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Solar cell varies output by load resistor

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I feel interest in solar cell. A site sells small solar cells. I calculated price per area of them. Solar cell price seems proportional to area. If area of solar cell is twice, output is also twice actually[5].

Tbl.1 Price per area
OutputSize [mm]Area [cm²]PricePrice/cm²
4VL70xW3524.5¥610¥25
2VL9xW252.25¥50¥22
2.4VL25xW102.5¥210¥84

I think that a small solar cell can measure illuminance witout external electric power. A site shows equivalent circuit of solar cell[1]. Illuminance depends air mass[2]. Air mass is proportional to atm and inverse propotional to zenith angle. A site shows solar output monthly. The power is one third in winter[3]. Chichibu is located in Kanto, so it is fine in winter. Output decreased in June. It is rainy season in June in Japan. Inverter is one of bottle neck of maintenance. Capacitors of inverter have to te replaced regulary, I suppose[4].

Trony photo cells

Two tiny solar cells were delivered today. I probed one of them by a digital meter. It output more than 1.5 V under a desk light. Looking the cross section of it, I found no layers. I thought of a Si wafer. Googling, it is a thin membrane solar cell[5]. It consits of 9 layers including electrodes. It prints 'TRONY' and 'SC1025IDS' inside. TRONY supplies for CASIO and CITIZEN[7]. If one changes 'TR' for 'S', TRONY is SONY. I show the specifications of it by a reseller. It has 4 electrodes inside. Two electrodes of the left side has no excited mV. They contact one another, maybe. The electrodes seem pasted. I will solder wires. How do I eliminate thermal effect while soldering? I soldered 2 thin wires on the electrodes. I don't know the wire gage correct, AWG26 or 28.

Tbl.2 Specifications of cell
W×L (mm)8.8×24.7
Voc (V) (TYP)2.0
Isc (uA) (TYP)6.5
Vmp (V) (TYP)1.5

Measurements by TDS310

I measured the open output by measurements of TDS310. Sampling is 5 ms/div (10kS/s). Illuminence of my desk may be more 200lx, because the specification shows that the output of the cell is 2.0 V under 200 lx. Room light fluctuates at 120 Hz. I live in area of commercial 60 Hz. It seems the solar cell has big capacitance, so the ripple of 60 Hz is measured. I loaded resistance of 56k and 6.8k Ω. Load resistance of 6.8 kΩ may measure room illuminence of 20 folds.
22:49 Oct22 (GMT+9)

Tbl.3 Load resistance effect
DIVRLAmplMeanHigh
200mV∞20mV
unstable		2.919V2.92
unstable
200mV56kΩ60mV
unstable		1.008V1.04
unstable
50mV6.8kΩ4-6mV
unstable		131mV134mV
unstable

I attached the solar cell with 6.8 kΩ on a west window. I read measurement of Min.

Tbl.4 Solar cell output on a west window
TimeMin [V]CH1MWeather
09:060.896200mV5msFine
09:140.928200mV5msFine
09:580.904200mV5msCloudy
10:191.160200mV100usCloudy
10:250.200200mV5msCloudy
11:141.120200mV5msCloudy
12:311.120200mV5msCloudy
13:171.230200mV5msCloudy
14:111.240200mV5msCloudy
15:020.856200mV5msCloudy
15:540.984200mV5msCloudy
16:021.296200mV5msSunset
16:080.664200mV5msCloudy
16:170.304200mV5msCloudy
16:230.228200mV5msCloudy
17:010.008-5msCloudy
0:16 Oct24 (GMT+9)

A program records the photo cell output

I wrote a program of Visual Basic to get illuminence on a tick of minutes. See My old PCs04 and PCs05 in My old personal computers. It was fine this morning. TDS310 and the program measured for an hour. The peak was 1.02003133297E0 at 9:35. E0 means index of power of 10, that is, 100 = 1. Parameters of TDS310 is the same before. I think of charging a battery. I had better Min and Max at the same time.

