Grid tied solar system.

[posplayr]

I am pretty sure a GTI inverter that works 100% in "Island mode" is possible. The question is how much will it cost to design & build, is the price really worth it and will the POCO's allow one to be connected to "their" power distribution system.

The anti island fail safe is a demand of the POCO and while SMA has built their SPS version inverter I am sure they needed to comply with a lot of regulations put on them by the POCO's to make it safe for the Line Man to work on a "dead" grid.

Island mode is more than just possible, it is also NOT any more illegal than running a generator with a transfer switch. Apparently the code requires a mutually exclusive selection between Island mode and Grid Tie. With a GTI inverter that is accomplished with a voltage sense and fail-safe auto-shutoff. The mutual exclusion is the real requirement. Whole house transfer is the most likely implementation of the requirement. A generator can have selective load transfer or a whole house transfer where now have flexibility independent of the POCO requirements but will surely still have to deal with NEC. A power island consisting of both PV GTI in island mode and generator on a whole house transfer is probably the most useful as we all know the sun does not always shine.

[posplayr]

On the solar edge website they show it paired with a tesla battery.

So it raises the question is the Tesla Battery anything else but an oversized UPS? Apparently they see them as linked and perhaps in the way being described.

[posplayr]

I don't understand your comment, maybe you've misunderstood the definition of a hybrid inverter?

I think you have stated you don't understand something, why assume I don't understand? What is it you don't understand.

[posplayr]

Not for the first time, you have written a lengthy post when you have no idea what you are talking about. This issue has nothing to do with 3 phase power: it is related to split phase systems used in the US. You seem like a smart guy and you make some interesting comments, but you need to turn your "dickishness" setting down to say 70 because its current level is more than most of us can stand.

I'm sure you're well aware you can avali yourself of all facilities the forum offset including the ignore option. Your unsolicited personal opinions do little to add to the technical discussion, but I will give you that you are not alone.

I will also assume till I read anything otherwise, that your comments are only a result of an inability to find fault with what I have written. In that light you comment is quite childish which I'll leave at that.

[tehan]

There are two cases: 1.) Either the GTI adopts another mode with output voltage regulation or 2.) an external voltage reference POCO surrogate comes into play. In case #1 a separate set of output are most likely as SB SPS is a prime example and already exists.

A major limitation of SPS is that it does not support split phase operation, precisely the issue that I had raised. So no, it is not an example of a solution to this problem that already exists.

[QUOTE=posplayr;168059In case #2 I have suggested a Double conversion 240V UPS to serve as the POCO surrogate and voltage reference. Unless I'm mistaken a 240V UPS is capable of dealing with any "normal" load imbalance that might be expected.[/QUOTE]

You are mistaken. Most 240V UPS systems do not support split phase operation. Yes, there are systems available that include an autotransformer but they are kind of expensive which was sort of my point.

The "dickishness" comment was indeed childish, but it was truly meant as a helpful suggestion rather than an insult. You are of course free to ignore it. There was sort of a "dickishness" vacuum here after SunKing left so I guess someone has to fill it

[inetdog]

A major limitation of SPS is that it does not support split phase operation, precisely the issue that I had raised. So no, it is not an example of a solution to this problem that already exists.

You are mistaken. Most 240V UPS systems do not support split phase operation. Yes, there are systems available that include an autotransformer but they are kind of expensive which was sort of my point.

The "dickishness" comment was indeed childish, but it was truly meant as a helpful suggestion rather than an insult. You are of course free to ignore it. There was sort of a "dickishness" vacuum here after SunKing left so I guess someone has to fill it

Yes, the SPS is 120V only.
I would take issue with your statement about UPS systems, especially those for the US market. You can get a UPS that is designed for a 240V line to line only load, but you can also get them for split phase (120/240) operation. Those do not necessarily incorporate an autotransformer, but they do need two separately driven 120V output stages.

FYI SK is back and seems to be on his best behavior, namely reasonably polite but still firm with people who are clueless and reject good advice.

[tehan]

Yes, the SPS is 120V only.
I would take issue with your statement about UPS systems, especially those for the US market. You can get a UPS that is designed for a 240V line to line only load, but you can also get them for split phase (120/240) operation. Those do not necessarily incorporate an autotransformer, but they do need two separately driven 120V output stages.

FYI SK is back and seems to be on his best behavior, namely reasonably polite but still firm with people who are clueless and reject good advice.

I sort of figured one of you guys who has installed a bunch of whole home backup systems would say that. So yeah, I certainly accept that the line interactive UPS do exist. But they are more complex, US only, and sort of distinct from the volume economies of the datacenter/telecom market so I stand by the "more expensive" part of my comment.

Must go hunt down SK - have been missing him!

[inetdog]

Must go hunt down SK - have been missing him!

Warning: Do not stick your head inside the Lion cage! It annoys the lion and is unsafe to boot.

[sensij]

I sort of figured one of you guys who has installed a bunch of whole home backup systems would say that. So yeah, I certainly accept that the line interactive UPS do exist. But they are more complex, US only, and sort of distinct from the volume economies of the datacenter/telecom market so I stand by the "more expensive" part of my comment.

Must go hunt down SK - have been missing him!

If the point of most of this thread was to develop support for the idea that a UPS based architecture with a standard grid-tie inverter would be less expensive than a proper hybrid system, the "more expensive" comment with respect to a high power split-phase UPS seems important. Certainly, the UPS used as an example in this post doesn't meet the split phase requirement (and I'm not even finding that model on ebay for the $2000 suggested).

Perhaps if posplayr produced an updated drawing showing his idea as it has been refined by the discussion since it was originally posted, it would be easier to evaluate against the existing methods of providing grid-down power that others have suggested. At this point, I am not convinced there is anything here that is more cost-effective than a standard hybrid system, but the technical discussion has been been interesting, even if plagued by misunderstandings and inaccuracies (my own posts not excluded).

[ButchDeal]

So it raises the question is the Tesla Battery anything else but an oversized UPS? Apparently they see them as linked and perhaps in the way being described.

The Tesla Powerwall battery is not a UPS. it is nothing more than a battery. To use it you need an inverter like the SolarEdge inverter.
SolarEdge has two modes of using a battery. Both have a replacement section at the bottom with the DC attachment and disconnects.
It will be initially available only on the SE7600 model and supposedly with upgrade capabilities for existing SE7600s. The new lower section has an additional DC connection point for the battery, and an additional AC connection for the emergency (backup) circuit panel.
To use it for backup capability an auto transformer is required.

[posplayr]

A major limitation of SPS is that it does not support split phase operation, precisely the issue that I had raised. So no, it is not an example of a solution to this problem that already exists.



You are mistaken. Most 240V UPS systems do not support split phase operation. Yes, there are systems available that include an autotransformer but they are kind of expensive which was sort of my point.

The "dickishness" comment was indeed childish, but it was truly meant as a helpful suggestion rather than an insult. You are of course free to ignore it. There was sort of a "dickishness" vacuum here after SunKing left so I guess someone has to fill it

Tehan, despite being unable to know everything you have written and certainly not everything you are thinking, I do think that I'm in general agreement with most everything you have said here with the exceptions including this point you appear to be making.

If you look at the context of my statement I had divided the possibility of GTI operation for islanding into two classes 1.) GTI without output voltage operation on a single set of lines operating in either Island or non-island modes and #2) GTI operation on a separate output with voltage regulation. The point being that GTI operation on the primary outputs is always not output voltage regulated. So for output voltage regulation you would necessarily need to have a new set of dedicated outputs for Island Mode from a GTI. You could call the GTI with "added hardware" the new output but it has to be distinctly different to the floating GTI outputs.

The relevance of this characterization is that to meet NEC safety requirements for mutual exclusion with POCO power, the only approved method (and I dare say I can't think of another) other than a transfer switch is a default mode to shut off when line voltage drops. So you either find #1) an approved way to use the GTI inverter the way it is without output voltage regulation or #2 you create a separate capability.

From within these two classes split phase operation is a member of the class as well as SB SPS. BTW, I have described a means of doing split phase using two SB SPS with UPS powering a 240 panel for 120 loads. The two phases are total isolated and independent with separate voltage regulation provided by SPS and surge capability provided by the UPS. Is it possible, I think so. Is it practical only with a whole house transfer switch, is it likely? Probably not as it only uses a portion of the total PV output, puts an unorthodox set of line voltages on the panel and is not worth the effort is it is just as easy to get the whole enchilada.

Which gets back to the other thing that comes to mind that your wrote and I disagree with; a separate set of outputs from a GTI for islanding (case #2) is not likely despite the comments above but for the same reasons that you have explained. The GTI does not do output voltage regulation for single phase or split phase!! So if it needs to do it it has to be added. But that is not all that is needed namely, surge capacity (so sort of battery/charging system) as well as the probable utility of integrating a gen set as well and the need for safety interlock. So the GTI is missing too much to think it can do more by adding more stuff into it. It would be far cheaper to use it "as is" as a floating voltage power convertor and accommodate the other functionality outside.


