A thermal energy storage is provided comprising a housing, a thermal energy storage structure arranged within the housing, the thermal energy storage structure comprising thermal energy storage elements and a plurality of dividing elements, the plurality of dividing elements being arranged such that the thermal energy storage elements are divided into a plurality of layers, a fluid inlet, the fluid inlet being in fluid communication with the housing and adapted to receive a working fluid and provide a flow of working fluid towards the housing, and a convection reducing structure arranged adjacent the thermal energy storage structure at a side of the thermal energy storage structure that faces the fluid inlet. Furthermore, a method of storing thermal energy and a steam power plant for producing electrical energy are described.