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 <dtede...@taitem.com> 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 > >
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