What is Design Irradiance?
The Design Irradiance represents the amount of energy per second that the sun provides at a given location, usually represented by Latitude and Longitude coordinates. In areas such as Denver, CO, or Bozeman, MT, where the elevation is significantly higher than sea level, the amount of energy per second tends to be greater than 1000 W/m2. In areas like Seattle, WA, or Portland, OR, where cloud cover is present for much of the year, the amount of energy per second tends to be smaller than 1000 W/m2. The value 1000 W/m2 is the average value for the world, near sea level. If you want to find more detailed information you can look at the National Renewable Energy Laboratory website. (Taken from SMA-America ’07.
