I think the “solar oven” that Edmund Scientific sold decades ago could easily reach 1000 C at the focal point of its Fresnel lens. Anyway, hard to imagine a steel mill that only works in the daytime on sunny days. 8 hr startup time and then shut down for the night.
My vote is still for oil, coal, nuclear reactors and deep geothermal. Fusion maybe someday. Plenty of valid options without wind/solar crap.
It’s an interesting technology that might be employable during the day and then they switch over to hydrocarbons at night. What is really missing, that prevents society from adopting alternatives, is the ability to flick a switch that allows you to seamlessly switch between a powerplant and homegrown power.