Hello Tom, <br><br>" Rotational mass and system inertia are the things that keep your lights from flickering"<br><br>No that is incorrect. The type of light is one fundemental factor and the although less common now the fluorescent lamp was inclined to flicker, this was solved decades ago by a coating which gave persistance of vision. Incandescent lamps don't flicker neither do any fed internally by D.C.<br>What the rotational speed and inertia of large steam turbines does is help smooth the variability of demand and compensate for sudden drop or rise of that demand. Wind and solar cannot do this and makes them fundementally unsuited for large scale grid supply. We are following a dead end in persisting with this form of generation. The wind and solar farm operators , on the other hand, are doing very well finacially, thank you.,(reply>), Well, fast frequency response (from Li-ion batteries or demand-side response for example) can alleviate the issue of lower inertia. Of course some inertia will always be needed. Converter-based wind turbines can provide synthetic inertia but there is a time delay, the response is very limited and there are potential issues with the so called second dip due to non-optimal tip speed ratio.