BTW one other thing we can agree on is that your backhanded comments about Sunking are in the vein you suggested.

[posplayr]

You are mistaken. Most 240V UPS systems do not support split phase operation. Yes, there are systems available that include an autotransformer but they are kind of expensive which was sort of my point.

Are you saying this double conversion 240V UPS will not handle a typical household load imbalance? There are cheaper surplus example form decommissioned server farms but lets try this one first.

http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SURT10000XLT

http://www.ebay.com/itm/APC-Smart-UPS-RT-SURT10000XLT-10kVA-8kW-Single-Phase-200-240V-AC-6U-Rack-Mount-/161761955496?hash=item25a9c38ea8

[tehan]

Tehan, despite being unable to know everything you have written and certainly not everything you are thinking, I do think that I'm in general agreement with most everything you have said here with the exceptions including this point you appear to be making.

If you look at the context of my statement I had divided the possibility of GTI operation for islanding into two classes 1.) GTI without output voltage operation on a single set of lines operating in either Island or non-island modes and #2) GTI operation on a separate output with voltage regulation. The point being that GTI operation on the primary outputs is always not output voltage regulated. So for output voltage regulation you would necessarily need to have a new set of dedicated outputs for Island Mode from a GTI. You could call the GTI with "added hardware" the new output but it has to be distinctly different to the floating GTI outputs.

The relevance of this characterization is that to meet NEC safety requirements for mutual exclusion with POCO power, the only approved method (and I dare say I can't think of another) other than a transfer switch is a default mode to shut off when line voltage drops. So you either find #1) an approved way to use the GTI inverter the way it is without output voltage regulation or #2 you create a separate capability.

From within these two classes split phase operation is a member of the class as well as SB SPS. BTW, I have described a means of doing split phase using two SB SPS with UPS powering a 240 panel for 120 loads. The two phases are total isolated and independent with separate voltage regulation provided by SPS and surge capability provided by the UPS. Is it possible, I think so. Is it practical only with a whole house transfer switch, is it likely? Probably not as it only uses a portion of the total PV output, puts an unorthodox set of line voltages on the panel and is not worth the effort is it is just as easy to get the whole enchilada.

Which gets back to the other thing that comes to mind that your wrote and I disagree with; a separate set of outputs from a GTI for islanding (case #2) is not likely despite the comments above but for the same reasons that you have explained. The GTI does not do output voltage regulation for single phase or split phase!! So if it needs to do it it has to be added. But that is not all that is needed namely, surge capacity (so sort of battery/charging system) as well as the probable utility of integrating a gen set as well and the need for safety interlock. So the GTI is missing too much to think it can do more by adding more stuff into it. It would be far cheaper to use it "as is" as a floating voltage power convertor and accommodate the other functionality outside.


BTW one other thing we can agree on is that your backhanded comments about Sunking are in the vein you suggested.

I'm not going to respond to all the points in your long-winded and boring post. But most everything you say is wrong. And look, don't take my word for it. Go research the product roadmaps for Fronius and SolarEdge, both of whom have announced and publicly demonstrated GTI models with off-grid capability. In both cases, these products are based on modest adaptations to their existing GTI designs, not on the absurd UPS scheme you have suggested. There are many reasons this approach is superior: some economic, some safety-related, and some related to desirable product capabilities. But I really have no interest in debating any of this with you while you continue to have your "dickishness" level set to 11.

[tehan]

Are you saying this double conversion 240V UPS will not handle a typical household load imbalance? There are cheaper surplus example form decommissioned server farms but lets try this one first.

http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=SURT10000XLT

http://www.ebay.com/itm/APC-Smart-UP...item25a9c38ea8

I'm not going to go find the datasheet for that specific model. But I am very familiar with the UPS units typically found in datacenters and no, they generally do not support split phase operation.

[posplayr]

I'm not going to respond to all the points in your long-winded and boring post. But most everything you say is wrong. And look, don't take my word for it. Go research the product roadmaps for Fronius and SolarEdge, both of whom have announced and publicly demonstrated GTI models with off-grid capability. In both cases, these products are based on modest adaptations to their existing GTI designs, not on the absurd UPS scheme you have suggested. There are many reasons this approach is superior: some economic, some safety-related, and some related to desirable product capabilities. But I really have no interest in debating any of this with you while you continue to have your "dickishness" level set to 11.

Tapped you out I guess.