IIRC correctly we'd need to overprovision by more than 100%, and huge storage too. Is it less expensive then? Also what has the least impact on the environment?

IIRC correctly we'd need to overprovision by more than 100%, and huge storage too. Is it less expensive then? Also what has the least impact on the environment? On space and material requirements given the required massive overall of the grid (to move power across continents)?