Fuel Cell Stack Properties

Hello,

I'm currently using SAM to simulate a PV-FC-BAT model and was wondering how the data for "Fuel consumption of fuel cell (Mcf) was calculated. I can't seem to find a consistent pattern varying the stack size and nameplate values.

Thanks, 
RQ

Hi RQ,

In my tests, the annual fuel consumption increases with fuel cell nameplate capacity. These parametric results are from the "Default 200 kW Fuel Cell" case in the attached file. You can also compare the hourly fuel consumption between a 200 kW and 400 kW fuel cell by comparing the cases in the file.



I added a link to a recording of a 2019 webinar on SAM's Fuel Cell model to the PV Videos page:

sam.nrel.gov/photovoltaic/pv-videos.html

Best regards,
Paul.

Hi Paul, thanks for the prompt reply. It seems that it was an error on my end, which I believe I have identified.

Thanks to your file giving me a point of comparison, I found that a different parameter was changing when stack size was varied, which I'm assuming leads to the difference in fuel consumption. It seems that when varying the stack size or nameplate parameters, the calculated rate up/down limits change, while in the file you sent I noticed they remain the same regardless of stack size or nameplate value. Are there any pointers you could give me as to why this occurs?

Thanks again,
RQ

Hi RQ,

On the Fuel Cell page, you can change the units for the ramp rate up and down limits. The calculated values shown on that page remain constant if you choose the kW/h units, but change if you choose the %/hr units.

Best regards,
Paul.

Hi Paul,

Thanks for the info, I should've definitely noticed that! Another question, this time on the simulation side: What is the "system" referenced in the values simulated (e.g. "Electricity to grid from system" and "System power generated")? Looking at the numbers it sometimes seems as though "system" refers to all inputs summed as a whole, and sometimes it seems like it refers only to the PV input system.

Ryan

Hi Ryan,

Yes, our use of the term "system" is a bit confusing because of the way SAM has evolved over time from being a solar model to one with solar and non-solar technologies, and finally to one with electricity storage options.

For the outputs, "system power generated" includes power from any part of the system (PV array, battery, fuel cell).

For the version of SAM we are currently preparing to release, I changed the name of the "System Design" page to "PV System Design" to try to address this issue.

Best regards,
Paul.