Huge brick batteries

Here is one for Besoeker after arguing with me about sand batteries. It turns out a man in the US is doing a similar thing but with bricks. They are electrically heated via radiator heaters and they are discharged via collecting the heat with hot air. They are also heated much hotter than the 500C which was considered the practical limit ("thousands of degrees"), and in doing so a brick can store as much as an equivalent sized lithium battery, but at 1/10 of the cost. It looks like he also has some investment behind him, so I believe it is more than vapourware.