Bypass Diodes

[Mike90250]

...is this thinking totally silly? Mark

No. As long as you have thought it out, and are happy with the tradeoff's you mention.

The .GIF did not come out real clear on my work computer, I'll look at it tonight, I'm not sure how you will bypass the lower 5 cells, will they have their own diode ?

No way you are able to orient the panels to avoid the shade ? Bummer.

Also, have you thought how you will prevent moisture buildup in the array ?

[Solmark]

Mike,
I was planning on using some bypass diodes, the gif will hopefully explain, that said, schoolboy error on that drawing - all diodes placed the wrong way round!

Regarding Schottky Diodes, these seem to be freely available for about $0.75, how do their specs look to you? Array Max output 20v, 7.5A

Manufacturer: MULTICOMP
RoHS : Yes
Description : DIODE, SCHOTTKY, 16A, 45V
Diode Type:Schottky
Repetitive Reverse Voltage Vrrm Max:45V
Forward Current If(AV):16A
Forward Voltage VF Max:630mV
Forward Surge Current Ifsm Max:150A
Operating Temperature Range:-65

[Mike90250]

Those diodes should work OK. For the diodes you expect to be "active" when shaded, you should heatsink them - don't forget their case is electrically live.. With .63V @ 7.5A, you will be dissipating about 5 watts per diode, so chose a heatsink accordingly, strive to keep junction temp below 90C, sure their spec is 150C, but they won't last long that hot.

[Zardiw]

So where can you buy them.......do they make thin ones?

z

[Zardiw]

What about these.......would they work on a 60 cell (6"x6") Panel?
http://www.futureelectronics.com/en/...-TAP.aspx?IM=0

Edit. Found out those won't work. Too weak.

[Zardiw]

Holy Crapola.......look at these.....'Smart' Bypass Diodes: http://www.mouser.com/new/Texas-Inst...-bypass-diode/

z

[Mike90250]

Holy Crapola.......look at these.....'Smart' Bypass Diodes: http://www.mouser.com/new/Texas-Inst...-bypass-diode/

z

Those look like a winner !

[bcroe]

So where can you buy them.......do they make thin ones?

z

Thats a cool part. Its based on the idea that an FET tuned off looks like open in normal direction,
a diode in the reverse. Or a short (in either direction) when turned on. I used that concept for a
180A solid state power control a while back. The problem is, with only 2 terminals and only
26 mv voltage, where do they get enough voltage for gate drive? The video shows, they hickup
every so often back to a diode, to get enough voltage to recharge. Might generate some electrical
noise, not nearly as much as interrupting the current. Bruce Roe

[Zardiw]

I'm going to be building some 5 x 12 panels and due to the size of the glass I have available, I'll be putting them between every 2 strings of 5......should protect the panel really well against shading........z

[Zardiw]

WOW.....look at these.......they are thin enough to incorporate into the panel itself.......where the cells are.....not in the J Box.....only have .38V forward voltage drop........they are not 'smart' diodes though:

http://www.digikey.com/product-detai...ITR-ND/2791834


Edit: Those are the ones I'm gonna use.......only 1.42 at Mouser
z

[Guest]

I think wood would be okay for solar panels if done right. if you use, heat resistant, non flammable paint on the wood. and also couple of layers of Foil. Just my two cents.

[Mike90250]

Wood is barely OK for a toy panel you use for a year. Over time, and repeated heating in the summer sun, it will carbonize, warp and do all sorts of strange things. Year 3 it's likely to burn up for you, most likely in the middle of the day when you are gone.

[Guest]

I have to completely disagree with you there friend. Ive done plenty of Paint work for signs for business hand painted. And for over 10 years The wood remains as good as new.
No colorizing no warping even for the thinnest of wood my friend. It defiantly depends on the wood you use and how well you treat it.
But infact I use various techniques on my wood.
When your a artist who has done commercial signs by hand. You learn how to treat the wood for preservation for long periods of time.
And I do believe that my signs will go well over 25 years looking like new with no warp at all.

See what most people do when they use wood for solar, They dont do any sort of treatment to that wood. Let alone even paint it or seal it or varnish it nothing.
And Most of all.. Aluminum heats faster than wood. So in that regards you are only cooking your cells alot faster being encapsulated than you would with wood.

But if you dont agree that is fine. You wont always be correct. Im just saying this from experience with commercial sign work.
I know many frown upon it. But not many know how to treat wood at all.

Good conductors of heat: Copper, gold, Aluminium
poor conductors: Wood, plastic, glass, china, cork

[Zardiw]

I have to completely disagree with you there friend. Ive done plenty of Paint work for signs for business hand painted. And for over 10 years The wood remains as good as new.
No colorizing no warping even for the thinnest of wood my friend. It defiantly depends on the wood you use and how well you treat it.
But infact I use various techniques on my wood.
When your a artist who has done commercial signs by hand. You learn how to treat the wood for preservation for long periods of time.
And I do believe that my signs will go well over 25 years looking like new with no warp at all.

See what most people do when they use wood for solar, They dont do any sort of treatment to that wood. Let alone even paint it or seal it or varnish it nothing.
And Most of all.. Aluminum heats faster than wood. So in that regards you are only cooking your cells alot faster being encapsulated than you would with wood.

But if you dont agree that is fine. You wont always be correct. Im just saying this from experience with commercial sign work.
I know many frown upon it. But not many know how to treat wood at all.

Good conductors of heat: Copper, gold, Aluminium
poor conductors: Wood, plastic, glass, china, cork

How are you going to seal the cells......will you use glass on the front?.....I think you should go glass/glass and seal it with silicone. That's what I'm gonna do. Found some old patio doors that are tempered glass.....will build it on that and then silicone the back with sheets of single strength glass.....should last 50 years.....lol......That's what the top solar panel mfgr is doing now. Getting away from encapsulating with EOV or whatever it is..........z

[J.P.M.]

More $0.02: While wood is a fine material for many applications, my experience is such that it's particular characteristics, one of which, BTW, is relatively good thermal insulating qualities compared to most metals, make wood less than ideal for solar panel applications, either for module framing or panel/array support, pretty much regardless of surface coating or other treatment.