It's still not earning you money to spend electricity because you still have to pay the transfer fee which is around 6 cents / kWh but it's pretty damn cheap nevertheless, mostly because of the excess in wind energy.
Last winter because of a mistake it dropped down to negative 50 cents / kWh for few hours, averaging negative 20 cents for the entire day. People were literally earning money by spending electricity. Some were running electric heaters outside in the middle of the winter.
I don't see why that would follow.
If supply is higher than demand, then getting rid of that excess supply costs money, and the producer might have to pay someone to take it away. It applies to grocery stores that over order inventory of perishable goods, to oil companies that run out of space to store oil, and electricity grids that need to get rid of damaging/dangerous excess power.
That is all absolutely correct, and that is all completely irrelevant. That scenario only exists after shaping efforts have failed to match supply and demand.
The purpose and intent is to sell power at a profit. Where demand cannot be increased enough for rates to remain profitable, demand shaping has not achieved its intended purpose. Negative rates are not an example of demand shaping. Negative rates are an indication that demand shaping has failed.
The dumpster behind the grocery store is "disposal", not "demand". The solution to negative rates is not for the power companies to find a dumpster in which to dispose of their excess power.
The supply shaping solution to this problem is reduced solar and wind production, augmented by flexible peaker plants, and drawing on previously stored grid power.
The demand shaping solution to this problem is flexible loads that can be added or removed from the grid as needed, and storing grid power for future use.
I don't know why you're framing this as solely a demand problem, or why you think the elasticity of demand won't extend to negative prices. Negative prices tend to show up only during periods of very high supply, due to a confluence of factors like weather, so supply is part of it (low or even negative prices can induce producers to curtail production). There's nothing special about the number zero.
And negative prices therefore take the place of disposal: oversupply and the need to expand real resources taking that energy off of the grid in that particular moment. That's demand, too: incentivizing people to do what needs to be done, and get rid of that excess energy by disposing it or whatever.
That is a very good question that has a very simple answer:
The supply shaping solutions to excess solar and wind power are to figure out how to store power, or to stop building renewables. Both of those approaches absolutely suck. We need more renewables, not less, and grid scale storage isn't sufficiently scalable to meet our needs.
Demand Shaping offers a wide variety of potential solutions compatible with increased renewable adoption, and without massive infrastructure projects.
Until 100% of our demand is continuously met by renewable generation, curtailment is not a solution. Curtailment is what you do when you can't find a solution.
Disposal is not a solution. Disposal is what happens when you can't find a solution.
Until 100% of our power needs are met by renewables, curtailment and disposal both suck.
Demand Shaping is a solution. Demand Shaping moves subtracts load from when it can only be met with non-renewables, and adds load when it can be met with renewables. Demand Shaping makes non-renewables less profitable and renewables more profitable.
Demand Shaping fixes the problem in such a way that encourages renewable growth. Curtailment and disposal makes renewable less profitable. Curtailment and disposal resolves the problem in such a way that discourages renewable growth.