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Hector Gasquet
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Join Date: Aug 2015
Posts: 3

Average Number of Cloudy Days

08/05/2015 2:31 PM

I'm 84years old now, but many years ago I dedicated a good number of years to write a PV manual (in Spanish). It was then when I realized that is relatively easy for a designer of a stand-alone system to learn the length of the average Solar day, including data for different tilts of the array, the average wind, and temperature of a given site on Earth. What I never found was collected information on the average number of day (Per season) of consecutive cloudy (too low solar radiation). This data is more than needed to size the battery reserve bank, if you like to achive a minimum system dependability, w/o shortening the life expectancy of the bank of batteries by forcing them to a high DOD, and , more likely, a defficient recharge the next day.

Am I full of s..t? Am I an idiot that didn't know where to look?

I will deeply aprreciate a comment (or two) on the subject.
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Anonymous Hero
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#1

Re: Average number of cloudy days

08/05/2015 2:43 PM

I did some sizing calculations a few years ago and just Googled for the information for my location.

At least in the US it available. I suspect that you can find it for your own area, too.

I just googled "number of sunny days in XXXX" <== just fill in XXXX with your city, country - mine came up right at the top of the search list.
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Hector Gasquet
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Join Date: Aug 2015
Posts: 3
#4
In reply to #1

Re: Average number of cloudy days

08/05/2015 5:40 PM

I didn't know I could Google, so thanks, but and that is a BIG but, the book was intended for all Spanish speaking areas, so I don't know if they can or can't doit.

Anyhow, if anybody ask me, at least there is an avenue.

BYE
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SolarEagle
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Location: by the beach in Florida
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#2

Re: Average number of cloudy days

08/05/2015 3:12 PM

Well the average is 1 to 2 days of electrical requirement...If it's a critical application, then an additional power source is recommended...

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Hector Gasquet
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Posts: 3
#6
In reply to #2

Re: Average number of cloudy days

08/05/2015 11:42 PM

Your answer is what I call an American answer. Think about places in the middle of nowhere in South America, where getting an engine and, on top, fuel and service is next to impossible.

Thanks, anyhow
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JohnDG
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#3

Re: Average Number of Cloudy Days

08/05/2015 4:55 PM

Don't know if you have similar for your location, but this: https://badc.nerc.ac.uk/data/surface/radt_file_format.html will yield a record of insolation hour-by-hour for about 103 locations in the UK from 1900 to present. You may need to do a bit of work with the data to get your required figure.

Follow some links and you can get back to 1853.

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Brave Sir Robin
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#5

Re: Average Number of Cloudy Days

08/05/2015 8:25 PM

If it is for the U.S., the National Renewable Energy Laboratory provides some very nice maps that have monthly average and annual average daily totals.

http://www.nrel.gov/gis/solar.html

Good luck with your quest.
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Usbport
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#7

Re: Average Number of Cloudy Days

08/06/2015 7:46 AM

Don't know if this will help, but take a look:

World weather (avg US Cloud Cover Maps)

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Users who posted comments:

Anonymous Hero (1); Brave Sir Robin (1); Hector Gasquet (2); JohnDG (1); SolarEagle (1); Usbport (1)

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