You need to be able to throttle the power output up and down. That is harder to design and harder to make efficient. Or you need lots of batteries, which is expensive. And it all has to be sized for peak demand rather than being able to benefit from flows across the grid.
The one application I'm aware of that can cost-effectively use excess power of that sort is crypto mining, since there the vast majority of the cost is electricity; the capital cost is relatively low. Unfortunately it's arguable whether it does anything useful besides enriching the producer.
Not if you reverse the grid - instead of providing power to the nodes it takes excess away to scalable workloads. And you have grid access as a backup.
Almost any "scalable workload" actually capable of scaling up will have a high $$$ upfront cost for all the machinery / infrastructure involved.
If a decarbonation plant costs many millions of dollars to set up, nobody is going to let it sit idle waiting for some excess power.
The best use case for smoothing the demand curve IMO is thermal "storage". While production is high, people can crank the AC or heat. That way they don't have to use as much energy when production is lower.
I’m less certain about the other things - not many people will eg. put off a load of laundry to a less-convenient time to save 21 cents. And if my partner is too hot because the heater has been running for 30 minutes I really do not want to have a discussion with her about “thermal storage” :)
I believe in some places this is already done.
It is so much nicer to cool/heat pre-emptively. The power company has a very accurate view of what the next 12-24 hours will look like. If they know The sun will be shining bright and there will be an excess of solar energy, they should crank up people's AC so that they don't need to draw as much power later in the day. This way we smooth the demand curve without letting pipes freeze or giving people heat stroke.
> Unfortunately it's arguable whether it does anything useful besides enriching the producer.
I'd prefer to do something really useful, like desalination, pre processing of waste water prior to dumping it into the sewers, and so on, but all these would require a lot of plumbing.