Issue with the DNI data and weather file before the simulation.

Hi,
I am working on the SAM in CSP with parabolic trough (physical model). I put the values of the all the parameters for the location 28.428, 77.159. (1MWe National solar thermal power plant Gurgaon, Haryana, India) I attached the SAM file. And also attached the excel file for the reference 2020 year data. I have the data of the DNI that I want to see in the results but when I put this data in the excel and then upload on the SAM and simulate so I am not able to get the exact data of the DNI in the results. It saw like something difference between what I put and what I got.
1.My problem here is about how can I get the same data that I had put before the simulation and also the terms like clearsky DNI, DHI, GHI affects it or not. If these terms affects it then how can I calculate these values according to my DNI data and will put in the SAM ?
2. And also I am able to getting the data from 30 minutes, 5  minutes, So if I am change for I minutes and 1 seconds in the excel, is it works or not ?
3. And this all data(DNI, clearsky DNI, alpha, cosine, ozone etc.) are for the year 2020. Where can I find out these data for this location in present(2025 or 2024) ?

Hi Abhishek,

1. SAM's Physical Trough model does not report data from the weather file in the results. You can display data from the weather file by clicking View data on the Location and Resource page. The simulation output variable "Field collector DNI-cosine product (W/2)" is the DNI available to the collector in the collector plane. You can calculate the weather DNI value from that variable and the "Field collector cosine efficiency" output variable:

DNI from Weather File (W/m2) = Field collector DNI-cosine product (W/m2) / Field Collector Cosine Efficiency

2. Yes, the Physical Trough model work with 5-minute and 30-minute weather data. The weather file format must meet the requirements described in the "SAM CSV Format for Solar" topic in Help:  samrepo.nrelcloud.org/help/weather_format_sam_csv_solar.html

3. The NREL NSRDB does not have data for 2024 or 2025 for locations in India. The Weather Data page of the SAM website lists additional sources of weather data:  sam.nrel.gov/weather-data.html .

Best regards,
Paul.

 

Hi Paul,
Thanks for the above reply. I have more question regarding this project like(I attached the image below)
1.If I have the mass flow rate constant in the PTC like 8.53 kg/s then how to I calculate the values like min. and max. mass flow rates(in the image the values are default) ?
2. If I have the 5 min weather data for the my project(28.428,77.159). Now I want the one minute data so I am using matlab to make the google excel for the minute. If I have the values of the DNI, temperature or like these parameters for the 5 minute and I want to get the data for the 1 minute how can I get this(interpolation or some other way)?
3. How to calculate the PC HTF mass flow rate (kg/s)? Is there any relation b/w min. and max. mass flow rate?
4. Also i didn't understand the Dispatch control in the system control section what is the mean of schedule , turbine output fraction?
Please solve and explain me ?

Hi Abhishek,

1. The minimum and maximum HTF mass flow rates at the design point shown on the Solar Field page for the physical trough model depend on a number of factors. The calculation is a bit complicated to explain here, but you can see the equations in the source code on GitHub here: github.com/NREL/ssc/blob/e97a19f8e035b6c8845690ee23c01b598c36d550/tcs/csp_solver_trough_collector_receiver.cpp#L596 . (Note that these are calculations for design-point values, which are different from the calculations during the simulation of the system's operation.)

2. I am not sure what the benefit of interpolating your 5-minute data to 1-minute would be. SAM's "Solar Resource Interpolation" macro converts hourly data to 30-, 15-, 10-, 5-, or 1-minute data, so you could use that as an example for your own conversion script. To see the macro code, in SAM, click Macros under the Simulate button and then choose Solar Resource Interpolation from the list and click View code (at the top right corner of the window) to see the code.

3. SAM calculates the mass flow rate of fluids at different points in the system and reports them in the simulation results. You can find the variables for these values on the Data Tables tab of the results page by filtering the variable list for "flow". These values are calculated during the simulation. You can refer to the physical trough model technical documentation to see how the values are calculated:  sam.nrel.gov/concentrating-solar-power/csp-publications.html .

4. The dispatch control inputs on the System Control page are described in the "System Control" Help topic: Press the F1 key or click the Help button from the System Control page to find these descriptions.

Best regards,
Paul.