[RE-wrenches] Battery Back-up and Grid Tie

Fri Apr 26 13:50:57 PDT 2013

my biggest issue with bbgt systems is the inefficiency. my 4.3 kW (stc) array typically sells 2.8 kW.

5 years of tracking dc input versus ac output shows the obfx inverter runs around 87% efficiency. add battery maintenance and the extra wiring to split off "backed up loads" and the economics just dont work out.

then, if you make this scenario even worse by adding battery cycling inefficiency and more frequent replacement... (to supposedly make money??) it is a no-brainer your customers "creative" idea is actually a hair brained scheme which will result in a net loss and increased consumption of resources. his money would be better spent on upgrading to more efficient appliances, improvements to his building thermal performance and conservation.

i would not do this for a customer... and if they insisted, i'd let them hire someone else to implement these stupid (greenwashing) ideas for him. 

remember, you are the expert and your integrity and ethics are on the line here.

todd

On Friday, April 26, 2013 12:24pm, "SunHarvest" <eric at harvesthesun.com> said:

I have a crazy...I mean creative customer  who wants a BB system so that he can run off-grid during peak and partial-peak  rate hours: 1 to 7pm is peak, 7 to 9pm is partial from PG&E. He got this  great idea from a tech at a reputable power optimizer manufacturer, whom I will  not name here, who said, "you've got the batteries just sitting there;  why not put them to work?"

Initially he wanted his PV to operate while the sun  is shining and the grid is down...and his batteries to supply power when the sun  and grid is down. But now he wants his back-up system to do it all.  We've touched on all the obvious points: 

- Peak buying is also peak selling
- Physics and efficiency losses determine that the  energy he "saves" will never equal the energy he can put back into his  system.
- Decreased battery life due to increased  cycling
- Costs for batts and special inverters versus  generator

What is the definitive argument against BB  in general and this "peak shaving" idea in particular?

Thanks pros.

Eric
SunHarvest

----- Original Message -----
From: [mailto:toddcory at finestplanet.com] toddcory at finestplanet.com
To: [mailto:re-wrenches at lists.re-wrenches.org] RE-wrenches
Sent: Friday, April 26, 2013 11:57    AM
Subject: Re: [RE-wrenches] Battery    Back-up and Grid Tie
our    power outages generally come from bad weather too... and of course when the    weather is bad the pv does next to nothing. so for emergency backup, i    recommend a generator.

todd

On    Friday, April 26, 2013 10:33am, "Bill Turberville" <[mailto:billturb at ece-llc.com] billturb at ece-llc.com>    said:

Not very often, and usually for    no more than an hour or two, although it has been down as long as 5 days,    either during tornado season, or ice taking down power lines.  What these    people are looking for is Just In Case a big event happens.  They do not    want to have all those panels just sitting there.

From: [mailto:re-wrenches-bounces at lists.re-wrenches.org] re-wrenches-bounces at lists.re-wrenches.org [mailto:[mailto:re-wrenches-bounces at lists.re-wrenches.org] re-wrenches-bounces at lists.re-wrenches.org]    On Behalf Of Jay Peltz
Sent: Friday,    April 26, 2013 12:25 PM
To: RE-wrenches
Subject: Re: [RE-wrenches] Battery Back-up and    Grid Tie

Hi bill

Just how often is your grid down?

Jay

Peltz power

Sent from my iPhone

On Apr 26, 2013, at 10:01 AM, Bill Turberville <[mailto:billturb at ece-llc.com] billturb at ece-llc.com>    wrote:

I live in a TVA area where there is a Feed In Tariff.       Everything that is generated by the PV array feeds into the grid through a      Generation Meter that ties-in ahead of the house meter.  I have started      getting calls from customers who hate having a solar array that does not      generate when the grid is down but the sun is shining, but who also want to      get the $.12 premium when the grid is connected.  We have lots of      systems with SMA Sunnyboy inverters, but more with Enphase      micro-inverters.  Rather than trying to reinvent the wheel, what you      found to be the best solution for this type of installation?

W.C. (Bill) Turberville P.E.
President

ECE Solar
Electrical Contracting Enterprises LLC
3080 Stage Post Road Suite 107
Bartlett, TN 38133

901-348-9230 ext 101 phone
901-348-2192 fax
901-289-6346 cell
[mailto:billturb at ece-llc.com] billturb at ece-llc.com

NABCEP Certified PV Installation Professional 032611-320

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