Dave yes on simulation, mine too has been about 95% complete for a couple of years now. I use Matlab Simulink, who employ the cleverest folk I know from all over the world, specialising in the various Engineering domains it covers, It is expensive for that reason, but worth it, since System modeling, simulation, and model based design has been my specialty as a Model Based Systems Engineer throughout my time Engineering, including as a PhD candidate. The toolset "Simscape" suite includes the latest known bench proven technology in all things Engineering including hydrogen and solar, which is moving on rapidly at the moment, we have no sooner familiarised with one set of primitives, than another set has come along to supersede, hence the reason I seem to be at perpetual 95% complete, but I am not complaining, it is exciting to watch the state of the art as it proceeds. I know this is where we see the practical technology maturing first.
My definition of "Complete", is that the siumlation must reflect and specify an actual practically buildable system that we know will perform identically when physically built.