Standalone Battery - NPV after chemistry update (2020.11.29 & 2021.12.2)

Hello, 

I modelled Standalone Battery in the previous software version (2020.11.29) using Generic Battery, Commercial performance model. I compared two different chemistries.
The battery power and capacity was constant for this comparison, i.e., 162.981kW & 437.424kWh. The change in NPV when only switching the battery chemistry is very substantial. For 'Lead Acid: Flooded' NPV is $30,210, while for the 'NCM/Graphite' it equals to $-164,665. Batteries are of the same size, the same CAPEX assumed. There is a substantial difference in 'Net savings with system' between these two as well, $48,099 and $16,612 respectively, which definitely influences the NPV itself. 
What is a reason for a such substantial difference between these two chemistries and their performance in the older version of the software? Were there any issues with this calculation?

I did the same exercise using the newest version of the software (2021.12.2). The difference in NPV and 'Net savings with system' is much smaller, ΔNPV=$33,629, ΔNet savings=$1,627. 

What were the changes between these two versions of the software?

Many Thanks in advance! 
Regards,
Agnes

Hi Agnes,

We are actively developing SAM's battery models, so you can expect to see differences in results between versions of SAM. This is particularly true for standalone batteries, which has required changes to properly model the various dispatch options. See the SAM release notes (also available from the blue buttons on the SAM Download page ) for a list of changes between versions.

As for the difference in NPV for Li-ion NMC/Graphite and flooded lead-acid batteries, I suspect that is caused by the cost of replacing the batteries. Depending on how the battery is being operated, a Li-ion battery of a similar capacity may require fewer replacements than a lead-acid battery. You can see that on the Cash Flow tab: The battery replacement cost line item is listed under "Operating Expenses."

Best regards,
Paul.