As of 2019 my main free software coding project is
PyPSA: Python for Power System Analysis
PyPSA is a toolbox for simulating and optimising modern electric power systems.
We have also animated some of our results using D3.js, see the live example for Europe with 95% renewable electricity made using PyPSA-animation.
I've also built an online tool for modelling very simplified zero-direct-emission energy systems: