William, I agree with you with Radian, Fortress and just add a subpanel identical to the main grid panel as close possible. Put all critical loads on sub and larger loads on grid panel. Being side by side, swapping circuits is easy. I also install an iota charger for generator redundancy. OpticRE works great for monitoring.
John Blittersdorf On Wed, Mar 3, 2021 at 1:19 AM William Miller <will...@millersolar.com> wrote: > Friends: > > > > I am getting asked more often to provide design for grid-tied battery > backup systems. I generally try to talk clients out of battery backup > because I have always felt that the grid is the greenest battery and that > the grid reliability is better than one might remember. However, with > climate change and media attention, the need and market pressure is > becoming stronger. > > > > I am really interested in what others have created in the way of solutions > to this question. I have thought about it a lot. If its ok, I’d like to > free-associate about some of my concerns and conclusions then ask if any of > you are willing to share your ideas on how best to fill this need. Here > goes: > > > > I am a firm believer in segregate load delivery for these reasons: > > 1. To back up an entire grid service you have to, in good conscience, > perform a thorough load study and provide enough through-transfer to > provide for maximum load conditions during grid up-time. The backup system > cannot be a supply bottle-neck. > > 2. I don’t accept manual load-shedding for one moment. What if the AC > and the dryer are running when the grid goes out? The system crashes. > > 3. In a home with whole-house backup, it is difficult for the consumer > to know there is an outage and to conserve. Cellphone notification > features are now more common, but cell phone batteries die and phones get > left in the other room with the ringer off, so it is possible for > homeowners to leave consumptive loads on after the grid goes down. > > > > Conclusion: With segregated loads, the transfer, inverter and storage can > be scaled down and the reliability increases. Less cost, better > performance. > > > > So given that the system sizing will be modest, has anyone come up with a > reasonable design using standard, grid-sell capable battery inverters? > > > > Here is how I am imagining such a system: > > > > I see a modest battery system with a 4 to 8 KW inverter, DC coupled PV and > a matching no-maintenance battery system. It would have these components: > > > > Inverter: Must have a dedicated generator and grid input and good remote > monitoring, robust web interface and email notification. Outback Radian. > > > > Batteries: Gel or lithium. I have a client that has been grid-floating a > set of MK Powered gel batteries since 1999. Or a Blue Planet or Fortress > cabineted system. > > > > Generator: Small pad-mount natural gas or propane fueled generator or a > portable gas powered unit with stabilized gas. If the generator is > portable, provide an AC flanged inlet and sturdy cord long enough so > generator can be 10 feet from any opening in the home. Provide durable > signage on the generator indicating CO safety practices. > > > > PV: DC coupled for simplicity. Sized based on annual energy needs, not on > critical loads. Grid power is likely to go down in the stormy winter > months or smoky fire season, so PV is not a reliable energy source during > grid outages. > > > > AC Distribution: Segregated loads with at least one commonly used > lighting circuit not on the critical loads panel so the homeowner soon > realizes the power is out. > > > > Unless you are a Tesla dealer, I am sure many of you have gone through the > same mental acrobatics trying to figure out the best solution to this > design request. I am very interested in what the rest of you may have come > up with. > > > > Thanks in advance. > > > > William Miller > > > > Miller Solar > > 17395 Oak Road, Atascadero, CA 93422 > <https://www.google.com/maps/search/17395+Oak+Road,+Atascadero,+CA+93422?entry=gmail&source=g> > > 805-438-5600 > > www.millersolar.com > > CA Lic. 773985 > > > > > _______________________________________________ > 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 > > There are two list archives for searching. When one doesn't work, try the > other: > https://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/ > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > http://www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > http://www.members.re-wrenches.org > >
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