[mikeyouse]

Desal plants are also extraordinarily expensive and need to operate at very high 'capacity factors' in order to payoff the capital investment that was required to build them. Operating for a a few hours every day because your operating costs are low/negative only works if you don't have a hugely expensive piece of infrastructure depreciating as you wait for those prices to come down.

[amoshebb]

could we build them different if the goal is just to waste excess energy?

Why couldn’t it just be a giant heating element and some sort of steam condenser at the top and some way to flush it periodically?

It might burn some laughable 3kWh per kg of water, but who cares? every water utility on the coast could add a few megawatts of tea kettles and get opportunistic little splashes of water in volumes small enough they can probably already handle them and the brine discharge would be so small, disperse, and infrequent it’d be easier to deal with, and it’d basically cost nothing

[ema]

It doesn't only need to make economic sense now but you also need to be fairly certain that all the battery capacity that is likely to be added to the grid in the future will still allow this to be profitable until your expected break even point.