> There are many instances where solar electricity price is negative.

That's not how it works. When someone wants to buy power they get bids, the bids are sorted by price, and capacity.

Then they work their way through the list, cheapest first, till they meet the capacity they need.

And then pay the (same) TOP price to everyone! NOT the price they bid.

So "negative" is just a tactic to get a good position on the list. Risky if you are a normal fuel-based plant, since you might actually have to make good on it. Not risky for solar power (but not something they actually want).

If everyone was solar, they would never use negative prices - they might actually have to make good on that. It only works because their capacity is so low they are never the top bid.