I'm getting this error when trying to start the game with this mod:

Failed to load mods: NapusMod/prototypes/_functions_accumulator.lua:7: attempt to concatenate local 'size' (a nil value)
stack traceback:
NapusMod/prototypes/_functions_accumulator.lua:7: in function 'accumulator_picture'
bobpower/prototypes/entity/accumulators.lua:112: in main chunk
[C]: in function 'require'
bobpower/data.lua:14: in main chunk

It looks like Napu's Mod is overwriting a base game function! I've posted on that mod's discussion page, telling what the issue is and how to fix it. Hopefully they will update soon!

https://mods.factorio.com/mod/NapusMod/discussion/68109d28de4a522db5831fbd