To me this is an example of extravagant and inefficient use of money. Instead, it should have been used to find a huge pool cavity somewhere high on one of the

To me this is an example of extravagant and inefficient use of money. Instead, it should have been used to find a huge pool cavity somewhere high on one of the Hawaiian mountain or enlarge one. And then pump up the water to the pool when the electricity is cheap, and release/generate electricity when it is in demand. Stupid and robust implementation that just works and certainly less expensive than $219M.