Components of Total Parasitic Consumption & eEffect on Annual

What are the elements that combine to Total Parasitic Consumption? I'm working with the Power Tower Field Optimization sample that's included with SAM 2011.12.2

I've summed the following and still come up short of the total (system.hourly.Par_total).

Auxiliary heater operation parasitic load (system.hourly.Par_aux)
+ Balance of plant parasitic load (system.hourly.Par_plant_bal)
+ Cooling system parasitic power(system.hourly.Par_cooling_tower)
+ Fixed parasitic load (system.hourly.Par_fixed)
+ Heliostat drive electrical consumption (system.hourly.Hel_track_power)
+ Receiver pumping power consumption 9system.hourly.Rec_pump_power)

Also, what is the difference between sv.annual_output and the sum of 8760 entries of system.hourly.e_net? I can set the heliostat drive consumption values (csp.pt.par.heliostat_startup_energy and csp.pt.par.heliostat_tracking_power) to zero and the drive electrical consumption parasitic (system.hourly.Hel_track_power) goes to zero as expected, the total parasitics decrease by the same amount and the sum of system.hourly.e_net also decreases by that amount BUT the annual energy output decreases by a tiny smidge more.

Thanks,
Mike

The total parasitic losses (Par_total) for the power tower molten salt model are the sum of:

Rec_pump_power
Hel_track_power
Par_store_pump
Par_plant_bal
Par_cooling_tower
Par_pipe_loss
Par_tank_htr
Par_recirc_htr
Par_fixed
Par_aux

It looks like you excluded the following from your sum:

Par_store_pump
Par_pipe_loss
Par_tank_htr
Par_recirc_htr

Best regards,
Paul.

The difference between annual output and the sum of e_net is the availability factor input on the System Performance page, which is 96% by default for the tower models:

Annual Output = [availability factor / 100 ] x [sum of 8760 e_net values]

Here's a SamUL snippet that shows the difference:

[begin snippet]

SetActiveCase("New CSP Molten Salt Power Tower Case 1")

availability = GetInput("system.availability")

OutLn("Availability factor: " + availability + "%")
OutLn("")

annual_e_net=0

Outln("Calculating...")

for ( i = 0; i < 8760; i = i+1 )

hourly_e_net = GetOutput("system.hourly.E_net")
annual_e_net = annual_e_net + hourly_e_net

end

annual_e_net_availability = annual_e_net*availability/100
annual_output_mwh = GetOutput("sv.annual_output")/1000

OutLn("")
OutLn("Annual Output: " + annual_output_mwh + " MWh")
OutLn("E net: " + annual_e_net + " MWh")
OutLn("E net x Availability: " + annual_e_net_availability + " MWh")

[end snippet]

Thanks,
Paul.

Paul, thanks. I searched in the output variable browser for everything that seemed "parasitic" but didn't see these.

Ah, of course. Thanks.

-M

Not all of the hourly outputs are available in the output variable browser (Data Tables) on the Results page.

You can see the simulation engine's raw output file with all of the output variables in the temporary simulation folder: After running simulations, press Shift-F9 to display the folder. The output file has the extension .out. It is a tab delimited, so you can open it with a text editor, spreadsheet program or DView.

Thanks,
Paul.