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
The price was known ~1 day in advance so I had the choice to fill up the battery with cheaper (but still high) prices overnight and reduce the impact
Business energy users aren't protected, so they buy long-term contracts, hedge, or go-under in the event of an unforeseen energy-shortage.
Back yard plasma furnace? Artificial diamond making? Aluminum smelting?
https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag...
https://en.wikipedia.org/wiki/Energy_storage
There have wildly different prices for unit of stored energy and wildly different storage times.
https://css.umich.edu/publications/factsheets/energy/us-grid...
It's not cost effective run aluminum smelting only during peak electricity production.