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--></style></head><body lang="EN-US" link="blue" vlink="purple"><div class="WordSection1"><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Friends:</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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\u2019d 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:</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">I am a firm believer in segregate load delivery for these reasons:</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">1.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">2.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">I don\u2019t accept manual load-shedding for one moment. What if the AC and the dryer are running when the grid goes out? The system crashes.</span></p><p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo1"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""><span style="mso-list:Ignore">3.<span style="font:7.0pt "Times New Roman""> </span></span></span><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Conclusion: With segregated loads, the transfer, inverter and storage can be scaled down and the reliability increases. Less cost, better performance.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">So given that the system sizing will be modest, has anyone come up with a reasonable design using standard, grid-sell capable battery inverters?</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Here is how I am imagining such a system:</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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: </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Inverter: Must have a dedicated generator and grid input and good remote monitoring, robust web interface and email notification. Outback Radian.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">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.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">Thanks in advance.</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif"">William Miller</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Verdana","sans-serif""> </span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">Miller Solar</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">17395 Oak Road, Atascadero, CA 93422</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">805-438-5600</span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif""><a href="http://www.millersolar.com/">www.millersolar.com</a></span></p><p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial","sans-serif"">CA Lic. 773985</span></p><p class="MsoNormal"> </p><p class="MsoNormal"> </p></div></body></html>