- I have been observing the atmospheric attenuation at the SPT model in SAM for a while now and I seem to have a problem. In the heliostats field page, the atmospheric attenuation section, when I set the polynomial coefficients to zero, the average attenuation loss display in SAM gives a zero percentage which is logic. In addition, when I use some polynomial coefficients that correspond to a higher value of Aerosols like in my case (0.3205 AOD for the annually averaged AOD that I assembled) the average attenuation loss in SAM gives 6.6% which is also a good sign as higher AOD must result in higher attenuation percentages.
The problem is that somehow for the scenario of zero AOD and an average attenuation loss of 0% I get way lower generated energy which is not logic. Using the coefficients that corresponds to a higher AOD value normally should give a lower generated energy, but in my case it does give higher energy despite showing higher average attenuation loss percentage in SAM display.
I used Jesus Polo mathematical model to calculate the polynomial coefficients based on the AOD values and it is indeed linear with the average attenuation loss in SAM as the higher the AOD value gets, the higher average attenuation loss percentage SAM displays, however the problem remains in the energy output.
I had a look on the receiver incident thermal power for the zero AOD scenario and it is lower while it should the highest scenario out of all other scenarios as the generated energy..
I even did a parametric analysis for AOD values from 0 to 1.5, the range is linear with the average attenuation loss percentage displayed in SAM, however the generated energy is really random.
Note:
I attached:
- the SAM file that I am using.
- a CSV file with the polynomial coefficients for two cases, i.e. the zero AOD scenario and the 0.3205 AOD scenario.
- The weather file I am using.
- Jesus Polo attenuation model is:
a= 3.13 AOD3 – 1.9 AOD2 + 1.6 AOD – 0.133 / 100
b = – 14.74 AOD3 + 2.49 AOD2– 11.85 AOD + 0.544 / 100
c = 28.32 AOD3 – 7.57 AOD2+ 48.74 AOD + 0.371 / 100
d = – 2.61 AOD3 + 3.70 AOD2– 2.64 AOD + 0.179 / 100