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IAM AdjustmentPart 1  Performance Basics  Part 2  Understanding IAM  Part 4  Collector Comparison When calculating the heat output of a collector, the IAM performance adjustment factor (K) should be included in the efficiency formula. The key difference to that formula presented on the first page of this section is the If we continue with the example from section 1: Eg. At 2:40pm; transversal angle of 40^{o} = IAM of 1.37; ambient temperature of 25^{o}C x = (5025)/800 = 0.03125 Now enter all the values into the efficiency formula: h(x) = 1.37*0.717  (1.52*0.03125)  (0.0085*800*0.031252) h(x) = 0.98  0.0475  0.0066 = 0.926 The performance value calculated with the above formula can then be used to calculate Heat Output = Performance x Insolation x Collector Surface Area Example: Performance @ 40^{o} angle= 92.6% Insolation = 800 Watts/m2 Absorber Surface Area = 2.4m2 Heat Output = 0.926 x 800 x 2.4 = 1777Watts Simplifying IAM Adjustment Calculations The calculation completed above is only for a specific point in time, and does not give an indication of the the actual performance over an entire day. Using performance modeling software, hour by hour calculations can be made taking into consideration average daily temperature changes, cold water temperatures, hours of sunlight, solar insolation levels To complete a simple single day calculation for the purpose of comparing collector performance, an average IAM value can be use, along with an average Watt/m2 value. Although this won't give a completely accurate indication of the heat output for the day, As the majority of useful solar radiation falls during the middle 67 hours of the day, an average of the IAM values during this period can be used. If 1 hour corresponds to 15^{o}
