Hello,
In general, variables with kW/m2 units in SAM are for solar radiation data in the weather file, or for incident radiation values calculated from the weather file data. For weather files that follow the TMY file format convention (For example, see Table 1-3 in the TMY3 Users Manual [
PDF 1.7 MB]
), the data represents a total amount of radiation in kWh (or Wh) received in one hour by one square meter of a surface with a given orientation. Because the data is hourly data, the units are kWh/m2 per h, which can be written as kW/m2. In SAM, as long as you are working with hourly data, kWh/m2 and kW/m2 are equivalent units.
Some of SAM's performance models report both a total kW/m2 value and a maximum kW/m2 value. That is because we are developing sub-hourly versions of some of the models. For solar radiation data with a subhourly time step (e.g., 1-minute, 10-minute, or 15-minute), for each hour, SAM records two values: The total radiation in the hour, and the radiation for the timestep within the hour with the maximum value.
For now (SAM 2012.11.30), only the physical trough model fully supports subhourly weather data.
Best regards,
Paul.