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Author Topic: How to copy this solar data out of WD?  (Read 794 times)

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Offline beun.net

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How to copy this solar data out of WD?
« on: August 14, 2019, 07:35:09 PM »
In WD, click 'View', then 'Advanced graphs', and then the tab 'Solar KWH'...
The data that's being displayed in there... How can I copy that info into (for instance) Excel?

Anyone any suggestion?

Thanks!
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Offline Weather Display

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Re: How to copy this solar data out of WD?
« Reply #1 on: August 15, 2019, 07:56:09 AM »
there is a log file with the solar wm/2 in it
e.g 82019vantagelog.txt
and so you could use that data to calculate that kw/h value in excel (import as space delimited)

Offline beun.net

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Re: How to copy this solar data out of WD?
« Reply #2 on: August 15, 2019, 12:04:36 PM »
Found the data. Imported correctly into Excel. Thanks.
But I don't know what formula to use in order to combine 1440 seperate minute entries into one KW/h value for the day. How does one calculate that?
Thx!
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Offline Martyn

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Re: How to copy this solar data out of WD?
« Reply #3 on: August 15, 2019, 01:11:31 PM »
One way would be to use the following formula in a cell (assuming all the solar values per minute are in column A - change as necessary).
=(SUM(A1:A1440)/164)/(COUNTIF(A1:A1440,">0")/60)
which adds up all the solar values of the day and divides by 164 (the average over the entire earth per day) then divides that result by the total number of minutes with a solar reading above zero divided by 60 (giving the number of hours for the day) to produce a kWh value which is close but not exact to the value from WD as I have tested with my data, so not sure what formula WD uses.
« Last Edit: August 16, 2019, 09:26:04 AM by Martyn »
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Offline beun.net

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Re: How to copy this solar data out of WD?
« Reply #4 on: August 16, 2019, 09:25:56 PM »
Thanks. That works!

However... I am curious as to why there is a difference with WD... Your calculation seems logical, so how does WD get to its KW/h number........
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Offline niko

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Re: How to copy this solar data out of WD?
« Reply #5 on: August 16, 2019, 10:27:03 PM »
One way would be to use the following formula in a cell (assuming all the solar values per minute are in column A - change as necessary).
=(SUM(A1:A1440)/164)/(COUNTIF(A1:A1440,">0")/60)
which adds up all the solar values of the day and divides by 164 (the average over the entire earth per day) then divides that result by the total number of minutes with a solar reading above zero divided by 60 (giving the number of hours for the day) to produce a kWh value which is close but not exact to the value from WD as I have tested with my data, so not sure what formula WD uses.

What is the 164?

Offline niko

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Re: How to copy this solar data out of WD?
« Reply #6 on: August 16, 2019, 10:31:06 PM »
Thanks. That works!

However... I am curious as to why there is a difference with WD... Your calculation seems logical, so how does WD get to its KW/h number........

If you are using this to estimate the output from solar panels don't forget that the Davis sensor is horizontal but a solar array would be mounted at an angle for maximum collection efficiency. You would also need to adjust for the efficiency of the panels.
« Last Edit: August 16, 2019, 11:47:45 PM by niko »

Offline niko

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Re: How to copy this solar data out of WD?
« Reply #7 on: August 16, 2019, 11:45:40 PM »
Found it! According the this old thread the WD calculation is:

(w/m2 summed each minute) / (60*1000) = kilowatt-hours (kWh)

In other words each minute solar value is considered to be watt-minutes, which are summed and converted to kilowatt-hours.