Generation curtailment is expected though in a 100% VRE power grid because it's necessary to overbuild, and this strategy is found to be economically viable almost anywhere on the planet.[1][2] Generation curtailment could be minimised though with demand-side flexibility (eg. turn on aluminium smelters when it's windy), not necessarily just with pumped storage hydro and/or lengthy transmission line builds to other regions where solar generation can be used to supplement wind generation.

Relevant quotes:

"this report infers that, almost anywhere on the planet, nearly 100% VRE power grids firmly supplying clean power and meeting demand 24/365 are not only possible but would be economically viable, provided that VRE resources are optimally transformed from unconstrained run-of-the weather generation into firm generation."[1]

"VRE overbuilding and operational curtailment (i.e., implicit storage) are key to achieving economically acceptable firm 24x365 solutions. Because firm power generation could be achieved locally/regionally in many cases with a small premium, optimum implicit storage solution could alleviate the need for major power grid enhancement requirements."[2]

[1] https://iea-pvps.org/key-topics/firm-power-generation/

[2] https://iea-pvps.org/wp-content/uploads/2023/01/Report-IEA-P...