Solar Power Topics

Current Solar Energy Plot

Determining solar panel output for a known Solar Energy value:

  1. Determine the current Solar PV output e.g. 2800 watts when the Solar Energy reading is 571w/M2
  2. Calculate the Solar PV surface area e.g 14-panels each of 1.67M x 1M = 23.38M2
  3. Multiply panel Surface Area x Solar Energy = 23.38M2 x 571Watts = 13350 Watts
  4. However, actual output was: 2800 Watts, therefore conversion efficiency = 2800 / 13350 = 0.21 or 21%
  5. Example: Solar Energy required for 1000Watts output = 1000 * 0.21 = 210W/M2
  6. Example: Solar Energy = 210W/M2 then expected output = 210/0.21 = 1000Watts

 

Making a Solar Energy Meter

Solar panel connected to a load RL:

  1. Obtain a known voltage solar cell, say a 5volt 1W type
  2. Measure the area of your solar panel e.g. 100mm x 150mm or 0.1M x 0.15M
  3. Surface area = 0.1M x 0.15M =  0.0015M2
  4. Attach a load resistor, say 22R would be suitable for a 1W panel
  5. Measure voltage in sunlight, say the result is 4.2volts
  6. Now calculate power output using the formula Power = V2 / R
    1. 4.22 / 22 = 0.802W
  7. Solar radiation is defined as : power / area and the units are Watts / Square Metre
  8. Solar radiation for the output was = 0.802 / 0.0015 = 535 W/M2
  9. Compare with a known (accurate) Solar Energy meter e.g. Weather stations
  10. If actual Solar Energy was 571W/M2 when the output was measured, then apply a calibration factor in this example of : 571/535 = 1.067 to account for panel characteristics.
  11. Now Solar Energy can be determined by measuring the solar panel output under load using a microcontroller ADC input, that measures the RLoad voltage
  12. Then Solar Energy  = ( (VRLoad) 2/ Rload ) / 0.0015 * 1.067

float Solar Energy = sq(analogRead() * calibrationfactor) / Rload / 0.0015 * 1,067;

where ‘calibrationfactor’ is an ADC correction constant used to adjust ADC for accuracy, eg true voltage is 3v but ADC measured 2.9v, then factor = 3/2.9

Solar System Schematic