Re: [RE-wrenches] Running a grid tied system when the grid is down
Yes it can be done, I was testing the sma1800 years ago with an outback 24 volt inverter and it worked fine with in its power range. On Fri, Sep 20, 2019, 6:41 AM Dave Tedeyan wrote: > Hi all, > > I get asked this question frequently, as I am sure many others do, and of > course the first answer is "it cannot be done". But can it? I have a > customer who is very keen on trying to make this happen. After a few > lengthy conversations, he still wants to try it, even after understanding > the limitations (i.e. a cloud passes by and now you cannot power loads...) > > I have some thoughts on how to make this work, and thought I would post it > here to get others comments who I am sure have more experience in something > like this than I do. > > -PV system would have to be backfed, so that they can turn off the main > breaker to disconnect from the utility entirely (and then have to look at > the neighbors, or guess when the grid comes back) > -Have a fairly small 12V off grid inverter/charger than can be powered by > a single 12v battery. This inverter would have to be manually turned off > until after the grid is down and the main breaker is disconnected. > -Would also need an auto transformer to bump up the voltage to 240V. > Something like the Outback PSX240. > -Once the main breaker is off and the off grid inverter is on, would it be > able to wake up the grid tied inverters? On this project, there are two SMA > SB-40 inverters. > -There would need to be some kind of dump/diversion load to deal with > excess power coming from the GT inverters. I have not used these in the > past, but are the controllers smart enough to just deal with any excess > power in the system? > -Have a trickle charger on the battery to keep it topped off most of the > time. > > -Another thought would be to DC couple. This would involve having a DC > switch in one of the strings going to the GT inverter, such that when the > house is islanded from the grid, they can flip the switch and have that one > string go to a high voltage CC. Then they could just run some small loads > off the power from that one string, or maybe we could allow it to try to > wake up the GT inverters as well. > > This particular homeowner specifically does not want much in the way of > batteries and has a smaller budget than will allow something sensible like > a Sunny Island. > > At least in upstate NY, there are many people who would like to be able to > take advantage of their solar when the sun is shining, but who just do not > have the budget for a legit battery system. I am somewhat surprised that > there is no simple industry solution for this yet, although maybe it is > more complicated than I am making it out to be. And of course, you need a > very hands on homeowner who very well understands the limitations of this > kind of setup. > > I would certainly appreciate any feedback or comments on this, and also > would like to hear if anyone has tried this kind of setup before. > > Thanks much! > -Dave > > *Dave Tedeyan, PE* > Senior Engineer | Taitem Engineering, PC > > 110 South Albany Street | Ithaca, NY 14850 > o. *607.277.1118 x121* f. 607.277.2119 > www.taitem.com > > Solar • Sustainability • Energy • Design > B-Corporation Best for the World 2018 Honoree > ___ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > ___ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] Running a grid tied system when the grid is down
If using SMA’s Rapid Shutdown System, the SPS function is available as RS is initiated in the manner you described. If using the TS4 units for 2017 690.12 compliance, the SPS function is not available on the SB US-40. Each SPS circuit is independent – there is no way for two Sunny Boys to synchronize their SPS waveforms. One SPS output can be wired to safely power existing circuits to avoid having to swap plug location for loads to be run by SPS. A small 120VAC circuit transfer switch like the unit from Reliance that Goal Zero shows in REIs can do the trick (link below). The one shown by Goal Zero shows a NEMA 5-15 plug installed but since the SPS can provide 2000W, you would want to hardware the SPS into the similar hardwire Reliance unit rather than the unit with 15A plug. This transfer switch allows homeowners to swap up to four exiting home circuits from grid to SPS power should the grid fail. The SPS switch for the Sunny Boy is still required in addition to this transfer switch https://www.goalzero.com/shop/yeti-accessories/yeti-home-integration-kit/ Best regards – Mike