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Kolumam

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Posts: 8
Reply with quote  #1 
Hi All,

I have a data logger that is pushing irradiance data every minute which means 1441 lines/day of irradiance data. From that how do I calculate the irradiation?

Eg. When I add all the values of irradiance, I get 393578.019. When I divide it by 1441, I am getting a wrong value. 

What is expecting is something like this. Irradiation = 5.07.

Please help. 

Thank you in advance.

stmbtwle

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Reply with quote  #2 
would you be talking about INSOLATION?

"Irradiance is an instantaneous measurement of solar power over some area. ...Insolation is a measurement of the cumulative energy measured over some area for a defined period of time (e.g., annual, monthly, daily, etc.). The common unit ofinsolation is kilowatt hours per square meter."

https://pvpmc.sandia.gov/modeling-steps/1-weather-design-inputs/irradiance-and-insolation-2/




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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Kolumam

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Posts: 8
Reply with quote  #3 
Yes, what I meant is insolation. Kindly see my example. Am I making a mistake with the denominator?
stmbtwle

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Reply with quote  #4 
I don't see an example. What are you looking for, an average, or a total?

Is your equipment's output in watts/sqm? If not you may need a conversion factor. You might also have a calibration error. Might be something as simple as a misplaced decimal.

Also what is maximum individual reading? That should give you an idea where to start.

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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay
Kolumam

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Posts: 8
Reply with quote  #5 
Hi Willie,

Please find the attached file containing the column "AvgGSI". I am not sure what's the unit of it. Can you tell me how to calculate the irradiation from the file of that day. It has irradiance data every minute.

 
Attached Files
xlsx Irradiance.xlsx (41.34 KB, 1 views)

stmbtwle

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Reply with quote  #6 
OK as the highest reading is around 1000, I'm going to assume the units are watts per sq meter

The interval is 1 minute so you're measuring watt-minutes / sq m

Total them all up and you get 224990.837 watt minutes /sq m for the day

Divide by 60 and you get 3749.85 watt hrs / sq m

Divide by 1000 and you get 3.750 kwh/sq m  which is reasonable, depending on weather and location.

 
Attached Files
xls Irradiance.xls (110.50 KB, 3 views)


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Solar is like the wind. It may be free, but putting it to work isn't!
Willie, Tampa Bay

Kolumam

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Posts: 8
Reply with quote  #7 
Thank you so much!
Rick H Parker

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Reply with quote  #8 
Irradiance is power per sq meter (W/m2) or kilowatts per square meter (kW/m2).
Insolation is energy per sq meter (Wh/m2/day) or kilowatt-hours per square meter per day (kWh/m2/day) or even (kWh/m2/year).

The math is the same as Watts to killwatt-hours. Power * Time = energy. 

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Rick H Parker
Kansas, USA
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