Dear Pierre,
The solar multiple is a measure of the solar field aperture area as a function of the power block's nameplate capacity.
For the empirical trough model, SAM calculates a value called the "exact aperture reflective area" that is the solar field aperture area required to deliver the power cycle's "design turbine thermal input" thermal energy at the direct normal radiation, ambient temperature, and wind velocity shown under "Solar Multiple Reference Conditions." The "exact" aperture area is equivalent to a solar multiple of one.
The solar multiple is:
Solar Multiple = Aperture Reflective Area / Exact Aperture Reflective Area
For explanations of the calculated values on the input pages, see the Help system. For example, the Solar Field page variables are described
here
.
Best regards,
Paul.