Solar cell mounting

parts-man73

While at the Propeller Expo in Ohio last weekend. I Picked up some solar cells that Bean was selling for a great price.

Now I want to mount them in a weatherproof, permanent enclosure. My aim is to charge a battery and power some white LED's to give some dim accent lighting near the fence that encircles my backyard.

Looking for any ideas on...

• what to attach the Solar cells with
• what to cover the cells with...such as Lexan, plexiglass or real glass
• leave an air gap between the cells and the clear cover just mentioned?
• are solar cells tolorant of cold? Should this be mounted in such a way that I can easily bring it in during the winter? I'm in upstate NY where the temps can go down around zero during the winter

Thanks in advance!

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Brian

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kelvin james

Since i do not know the paticulars of what cells you have, i cannot answer the first 3. But solar cells work better in cooler climates, being made from silicon, the hotter they get, the less power they put out. Actually the northern climates are more suited to solar, though there is less sunlight overall. There is some good info on wiki about pv worth reading. In the winter, if snow and ice accumulates on them, then you will get virtually nothing from them. Since all the cells in an array are connected in series, if part of it gets blocked from the light, then the output drops a large amount. I don't consider freezing an issue, maybe to the enclosure, but not the cell.

LoopyByteloose

If at all possible, I would cover with real glass rather than any plastic material. All transparent plastic products yellow with age and suffer from scratching. And glass will clean better with solvents and scrubbing. Try to figure what you want your useful life to be - 5 years or 20 years?

Ironically, the passiveness of the solar cell seems to work against itself. If you have a wind turbine producing the same electricity, all that spinning is in some ways self-cleaning.

Snow is a wonderful reflector of light and will often boost your output in the winter far above the output in the summer. Passive solar heated homes in snow country have been able to reach 95% of their winter heating requirements with solar energy alone.

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It's sunny and warm here. It is always sunny and warm here.... (unless a typhoon blows through).

Tropically, G. Herzog [noparse][[/noparse] 黃鶴 ] in Taiwan

Oldbitcollector (Jeff)

parts-man,

I got a bunch of them from the show as well.. As soon as I figure out how many
I need to create around 7-9 volts, (both voltage and amp) I'm planning on
buying two pieces of plexi from the hardware store and mounting them in between.

Should protect them from damage. Better ideas?

OBC

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T&E Engineer

Solar Cells are nothing more than a piece of silicon sliced thin. The negative plate is on the backside with the positive wire soldered on the front. Each solar cell provides about 0.5 vdc and the current is limited by the physical size of the solar cell. So if you have a really big single solar cell you will have more current but always have 0.5 vdc in voltage.

Think of them like a battery and you can do the following:

1. Connect them in series (+ to -) (- to +) etc. to get a higher voltage level. To get·6 volts you would need 12 of them in series (e.g. 12 * 0.5 = 6).

(neg)<---(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)-
··································································································································· ········· ··|··········
(pos)<

---

2. Connect the series connected·6 vdc solar cells now in parallel to increase the current (+ to +) and (- to -).

(neg)<---(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)
·············· |· |····· |· |····· |· |····· |· |····· |· |····· |· |····· |· |····· |· |······|··|····· |· |····· |· |····· |· |
············ (-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)
·············· |· |····· |· |····· |· |····· |· |····· |· |····· |· |····· |· |····· |· |······|··|····· |· |····· |· |····· |· |
············ (-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)
·············· |· |····· |· |····· |· |····· |· |····· |· |····· |· |····· |· |····· |· |······|··|····· |· |····· |· |····· |· |
············ (-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)--(-)(+)-
··········································································································································· ··· |··········
(pos)<

---

··········································
··············
Here you still have the 6 vdc but at 4 times the current.



Post Edited (T&E Engineer) : 8/29/2008 1:51:20 PM GMT

parts-man73

Kramer said...
Snow is a wonderful reflector of light and will often boost your output in the winter far above the output in the summer. Passive solar heated homes in snow country have been able to reach 95% of their winter heating requirements with solar energy alone.

I was somewhat misleading there.... I was more worried about the battery in the cold. It's a 12 V lead acid battery. And the lights it will be powering really are only needed during warmer weather. I won't be out in the backyard at night during the winter.

I should clarify my mounting question some.... The cells are glass encased with just 2 foil strips for the electrical connections on the rear. There is no mounting holes. I thought about hot glue, but the constant heating and cooling....I've never had good luck with hot glue.

The adhesive is what I was looking for ideas on.

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Brian

uController.com - home of SpinStudio - the modular Development system for the Propeller

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MSDTech

The three cells I mounted on the weather station are held in place with a good silicone caulk and an L bracket on 3 sides. The L brackets are loose enough to allow for differential expansion between the cells and the base they sit on, the caulk was used to weatherproof the electrical connections. They seem stable and I haven't noticed any problems yet.

Leon

Some silicone sealants contain acetic acid which can cause corrosion.

Leon

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sam_sam_sam

Leon or AnyOne Else

Do you of any thing better to use

I have use hot glue this not work very well in the sun

I am looking for some thing that is better than this any· ·s

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··Thanks for any··that you may have and all of your time finding them

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Sam

Post Edited (sam_sam_sam) : 8/29/2008 11:02:10 PM GMT

Beau Schwabe

sam_sam_sam,

Use Caulk designed for high heat outdoor use, but as mentioned, make sure it doesn't have acetic acid.... A quick test, if it smells like vinegar, it's the wrong stuff.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

Phil Pilgrim (PhiPi)

Ditto the acetic acid warning. You might consider a marine-grade product like BoatLIFE silicone rubber sealant. It's acid-free.

-Phil

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parts-man73

Very good suggestions. I'm headed to the hardware stores tommarrow to get some glass and acid free caulk. Thank you all for your help!

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Brian

uController.com - home of SpinStudio - the modular Development system for the Propeller

PropNIC - Add ethernet ability to your Propeller! PropJoy - Plug in a joystick and play some games!

SD card Adapter - mass storage for the masses Audio/Video adapter add composite video and sound to your Proto Board

Oldbitcollector (Jeff)

parts-man,


Before I re-invent the wheel, have you already determined the number of cells required
for powering your SpinStudio board? [noparse]:)[/noparse]

OBC

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New to the Propeller?

Getting started with a Propeller Protoboard?
Check out: Introduction to the Proboard & Propeller Cookbook 1.4
Updates to the Cookbook are now posted to: Propeller.warrantyvoid.us
Got an SD card connected? - PropDOS

sam_sam_sam

Phil

Thank You For that link to the marine-grade product like BoatLIFE silicone rubber sealant

That will help a lot

One thing·I want to ask you dose this·turn yellow in the sun after a while

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··Thanks for any··that you may have and all of your time finding them

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Sam

parts-man73

OBC said...

Before I re-invent the wheel, have you already determined the number of cells required
for powering your SpinStudio board? [noparse]:)[/noparse]

I have to admit, I'm using these for a non-propeller application (gasp!)


They are 4 volts open circuit, less under load. 80 mA short circuit. I would figure 3 in series to produce the voltage you might need, then put more strings of 3 in parallel to increase the amperage. you may end up with a 3x3 array, or 3x10 array, however many cells you happen to have bought.

I'm hoping to charge a 12 V battery, so I may use 4 cells in series. I'll have to do some more tests before I mount them permanently.

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Brian

uController.com - home of SpinStudio - the modular Development system for the Propeller

PropNIC - Add ethernet ability to your Propeller! PropJoy - Plug in a joystick and play some games!

SD card Adapter - mass storage for the masses Audio/Video adapter add composite video and sound to your Proto Board