SMA America Michael Mahon Technical Trainer, Solar Academy 6020 West Oaks Boulevard, Suite 300 Rocklin, CA 95765 U.S.A. Mobile: +1 916 918 9412 www.SMA-America.com<http://www.sma-america.com/> Solar Academy: www.SMA-America.com/partners/sma-solar-academy/overview.html<http://www.sma-america.com/partners/sma-solar-academy/overview.html> Full training schedule: https://www.sma-america.com/partners/sma-solar-academy/seminars/trainings/training/list.html [http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/facebook.jpg]<http://www.facebook.com/pages/SMA-America/140290312717395>[http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/twitter.jpg]<http://twitter.com/SMA_America> [http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/wordpress.jpg] <http://www.smainverted.com/> [Linkedin Logo] <http://www.linkedin.com/company/364675> [http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/youtube.jpg] <http://www.youtube.com/playlist?list=PL840A5336CAC32332> [SMAAFORUM_ICON] <http://smaadvance.com/signup/> [cid:image008.jpg@01D54D07.DC1BFFF0]<https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.sma-america.com%2Fhome-systems%2Fpv-solar-and-storage-solutions.html=02%7C01%7CMichael.Mahon%40sma-america.com%7Cc4bcd59d55584c70681208d71b72e485%7Ca059b96c28294d1188374cc1ff84735d%7C0%7C0%7C637008052588484449=itzAGcXAYe0xd5Zhzjuljm6dijJW%2FRGtItHrvxRkrTI%3D=0> This email and any attachments thereto may contain SMA America, LLC confidential, privileged and private material for the sole use of the intended recipient. Any review, copying, or distribution of this email (or any attachments thereto) by others is strictly prohibited. If you are not the intended recipient, please contact the sender immediately and permanently delete the original and any copies of this email and any attachments thereto. Thank you. From: RE-wrenches On Behalf Of Dave Tedeyan Sent: Friday, September 20, 2019 8:52 AM To: RE-wrenches Subject: Re: [RE-wrenches] Running a grid tied system when the grid is down Hi Brad, Not a bad idea with this one to run the loads off the SPS's. Has anyone ever tried wiring these directly into a panel, rather than into an outlet? And do you know if the 120V signal from each one would match up, or do they work independantly? In other words can you wire both SPS into the same panel either on different legs, or on the same leg and use an autoxfr? And with the Rapid shutdown and SPS. Does it not work with SMA's rapid shutdown box? I thought with those, the grid going down would not affect the rapid shutdown, and that it needs the signal from the controller to initiate RSD. So this way it will continue to work with the grid down. Cheers, Dave Dave Tedeyan, PE Senior Engineer | Taitem Engineering, PC [https://www.taitem.com/signatures/logo.png] 110 South Albany Street | Ithaca, NY 14850 o. 607.277.1118 x121 f. 607.277.2119 www.taitem.com<https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.taitem.com=02%7C01%7Cmichael.mahon%40sma-america.com%7C47e56e91c6db4419d10308d73dda238b%7Ca059b96c28294d1188374cc1ff84735d%7C0%7C0%7C637045879462991829=l%2Fy5ThDRnjZAvBhv46d7F0Jjnj3IXhFgayrS8%2BBNwcE%3D=0> Solar • Sustainability • Energy • Design B-Corporation Best for the World 2018 Honoree On Fri, Sep 20, 2019 at 10:33 AM Bradley Bassett mailto:bbasse...@gmail.com>> wrote: If you're not using the SB -40 inverter's rapid shutdown system, it has the SPS Secure Power Supply which does just what your customer wants. My understanding from talking to inverter mfg, is that trying to do AC coupling with a smaller battery inverters does not work because the anti-islanding in the grid tie inverter will be able to push the frequency off too easily. Morningstar makes a 600 VDC charge co
Re: [RE-wrenches] Running a grid tied system when the grid is down
I replied to another message about code/RS. Each SPS circuit is independent, so no 240V waveform possible. And as was mentioned by Dave, be careful about planning to have motors or pumps be started by the SPS. The array cannot provide surge current like a battery, so the inverter is limited too. So check the specs of heat pump… Best- Mike SMA America Michael Mahon Technical Trainer, Solar Academy 6020 West Oaks Boulevard, Suite 300 Rocklin, CA 95765 U.S.A. Mobile: +1 916 918 9412 www.SMA-America.com<http://www.sma-america.com/> Solar Academy: www.SMA-America.com/partners/sma-solar-academy/overview.html<http://www.sma-america.com/partners/sma-solar-academy/overview.html> Full training schedule: https://www.sma-america.com/partners/sma-solar-academy/seminars/trainings/training/list.html [http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/facebook.jpg]<http://www.facebook.com/pages/SMA-America/140290312717395>[http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/twitter.jpg]<http://twitter.com/SMA_America> [http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/wordpress.jpg] <http://www.smainverted.com/> [Linkedin Logo] <http://www.linkedin.com/company/364675> [http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/youtube.jpg] <http://www.youtube.com/playlist?list=PL840A5336CAC32332> [SMAAFORUM_ICON] <http://smaadvance.com/signup/> [cid:image008.jpg@01D54D07.DC1BFFF0]<https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.sma-america.com%2Fhome-systems%2Fpv-solar-and-storage-solutions.html=02%7C01%7CMichael.Mahon%40sma-america.com%7Cc4bcd59d55584c70681208d71b72e485%7Ca059b96c28294d1188374cc1ff84735d%7C0%7C0%7C637008052588484449=itzAGcXAYe0xd5Zhzjuljm6dijJW%2FRGtItHrvxRkrTI%3D=0> This email and any attachments thereto may contain SMA America, LLC confidential, privileged and private material for the sole use of the intended recipient. Any review, copying, or distribution of this email (or any attachments thereto) by others is strictly prohibited. If you are not the intended recipient, please contact the sender immediately and permanently delete the original and any copies of this email and any attachments thereto. Thank you. From: RE-wrenches On Behalf Of Dave Tedeyan Sent: Friday, September 20, 2019 9:07 AM To: RE-wrenches Subject: Re: [RE-wrenches] Running a grid tied system when the grid is down Hi Mike, For rapid shutdown, we are on NEC2014 in NY. So module level is not necessary. And the SPS is a huge reason for the SB inverters on this one. And in this case, it is almost exactly what the homeowner is looking for. But with the two inverters, can those SPS be wired into a panel rather than just into an outlet? So far, this customers house has not even been built yet. The barn is up, which is where the solar is going. So I am not 100% sure about loads, but there will likely be heat pumps. So if the SPS's can put power the same panel, then that might be just what I am looking for in this particular case. Although I am still curious if others have retrofitted other systems with something like I was initially talking about for an inverter that does not have a SPS. I think that at least in this market a low end 3rd party solution could gain a lot of traction. Dave Tedeyan, PE Senior Engineer | Taitem Engineering, PC [https://www.taitem.com/signatures/logo.png] 110 South Albany Street | Ithaca, NY 14850 o. 607.277.1118 x121 f. 607.277.2119 www.taitem.com<https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.taitem.com=02%7C01%7Cmichael.mahon%40sma-america.com%7Ca0cd26ef34764822fec208d73ddc4180%7Ca059b96c28294d1188374cc1ff84735d%7C0%7C0%7C637045888514385004=akgnbkMo1%2FmNn9%2FSBccmGbEk%2F6bJEEeA9x7lBwOjjt4%3D=0> Solar • Sustainability • Energy • Design B-Corporation Best for the World 2018 Honoree On Fri, Sep 20, 2019 at 10:58 AM Harry Mahon mailto:michael.ma...@sma-america.com>> wrote: Dave – how is Rapid Shutdown being complied with? And what load requires 240V – or is that needed to “fool” the PV inverters? With two SB-40s, you have the ability to wire for the homeowner two Secure Power Supply circuits – and get up to 2000W (at 120VAC) from each when sun is up and grid is down, no batteries or extra inverter needed. This is exactly the “simple industry solution” you mention, and it has been available in US from Sunny Boys only since 2013. Best regards - Mike SMA America Michael Mahon Technical Trainer, Solar Academy 6020 West Oaks Boulevard, Suite 300 Rocklin, CA 95765 U.S.A. Mobile: +1 916 918 9412 www.SMA-America.com<https://eur02.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.sma-america.com%2F=02%7C01%7Cmichael.mahon%40sma-america.com%7Ca0cd26ef34764822fec208d73ddc4180%7Ca059b96c28294d1188374cc1ff84735d%7C0%7C0%7C637045888514385004=kB7N%2BWcEAGDtmqJerT8POyIi8KbEPG0%2FODJ5FeTMeO4%3D=0> Solar Acad
Re: [RE-wrenches] Running a grid tied system when the grid is down
