In order to calculate energy output you must input the following variables:
Insolation level-Before you calculate your energy output, you should know the solar insolation level in your region. Take note of your max and min levels throughout the year as well as the annual average value. When assessing potential energy savings, input annual average insolation, and take note of the “per year” energy output value.
Energy must be input in unit as kwh/m2/day. 1kwh/m2/day =317.1 Btu/ft2/day
Collector size- you must enter the collector size.
The common absorber surface area of the carious tubes sizes are as follows:
47/1500mm=0.0575m2 per tube; 58/1800mm=0.0805m2 per tube.