Trace ST problems [RE-wrenches]

Thu Feb 22 13:11:34 PST 2001

Travis / Carl:

Sounds like more smoke and mirrors to me.

>From the MPPT perspective I really don't think thin films are all that
different than crystalline .
Most thin films have a lower fill factor, i.e.
 softer knee on the IV curve.
If you draw the power curve for a module using the IV curve data you see a
hump that peaks out near the knee of the IV curve.
For thin films the hump is typically broader so they are less sensitive to
changes in operating voltage.
Usually this means that thin films are easier to track than crystalline
since they are less sensitive to variations in operating voltage.

The main issue with thin films is the higher Voc to Vmp ratio.
The original genesis of the ST was for EPV modules as part of SMUD's PV
program.
Unfortunately, the MPPT window is too narrow to work with most thin film.
With the MPPT window being only 52 to 85 it is very difficult to find an
array configuration that it will power track year round.
You really need an DC input voltage MPPT window of 2 to 1 or more to track
year round in most locations.

Most module companies will supply you with the temperature coefficients for
voltage, current, and power if you ask.
Ideally you want to design the system so that the inverter can track the
array all the time.
There are simulation programs out there that will give you the Max power
voltage but you can "back of the envelope it" pretty close by using the
coefficients and the ambient temperature plus 20 C for cell temperature.

Another problem with the ST and thin films is the maximum UL allowed voltage
of 120 Vdc.
This is another reason why you can only use it with 4 crystalline modules in
series.
This means the ST will violate the UL Listing if you hook up two EPV modules
in series (or five crystalline module) if the temperature falls below
freezing.
The rumor is that SMUD is none too happy about that.

An then there is the ambient specification of 0 to 45 C -
Hmmm, where can I use it where the temperature never is hotter than 45 or
lower than 0 => indoors only!
And then there is the fan that comes on at 150 to 200 Watts and stays on
(NOT a UL requirement by the way)
I heard from an installer yesterday that had a call back to move the
inverter because it vibrated the wall so badly that the people couldn't
stand it.

And then ...

-----Original Message-----
From: Travis Creswell, Ozark Solar [mailto:ozsolar at ipa.net]
Sent: Thursday, February 22, 2001 7:06 AM
To: RE-wrenches at topica.com
Subject: Re: Trace ST problems [RE-wrenches]

Now that my hands are warmed up I can hit the right keys and I'll even
proofread this message.  Sorry about that last one..  really, I am literate

I was reminded yesterday that the ST was designed specifically for thin film
PV.  Actually the MPPT in the ST is designed/set up for thin film.
Supposedly thin film has a much different I-V curve but I have no experience
with it.  I can remember a Trace engineer speaking at a Trace training
session I attended last year about that but it didn't seem like he said that
it would work poorly with standard modules.

Travis
----------
>From: carl reuter <creuter at rocketmail.com>
>To: RE-wrenches at topica.com
>Subject: Trace ST problems [RE-wrenches]
>Date: Thu, Feb 22, 2001, 3:52 AM
>Today while on the phone to a Trace tech, I brought up the Suntie and
>asked if they had ironed out the bugs and the guy got very
>defensive,claimed they'd only had "a few" instances of problems and
>went on about mud slingers giving the product a bad name, etc.
>Apparently they dont like us wrenches down there.
> Latter in the day,one of my suppliers mentioned that of 19 units
>that his company sold,12 came back in with the same problems that
>we've discussed here.This is the same old thing with Trace,major
>denial and piss poor lying skills.Ive never heard them cop to
>anything.
>I have been considering the much smaller AEI GC 1000 a contender
>until speaking with an official today from Pacific Gas & Electric,
>who told me the darn thing wasn't on his list of PG&E approved
>inverters for grid tie,yet he didn't have any more info than that and
>not even a copy of their list to send me. Darn frustrating, this
>business. Carl Reuter
>
>=====
>Land and Sea Solar, Renewable Energy Systems.  Email:
>carl at landandseasolar.com.   Phone:831-252-5040
website:www.landandseasolar.com
>
>__________________________________________________
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 michael.welch at homepower.com

____________________________________________________________
T O P I C A  -- Learn More. Surf Less. 
Newsletters, Tips and Discussions on Topics You Choose.
http://www.topica.com/partner/tag01