Tbl.5 Illuminence on a tick
TimeMin [V]
08:317.56812512875E-1
08:326.71812534332E-1
08:336.64000034332E-1
08:346.5196877718E-1
08:356.25531256199E-1
08:366.31656289101E-1
08:376.45750045776E-1
08:387.76437520981E-1
08:396.61125004292E-1
08:406.51000022888E-1
08:416.44250035286E-1
08:427.53968775272E-1
08:436.50031268597E-1
08:446.41437530518E-1
08:457.91843771935E-1
08:468.04968774319E-1
08:478.20000052452E-1
08:488.32000017166E-1
08:498.44125032425E-1
08:508.3718752861E-1
08:518.85125041008E-1
08:529.06968772411E-1
08:539.27062571049E-1
08:548.90625059605E-1
08:558.83031308651E-1
08:568.56625020504E-1
08:578.21125030518E-1
08:588.38375031948E-1
08:598.50750029087E-1
09:008.75562548637E-1
09:018.6062502861E-1
09:028.63937556744E-1
09:038.44125032425E-1
09:048.45531284809E-1
09:058.5659378767E-1
09:068.64468812943E-1
09:078.88000071049E-1
09:088.98312568665E-1
09:099.28343772888E-1
09:109.41437542439E-1
09:119.39593791962E-1
09:129.43000018597E-1
09:139.66312527657E-1
09:149.67468798161E-1
09:159.7781252861E-1
09:169.51437532902E-1
09:178.7612503767E-1
09:188.71375024319E-1
09:198.73812556267E-1
09:208.84250044823E-1
09:219.21750068665E-1
09:229.65750038624E-1
09:239.21125054359E-1
09:241.027999997139E0
09:251.004218816757E0
09:261.007250070572E0
09:271.016968846321E0
09:281.011000037193E0
09:291.004999995232E0
09:301.008187532425E0
09:311.00640630722E0
09:321.014437556267E0
09:331.016437530518E0
09:341.005125045776E0
09:351.02003133297E0
09:361.01421880722E0
09:371.012562513351E0
09:381.018000006676E0
09:391.015718817711E0
09:401.015250086784E0
09:411.012156248093E0
09:421.00590634346E0
09:431.012062549591E0
11:09 Oct27 GMT+9

The program records 2 Measurements

It is rainy this morning. I rewrote the program to get 2 Measurements of TDS310. Average ofTDS310 is 2. Max differs approximate 20 mV from Min. I think this is noise. Averaging is 2. I began measuring at 5 ms/div as usual, but the displayed measuremt values continue to show the same value. I found that 'Auto' or 'Trig?' had to show alternative, when I measure a varying value slowly. I changed time division into 25 ms/div.

Tbl.6 Illuminence on a tick Oct28
TimeMaxMin
07:481.19750007987E-11.00531257689E-1
07:491.19187504053E-11.00875005126E-1
07:501.03437505662E-18.7875001132E-2
07:518.8031254709E-26.9687500596E-2
07:528.9500002563E-27.3031254113E-2
8:34 Oct28 GMT+9

The program records 4 Measuremnents

Fig.1 Two cells

I added another solar cell with a load of 6.8 kΩ. It was fine. I measured the outputs of the two cells by 2 channles at sampling rate of 2KS/s. The sampling rate is 25 ms/div. The both vertical range were 500 mV/div. Output of Ch2 was different from Ch1 by 7 %. The resistor of load have only 1 % error. Why did they have different characteristics?

