How efficient solar panels and can they power your electronic?

In this article we discussed the solar power and how to calculate needed solar panel size.

Also we have discussed some solar devises here.

Here I would like show a few examples of how bad it can be. Life is not always the first class seat and most of us do not watch or read The Secret or the Law of Attraction and get the real deal from what wold has to offer. Therefore we must learn how to characterize and deal with that appropriately.
1. Example of broken solar wafers. It was purchased from ebay as a grade B, which means it could have some imperfections/cracks, but in working condition.
The package was sitting in my storage shelf for almost 10 years and I decided to test those wafers among other solar devices.
After unpacking, first thing I discovered the wafers were cracked and the top wafers are broken to peaces.

vertically broken wafer

I took one of the broken vertically and one broken longitudinally. The first one (vertically  broken) is in the picture above. Size  8cm x 14.8cm but small corner is totally missing (can't be soldered or connected). It had to be soldered with thin wireds in the back to connect anode plates together. The cathode (negative electrode) had two connection bands coming out of wafer. And both broken peaces had bands. The picture above is showing the front side with cathode (negative strips), I'm describing this with lots of details to show the situation about discussed samples.
Measurement of short circuit current gave me 570mA on the  sun, but behind the doubble glass window and horizontally.
80% visibility (hazy) day but with sun yield 320mA.
This is with expected and measured 0.52V no load voltage. Dust effects power generation. 495mA was measured after 1 week, when dust settled on top of the same wafer on bright sunny day (compare to 570mA clean wafer).
Another sample:
Horizontally broken (cracked) same size 8cm x 14.8cm. You can't see the crack, but ot is almost in the middle and goes horizontally. In this case I just joint together all the anode pads in the back and connect both cathode strips in the front. Results are better as we expected: Isc 100% sun 612mA, hazy 80% = 412mA with the same 0.52V open circuit voltage.
Thus: Horizontally broken wafer with 118.5cm2 or 0.01185 m2 gave me 0.2387 Watt on bright sun and 0.1607 Watt on 80% hazy day. All is behind the window in mid winter and placed horizontally. All according to trusty wattage calculator here.

Broken corner is about 2.5 cm2 or 0.0116 m2. It has 0.2223 Watt on the sunny day and 0.1248 Wat during hazy day according to my estimates.
How is that correlated with this watt calculator : ideally with sun having altitude of 19deg, it should have been 0.5 Watt on the sunny day but considered it is behind the double sided glass window, dirty from previous number of years, it is not that bad fit.

Another example is the 3 led flash light, which I got as a gimmick gift.

3 led light

fake solar led

  Solar panel inside is really tiny :3.7 x 2.2 cm or 0.000814m2

Opening it reveled an astonishing truth: solar panel was not connected o anything and non rechargeable CR1616 battery was connected to PCBA as a source of power. I cut the panel out (it was glued to PCBA) and soldered wires for testing.
Theoretically we can expect whopping 0.0338 Watts! Here I'm very ashamed to put capital W in front of Watts.
Let's look at reality check: On the sun Isc=3mA Vop=5.5V, gave me according to this calculator 0.0124 Watt. And again we missed it by 2x the theoretical value. I may have to revisit my calculator page to include windows or transparent obstacles in to calculation.

Here we not discussing usefulness of this whole contraption as there are more appropriate sites to do so.

We are only concentrating our attention on pure mathematical and physics value of solar power itself.

Third example is from broken garden light, powered by solar power and two double A NiCad batteries.

  It was nothing special , not working device to begin with, but I wanted to use the solar panel for miscelenius perposes and removed it from the frame long time ago. Size:5.2 x 6.4 cm or 0.003328 m2. Reader might notice, I transcode every information in to International System of Units (SI ). Some humans might insist on their standards, more power to them and good luck to calculate things without making errors.

This panel gave 4V, 1.3mA with no load voltage and short circuit current accordingly on the sun, which suppose to be 0.0039 Watt according to power calculator.

Theoretic power suppose to be 0.1229 Watt! So this panel is really doing bad in terms of real power. After removing crud from the top, I saw a few solar panes have been cracked. Most likely this is needed to be ether revisited with repair attempt or good for dumpster.

Fourth example is solar charged power bank. It didn't work since day one and it was opened to investigate why it never worked.

It consist of two sides and from a distance looks like a flip-phone. Solar panels here consist of two pars, 4.5cm x 6cm each. Looking at them carefuly on the bright sum, it was discovered they consist of wafers,  generously spaced between each other. Therefore I downgraded actual size  to : 4mm x 20 mm and 22pcs on each panel = 1760mm = 17.6cm2 per each or 35.3cm2 for two clams it would be 0.0035m2. Supposedly this would be 0.1293 Watt.
Real measurements: 11.2V No load and 12mA shirt circuit would be around 0.1 Watt. Not too bad for matching theory and real measurements.


1.Calculators for solar panels worked up to margin of error due to measurement circumstances.

2. Powers produced by small solar panels are way too small to be used for anything productive, including LED lights. Smallest dim LED is around 0.03Watt.

3. Most of solar panels are not as good as they are suppose o be even for theoretical area of usage.

4. Omitted in the discussion above many real time measurements shows that solar power dependent on angles and transparency of medium standing in front of them. Glass, hazy weather, dust, crud will effect solar generation so much that investment can be rendered useless.

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