In the UK you can get energy plans with a price that updates every half hour, published a day ahead. From 12:30pm - 4pm today that price is negative. It was also negative for around 16 hours of Easter Sunday. https://www.octopriceuk.app/agile
Well dynamic pricing only ever works until you have a power outage in the winter and suddenly you pay a years worth of money for the 1 hour you could use your fridge, during a snowstorm.
You need something that's valuable, energy intensive, easy to stop and start, and cheap to build capacity for. Either or both of those last two tend to be the problem for most industrial processes (and also crypto mining).