The next generation of solar energy collectors could be rocks

https://techxplore.com/news/2023-05-generation-solar-energy-collectors.html

"granite samples store solar heat... Magnesite in soapstone high energy density and stability at high temperatures... When heated to  soapstone samples and the Usagaran granite had no visible cracks temperatures >1800°F.. Additionally, the soapstone was more likely to release its stored heat than the granite. In all, the Craton soapstone had the best performance as a TES, able to absorb, store and transmit heat effectively while maintaining good chemical stability and mechanical strength"

Related: New review discusses progress in the design of porous volumetric solar receivers

https://techxplore.com/news/2023-08-discusses-porous-volumetric-solar.html