Abstract: Provided is a heat accumulator including a heat exchange chamber having a lower portion and an upper portion and being configured to accommodate therein heat storage elements for storing thermal energy, wherein the heat exchange chamber includes an inlet which is configured to supply a working fluid into the heat exchange chamber. A passively controlled first pressure loss regulating device is arranged within the flow of the working fluid in the heat exchange chamber and configured to pass the working fluid through, wherein the first pressure loss regulating device is configured to form a first flow resistance for a flow of the working fluid in the first pressure loss regulating device being different to a flow resistance for a flow of the working fluid in the heat exchange chamber adjacent and outside the first pressure loss regulating device.