Small CSP Power Tower

I am using the latest version of SAM to model a small 1.2MW (thermal) heliostat field with a 25m tower. The heliostat positions are defined in x-y coordinates and the field has overall dimensions of 110m X 70m. Using the 'CSP Molten Salt Power Tower' case and entering the appropriate field, tower and power cycle parameters the program returns results of zero for all relevant outputs, including thermal energy incident on receiver, thermal energy to power cycle and receiver mass flow rate. Do you have any ideas about what might be going wrong?

Thanks in advance.
Nicole

Dear Nicole,

Would you mind attaching a copy of the .zsam file to your original post? (Click Edit, and then scroll down to see the attachment options.)

Best regards,
Paul.

Dear Nicole,

I have the following observations based on the file you emailed me:

1. You are modeling a solar field with heliostats one one side of the tower, which suggests the design is for a cavity receiver rather than the external receiver specified in SAM. To change the receiver to a cavity receiver, on the Tower and Receiver page, choose Cavity Receiver, and, because you are using your own heliostat layout, click No in the message asking about running the optimization wizard. Then, change the receiver dimensions in the Cavity Receiver box to the dimensions of your reciever.

2. In our tests with small power tower systems, the solar field characterization calculations seem to fail when the receiver design thermal power (shown as a calculated value on the Tower and Receiver page) is around 1 MWt or less. That's because the algorithms are designed for larger systems and we did not test them for smaller systems. We don't know exactly why the calculations fail, but are investigating. We can't promise a fix for this at the moment, but it is helpful for us to hear from people who want to model small tower systems to give us a sense of how many are affected by this limitation of SAM.

Best regards,
Paul.

Thanks for your help Paul. The receiver we are trying to model is not a cavity receiver, it is external, but the shape and design is different to anything that is available in SAM. It may be that it is impossible to properly model the system for this reason.