to generator power.

So what would really be needed is the intelligence to selectively disable the output of some or all of the solar panels to try and match the actual building load, using the batteries to deliver/absorb the difference. With a system like that I'd only need about 5 of these battery units to make it through a typical winter evening assuming the panels operated during the day to make it up.

You can count on this system being able to effectively island. It will require a utility disconnect to prevent the grid from being energized when doing so.

In a true power emergency, you will be able to cut out non-critical loads - 5 is probably a decent number, but I figure that a typical house will probably want 10 or so, which is why I feel that 1.2 kWh is small. It seems that they purposely limited the size so that each unit was a manageable weight at ~40 lbs. But I think even 50-60 lbs would have been fine and it would have gotten the size up a bit.

I find it interesting that each storage unit will be offered in two power capacities of 275/550W. I suppose if you only have 5 of these you will probably want the 550W version. But if you have 20 of them, you might be able to get away with the 275W version.
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Re: The Enphase Energy Management System

Thu Nov 06, 2014 5:59 am

drees wrote:You can count on this system being able to effectively island.
I see no indication that this system will be able to island. In fact, everything I see tells me that this unit will perform anti-islanding as effectively as the current Enphase inverters. Here are a few indications:

- No mention of grid-out capabilities from Enphase for this system. What are listed are utility-bill reduction and grid stabilization for higher levels of grid penetration. Truly this product is designed to prevent Enphase's PV market from saturating.
- S275 inverters are specified for both the PV inverters and the battery inverters. While they will likely have different firmware, the will likely share the strong anti-islanding reputation that Enphase has built in order to be accepted by regulatory agencies and utilities.
- The AC Battery is connected in parallel with the grid. As such, it is likely REQUIRED to anti-island by code. Relying on communication with an external unit to permit islanding likely does not meet safety requirements.
- Prior art from Enphase in their patent disclosures indicates that their inverters are current sources on the AC side. This new inverter is certainly different than the older ones, but I suspect when it is used as an inverter (versus as a charger) it will operate in a similar manner to the PV inverters to maximize efficiency.

My expectation is that the Enphase will release an additional component in the future for their energy management system which will enable islanding. This component will likely be equivalent to the SMA Sunny Island and will provide the disconnect equipment, a voltage-source inverter to act as the grid reference and a controller for the PV inverters and the AC Battery units. Until they field some sort of storage unit, they are not able to provide any answer to the Sunny Island.
RegGuheert
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Enphase Inverter Measured MTBF: M190, M215, M250, S280

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Re: The Enphase Energy Management System

Thu Nov 06, 2014 6:04 am

DNAinaGoodWay wrote:Even without solar, if you could charge them at super off peak rates, and use that energy during peak rate times, they could pay for themselves.
The utility companies fear the destruction of their business model for this very scenario . . . . PV owners loading up batteries at the cheep rate ... then selling it back to the utility during high demand. Their lobby has already made inroads with attempting to assure PV is a looser for prospective installations - so that this scenerio will not happen.
.

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Re: The Enphase Energy Management System

Thu Nov 06, 2014 8:02 am

RegGuheert wrote:I see no indication that this system will be able to island.

Me neither, and that makes this tech more of a curiosity than anything practical, at least as far as what I'm looking for.

You would still need an AC coupling inverter and a (small) battery/generator to make this system work as an island. The coupling inverter performs the grid isolation and takes a small amount of power from a battery or other source to provide "grid quality" voltage and frequency to get the solar equipment to wake up. Since the Enphase battery packs almost certainly want to see grid frequency you can't use them as the "seed" power source. Might as well use a traditional battery bank and charge manager.
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Re: The Enphase Energy Management System

Sun May 31, 2015 4:29 am

RegGuheert wrote:
drees wrote:You can count on this system being able to effectively island.
I see no indication that this system will be able to island. In fact, everything I see tells me that this unit will perform anti-islanding as effectively as the current Enphase inverters. Here are a few indications:

- No mention of grid-out capabilities from Enphase for this system. What are listed are utility-bill reduction and grid stabilization for higher levels of grid penetration. Truly this product is designed to prevent Enphase's PV market from saturating.
- S275 inverters are specified for both the PV inverters and the battery inverters. While they will likely have different firmware, the will likely share the strong anti-islanding reputation that Enphase has built in order to be accepted by regulatory agencies and utilities.
- The AC Battery is connected in parallel with the grid. As such, it is likely REQUIRED to anti-island by code. Relying on communication with an external unit to permit islanding likely does not meet safety requirements.
- Prior art from Enphase in their patent disclosures indicates that their inverters are current sources on the AC side. This new inverter is certainly different than the older ones, but I suspect when it is used as an inverter (versus as a charger) it will operate in a similar manner to the PV inverters to maximize efficiency.

My expectation is that the Enphase will release an additional component in the future for their energy management system which will enable islanding. This component will likely be equivalent to the SMA Sunny Island and will provide the disconnect equipment, a voltage-source inverter to act as the grid reference and a controller for the PV inverters and the AC Battery units. Until they field some sort of storage unit, they are not able to provide any answer to the Sunny Island.
Here is a fairly-recent article written by a manager at Enphase. She discusses a use case (in Hawaii, of course) in which the homeowner saves almost $40,000 in 15 years by time-shifting with these things: Weighing the Advantages of Distributed and Centralized Energy Storage. Unfortunately, she only vaguely mentions e assumptions used in that analysis, so it cannot be easily verified. Perhaps we can take a poke at it sometime.

But she does also mention grid-independent modes of operation, so it is on definitely on Enphase's radar. I'll stand by my assertion above that this will not come in the first wave of the AC Battery product offerings. Time will tell.
RegGuheert
2011 Leaf SL Demo vehicle
2011 miles at purchase. 10K miles on Apr 14, 2013. 20K miles (55.7Ah) on Aug 7, 2014, 30K miles (52.0Ah) on Dec 30, 2015, 40K miles (49.8Ah) on Feb 8, 2017.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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