Well, in principle one could store solar energy in the form of a flammable fuel which can be used to rapidly spin up a turbine, by constructing ethanol/methane

Well, in principle one could store solar energy in the form of a flammable fuel which can be used to rapidly spin up a turbine, by constructing ethanol/methane from carbon dioxide and water. We can't do it at scale yet, but this is the realm of e.g. Prometheus Fuels.