Hi Kurban,
There is an implied multiplication of FRta by 1000 W/m2:
system_capacity [W] = total_collector_area [m2] * ( FRta [] * 1000 W/m2 - FRUL [W/m2-C] * 30 [C] )
Converting to kW:
system_capacity [kW] = total_collector_area [m2] * ( FRta [] * 1 kW/m2 - FRUL [W/m2-C] * 30 [C] / 1000 W/kW )
The rated system size equation is derived from Equation 2.1.4 of the draft technical manual and assumes an irradiance of 1000 W/m² and temperature difference of 30°C.
DiOrio, N.; Christensen, C.; Burch, J.; Dobos, A. (DRAFT 2014). Technical Manual for the SAM Solar Water Heating Model. (
PDF 150 KB
)
We will revise the description in Help to make that clearer.
For more information about SAM's solar water heating model, see:
sam.nrel.gov/solar-water-heating.html
samrepo.nrelcloud.org/help/solar_hot_water.htm
Best regards,
Paul.