ianganderton
Auckland, NZ
I have the following insolation data for a location. How would I predict/estimate output for a PV panel using this data?
Thanks for any input
Thanks for any input
How do I use insolation data to estimate output?
- Thread starter ianganderton
- Start date
svetz
Works in theory! Practice? That's something else
A 100W panel only generates 100W at Standard Test Conditions (aka STC, e.g., 1000 W/m^2 at 25C at 1.5 air masses, perfect alignment towards the sun, etc.). Those conditions don't occur very often, usually around solar noon on a cool day. Warmer days you'll do worse, cold days you'll do better.
Before and after solar noon, the sun's rays go through more atmosphere and you get less and less solar irradience as the sun gets lower in the sky.
The insolation value takes all the power the panel could generate throughout the day and boils it into the number of hours a panel would generate. For example you might have 12 hours of sun for a given day, but at 8 AM it's only 5% of full strength, at 10 it's 60%, at noon it's 100%... add all the power under the curve and you get the insolation number, it's essentially the number of hours per day at the equivalent of full power sunlight. It makes quick and rough power estimates pretty easy. If you want better numbers that include your local weather patterns use PVWatts or SAM to add in your exact equipment and some economics.
Once you know your insolation number you multiple it by your array size. For example, if you have an insolation value of 4.5 and a 100W panel you'd generate (on average) 100W x 4.5 hrs/day = 450 Wh for that day. Usually on an insolation map you get the yearly average. See this post for more.
Before and after solar noon, the sun's rays go through more atmosphere and you get less and less solar irradience as the sun gets lower in the sky.
The insolation value takes all the power the panel could generate throughout the day and boils it into the number of hours a panel would generate. For example you might have 12 hours of sun for a given day, but at 8 AM it's only 5% of full strength, at 10 it's 60%, at noon it's 100%... add all the power under the curve and you get the insolation number, it's essentially the number of hours per day at the equivalent of full power sunlight. It makes quick and rough power estimates pretty easy. If you want better numbers that include your local weather patterns use PVWatts or SAM to add in your exact equipment and some economics.
Once you know your insolation number you multiple it by your array size. For example, if you have an insolation value of 4.5 and a 100W panel you'd generate (on average) 100W x 4.5 hrs/day = 450 Wh for that day. Usually on an insolation map you get the yearly average. See this post for more.
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