[RE-wrenches] smart mount racking
Geoff Greenfield
geoff at third-sun.com
Fri Oct 31 13:00:02 PDT 2008
Hey Jeff-
Some disagreement on whether or not it is a "true" flashed detail (ie: Oatey is fully lapped, but smartmount relies on sealant (new metal to new metal). Similar questions about QuickMount. My call was that I trust it as 25 years plus.
Definately a time saver and a design advance... EXCEPT on uneven (wavy) roofs as the shimming difficulties to obtain clean lines offsets any other time savings. We use the slop in those ovalized holes of unirac more often than we think!
May need to educate some design review folks that are used to lags in trusses... but this is an engineered solution with many points of attatchment. I expect to see copy-cat solutions soon.
For a brighter energy future,
Geoff Greenfield
Founder and CEO
Third Sun Solar & Wind Power Ltd.
340 West State Street, Unit 25
Athens, OH 45701
740.597.3111 Fax 740.597.1548
www.Third-Sun.com
Clean Energy - Expertly Installed
----- "Jeff Blick" wrote:
> Hi wrenches,
> Have any of you all installed the smart mount system for panel racking?
> Smart mount is a penetrationless racking system that is sold by Sunpower.
> We are thinking of using it, though we wonder how it has proven itself in
> the real world. Thanks for your expertise and advice everyone......
>
>
> Jeff Blick
> PV installer
> Sunlight Solar Inc.
> 4 NW Franklin
> Bend, OR 97701
> direct: 541-306-4196
> fax: 541-322-1911
> jeff.blick at sunlightsolar.com
> www.sunlightsolar.com
>
> -----Original Message-----
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of
> re-wrenches-request at lists.re-wrenches.org
> Sent: Friday, October 31, 2008 11:39 AM
> To: re-wrenches at lists.re-wrenches.org
> Subject: RE-wrenches Digest, Vol 1, Issue 258
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> Today's Topics:
> 1. Request for signage, disconnect, other safety photos (Dan Fink)
> 2. Re: Trouble Shooting Bad Diode (Bill Brooks)
> 3. Re: mix-n-match Unisolar (Bill Brooks)
> ----------------------------------------------------------------------
> Message: 1
> Date: Fri, 31 Oct 2008 12:22:20 -0600
> From: Dan Fink <danbob at hughes.net>
> Subject: [RE-wrenches] Request for signage, disconnect, other safety
> photos
> To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
> Message-ID: <490B4CDC.6080302 at hughes.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> Hi all. In addition to being a solar and wind system consultant and
> author, I'm an officer on a volunteer fire department in a remote area
> of the Northern Colorado mountains. About 5 percent of the residences in
> our response area are off-grid, though the gridless area comprises over
> 75% of the district. We are a classic "urban interface" department, both
> wildland and structural.
> I'm working on a short powerpoint presentation about renewable energy
> systems to give at meetings of other local urban-interface fire
> departments, and likely make available free on the internet. I'm the
> only responder on our department who lives off-grid, and most
> firefighters don't realize the special issues with off-grid systems.
> They expect that when you swing your axe and chop the mains off from the
> powerline (or, preferably, throw the switch, but that's not always
> possible), all circuits in the home, outbuildings and property are dead.
> This is not the case with islanding systems, nor with solar arrays and
> wind turbines using non-islanding grid-tie. And now that we commonly
> wire PV and wind at voltages over 100v, it could be hazardous to the
> firefighter that was not informed. Other aspects of the presentation
> include wind turbine tower guy wires and their anchors that are
> vulnerable to weakening from vegetation burning under them, the hazards
> of battery banks, various ways well pumps might be connected (nice to
> have water at the scene), and more.
> Please contact me off list if you have any photos you would be willing
> to share, with credit and copyright notice to you. Images of signage,
> interesting system disconnects (not everyone has a factory-built power
> panel) and their labeling, anything that might relate to firefighter
> safety, would be much appreciated.
> DAN FINK
> Technical Director
> http://www.otherpower.com/
> Rist Canyon Volunteer Fire Department
> http://rcvfd.org/
> KC0VRD
> WQGS890
> ------------------------------
> Message: 2
> Date: Fri, 31 Oct 2008 11:33:51 -0700
> From: "Bill Brooks" <billbrooks7 at yahoo.com>
> Subject: Re: [RE-wrenches] Trouble Shooting Bad Diode
> To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
> Message-ID: <000801c93b87$39cefce0$ad6cf6a0$@com>
> Content-Type: text/plain; charset="us-ascii"
> Kirpal,
>
> When you parallel, your voltages have to be the same, so you are correct in
> that assumption.
>
> Your assumption about the diodes is not correct. Diodes don't work like
> that. You could have a shorted module (all three diodes shorted) which would
> lower the Voc by one module. It looks like you have nearly two modules worth
> of problems. It could be a total of 5 bad diodes, but that would be weird.