The downside of the SMA SPS is there is very little headroom to surge and start a well pump or a fire pump. There is also the major problem of sundown. Dave Angelini Offgrid Solar "we go where powerlines don't" http://members.sti.net/offgridsolar/ [1] e-mail offgridso...@sti.net [2] text 209 813 0060 On Fri, 20 Sep 2019 11:07:12 -0400, Dave Tedeyan wrote: Hi Mike, For rapid shutdown, we are on NEC2014 in NY. So module level is not necessary. And the SPS is a huge reason for the SB inverters on this one. And in this case, it is almost exactly what the homeowner is looking for. But with the two inverters, can those SPS be wired into a panel rather than just into an outlet? So far, this customers house has not even been built yet. The barn is up, which is where the solar is going. So I am not 100% sure about loads, but there will likely be heat pumps. So if the SPS's can put power the same panel, then that might be just what I am looking for in this particular case. Although I am still curious if others have retrofitted other systems with something like I was initially talking about for an inverter that does not have a SPS. I think that at least in this market a low end 3rd party solution could gain a lot of traction. DAVE TEDEYAN, PE Senior Engineer | Taitem Engineering, PC 110 South Albany Street | Ithaca, NY 14850 o. 607.277.1118 x121 f. 607.277.2119 www.taitem.com [3] Solar * Sustainability * Energy * Design B-Corporation Best for the World 2018 Honoree On Fri, Sep 20, 2019 at 10:58 AM Harry Mahon wrote: Dave - how is Rapid Shutdown being complied with? And what load requires 240V - or is that needed to "fool" the PV inverters? With two SB-40s, you have the ability to wire for the homeowner two Secure Power Supply circuits - and get up to 2000W (at 120VAC) from each when sun is up and grid is down, no batteries or extra inverter needed. This is exactly the "simple industry solution" you mention, and it has been available in US from Sunny Boys only since 2013. Best regards - Mike SMA America Michael Mahon Technical Trainer, Solar Academy 6020 West Oaks Boulevard, Suite 300 Rocklin, CA 95765 U.S.A. Mobile: +1 916 918 9412 www.SMA-America.com [5] Solar Academy: www.SMA-America.com/partners/sma-solar-academy/overview.html [6] Full training schedule: https://www.sma-america.com/partners/sma-solar-academy/seminars/trainings/training/list.html [7] This email and any attachments thereto may contain SMA America, LLC confidential, privileged and private material for the sole use of the intended recipient. Any review, copying, or distribution of this email (or any attachments thereto) by others is strictly prohibited. If you are not the intended recipient, please contact the sender immediately and permanently delete the original and any copies of this email and any attachments thereto. Thank you. FROM: RE-wrenches ON BEHALF OF Dave Tedeyan SENT: Friday, September 20, 2019 7:41 AM TO: RE-wrenches SUBJECT: [RE-wrenches] Running a grid tied system when the grid is down Hi all, I get asked this question frequently, as I am sure many others do, and of course the first answer is "it cannot be done". But can it? I have a customer who is very keen on trying to make this happen. After a few lengthy conversations, he still wants to try it, even after understanding the limitations (i.e. a cloud passes by and now you cannot power loads...) I have some thoughts on how to make this work, and thought I would post it here to get others comments who I am sure have more experience in something like this than I do. -PV system would have to be backfed, so that they can turn off the main breaker to disconnect from the utility entirely (and then have to look at the neighbors, or guess when the grid comes back) -Have a fairly small 12V off grid inverter/charger than can be powered by a single 12v battery. This inverter would have to be manually turned off until after the grid is down and the main breaker is disconnected. -Would also need an auto transformer to bump up the voltage to 240V. Something like the Outback PSX240. -Once the main breaker is off and the off grid inverter is on, would it be able to wake up the grid tied inverters? On this project, there are two SMA SB-40 inverters. -There would need to be some kind of dump/diversion load to deal with excess power coming from the GT inverters. I have not used these in the past, but are the controllers smart enough to just deal with any excess power in the system? -Have a trickle charger on the battery to keep it topped off most of the time. -Another thought would be to DC couple. This would involve having a DC switch in one of the strings going to the GT inverter, such that when the house is islanded from the grid, they can flip the switch and have that one string go to a high voltage CC. Then they could just run some small
Re: [RE-wrenches] Running a grid tied system when the grid is down
