LEAC and Energy Rates on Guam

Hi Paul,
I meant system_use_lifetime_output.  It is the "Lifetime hourly system outputs" system input for utilityrate5.  Sorry my typo caused you grief. 
Rob

Hi Rob,

Thanks for the clarification.

The SSC variable gen is the time series output of the system in kW. It is an array of length n_ts_sim, where

n_ts_sim = n_ts_hr * 8760 hours/year * n_yr_sim

and n_ts_sim is the number of time steps in the simulation, n_ts_hr is the number time steps per hour, and n_yr_sim is the number of years in the simulation. The number of time steps per hour is determined by the number of time steps in the weather file: For hourly data, n_ts_hr = 8,760 h/year, for subhourly data, n_ts_hr =time steps in weather file / 8760. (These variable names in italics are ones I made up for this description, not variables in SAM or SSC.)

The SSC variable system_use_lifetime_output is a boolean value (0 or 1) that indicates whether the gen array is for what we call a "lifetime simulation," meaning that the simulation time step spans more than one year. For most  situations the weather file contains hourly data and system_use_lifetime_output = 0, so SAM runs an hourly simulation for one year, and the financial models like utilityrate5 and cashloan use a degradation rate to estimate system output (kW and kWh) in years later than Year 1, and an annual escalation rate to calculate costs ($) in years later than Year 0. If you set system_use_lifetime_output = 1, then SAM runs a simulation (using the same weather file) for each year in the analysis period.

Depending on the number of time steps in the weather file and how you define other inputs, the simulation may be hourly over one year,  subhourly over one year, hourly over the analysis period (analysis_period in SSC), or subhourly over the analysis period.

Example 1: Hourly over one year

system_use_lifetime_output = 0
analysis_period = 25
time steps in weather file = 8,760
length of gen: n_ts_sim = 1 * 8,760 * 1 = 8,760

Example 2: Hourly over 25 years

system_use_lifetime_output = 1
analysis_period = 25
time steps in weather file = 8,760
length of gen: n_ts_sim = 1 * 8,760 * 25 = 219,760

Example 2: 15 minutes over one year

system_use_lifetime_output = 0
analysis_period = 25
time steps in weather file = 35,040
length of gen: n_ts_sim = 4 * 8,760 * 1 = 35,040

Example 3: 10 minutes over 30 years

system_use_lifetime_output = 1
analysis_period = 30
time steps in weather file = 52,560
length of gen: n_ts_sim = 6 * 8,760 * 30 = 1,576,800

Thanks,
Paul.

Hi Rob,

The SDKtool does seem to be missing from 2020 SAM Beta versions for Linux (it is there for the Windows version). We'll try to make sure it is in any new Beta versions we build.

If you have a different version of SAM installed on your computer, you can run SDKtool from that version, and use it to load the SSC library from the Beta version. The SDKtool itself hasn't been updated for a while, so older versions of SDKtool will work with newer SSC libraries.

Thanks,
Paul.

Hi Paul,

I am taking your suggestion to account for variable LEAC, by breaking the 25 year SAM simulation into two parts.  I am doing this by hand to make sure I understand what I'm doing, before I work on a python script to automate it.  It isn't working, and I'm really hoping you can help me understand what I'm doing wrong.  
Here is what I'm doing:

1. I set the degradation rate to 0 for the original 25 year simulation.  (I don't want to deal with this complication until I know my ideas are right about the basics.)
2. I make two duplicates of the original 25 year simulation, and rename them 6 and 19 for the first six years and the remaining 19 years.
3. I change the analysis periods to 6 and 19 on the appropriate duplicates.
4. I run all the simulations.
5. I take the (19 year npv + 19 year net capital cost)/(1+nominal discount rate)^6+the npv of the six year simulation.  This is to correct the 19 year npv, because I didn't acutally invest capital after six years, and move the npv for the 19 years back six years to the start.  This is added to the npv of the first six years.
6. I think it should equal the npv of the 25 year simulation, but it is off in a significant way.

I'm puzzled, and obviously don't understand what is going on with this.  Do you have any ideas where I went wrong?
Thanks,
Rob
P.S.  I'm attaching a .sam file.  And by the way, thanks for fixing it so I don't have to change the suffix to .log!

Hi Paul,

Using the 2018.11..11 doesn't help.  I should mention I zeroed taxes and made there be no loan, and some other things to make sure it wasn't to complicated.

Thanks,

Rob

Hi Paul,

I figured out my problem.  I was using the nominal discount rate, and I should have been using the real discount rate.  The electricity rates are assumed to go up with inflation, but duplicating the setup doesn't do that, so you should bring it back to present with the real discount rate.  Thanks for letting me explain my problem to you.  It helped me figure it out.

Rob