An energy storage device includes a plurality of plates, each having a first and second surface, with at least one of the surfaces having a plurality of grooves formed therein. The device further includes inlet and outlet plenums for providing or receiving a heat transfer medium to or from the grooves. At least one of the first surface and the second surface having the plurality of grooves formed therein of a first plate is disposed in direct contact with the other one of the at least first surface and second surface of an adjacent second plate. Heat from the transfer medium is transferred to the plates in a charging mode of operation or transferred from the plates to the transfer medium in a discharging mode of operation when the heat transfer medium is passed along the grooves.