The idea that the inputs to an industrial process could go so negative in price that the outputs would also go negative in price is a fantasy.

Let's say A is running a desalinated water giveaway and B is storing the excess electricity as potential energy, which can be sold as electricity when the price goes positive.

B can afford to take the energy for a less-negative price, so outbids A by accepting less money with the juice.

Sure, if things get ridiculous enough, it might be a race to see who can afford to give away the most water / aluminium / nighttime power / Funko Pops.

But, it won't.