Hi Mike, For rapid shutdown, we are on NEC2014 in NY. So module level is not necessary. And the SPS is a huge reason for the SB inverters on this one. And in this case, it is almost exactly what the homeowner is looking for. But with the two inverters, can those SPS be wired into a panel rather than just into an outlet? So far, this customers house has not even been built yet. The barn is up, which is where the solar is going. So I am not 100% sure about loads, but there will likely be heat pumps. So if the SPS's can put power the same panel, then that might be just what I am looking for in this particular case. Although I am still curious if others have retrofitted other systems with something like I was initially talking about for an inverter that does not have a SPS. I think that at least in this market a low end 3rd party solution could gain a lot of traction. *Dave Tedeyan, PE* Senior Engineer | Taitem Engineering, PC 110 South Albany Street | Ithaca, NY 14850 o. *607.277.1118 x121* f. 607.277.2119 www.taitem.com Solar • Sustainability • Energy • Design B-Corporation Best for the World 2018 Honoree On Fri, Sep 20, 2019 at 10:58 AM Harry Mahon wrote: > Dave – how is Rapid Shutdown being complied with? And what load requires > 240V – or is that needed to “fool” the PV inverters? > > > > With two SB-40s, you have the ability to wire for the homeowner two Secure > Power Supply circuits – and get up to 2000W (at 120VAC) from each when sun > is up and grid is down, no batteries or extra inverter needed. > > > > This is exactly the “simple industry solution” you mention, and it has > been available in US from Sunny Boys only since 2013. > > > > Best regards - > > Mike > > > > SMA America > Michael Mahon > Technical Trainer, Solar Academy > 6020 West Oaks Boulevard, Suite 300 > > Rocklin, CA 95765 > > U.S.A. > Mobile: +1 916 918 9412 > * www.SMA-America.com <http://www.sma-america.com/>* > > > > Solar Academy: > www.SMA-America.com/partners/sma-solar-academy/overview.html > <http://www.sma-america.com/partners/sma-solar-academy/overview.html> > > > > Full training schedule: > https://www.sma-america.com/partners/sma-solar-academy/seminars/trainings/training/list.html > > > > > > [image: > http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/facebook.jpg] > <http://www.facebook.com/pages/SMA-America/140290312717395>[image: > http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/twitter.jpg] > <http://twitter.com/SMA_America> [image: > http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/wordpress.jpg] > <http://www.smainverted.com/> [image: Linkedin Logo] > <http://www.linkedin.com/company/364675> [image: > http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/youtube.jpg] > <http://www.youtube.com/playlist?list=PL840A5336CAC32332> [image: > SMAAFORUM_ICON] <http://smaadvance.com/signup/> > > [image: cid:image008.jpg@01D54D07.DC1BFFF0] > <https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.sma-america.com%2Fhome-systems%2Fpv-solar-and-storage-solutions.html=02%7C01%7CMichael.Mahon%40sma-america.com%7Cc4bcd59d55584c70681208d71b72e485%7Ca059b96c28294d1188374cc1ff84735d%7C0%7C0%7C637008052588484449=itzAGcXAYe0xd5Zhzjuljm6dijJW%2FRGtItHrvxRkrTI%3D=0> > > > > > > This email and any attachments thereto may contain SMA America, LLC > confidential, privileged and private material for the sole use of the > intended recipient. Any review, copying, or distribution of this email (or > any attachments thereto) by others is strictly prohibited. If you are not > the intended recipient, please contact the sender immediately and > permanently delete the original and any copies of this email and any > attachments thereto. Thank you. > > > > *From:* RE-wrenches *On > Behalf Of *Dave Tedeyan > *Sent:* Friday, September 20, 2019 7:41 AM > *To:* RE-wrenches > *Subject:* [RE-wrenches] Running a grid tied system when the grid is down > > > > Hi all, > > > > I get asked this question frequently, as I am sure many others do, and of > course the first answer is "it cannot be done". But can it? I have a > customer who is very keen on trying to make this happen. After a few > lengthy conversations, he still wants to try it, even after understanding > the limitations (i.e. a cloud passes by and now you cannot power loads...) > > > > I have some thoughts on how to make this work, and thought I would post it > here to get others comments who I am sure have more experience in something > like this than I do. > > > > -PV system would have to be backfed, so that they can turn off the main > breaker to discon
Re: [RE-wrenches] Running a grid tied system when the grid is down
