Thermal Energy Storage System with Radiation Cavities

An apparatus includes one or more thermal storage blocks that define a radiation chamber and a fluid flow slot positioned above the radiation chamber to define a fluid pathway in a first direction. The apparatus includes a heater element positioned adjacent to the radiation chamber in a second, different direction, wherein the radiation chamber is open on at least one side to the heater element. The apparatus includes a fluid movement system configured to direct a stream of fluid through the fluid pathway in the first direction.