Dear Dirk,
Thank you for the feedback. I will share it with the rest of the development team.
SAM's cash flow models were originally designed on the assumption that the PV system in Year 1 is representative of its performance over the life of the project, with an optional annual degradation rate to account for module degradation. The model was designed to be used with typical-year weather data, where one year's worth of hourly data represents the solar resource over a multi-year historical period.
When we added batteries to SAM with explicit modeling of battery replacement costs and schedules, we added the "PV simulation over analysis period" option on the Lifetime input page, which causes SAM to run a separate simulation for each year of the analysis period so that SAM can account for the effect of replacing batteries. When you choose this option, SAM still uses a single weather file for the simulation.
Given that annual weather data with separate files for each year of a historical period is more readily available, it makes sense for use to move toward allowing SAM to run separate simulations for each year in the project life using a different weather file for each year (as it does for the P50/P90 analysis). That would make it possible to change the system design in the course of that period, for example to add or replace batteries, upgrade or replace inverters, add or replace modules, change the load profile, or make other changes.
We are aware of the benefits of this modeling approach, and considering ways to make that possible, hopefully without making the user interface too complicated.
Best regards,
Paul.
