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November 5, 2013 – 12:21 pm

Solar Panel Test in Moonlight: 3.5 microampere short-circuit current
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Image by yellowcloud
** I wondered how the solar panels to provide power at night in the moonlight. Except for the questionable statements I found nothing on the web yet. So here I present my size: – New monocrystalline solar panel labeled “30 watt” with 36 cells connected in series-quarter Moonlight, two days before the full moon-normal-incidence temperature of the panel of about 18 degrees centigrade-93 calculated the percent transmission of light through the mesh of the safety cat you see in the picture-No streetlights or car headlights shining on the panel-> Moonlight open-circuit voltage Voc measured with a 10 megohm multimeter: 16 millivolts-> Luna short-circuit current circuit current Isc: 3.5 microampereLa maximum output power would be lower than Isc * Voc = 56nanowatts, with the characteristic pn junction in mind, I would say 35nW.Se you compare this with the sunlight (measured) values ​​Voc = 22 volts and Icc = 1.6 amperee a power of more than 20 watts output, this panel provides less than a billionth of electricity in the moonlight in the sun. Wikipedia says that the light of the full moon is 400,000 times fainter than the sun, so this does not coincide with the large ratio of potenza.Ma from my day job as an electrical engineer in a photonics company know that the power of light is proportional to the short-circuit photocurrent of a silicon detector. The relationship between Isc out of my panel of sun and moon is 1.6 amps / 3.5 microamps = 457000. voila! So, with regard to the short circuit current, the solar panel works well and proportional. The big booh comes when you see the tiny tension that builds up. This is for the high cost ratio vector recombination to the creation of small light levels, the leakage of electricity generated via its inside cells. Only when short circuit, the charge carriers are able to flow out of the cell in amounts ragionevole.Il efficient photovoltaic conversion of the moon would be a great, focusing Fresnel lens and a tiny solar cell the size of those that use pocket calculators, to obtain a high density light to a minimum area of ​​cella.NB: Do not blame the input resistance of 10 megohms of my multimeter short circuit of UOC moonlight up to 16MV! 10 megohms is far higher than the output resistance of the panel and not short it: if we assume the panel would have an output resistance of 10 megohms or greater in moon and a high open circuit voltage (for example, up to 20 volt), then it could never provide a short circuit current of 3.5uA one side and down to be shorted 16MV from 10 megohms other. In fact, I assume the panel has an output resistance in the moonlight lower Voc / Isc = 16mV/3.5uA = 4.5 kOhm. Lower due to the “tension-hard” feature user interface of the pn junction in the direction avanti.Notizie measurement: an area at low cost 3×3mm photodiode (BPW34) reliably results in 60millivolt Voc to my multimeter when put in moonlight WITHOUT CONCENTRATION, so forget the solar cells in the moonlight, they just are not comparable with real photodiodes on the strength of 300×300mm shunt.Con a Fresnel lens (a lens of an arrangement of two lenses) recovered from an overhead as a “concentrator moon”, I measured Voc = 300mV and Isc = 7.0microampere!

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