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Hello According to the TRNSYS manual, the IAM for the Type94a PV module is calculated using the equation taken from King et. al (1997) (page 74 in the mathematical reference PDF TRNSYS 16) Now when I used this model and activated the IAM modifier by setting the TAU-ALPHA product to -0.9, the total yearly production of an array with 9 series modules and 73 parallel strings was 338,287 kWh And I also manually calculated the effective global irradiation on the array (slope=49) and it was 2,200 kWh/m2 Now when I tried to use the ASHRAE empirical equation (I.e. IAM=1-bo*(1/cos(Theta)-1) and equation 5.10.1-12 (page 337 in the mathematical reference PDF TRNSYS 16) after setting the TAU-ALPHA product to +0.9 in type94a to disable the internal
IAM modifier calculations, the yearly production increased to
354603 kWh which matches the results I obtained from another software (PVSYST) And when I manually calculated the
effective global irradiation on the array I got a value of 2130 kWh/m2 ( a lower effective incident irradiation while the yearly PV output is higher compared to the case discussed above) This makes me suspect the internal calculations in the Type94a model or equation 5.2.5-25 on page 75 which uses the tilted irradiation for all components. I mean it is obvious that the internal calculations lead to a lower effective global
irradiation than what I have manually calculated. Any ideas? Thanks Regards, Amir Nashed PhD Candidate School of Renewable Energy and Photovoltaic Engineering University of New South Wales Phone:+61405979282 Email:a.nashed@unsw.edu.au |