Tom Murphy covered this in the series as well. While there are absolutely cases where pumped hydro is extremely effective (e.g., Dinorwig Power Station), the in

Tom Murphy covered this in the series as well. While there are absolutely cases where pumped hydro is extremely effective (e.g., Dinorwig Power Station), the inherent problem is that it requires need very specific geological features. Unsurprisingly, we've hit much of the good low-hanging fruit, so future projects will be less efficient in terms of capacity per dollar invested. And also unsurprisingly, these features are not evenly geographically spaced around the globe. https://dothemath.ucsd.edu/2011/11/pump-up-the-storage/ https://dothemath.ucsd.edu/2011/11/pump-up-the-storage/