array expansion strategery [RE-wrenches]

[Kelly Keilwitz]

Hi Andy,
First, I would recommend getting rid of the SW/GTI/C-40 system altogether
for a grid-tie. It's terribly inefficient - probably less than 50% from PV's
to AC. They can be resold easily on Ebay. The C-40's are great to use for
secondary dump loads or load controls.

Then:
If battery backup is important (say for a well) go with an Outback GTFX
system with the existing batteries, plus a MX-60 charge controller. A 3048
can handle all of the existing plus new array size. A second inverter could
be added later to handle more expansion. Or, use a single, vented (3648)
inverter for the entire future array size. Besides being much more
efficient, the Outback inverter (made in WA) gets your customer an
additional 3 cents/KWH in the WA State production incentive program, which
pays off well over time (use this as a selling point).

If battery backup isn't so important as cost effectiveness then get a
grid-tied inverter sized for the entire future array size. If the new PV's
are different than the existing ones you may want to consider a multi-string
inverter (with separate MPPT).

That's my 2-cents. More than a penny, I know, but with the price of
copper....


Kelly Keilwitz, P.E.
Whidbey Sun & Wind, LLC
Renewable Energy Systems
NABCEP Certified PV Installer
987 Wanamaker Rd, 
Coupeville, WA 98239
PH & FAX 360-678-7131
sunwind at whidbeysunwind.com


On 8/10/06 11:28 AM, "Andy Cochrane" <andy at powertripenergy.com> wrote:

> 
> 
> Hi Wrenches,
>  
> My partner and I are having a discussion about the best way to fulfil an
> existing customer's request for expansion.
>  
> The system we put in in Apr 2004 is currently:
> 2.2 KW on a tracker
> Xantrex SW 4024 (grid-tied w/GTI), (2) C-40's, and Xantrex DC panel,
> ~900AH 24 V battery bank
>  
> The customer wants another 1.1 KW now and maybe yet another 1.1 KW next
> year.  These arrays will be fixed mount to the deck railing, from which
> access to the existing power equipment is not difficult.
>  
> The question is whether to use another charge controller (an MPPT model
> this time) and add this array to the existing system, or whether to use
> a small SunnyBoy grid-tied inverter separately intertied into the same
> subpanel.
>  
> The main question is whether the efficiency losses by going thru the
> SW/battery system (batteries never used) make it worth avoiding those
> efficieny losses by using an efficient synchronous inverter, which would
> be slightly more expensive.
>  
> Penny for your thoughts.
>  
> 
> Andy Cochrane
> 
> Power Trip Energy Corp
> 
> 2343 Thomas St
> 
> Port Townsend, WA 98368
> 
> (360) 643-3080
> 
> www.powertripenergy.com
> 
>  
> 
>  
> 
> [Non-text portions of this message have been removed]
> 
> 
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Kelly Keilwitz, P.E.
Whidbey Sun & Wind, LLC
Renewable Energy Systems
NABCEP Certified PV Installer
987 Wanamaker Rd, 
Coupeville, WA 98239
PH & FAX 360-678-7131
sunwind at whidbeysunwind.com
 


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