Dave – how is Rapid Shutdown being complied with? And what load requires 240V – or is that needed to “fool” the PV inverters? With two SB-40s, you have the ability to wire for the homeowner two Secure Power Supply circuits – and get up to 2000W (at 120VAC) from each when sun is up and grid is down, no batteries or extra inverter needed. This is exactly the “simple industry solution” you mention, and it has been available in US from Sunny Boys only since 2013. Best regards - Mike SMA America Michael Mahon Technical Trainer, Solar Academy 6020 West Oaks Boulevard, Suite 300 Rocklin, CA 95765 U.S.A. Mobile: +1 916 918 9412 www.SMA-America.com<http://www.sma-america.com/> Solar Academy: www.SMA-America.com/partners/sma-solar-academy/overview.html<http://www.sma-america.com/partners/sma-solar-academy/overview.html> Full training schedule: https://www.sma-america.com/partners/sma-solar-academy/seminars/trainings/training/list.html [http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/facebook.jpg]<http://www.facebook.com/pages/SMA-America/140290312717395>[http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/twitter.jpg]<http://twitter.com/SMA_America> [http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/wordpress.jpg] <http://www.smainverted.com/> [Linkedin Logo] <http://www.linkedin.com/company/364675> [http://sma-planet.sma.de/fileadmin/fm-dam/infos/social_media/youtube.jpg] <http://www.youtube.com/playlist?list=PL840A5336CAC32332> [SMAAFORUM_ICON] <http://smaadvance.com/signup/> [cid:image008.jpg@01D54D07.DC1BFFF0]<https://eur02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.sma-america.com%2Fhome-systems%2Fpv-solar-and-storage-solutions.html=02%7C01%7CMichael.Mahon%40sma-america.com%7Cc4bcd59d55584c70681208d71b72e485%7Ca059b96c28294d1188374cc1ff84735d%7C0%7C0%7C637008052588484449=itzAGcXAYe0xd5Zhzjuljm6dijJW%2FRGtItHrvxRkrTI%3D=0> This email and any attachments thereto may contain SMA America, LLC confidential, privileged and private material for the sole use of the intended recipient. Any review, copying, or distribution of this email (or any attachments thereto) by others is strictly prohibited. If you are not the intended recipient, please contact the sender immediately and permanently delete the original and any copies of this email and any attachments thereto. Thank you. From: RE-wrenches On Behalf Of Dave Tedeyan Sent: Friday, September 20, 2019 7:41 AM To: RE-wrenches Subject: [RE-wrenches] Running a grid tied system when the grid is down Hi all, I get asked this question frequently, as I am sure many others do, and of course the first answer is "it cannot be done". But can it? I have a customer who is very keen on trying to make this happen. After a few lengthy conversations, he still wants to try it, even after understanding the limitations (i.e. a cloud passes by and now you cannot power loads...) I have some thoughts on how to make this work, and thought I would post it here to get others comments who I am sure have more experience in something like this than I do. -PV system would have to be backfed, so that they can turn off the main breaker to disconnect from the utility entirely (and then have to look at the neighbors, or guess when the grid comes back) -Have a fairly small 12V off grid inverter/charger than can be powered by a single 12v battery. This inverter would have to be manually turned off until after the grid is down and the main breaker is disconnected. -Would also need an auto transformer to bump up the voltage to 240V. Something like the Outback PSX240. -Once the main breaker is off and the off grid inverter is on, would it be able to wake up the grid tied inverters? On this project, there are two SMA SB-40 inverters. -There would need to be some kind of dump/diversion load to deal with excess power coming from the GT inverters. I have not used these in the past, but are the controllers smart enough to just deal with any excess power in the system? -Have a trickle charger on the battery to keep it topped off most of the time. -Another thought would be to DC couple. This would involve having a DC switch in one of the strings going to the GT inverter, such that when the house is islanded from the grid, they can flip the switch and have that one string go to a high voltage CC. Then they could just run some small loads off the power from that one string, or maybe we could allow it to try to wake up the GT inverters as well. This particular homeowner specifically does not want much in the way of batteries and has a smaller budget than will allow something sensible like a Sunny Island. At least in upstate NY, there are many people who would like to be able to take advantage of their solar when the sun is shining, but who just do not have the budget for a legit battery system. I am somewhat surprised that there is no
