Laser inquiry [RE-wrenches]

[Bill Brooks]

Wrenches and LASERs.

The laser grooving in the "Saturn" BP cell is designed to provide more
contact area for the surface conductor and take up less roof on the surface
of the cell. This produces higher current and voltage. Additionally the
"Saturn" cell cuts the crystal in such a way that it gives the surface a
better, off-angle performance.

How these design changes affect hot temperature performance may be difficult
to determine. Starting at a higher voltage will mean that you are less
likely to fall off the I-V curve on a hot day. This is not an issue very
often with off-grid systems because our array utilization (amount of kWh out
per kWh solar in) is very poor since we throw away a lot of our summer power
in the controller. For grid-connected systems it is very important. On a hot
+100F day in the summer, our modules can be running at 150F and our typical
PV module will run at about 13.5Vmp while a "Saturn" module might run at
14-14.5V (have to do the temp calculation). This could make a difference.
How big a difference, we need to test side-by-side to compare.

Bill.


> -----Original Message-----
> From: jay peltz [mailto:jay at asis.com]
> Sent: Sunday, April 01, 2001 2:09 PM
> To: RE-wrenches at topica.com
> Subject: Re: Laser inquiry [RE-wrenches]
>
>
> Hi Travis,
>
> Yes I agree that the higher voltage works really well in the
> summer, but that is
> never a problem load time.  I mean the batteries are always full
> in the summer
> at least in this part of the world.
>
> For me, the in this area, the BP-85's are the choice for array
> direct pumping, (
> but thats getting more and more rare).
>
> I think the added money would be better spent for more amps, and
> thats way more
> amps during the cooler days of fall and winter when we need them.
>
> These panels do work really well, and now that they have better
> frames and J
> boxes they are even better.  Specialtly products for sure,
>
> jay
> Peltz Power
>
> "Travis Creswell, Ozark Solar" wrote:
>
> > I like the BP585's  and 590's that I've used. They do seem to
> perform very
> > well but I can't prove they are performing better than anything else.
> >
> > Another benefit of the higher power point voltage could be the increased
> > output in summer when the stuff with lower PPV is really
> getting hurt by the
> > heat.  This laser groove stuff was invented in Australia by the way.
> >
> > I can't rattle off the decrease in volts for every degree
> Celsius but I have
> > seen it before and it is rather significant.  By the way, amps
> goes up with
> > heat, if I'm not mistaken, but the decrease in voltage more than offsets
> > that increase and you get lower watts.
> >
> > Bill Brooks are you reading this?  What would the OCV of a typically
> > crystalline cell be on a 100 degree (F) day?  Of course that
> means that the
> > panels themselves are easily approaching 140.  Do you have a "rule of
> > thumb"?
> >
> > Travis Creswell
> > Ozark Solar.
> > ----- Original Message -----
> > From: "Bob-O Schultze, Electron Connection" <econnect at snowcrest.net>
> > To: <RE-wrenches at topica.com>
> > Sent: Saturday, March 31, 2001 9:37 PM
> > Subject: Re: Laser inquiry [RE-wrenches]
> >
> > > Yo Sharkey,
> > > I don't know the mechanics of HOW it does it, but the laser grooving
> > > method gives a higher cell voltage than single or multicrystal cells.
> > > Doesn't do anything for extra current however.  You you get a module
> > > that is rated a 18.5V instead of 17V at the power knee. Since the
> > > manufacturers figure the selling price based on peak V X A = Watts,
> > > what would be a 75W Siemens, for example, comes out as an 85W BP
> > > laser grooved. Hence, the extra bucks. The extra voltage might come
> > > in handy in a place where it is overcast a lot. It might come in
> > > handy in an array direct application like water pumping. And, it
> > > might buy you something if used in conjunction with a good MPPT
> > > charge controller. Is it worth the extra dough? I don't think so, but
> > > then I'm a Siemens kinda guy too. Some folks like Fords, others
> > > prefer Chevy or Dodge.
> > > Bob-O
> >
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