> It could be you have a ground fault, and haven't tripped the GFP yet because
> of lower sunlight levels-(it has to be very low sun to stay under 1 amp).
> You also could have a wiring mistake, either because the factory reversed
> wired a module (rare, but it happens)-that would be 2 modules low; or, you
> could have skipped two modules somehow.
>
> It does seem like a quarter of the bad string is out. Your assumption about
> bad diodes could be correct, but it only affects the groups of cells its
> connected to. Each diode protects 24 cells-it looks like you have 5 diodes
> worth of loss. It could be in 2 modules, or up to 5 modules.
>
> The shading test is the best way to find bad diodes. Disconnect the bad
> string from the good one and take a piece of cardboard the dimension of the
> module. With your meter testing Voc on the back string, completely cover
> each module, one at a time. When the Voc is not affected by complete shading
> of a module, that module is completely bad. If the shaded module only loses
> a portion of one module's Voc, then you have one or two, of the three
> diodes, bad.
>
> This is a great opportunity to learn how to troubleshoot a PV array. Take
> the time, and the effort, to run through it carefully, learn the problems,
> and report back with your findings. It's a beautiful thing to learn
> something new.
>
> Bill.
>
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Kirpal
> Khalsa
> Sent: Friday, October 31, 2008 10:43 AM
> To: RE-wrenches
> Subject: [RE-wrenches] Trouble Shooting Bad Diode
>
> Greetings all......I was hoping i could have someone help me confirm a
> troubled series string on a system we have installed.....
> System consists of 16 BP 170 W 24V nominal modules......2 strings of 8
> modules.....Vmp of each module is roughly 34V and Voc of each module is
> roughly 41V. One string is under-producing......String 1 Voc is 346V and
> String 2 Voc is 272V. String 1 Vmp under load is 270V and String 2 Vmp
> underload is 270V. I am hypothesizing that String 2 has a bad diode on the
> 3rd panel in and is reducing the Voc of that string by th 2 panels ahead of
> it in the string. I am hoping to figure this out without removing the
> entire string and checking each panel if possible.....
> I think the Vmp is equal due to the fact that both strings are paralleled in
> the inverter and the 1st string is being pulled to the same level V as the
> 2nd string under load......Is my logic good?
> Thanks for the help and advice.....
> Cheers,
> Kirpal Khalsa
> Renewable Energy Sytems
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> ------------------------------
> Message: 3
> Date: Fri, 31 Oct 2008 11:38:55 -0700
> From: "Bill Brooks" <billbrooks7 at yahoo.com>
> Subject: Re: [RE-wrenches] mix-n-match Unisolar
> To: "'RE-wrenches'" <re-wrenches at lists.re-wrenches.org>
> Message-ID: <001201c93b87$ef0c3c30$cd24b490$@com>
> Content-Type: text/plain; charset="us-ascii"
> Geoff,
>
> The ultimate issue is how many cells are in each series string and is the
> voltage of the cells nearly the same. As long as the number and the voltage
> of the cells match up for each string, it makes no difference what
> arrangement the modules are in.
>
> You could have 5 + 6 + 7 = 18 cells in one group and 3+10+5 =18 cells in
> another group, and its all good as long as they are similar cells. Unisolar,
> due to the low fill factor, is actually pretty forgiving of difference
> modules and cells. If you need help, let me know.
>
> Bill.
>
> From: re-wrenches-bounces at lists.re-wrenches.org
> [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Jason
> Lombard
> Sent: Friday, October 31, 2008 8:55 AM
> To: RE-wrenches
> Subject: Re: [RE-wrenches] mix-n-match Unisolar
>
> You are correct and they are not. The entire string or array will drop the
> lowest performing panel and seriously detain performance.
> On Thu, Oct 30, 2008 at 2:29 PM, Geoff Greenfield <geoff at third-sun.com>
> wrote:
> I thought I knew the answer to this one, but wanted to run it by the list.
>
> We are responding to a bid where the electrical engineer has designed a
> system with different sized Uni-solar laminates in some series strings
> paralelled with consistant full size strings. (this was done to work around
> skylights etc).
>
> We suggested that this was a poor design and will lead to "least common
> denomenator" performance, exacerbated by MPPT confusion. The EE responded
> that "the bypass diodes allow for this".
>
> Any experience with this in practice?
> For a brighter energy future,
> Geoff Greenfield
> Founder and CEO
> Third Sun Solar & Wind Power Ltd.
> 340 West State Street, Unit 25
> Athens, OH 45701
> 740.597.3111 Fax 740.597.1548
> www.Third-Sun.com
> Clean Energy - Expertly Installed
> _______________________________________________
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> --
> Jason Lombard
> Open Hand Solar LLC.
> HC74 Box13
> Pecos, NM. 87552
> 505 795 8646
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