Re: [RE-wrenches] Running a grid tied system when the grid is down
Hi Brad, Not a bad idea with this one to run the loads off the SPS's. Has anyone ever tried wiring these directly into a panel, rather than into an outlet? And do you know if the 120V signal from each one would match up, or do they work independantly? In other words can you wire both SPS into the same panel either on different legs, or on the same leg and use an autoxfr? And with the Rapid shutdown and SPS. Does it not work with SMA's rapid shutdown box? I thought with those, the grid going down would not affect the rapid shutdown, and that it needs the signal from the controller to initiate RSD. So this way it will continue to work with the grid down. Cheers, Dave *Dave Tedeyan, PE* Senior Engineer | Taitem Engineering, PC 110 South Albany Street | Ithaca, NY 14850 o. *607.277.1118 x121* f. 607.277.2119 www.taitem.com Solar • Sustainability • Energy • Design B-Corporation Best for the World 2018 Honoree On Fri, Sep 20, 2019 at 10:33 AM Bradley Bassett wrote: > If you're not using the SB -40 inverter's rapid shutdown system, it has > the SPS Secure Power Supply which does just what your customer wants. > > My understanding from talking to inverter mfg, is that trying to do AC > coupling with a smaller battery inverters does not work because the > anti-islanding in the grid tie inverter will be able to push the frequency > off too easily. > > Morningstar makes a 600 VDC charge control that has an array transfer > switch, so that during an outage you can switch it to use one or two > strings to charge a 48 V battery bank and power any 48 V inverter. It is > manual so the operator needs to change it back when the power comes back on. > > Brad > > > > On Fri, Sep 20, 2019 at 6:41 AM Dave Tedeyan wrote: > >> Hi all, >> >> I get asked this question frequently, as I am sure many others do, and of >> course the first answer is "it cannot be done". But can it? I have a >> customer who is very keen on trying to make this happen. After a few >> lengthy conversations, he still wants to try it, even after understanding >> the limitations (i.e. a cloud passes by and now you cannot power loads...) >> >> I have some thoughts on how to make this work, and thought I would post >> it here to get others comments who I am sure have more experience in >> something like this than I do. >> >> -PV system would have to be backfed, so that they can turn off the main >> breaker to disconnect from the utility entirely (and then have to look at >> the neighbors, or guess when the grid comes back) >> -Have a fairly small 12V off grid inverter/charger than can be powered by >> a single 12v battery. This inverter would have to be manually turned off >> until after the grid is down and the main breaker is disconnected. >> -Would also need an auto transformer to bump up the voltage to 240V. >> Something like the Outback PSX240. >> -Once the main breaker is off and the off grid inverter is on, would it >> be able to wake up the grid tied inverters? On this project, there are two >> SMA SB-40 inverters. >> -There would need to be some kind of dump/diversion load to deal with >> excess power coming from the GT inverters. I have not used these in the >> past, but are the controllers smart enough to just deal with any excess >> power in the system? >> -Have a trickle charger on the battery to keep it topped off most of the >> time. >> >> -Another thought would be to DC couple. This would involve having a DC >> switch in one of the strings going to the GT inverter, such that when the >> house is islanded from the grid, they can flip the switch and have that one >> string go to a high voltage CC. Then they could just run some small loads >> off the power from that one string, or maybe we could allow it to try to >> wake up the GT inverters as well. >> >> This particular homeowner specifically does not want much in the way of >> batteries and has a smaller budget than will allow something sensible like >> a Sunny Island. >> >> At least in upstate NY, there are many people who would like to be able >> to take advantage of their solar when the sun is shining, but who just do >> not have the budget for a legit battery system. I am somewhat surprised >> that there is no simple industry solution for this yet, although maybe it >> is more complicated than I am making it out to be. And of course, you need >> a very hands on homeowner who very well understands the limitations of this >> kind of setup. >> >> I would certainly appreciate any feedback or comments on this, and also >> would like to hear if anyone has tried this kind of setup before. >> >> Thanks much! >> -Dave >> >> *Dave Tedeyan, PE* >> Senior Engineer | Taitem Engineering, PC >> >> 110 South Albany Street | Ithaca, NY 14850 >> o. *607.277.1118 x121* f. 607.277.2119 >> www.taitem.com >> >> Solar • Sustainability • Energy • Design >> B-Corporation Best for the World 2018 Honoree >> ___ >> List sponsored by Redwood Alliance >> >> List
