Solar Irradiance is a measure of how much solar power you are getting at your location, while solar insolation is a measure of solar irradiance over of a period of time - typically over a day.
The solar irradiance/insolation varies throughout the year depending on the seasons. It also varies throughout the day, depending on the position of the sun in the sky, and the weather.
This solar irradiance database provides the monthly and annual average irradiance in KWh/m2.month and KWh/m2.year, respectively. This information can then be used to calculate the average daily, monthly, and annual energy generation a photovoltaic system will produce per day, month, and year.
This solar irradiance database includes data for Iraq only, it includes data for 24 cities, 9 directions, and 6 tilt angles. To use this solar irradiance database: