[RE-wrenches] Battery bank during peak times

[Jesse Dahl]

Very good numbers. I've found their monthly "enlightener" that they send with each bill on line and found this interesting tidbit. 

" if considering a PV system, know that not all contractors are the same.  We are installing a model PV system at our main office so our customers can come to us with questions about PV systems a costs."  

They are very "pro-coal", and I think I'm getting used.  This system will be nothing like a system a residential customer would have installed and will cost significantly more that a GDI system.  Do you think they will mention this to their co-op members that inquire about PV?

Jesse

Sent from my iPhone

On Jun 25, 2013, at 12:27 PM, "SunHarvest" <eric at harvesthesun.com> wrote:

> 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
> To: RE-wrenches
> 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: RE-wrenches at lists.re-wrenches.org
> 
> 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
> 
> Check out participant bios:
> www.members.re-wrenches.org
> 
> _______________________________________________
> List sponsored by Home Power magazine
> 
> List Address: RE-wrenches at lists.re-wrenches.org
> 
> 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
> 
> Check out participant bios:
> www.members.re-wrenches.org
> 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org/attachments/20130625/750429eb/attachment-0004.html>