Re: [RE-wrenches] Running a grid tied system when the grid is down
If you're not using the SB -40 inverter's rapid shutdown system, it has the SPS Secure Power Supply which does just what your customer wants. My understanding from talking to inverter mfg, is that trying to do AC coupling with a smaller battery inverters does not work because the anti-islanding in the grid tie inverter will be able to push the frequency off too easily. Morningstar makes a 600 VDC charge control that has an array transfer switch, so that during an outage you can switch it to use one or two strings to charge a 48 V battery bank and power any 48 V inverter. It is manual so the operator needs to change it back when the power comes back on. Brad On Fri, Sep 20, 2019 at 6:41 AM Dave Tedeyan wrote: > Hi all, > > I get asked this question frequently, as I am sure many others do, and of > course the first answer is "it cannot be done". But can it? I have a > customer who is very keen on trying to make this happen. After a few > lengthy conversations, he still wants to try it, even after understanding > the limitations (i.e. a cloud passes by and now you cannot power loads...) > > I have some thoughts on how to make this work, and thought I would post it > here to get others comments who I am sure have more experience in something > like this than I do. > > -PV system would have to be backfed, so that they can turn off the main > breaker to disconnect from the utility entirely (and then have to look at > the neighbors, or guess when the grid comes back) > -Have a fairly small 12V off grid inverter/charger than can be powered by > a single 12v battery. This inverter would have to be manually turned off > until after the grid is down and the main breaker is disconnected. > -Would also need an auto transformer to bump up the voltage to 240V. > Something like the Outback PSX240. > -Once the main breaker is off and the off grid inverter is on, would it be > able to wake up the grid tied inverters? On this project, there are two SMA > SB-40 inverters. > -There would need to be some kind of dump/diversion load to deal with > excess power coming from the GT inverters. I have not used these in the > past, but are the controllers smart enough to just deal with any excess > power in the system? > -Have a trickle charger on the battery to keep it topped off most of the > time. > > -Another thought would be to DC couple. This would involve having a DC > switch in one of the strings going to the GT inverter, such that when the > house is islanded from the grid, they can flip the switch and have that one > string go to a high voltage CC. Then they could just run some small loads > off the power from that one string, or maybe we could allow it to try to > wake up the GT inverters as well. > > This particular homeowner specifically does not want much in the way of > batteries and has a smaller budget than will allow something sensible like > a Sunny Island. > > At least in upstate NY, there are many people who would like to be able to > take advantage of their solar when the sun is shining, but who just do not > have the budget for a legit battery system. I am somewhat surprised that > there is no simple industry solution for this yet, although maybe it is > more complicated than I am making it out to be. And of course, you need a > very hands on homeowner who very well understands the limitations of this > kind of setup. > > I would certainly appreciate any feedback or comments on this, and also > would like to hear if anyone has tried this kind of setup before. > > Thanks much! > -Dave > > *Dave Tedeyan, PE* > Senior Engineer | Taitem Engineering, PC > > 110 South Albany Street | Ithaca, NY 14850 > o. *607.277.1118 x121* f. 607.277.2119 > www.taitem.com > > Solar • Sustainability • Energy • Design > B-Corporation Best for the World 2018 Honoree > ___ > List sponsored by Redwood Alliance > > List Address: RE-wrenches@lists.re-wrenches.org > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > ___ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
