Southern California Edison (SCE) is now denying applications for interconnection and net metering IF the system can charge batteries by using grid power. It looks like they are worried about people using time-of-use metering in this way.
I think it's completely bogus, not only because of the questionable economics, but also because if a lot of people actually do this, it will help the grid, and the utility, not hurt it. I don't see how charging batteries is any different than running any other load during off-peak. Brian Teitelbaum AEE Solar From: [email protected] [mailto:[email protected]] On Behalf Of SunHarvest Sent: Tuesday, June 25, 2013 10:27 AM To: RE-wrenches Subject: Re: [RE-wrenches] Battery bank during peak times Hi Jesse, If I read this correctly your customer is wanting to go off-grid during peak hours. I recently went through this same thing with a customer. I received feedback from an old SMA tech and some Wrenchers (thread titled "Battery Back-up and Grid Tie"). Here's what I learned: 1. Inverters are more efficient at inverting than charging, anywhere from 5-10%. Add to that about 10% transmission loss...you'll always have significant energy losses associated with trying to put back that power that you're drawing out during those peak hours. Energy loss = $$ loss. 2. Compare the utility peak kWh cost against the cost of cycling the battery bank. Just for an example, let's say for a 48V system you're using 150Ah 12V Trojan AGMs $2000 for 8 batteries. If the specs say those batteries, at 50% discharge, get 1000 cycles in their lifetime, that's $2.00 per cycle. 300Ah X 48V X 50% = 7.2kWh. $2/7.2kWh = $0.28/kWh. Add to that 20% round-trip efficiency losses, you're up to $0.33/kWh. What else does daily, unnecessary cycling add: Extra maintenance? Shortened life so probably should factor in some replacement cost?... 3. Murphy's law says that the power will go out at the end of one of these non-essential discharge cycles. Then what? Probably not worth it. Eric Stikes SunHarvest 530-798-3738 ----- Original Message ----- From: Jesse Dahl<mailto:[email protected]> To: RE-wrenches<mailto:[email protected]> Sent: Monday, June 24, 2013 8:50 PM Subject: [RE-wrenches] Battery bank during peak times Hello, I was contacted by a local co-op about installing a PV system at their office. At first they wanted a straight grid-tied system, and after they received the bid they changed their minds and now want a battery based system price. What they want now is a system that will allow them to draw the battery bank down starting at 5pm during their peak demand time. Has anyone worked on or installed a system of this type? Thanks as always! Jesse ________________________________ _______________________________________________ List sponsored by Home Power magazine List Address: [email protected]<mailto:[email protected]> Change email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm<http://www.re-wrenches.org/etiquette.htm> Check out participant bios: www.members.re-wrenches.org<http://www.members.re-wrenches.org>
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