Solar Water Heating Parametric Study

Hi Paul,

For my engineering senior design project, we are using SAM's Solar Water Heating model to optimize how many collectors and what size tank we should choose for a solar water heating system on a roof of a campus building. In performing the study, I have run into the issue multiple times where I find a large output of system energy at a particular point which indicates an optimum system set-up, but if I switch the tank size say from 3.028 m³ to 3.027 m³ , I see a large reduction (30,000 kWh) of system energy output, demonstrating it is not after all an optimum system set-up. This has occurred on a couple occasions, and it makes me wary of trusting the numbers SAM is outputting. What might be going on here? Does it have to do with the Euler method being used to solve the DEQs? Let me know if you have any tips on spotting this issue or getting around it. 

Thanks,
Chase P.

  

Hi Chase,

Could you share a .sam file that demonstrates these results?

Best regards,
Paul.

Hi Paul,

I have attached the SAM file, and here is a video using that file demonstrating what I am referring to: 

Let me know if you have any other questions for me or if the file or video does not work.

Thanks, 
Chase P.

Hi Chase,

Thank you for sharing the file and video.

We'll need to investigate to see what is causing that anomaly. In the meantime, you can either ignore that particular case, or  change one of the input parameters slightly to avoid the anomaly.

Best regards,
Paul.

Paul,

Thanks for looking into this. Just to be clear, there have been similar anomalies at different points in the study resulting in skewed system energy results. The other cases of the anomalies have not been as extreme, so it is difficult to trust the results being output.

Thanks,
Chase P.

Hi Paul,

Just wondering if you and your team have had a chance to look into this issue?