Fresnel annual fuel usage

Hello,

I'm currently using SAM for running a CSP linear fresnel IPP with gas backup (each fossil fill fraction is set to 1).

I'm surprised because I found an "Annual Fuel Usage" of 74 294 MWh_th, and paradoxicaly, when I calculate the sum of "Solar Field Thermal Power Hourly", I found about 360 909 MWh_th, which means that the fuel usage should represent 789 689 MWh_th (because I run at full load 130000 MW_th evrery hour, and the "Thermal Energy to Power Block" indicates 1 150 598 MWh_th).

Is there a mistake (a forgotten zero) in "Annual Fuel Usage"? so I should read 742 940?

Thank you for your comments

bye
M.T.

You can compare the hourly "Power delivered by aux heater (MWh)" output variable with "Solar field thermal power (MWh)" and "Thermal energy to the power block (MWh)."

I think the Annual Fuel Usage value reported in Data Tables under Single Value is in MMBTU, but will need to confirm with the programmers. Note that the fossil boiler's LHV efficiency is an input variable on the Power Cycle page with a default value of 0.9.

Update (Feb 16, 2012): "The Annual Fuel Usage (kWht)" variable displays the wrong value in SAM 2011.12.2. It displays the solar field dumped energy instead of annual fuel usage. This will be corrected in the next version of SAM. The hourly variable "Power delivered by aux heater (MWh)" is the correct value. You can export that column to Excel and use the SUM formula to calculate the backup boiler annual energy.

Best regards,
Paul.