Secretive energy startup backed by Bill Gates achieves solar breakthrough

[Heyo]

Bingo! My thoughts exactly. The French had a solar furnace in the Pyrenees in the 1950s that did this (I read about it as a kid) and built a better one a decade later: Odeillo solar furnace - Wikipedia

What I'm unclear about is why it is better to get high temperatures this way rather than via electric heating, using electricity from solar panels. I can only presume they think they get better efficiency this way.

This is orders of magnitude more efficient. You get an efficiency of over 90%, depending on the quality of the mirrors. Solar panels have a typical efficiency of 20% and you loose more energy for transport and conversion of energy. Solar panels have the advantage that they produce electrical energy even on a cloudy day. The furnace only works in direct sunlight.

 

[Heyo]

That's not what I've read - it's a tenth of that. But if you provide a link to 5000, I'll change my mind.

See the post of exchemist with the link to Odeillo solar furnace. (Though I was off by 1500°, Wikipedia states 3500° C, but it's still better than 500° which is off by 3000°.)