Carbon or tungsten I don't know, but sand as a thermal energy storage medium can be quite economical. Energy loss scales with the surface area (^2), energy stored with volume (^3).
With grid scale, above certain dimensions, you can store energy for months while maintaining economic viability.
Even for single days or weeks it makes sense. You need hot water in your home 24/7, but sun doesn't shine every day in most regions.
With grid scale, above certain dimensions, you can store energy for months while maintaining economic viability.
Even for single days or weeks it makes sense. You need hot water in your home 24/7, but sun doesn't shine every day in most regions.