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they do not say how much time that "stored heat" can last and in let's say max 6h per day, I do not think you can heat so much any material that can last another 18h to push that thing generating energy.
For places where you have sunlight for 12-14h maybe I understand to have another 6-8h of stored heat in those bricks.
something doesn't add up with this, but is still interesting.