Hi Bernardo,
SAM does not impose a limit on the size of the system. However the default inputs for the CSP models are for relatively large power generation systems on the order of 100 MW nameplate capacity. To model smaller systems you will need to carefully review all of the inputs.
Here are some suggestions:
Pay special attention to inputs that are not normalized to the nameplate capacity. For example, an input that has units MWe/MW_design or % probably does not need to be changed, but an input that is MWe or MWt may need to be changed if you are changing the system size by an order of magnitude compared to the default size.
Neither the power cycle design efficiency input nor the default power cycle off-design inputs change with cycle capacity, so you will have to change those values.
After making these changes, run a simulation, and carefully review the time series results, especially for parasitic and pumping power loads, to make sure they are in the correct range. Change inputs as needed, and then run the simulation again until you are satisfied with the results.
Best regards,
Paul.