I hate to be the akshully guy but the big problem isn’t economics but usage. We can’t store electricity at any kind of meaningful scale so generation needs to be balanced to meet demand. Unused excess power needs to go somewhere, hence the negative prices (the market way of saying, “please somebody take this electricity it’s doing more harm than good on the grid”).

I like the system where the excess power is used to pump water into a reservoir up a mountain and when power is needed it runs it down a turbine into a lower reservoir.