In Paillard in France (where the Sun should be present) during the e-textile Summercamp 2015 the week started with a lot of sunshine, making it fun to play around with a few solar cells and a water pump.
It was easy to generate the necessary energy for the water pump and generate a nice splashy water sound. But you had to replace the bench quite often, because the Sun is moving in the sky faster then you happen to be aware off.
Then clouds and rain – even in France -, days without sunshine for the solar cells. The nice installation was getting dusty and was removed.
After a week the Sun came back, it was hot and you look for shady places. I charged small lipo’s using the LTC3105 (for setting a 4.2V even when using solar cells of only 0.5V):
(Using these 0.5V flexible solar cells.)
But then also: situated under a tree, the spot where the sun shines moves rather quickly.
Then warm wheather, but a slightly clouded sky, considerable less energy generated. I tried charging an Ipad with the small bunch of solar cells, but the energy generated with the small solar cells is insufficient, the Ipad tells you that the source is not adequate.
Concluding about the smaller solar cells: During these last years of experimenting using these small solar cells in the Netherlands and France, but this means Northern Europe, even during the summer it is practically not possible to generate the energy needed for charging cell phones and lipo’s. Using the solar cells in a coat is only adding problems: you don’t wear a coat when it is warm – you go in the shade when it is warm – if you like to sunbade, you wear the less textile possible …
If the sun really shines, and you have a window, a spot which is really good, then indeed you can get plenty “free” solar energy, but even then it takes many hours before an average lipo or comparable is charged, just like with a normal charger using an adaptor.
It doesn’t mean that the cells don’t generate energy, it is just the level which our devices are used to is still big, requiring much time, mostly more than a day of “real” sunlight.
Hand crank devices:
The smaller cheap ones (1-5 euro’s) can be really crappy:
Chinese light torch (ACTION) : pinching action, throws away half of the energy (using the LED’s as diode for the alternating current), fun for exploring, but bad for energy generating…mind the RSI in your hand after some pinching!
The emergency hand crank dynamo’s, bought at dx.com: cannot store energy, gears made of plastic wear out fast.
Still in the range is the IKEA Ljusa, which has a 1F supercap. About 90 seconds of light, dimming quickly:
Better are the small hand crank light torches bought at ACTION: charging a coin cell battery. This light stays on really longer
The bigger more expensive ( 10-20 euro’s) ones are really good for using as a torch at night, storing energy for 30 minutes easily. Some have multiple ways of generating energy, like the Conrad (nr 5755) version, which has a pulling cord, but also a solar cell. The VARTA 71680 has a bigger crank.
All together for the sizes:
The energy these hand crank devices deliver is mostly used for LED’s. Really charging cell phone devices will require long cranking or bigger dynamo’s. You must think of the bicycle shaped installations you can find in airports or IKEA – even then it costs a considerable amount of time to really charge your cell phone.
Concluding about hand crank: this works always (not depending on the Sun, but rather your energy). But is shows that we as humans – at this moment – consume far more energy, – and finding this normal – then we could ever generate by muscle power.
Concluding about small solar cells and hand crank devices: We like to think we can go “green” with either a bit of muscle power or a bit of sunlight and technology – and making this work, the sun or the muscles, is possible. But we underestimate the required energy and we quickly get frustrated by the time it takes to charge our cell phone either by sunlight or by hand cranking…