30 Watt Solar Panel Kit?
W9GFO
Posts: 4,010
YouTube just informed me that there is a new Parallax video out. A 30 Watt solar panel kit! At first I thought that it must be a typo, probably actually a 3 watt kit is more like it. But no, really a 30 watt 12 cell kit. I think I need one - or two.
The Parallax website seems to be hiding the details of this little gem even though the video has been up for nearly a week. Either I'm the first to notice (yay for me), or I haven't been paying attention.
Rich H
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The Simple Servo Tester, a kit from Gadget Gangster.
The Parallax website seems to be hiding the details of this little gem even though the video has been up for nearly a week. Either I'm the first to notice (yay for me), or I haven't been paying attention.
Rich H
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The Simple Servo Tester, a kit from Gadget Gangster.
Comments
-Patrick
www.parallax.com/StoreSearchResults/tabid/768/txtSearch/solar/List/0/SortField/4/ProductID/659/Default.aspx
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Alex Burke
"It is not how smart you are rather, it is how you are smart." -Jon Campbell
Rich H
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The Simple Servo Tester, a kit from Gadget Gangster.
"Thanks for sending this.· When I was studying about building a solar cell generator, I came across similar information.· The cells are very delicate and there are ways of building solar panels with broken cells just by attaching the broken pieces together with the conducting wires.· I also came across a site that shows how to encase the cells in acrylic to stabilize them."
If it is possible to fix solar cells then I think this is useful information for everybody to know.
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Rich H
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The Simple Servo Tester, a kit from Gadget Gangster.
Mono-crystalline solar cells are by their very nature, quite thin (0.008”[noparse];)[/noparse], brittle, and do break easily.· This Kit contains the same quality cells that are in commercially fabricated solar panels (like what you would buy through a dealer and have installed on your roof).·
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It is quite possible to build your own solar panel with broken cells, in fact this kit was developed in part, because of my experience in doing just that.· I initially learned how to solder cells with some broken ones.· The experience provides a great primer for how the cells work when interconnected in various ways.· However, results were disappointing (to me) because the final product was less than satisfactory in reliability, appearance, and power output.
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That being said, it may be well worth the time to get some broken cells and build your own panel, as this is an inexpensive way to not only get comfortable with solar, but it’s also a great learning experience, and here’s why…
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Think of a cell as a very flat flashlight battery, the top is negative and the bottom positive. ·No matter the physical size of the cell, it will only produce about 0.5 volts.· The size of the surface area of the cell determines the amperage that can flow through it.
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When you connect (2) cell in series, you get 1 volt, (3) cells in series = 1.5 volts, etc.· Even if the cells are all different sizes, the voltage still adds linearly.
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Amperage works differently.· Let’s assume you connect (3) cells in series. Let’s also assume the first cell has a surface area of 2 sq. inches (producing 200 ma.), the second cell is 4 sq. inches (400 ma.), and the third cell 10 sq. inches (capable of 1 amp).· If you add up the current capacity of all the individual cells we get 1.6 amps.· Logically we might conclude that power output would be:· 1.5 volts x 1.6 amps = 2.4 watts.· ·However, that’s not the case.
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The amount of amperage in a series of connected solar cells is limited to the smallest amperage cell in the circuit – think of the smallest cell like a kink in a garden hose – only the amount of water that the kink allows to flow through - gets through, regardless of the diameter of the rest of the hose.
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Therefore in this example, total power output is: 1.5 volts x 0.2 amps = 0.3 watts – a far cry from what we might have expected.
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It is for this reason that commercial quality solar panels not only have consistent solar cell sizes (read unbroken), but they are also “amperage matched” to each other within the panel.· (Every cell is tested for output at the factory, and are sorted based on efficiency – in the case of the 30 watt panel, each cell is 16.75% efficient and generates about 0.5 volts @ about 4.9 amps.)· Of course, this is under ideal laboratory test conditions, and “your mileage may (will!) vary” (just like commercially produced panels).
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So yes, you can build a full solar panel from lesser quality cells (I’ve done it), just be aware of the potential· results, and maybe temper your expectations on how much energy that panel may generate.
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One other thing to mention at this point:· Typically “roll your own” solar panel instructions and “kits” give you cells, flux pens, and wire too, but many times, that’s where it stops.· To make a panel that’s going to last, and be more robust than a “wind-chime”, you should mount and encase the (very) delicate cells in some way.· Acrylic has very good UV resistance and can be 15-20 times more resistant to breakage than glass.· Polycarbonate has almost as good UV resistance, but is 250 times more resistant to breaking than glass.· Of course you can use plain old glass too – choose your poison!·
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We weighed the advantages/disadvantages of each, and choose polycarbonate for the Parallax “Thirty”.· It’s virtually unbreakable, (it’s used in security window applications) can be milled relatively quickly (important to keep costs down), yet still provides a high degree of safety for the cells).· All that being said, no solar panel – no matter how it’s constructed – is indestructible.· Even the “Thirty” when fully assembled can break when subjected to sudden drops or high impact situations (after all, we’re talking about (12) pieces of 0.008” thick sheets of 5” square glass here) – external shock will break cells.· We’ve done the destructive testing here to prove it J ·
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And believe me, it was really hard to take a perfectly functional “Thirty” (after spending 10 or 12 hours to make it), and hit it, drop it, and kick it ‘til it broke!)
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Matt Gilliland