Tbl.7 Measurement of 2CH at 2KS/s (25ms)
TimeMeas1 Ch1 MaxMeas2 Ch1 MinMeas3 Ch2 MaxMeas4 Ch2 Min
13:408.40078115463E-18.10624957085E-19.39999997616E-19.02499973774E-1
13:418.94296884537E-18.66562485695E-11.008437514305E09.74843740463E-1
13:428.32499980927E-18.046875E-19.20703113079E-18.89999985695E-1
13:438.19999992847E-17.99843728542E-19.02499973774E-18.72500002384E-1
13:448.12578082085E-17.89999961853E-18.95390629768E-18.65000009537E-1
13:458.3859372139E-18.09921860695E-19.27343726158E-18.96874964237E-1
13:468.31249952316E-18.072655797E-19.17499959469E-18.89999985695E-1
13:479.35000002384E-19.08671855927E-11.066874980927E01.030468702316E0
13:489.39765632153E-19.19999957085E-11.074999928474E01.044999957085E0
13:499.43671882153E-19.20156240463E-11.080078125E01.045234322548E0
13:509.52499985695E-19.23749983311E-11.090000033379E01.060312509537E0
13:519.693749547E-19.4015622139E-11.104453086853E01.073125004768E0
13:529.67343747616E-19.400780797E-11.102578043938E01.077499985695E0
13:539.59999978542E-19.400780797E-11.104531168938E01.078984379768E0
13:549.58828091621E-19.303124547E-11.097499966621E01.069999933243E0
13:559.56249952316E-19.29218709469E-11.095624923706E01.068828105927E0
13:569.58828091621E-19.30000007153E-11.100000023842E01.068125009537E0
13:579.55624997616E-19.24999952316E-11.090000033379E01.0625E0
13:589.58749949932E-19.29921865463E-11.089921832085E01.059140563011E0
13:599.58749949932E-19.30703103542E-11.098593711853E01.064062476158E0
14:009.596093297E-19.35624957085E-11.094531178474E01.064999938011E0
14:019.59999978542E-19.39999997616E-11.098437428474E01.069999933243E0
14:029.60390627384E-19.400780797E-11.103359341621E01.074999928474E0
14:039.60312485695E-19.39999997616E-11.109921813011E01.070859313011E0
14:049.59765613079E-19.32578086853E-11.099531173706E01.070078134537E0
14:059.56562459469E-19.25078094006E-11.09500002861E01.06375002861E0
14:069.59140598774E-19.30000007153E-11.09515619278E01.067499995232E0
14:079.57578122616E-19.31406199932E-11.105156183243E01.069999933243E0
14:089.51093733311E-19.27421867847E-11.090468764305E01.059453129768E0
14:099.49609339237E-19.20312464237E-11.080859303474E01.050156235695E0
14:109.39453125E-19.19999957085E-11.080078125E01.044999957085E0
14:119.32578086853E-19.0499997139E-11.069687485695E01.033749938011E0
14:129.30624961853E-19.0499997139E-11.069687485695E01.032421827316E0
14:139.32500004768E-19.03750002384E-11.069453120232E01.037500023842E0
14:149.32500004768E-19.09374952316E-11.090000033379E01.061484336853E0
14:159.375E-19.12578105927E-11.12249994278E01.088750004768E0
14:169.59453105927E-19.296875E-11.15234375E01.12234377861E0
14:179.69999969006E-19.44999992847E-11.160312533379E01.13031244278E0
14:189.97578084469E-19.77499961853E-11.19867181778E01.16140627861E0
14:191.008437514305E09.80781257153E-11.18875002861E01.160312533379E0
14:209.58124995232E-19.35624957085E-11.108203053474E01.079999923706E0
14:219.69999969006E-19.42499995232E-11.126874923706E01.091328144073E0
14:221.016562461853E09.90624964237E-11.195234298706E01.164999961853E0
14:231.02999997139E01.002187490463E01.210156202316E01.183671832085E0
14:241.027500033379E01.000468730927E01.21875E01.178593754768E0
14:251.034999966621E01.007499933243E01.221328139305E01.182812452316E0
14:261.048515558243E01.020156264305E01.23968744278E01.204765558243E0
14:271.054999947548E01.024999976158E01.242343664169E01.210781216621E0
14:281.058750033379E01.031328082085E01.258749961853E01.22000002861E0
14:291.059765577316E01.038828134537E01.25515627861E01.221562504768E0
14:301.061874985695E01.040703058243E01.26101565361E01.231249928474E0
14:311.074999928474E01.044999957085E01.281562447548E01.244921803474E0
14:321.079218745232E01.049999952316E01.288593769073E01.250156164169E0
14:331.080937504768E01.05999994278E01.289999961853E01.259921789169E0
14:341.090000033379E01.060156226158E01.299999952316E01.259999990463E0
14:351.09249997139E01.064687490463E01.307812452316E01.269999980927E0
14:361.095312476158E01.068593740463E01.297734379768E01.268749952316E0
14:371.089687466621E01.0625E01.277499914169E01.240781188011E0
15:32 Nov06 GMT+9

[1] 太陽電池出力特性
[2] Sono 他 no 太陽電池特性
[3] Chichibu 動物病院太陽光発電所
[4] Inverter no 中身拝見
[5] Cell 段数 to Cell 面積 no 関係（照度一定）
[6] 薄膜 Silicon 太陽電池
[7] Introduction


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