Transportation is definitely one of the main issues. One of the reasons a place like Australia can manage so well in a simulation like this, is the huge size (c

Transportation is definitely one of the main issues. One of the reasons a place like Australia can manage so well in a simulation like this, is the huge size (combined with a generally very sunny interior). On a given day, a very large percentage of total power demand may have to be transported from one end of the continent to another. For other, smaller countries (like any European one except Russia), you also face political risk, like we're seeing currently with Russian natural gas. When relying on long distance transport of electricity to keep the grid stable, one or two bad actors may tear down the stability for everyone. Perhaps a smaller issue, but I would not be surprised if total transportation loss would be 10-20% if not higher, when counting both transmission lines, transformers, storage and similar. If the price of storage comes down enough, it might be a better source of stability, rather than relying on there being wind "somewhere".