That's a horrible solution. Water is even less portable than energy, even the driest desert can't afford to import water. You're trading a highly liquid but hard to transport commodity for a highly illiquid and hard to transport commodity.

Scenario 1: Your solar power is used near the site of the power installation. In this case, there must be people living near the site in order to use all that power. Those people require freshwater. Therefore, there will be a means to transport water to the site.

Scenario 2: Your solar power is used elsewhere. In this case, there must be a means to transmit power to the people who will use it. Those people are likely to live near seawater. The closest such people are also likely to have a limited supply of freshwater.

You are already either transporting water to the solar site, or transporting power away from it to somewhere else. So the idle capacity of the solar plant will be usable for desalination and/or wastewater reclamation. And I think aqueducts, particularly seawater aqueducts, are cheaper than you realize. The majority of energy required is in increasing the elevation of the water, and that can be done with surplus power, too.

> Water is [...] highly illiquid

Do you mean ice or steam? ;-)

Ah! I was going to write water pump reservoirs or at some price point electrolysis + fuel cells, but making cheap water in the daytime is also good.

We already have a solution to all our energy needs. Funny to see people come up with outlandish suggestions. I am not sure what I am missing. Because logic points to only one direction.

I don't think there is a viable solution for buffering solar or wind (or nuclear) with renewable sources, unless you happen to have access to a lot of hydro power.

Dynamic remote cut-off of heaters, chargers, and other non-critical consumers is one suggestion, but the equipment cost is probably at least 100 Eur per consumer.

Well... Outlandish is to think that replacing a huge amount of infrastructure of a type to another is as simple as your sentence makes it look like.

By no measure is reverse osmosis or flash distillation of water cheap even if the energy is free.

Imagine building a huge water desalination plant and only running it when there is excess power available on the grid.

I can't see anyone wanting to invest in that, except maybe a financially myopic government, and they tend not to last very long.

If the energy is free, you could just do electrolysis with huge carbon electrodes and immediately ignite the gases, bubbling the exhaust through your freshwater reservoir. You can knock together a setup like that in your own backyard from junkyard parts.

How you do it depends on whether you prioritize capital costs or operating costs.