Unisolar Roofing [RE-wrenches]

Bill Brooks billbrooks7 at earthlink.net
Thu Mar 15 09:09:02 PST 2001 

Jeff,

Don't believe it. You are being sucked into the dark side (a-Si). It is true
that most manufacturers of a-Si now present their "attenuated" performance
numbers. Don't believe for a minute that those are summer number--because
they absolutely are not. a-Si has a slightly lower temperature sensitivity
than does crystal, but we also like to refer to its poor sensitivity to
sunlight as well (efficiency). I believe that we need 8-10% efficient
technologies for the residential grid-connected markets, and I don't see the
evidence yet that even triple junction a-Si can do that for us. We have an
overall rating problem in our industry, but that is another story.

Also don't believe the garbage you read from manufacturers that a-Si does
better in cloudy areas and in different parts of the country. It is true
that every module has a different spectral response, but those are not
enough to make a big difference from climate to climate. They were making
those same claims 10 years ago when we were testing their tandum junction
products. We found that those products performed worse than any other
product in low light levels. That didn't stop the claims however.

Remember, without true 3rd party information on modules and inverters, you
should take any manufacturers information as marketing materials and not
fact. The number of flat-out wrong and false statements that come from
manufacturers is overwhelming. The a-Si industry has been more at fault than
others, but they all do it.

Bill.

> -----Original Message-----
> From: Jeffrey Wolfe, Global Resources [mailto:global at sover.net]
> Sent: Wednesday, March 14, 2001 9:01 PM
> To: 'RE-wrenches at topica.com'
> Subject: RE: Unisolar Roofing [RE-wrenches]
>
>
> Bill,
>
> Thanks for the post. Eventually, we need a whole lot more data like this,
> but this is the start, right? :)
>
> Things like the manufacturer of the PV cells can make a difference in
> annual output. But more so, things like PV technology and real
> weather have
> a greater effect. (Single and poly crystal vs a-Si). So the
> annual numbers
> will chage based on technology. Bigger change where the weather is less
> uniform (like New England compared to AZ....)
>
> I'm finding, (not yet really well supported, but coming up with the same
> conclusion a couple ways) that on-grid batteryless, we're getting about
> 1000 kWh per kW installed. This si from some looking at the output of my
> modules, some calcs based on combining all the efficiencies I READ for
> equipment, and some on computer sims.
>
> One factor that really differentiates single and poly crystal vs
> amorphous,
> but is not well documented, is the "nominal" rating. The single and poly
> crystals are "nominally" rated at a wattage higher than we'll ever see
> (Solarex SX-120 rated at 120 watts, but really is btwn 110 and 120 Watts
> due to wafer catagorizing, whereas the a-Si modules are typically
> rated at
> there lowest performance point, with better summer performance.
>
> So to compare apples to apples on price, space, etc., I'm about at the
> point where I derate the crystal and polycrystal by about 10%, then
> compare. ESPECIALLY on grid connect, where the majority of my kWh are
> created in medium or hot weather (i.e. the sun is shining and the snow's
> melted), and I can just about send the array south for the winter.
>
> Jeff
>
> Jeffery D. Wolfe, P.E.
> Global Resource Options, LLP
> A Woman-Owned Vermont Limited Liability Partnership
> 4 Kibling Hill Road
> P.O. Box 51
> Strafford, VT 05072
> 802/765-4632
> 802/765-9983 (Fax)
> global at sover.net
> http://www.globalresourceoptions.com
>
>
> ----------
> From: 	Bill Brooks[SMTP:billbrooks7 at earthlink.net]
> Reply To: 	RE-wrenches at topica.com
> Sent: 	Wednesday, March 14, 2001 6:47 PM
> To: 	RE-wrenches at topica.com
> Subject: 	RE: Unisolar Roofing [RE-wrenches]
>
> I realize that ASCII can be cruel, but hopefully you can read
> this. This is
> top secret so make sure you spread it around ;-). This chart tells us the
> impact of fixed orientation on annual energy production for a
> grid-connected, net-metered PV system. Do not use this for off-grid since
> we
> cannot predict array utilization nearly as well. The interesting thing
> about
> this chart is that it clearly shows that annual energy producting is not
> very sensitive to fairly wide variations in orientation (4:12 to 12:12, SE
> to SW only has about 5% loss from ideal). Moral of the story is don't tilt
> your modules on rooftop PV systems because it looks like hell, costs more
> to
> install, and often doesn't buy much as far as performance.
>
>
> Roof pitch	Flat	4:12	7:12	12:12	21:12	Vertical
> South		0.89	0.97	1.00	0.97	0.89	0.58
> SSE,SSW	0.89	0.97	0.99	0.96	0.88	0.59
> SE, SW	0.89	0.95	0.96	0.93	0.85	0.60
> ESE,WSW	0.89	0.92	0.91	0.87	0.79	0.57
> E, W		0.89	0.88	0.84	0.78	0.70	0.52
>
>
>
> Okay all you Wrenches out there, on the chart below are some real-life
> numbers you should be using for grid-connect PV systems that are properly
> oriented. This should generate some good controversy because nobody I know
> states numbers this low. However, these are real-life
> conservative numbers.
> A well installed system with minimal shading should be able to
> consistently
> produce this much electricity or more in a year. If it doesn't, there is
> something wrong with it (equipment or installation). The new California
> Buydown guidelines require a meter come June 1, 2001, so sharpen your
> pencil
> because customers are now going to need energy estimates. This means you
> need to do a detailed shading analysis with a Solar Pathfinder, use the
> chart above to adjust for orientation, and multiply that number by your
> location below and you're done! Piece of cake.
>
> CITY			kWh/kWstc
> Arcata		1092
> Shasta		1345
> San Francisco	1379
> Sacramento		1455
> Fresno		1505
> Santa Maria		1422
> Barstow		1646
> Los Angeles		1406
> San Diego		1406
>
>
> Anybody want to comment?
>
> Bill.
>
> > -----Original Message-----
> > From: William Miller [mailto:wrmiller at slonet.org]
> > Sent: Wednesday, March 14, 2001 2:13 PM
> > To: RE-wrenches at topica.com
> > Subject: RE: Unisolar Roofing [RE-wrenches]
> >
> >
> > Bill:
> >
> > I am located in San Luis Obispo County.  I have a client that
> > installed his
> > own ground mount array at 210 deg. true.  I need to know in this type of
> > situation, how much reduction in output will they have?  I would like to
> > own software that can determine this as it comes up frequently.
> >
> > William
> >
> >
> >
> > At 09:40 AM 3/14/01 -0800, you wrote:
> > >Where are you located. I have a chart for the state of California. It
> > >doesn't necessarily work in other locations. A similar chart was done
> for
> > >Colorado. It's just a series of PVFCHART simulations--works great.
> > >
> > >Bill.
> > >
> >
> >
> > __________________________________________________________________
> > William Miller
> > SLO Communications: Communications and Power Systems Consulting
> > PO Box 50, Santa Margarita, CA 93453
> > Voice :805-438-5600		Fax: 805-438-4607	VMail: 805-546-4875
> > email: wrmiller at slonet.org
> > License No. C-10-773985
> > _____________________________________________________________
> > Compatibility:
> > Word processor: WP7
> > Spreadsheet: Quatro Pro 7
> > CAD: Microstation 95, DXF, Visio 4.1T
> > _____________________________________________________________
> > "I stand by all the misstatements that I've made." Dan Quayle
> > __________________________________________________________________
> >
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 michael.welch at homepower.com

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