Abstract: A diffuser is provided for use in a thermal storage tank. The diffuser includes a fluid inlet to receive a flow of liquid into the diffuser, and a fluid outlet to discharge the flow of liquid out of the diffuser into an internal volume of the thermal storage tank. A flow circuit extends between the fluid inlet and the fluid outlet. A plurality of flow sections are sequentially arranged along the flow circuit. Each one of the plurality of flow sections defines a cross-sectional flow area for the flow of liquid. The cross-sectional flow area within any one of the plurality of flow sections is greater than the cross-sectional flow area within any of the plurality of flow sections arranged upstream of said one of the plurality of flow sections.