SPAM: Xantrex versus Sunny Boy [RE-wrenches]

Thu Jul 31 10:57:56 PDT 2003

Jeff C wrote:

> you just put the SBs and disconnects under or at the end of your racks

Jeff, do you mean like the SMA pictures of European installs?  (On their
backs with a tilt)  Are you insinuating that you can't put a PV on its
back and expect it to operate?  LOL

Seriously, folks... A couple of "issues" are missing from this thread.

1. Triple Orientation is a given factor, but at what slope(s)?  (Don't
assume it's a relatively flat install!)  The steeper the slopes, the
greater the difference in Power, Volts, Amps, Temperature, Etc. between
them.  It all adds up!  Power tracking the "average" of the different
slopes will yield a far greater (Estimated @ up to APPROXIMATELY 48%
annual) kWH using the SB option vs the single PV.... Assuming
Crystalline modules.  (This is not to be interpreted as the PV being 48%
less efficient than the SB!!!!!!  Please don't go there! Even though
John B & Kent S might want you to....).  That kind of production
difference (If my VERY ROUGH 3-BEER calcs are even close) factors
heavily into Customer satisfaction  (Read as: "Less headaches for me").
I wouldn't use the comparison in ANY presentation to a Customer, by the
way...Remember it is VERY ROUGH, based on the info I do have.  That # is
a simple comparison of projected kWH of one scenario to the other on an
annualized basis....The real objective is to develop the best overall
system option(s) for the Customer.  Many factors play into "best"....
Price, Performance, Reliability, Aesthetics, Warranty, "Feel Good",
Patriotism, "Payback", "Marketability", Confidence, "What my
Wife/Husband will think", Financing, Capitol Gains/Losses, Property
Taxes, Etc.  There is also the "what they intuitively think" factor
relating to future electricity rates and usage. 

2. Knowing (because I asked offlist) that the slope is 25 degrees, and
that the Hilo, HI latitude is ~20 degrees N, leads me to a
recommendation that the slopes not be combined on a single inverter.  At
the very least, balancing the factors I know, I would separate the
orientations to different inverters for this application.  Could be that
is 3 - PV10's.... Could be that is 12 - SB's.  Further penciling is
required to determine the "Best" option for the Customer.

Crystal Ball: 12 SB's beats 3 PV10's......

Two Palms and a Hammock to all!

Matt Lafferty
Universal Energies Institute
mlafferty at universalenergies.com
(916) 422-9772
(916) 628-7694 Cell
(916) 914-2247 Fax
www.universalenergies.com

-----Original Message-----
From: Jeff Clearwater [mailto:clrwater at earthlink.net] 
Sent: Thursday, July 31, 2003 9:11 AM
To: RE-wrenches at topica.com
Subject: RE: SPAM: Xantrex versus Sunny Boy [RE-wrenches]

Hey Bill,

Gotta disagree on the space and efficiency issues you raise.  The 36 
KW system with 12 SBs we are installing fits in a 6 x 8 power shed 
only using up the walls and you still have the whole room.  A PV50208 
(and the transformer) for that system would have required a fork lift 
and lots more space - wouldn't even have fit in the door!  And with 1 
Square D HU361  per 2 inverters  - that's only 6 -  5" wide 
disconnects - hardly a space issue.

And on commercial flat roof installs - especially retrofits - you 
just put the SBs and disconnects under or at the end of your racks 
and you don't need a whole dedicated power room.

As for efficiency including the transformer, aren't you at 90% with 
the PV whereas SB is at 94% and with a better efficiency curve?

respectfully,

Jeff C.

>I think there are several factors being overlooked in the responses. 
>COST is certainly one major one. I don't think SMA can come close to 
>competing with the PV series on cost. Efficiency I think is close to a 
>wash between the two even with the higher nighttime losses of the 
>isolation transformer. Both machines use IGBTs and they are very 
>efficient at high power--they are not efficient at low power. SPACE is 
>another problem. 30 kW of SunnyBoy inverters takes up tremendous space 
>with disconnects and all. I think the breakpoint between the SB and the

>PV is between 10-20 kW.
>
>I really don't think the MPPT issues with the different orientations is

>an issue. I do think the MPPT of the SB is slightly better than the PV 
>series in general, but I have not seen any good data to confirm that.
>
>Reliability--I think the PV series is every bit as reliable if not more

>so than the SB.
>
>Both great inverters--the best inverters we have in our industry. The 
>PV series is better suited for this installation (just to be a 
>contrarian--in your heart you know I'm right--to quote Barry 
>Goldwater).
>
>Bill.
>
>-----Original Message-----
>From: Marco [mailto:marco at pvthawaii.com]
>Sent: Wednesday, July 30, 2003 2:59 PM
>To: RE-wrenches at topica.com
>Subject: SPAM: Xantrex versus Sunny Boy [RE-wrenches]
>
>
>
>I'm getting differing opinions on a design question that's leaving me 
>in a bit of a quandry.  I'm pursuing a 30 kW DC grid-tied system sale 
>to the local healthfood store here in Hilo, ~19 degrees north 
>lattitude.  There's 3-phase 120/208 service at the store, so I'd like 
>to use a single Xantrex PV30208 inverter (and isolation transformer).  
>Since there's not enough roof space on the due south face for all 30 
>kW, the array would be split roughly equally among the southern, 
>eastern and western faces of the roof.  Each series  string of (12) 24V

>modules would be on one plane, i.e., no series string would span two 
>roof faces.  Now, I know very well that splitting this system onto 
>three planes is not ideal when using a single inverter. However, I'd 
>much prefer to use one inverter rather than (12) 3-phase SB2500s.  Nor 
>do I want to use three 10-kW PV10208 inverters--one each per roof face.

>So, my question to my esteemed PV wizards is, how poorly or 
>sub-optimally do you think such a system will perform?  Any of you out 
>there who have installed similar multi-plane, single-inverter systems?
>
>tanks,
>aloha,
>marco
>
>Marco Mangelsdorf
>President
>ProVision Technologies, Inc.
>69 Railroad Avenue, Suite A-7
>Hilo, Hawaii 96720 USA
>(808) 969-3281, fax 934-7462
>www.provisiontechnologies.com
>
>
>
>[Non-text portions of this message have been removed]
>
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-- 
~~~~~~~~~~~~~
Jeff Clearwater
Village Power Design Associates
Sustainable Energy & Water Solutions for Home & Village
http://www.villagepower.com gosolar at villagepower.com

877-SOLARVillage
413-256-6777,  Fax 413-825-0372
61 Baker Rd
Shutesbury, MA 01072

PO Box 115
Boonville, CA 95415
707-895-9015, Fax 707-897-0024
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