Understanding Solar Irradiance for Solar Panels
In another thread it was suggested that you could use the University of Arizona at Tucson solar data to determine the maximum expected solar panel output at that location. Using that data from 1/20/16 the expected maximum output would be 675/1000 or 67.5 percent at 1:00. That seemed reasonable to me at the time. Click here.
The data at this site is real world data meaning that the actual irradiance is measured and reflects clouds etc. 1/20/16 is basically a cloud free day at that location.
But further checking of the site for the summer time showed that data from 6/21/15 was not what I expected. Click here.
This would seem to suggest that a flat panel would produce more power than a tracking panel at 1:00 on 6/21/15 and this was generally true of other summer time days. What does this data mean and can it be used from this site and others as a reference for solar panels? The definitions of the data suggest this:
The data at this site is real world data meaning that the actual irradiance is measured and reflects clouds etc. 1/20/16 is basically a cloud free day at that location.
But further checking of the site for the summer time showed that data from 6/21/15 was not what I expected. Click here.
This would seem to suggest that a flat panel would produce more power than a tracking panel at 1:00 on 6/21/15 and this was generally true of other summer time days. What does this data mean and can it be used from this site and others as a reference for solar panels? The definitions of the data suggest this:
Direct Normal Irradiance is the amount of solar radiation received per unit area by a surface that is always held perpendicular (or normal) to the rays that come in a straight line from the direction of the sun at its current position in the sky. Typically, you can maximize the amount of irradiance annually received by a surface by keeping it normal to incoming radiation. This quantity is of particular interest to concentrating solar thermal installations and installations that track the position of the sun.
Global Horizontal Irradiance (GHI) is the total amount of shortwave radiation received from above by a surface horizontal to the ground. This value is of particular interest to photovoltaic installations and includes both Direct Normal Irradiance (DNI) and Diffuse Horizontal Irradiance (DIF). is the total amount of shortwave radiation received from above by a surface horizontal to the ground.
