Linear Fresnel IPH model be

Dear Paul,

I have been working with the Fresnel IPH model this Christmas and have encountered some issues during the simulations. It would be amazing if you could help me with the following:

Using the SAM Desktop version (2018.11.11) Linux:

• When designing the solar field, SAM performs a calculation to estimate the required number of loops. The receiver thermal derate (see aggregate weighted losses) is used to calculate the loop thermal efficiency at design point. When calculating this value, the average field temperature difference at design should be calculated using the field inlet temperature and the steam temperature. However, the steam temperature is fixed at 393 C (I checked this exporting the CSS file). This is probably coming from the CSP model using thermal oil. I believe the calculation of the numbers of loops would be more accurate if the saturation temperature of the heat sink inlet pressure is taken instead. Is my reasoning correct or am I misinterpreting something here?
• In the graphs (time series, data tables, profiles….), field transverse incidence angle is duplicated. The second one corresponds in reality to the longitudinal angle

Using the PYSAM version (2018.11.11):

• When the DNI is equal to 1, the model does not calculate the q_dot_rec_inc, q_dor_rec_abs.... From an annual perspective this error is less than the 1%, but it leads to confusion when comparing SAM’s results with other models. Is there any reason for this behaviour? [Using Daggett meteo this only happens 3 times (hour of year: 5075, 8297 and 8607) but with other locations like Fargo it happens more often, 274 times to be exact]

Suggestion

• The Technical Manual for the SAM Physical Trough Model describes how the endloss and shadowing effects are taken into account when calculating the optical efficiency. In the Fresnel model these two parameters are not taken into account in the optical efficiency calculation. It should be the user the one in charge of including these effects (and others like the geometry of the secondary receiver) through an optical efficiency value calculated using raytracing simulation right? In terms of the calculation it does not matter but, do you have a recommendation in which term of the optical efficiency effects should we include these effects? Geometry defects, general optical error...? I believe it would be more clear (for the Fresnel model) if one of the optical effects is renamed to “Optical efficiency at normal incidence” or something similar.

I realize that this forum is probably not the place for this kind of requests. I will open an issue entry at the github repository. My mistake. Miguel

Hi Miguel,

I'm waiting for one of the CSP engineers to address your questions and will post a response when I hear back from them.

Best regards,
Paul.