Concerning the help-example for Fuel curve intercept coefficient. Does the example have any relevance? From a technical data sheet provided by a fuel cell  manufacturer, the hydrogen consumption for a 1 kW FC is approx. 900 liters per hour at rated output. The FC in the help-example consumes some 6.5 liters per hour at 20 kW rated output! What are the assumptions made for this? Pressure levels? In the dialog box for FC's, the slope and intercept coefficients must be entered in kg/hr/kW but calculations are made in lr/hr/kW. What are the transformation coefficients?

 

I think you are referring to the help page on the fuel curve intercept coefficient.  The graph on that page refers to the diesel fuel consumption of an internal combustion engine generator.  6.5 L/hr of diesel fuel is a perfectly reasonable fuel consumption for that generator running at 20 kW, corresponding to an electrical efficiency of 31.3% (assuming a density of 0.82 kg/L and a lower heating value of 43.2 MJ/kg).

The fuel cell manufacturer's data that you mentioned refers to the volumetric consumption rate of hydrogen.  For a hydrogen-fueled generator, HOMER wants you to specify the fuel consumption rate in kg/hr, not in L/hr. We did that specifically to avoid the ambiguity associated with volumetric measurement of gaseous fuels.  It is therefore the manufacturer's assumption of density that you must determine, so that you can convert the value of 900 L/hr to an equivalent value of kg/hr.  Once you do so, you can enter the appropriate values for the fuel curve intercept and slope, and verify that the efficiency curve looks right.