All of the PPA single owner configurations except PV Battery and Generic Battery have ppa_soln_mode = 0 (Specify IRR target) as default. For the changes in this PR, I think we will need to change the default for all PPA configurations to ppa_soln_mode = 1 (Specify PPA price), which means that we have to decide on an appropriate default PPA price for these configurations. One option is to use the PPA price result for the current defaults. Our decision on this should be documented in SAM-documentation to ensure it is preserved when we update defaults for the release: https://github.com/NREL/SAM-documentation/tree/master/Defaults%20References%20and%20Tools/Fall%202021

When the Electricity Purchases option is "Use PPA or market prices" (ui_electricity_rate_option = 0) with the Specify IRR target option (ppa_soln_mode = 0), the simulation runs without indicating that there is a problem in spite of the red text on the Electricity Purchases page: "The Use PPA or Market Prices option is not available with the Specify IRR Target option on the Revenue (or Financial Parameters) page. Either change the option to Specify PPA Price, or change the option here to Use Retail Electricity Rate(s)." If this is not a valid combination of inputs, I think SSC should generate an error.

I'm not sure how to validate the effect of this on LCOE, but I am seeing reasonable changes in LCOE, NPV, and cash flow outputs as I try different combinations of options, so I think this is OK to merge after the issues above are resolved.

@cpaulgilman I introduced ssc errors for that combination in the FOM configs, and changed the default to the Specify PPA price option for all the configs although I still need to put in reasonable PPA prices like you were suggesting. The defaults are still a mess until I get some time to run the test script so I would wait on a re-review until that is resolved.

Looks good overall, one nitpick:

On the cash flow tab "Net energy to grid" is no longer used in the LCOE calculations, this should be replaced with energy sales:

Looks good overall, one nitpick:

On the cash flow tab "Net energy to grid" is no longer used in the LCOE calculations, this should be replaced with energy sales:

Can somebody push this change? My build is tied up with the test script on another branch. It should just be changing cf_energy_net to cf_energy_sales on line 676 of cashflow.lk

@brtietz @cpaulgilman I'm planning to merge this before there are more conflicts unless there are any objections