NOVELTY - Sodium-sulfur battery (1) (I) comprises: (a) a first compartment (104) containing a first solution comprising a solvent and sodium-containing salt; (b) a second compartment (204) containing a second solution comprising solvent and metallic sodium; (c) a solid electrolyte layer (301) separating the compartments; (d) a first storage tank (100); (e) a first pump; (f) a second storage tank; (g) a second pump; (h) a first electrical contact; and (i) a second electrical contact, where first and second electrical contact are operable to transmit electrical current to or from sodium-sulfur battery.    USE - The sodium-sulfur batteries are useful in electric vehicles, conventional automobiles, power storage and in the production of metallic sodium.    ADVANTAGE - The sodium-sulfur batteries: exhibits improved mobility and efficiency; do not utilize molten electrode materials, thus enabling the operation of the batteries at lower temperatures (less than 150 degrees C) compared to conventional sodium-sulfur batteries, and thus offers a much improved design concept and safer battery operation; avoids self-discharge by external storage of the electrochemically-active species as in flow batteries.    DETAILED DESCRIPTION - Sodium-sulfur battery (1) (I) comprises: (a) a first compartment (104) containing a first solution comprising a first solvent and at least one sodium-containing salt; (b) a second compartment (204) containing a second solution comprising second solvent and metallic sodium; (c) a solid electrolyte layer (301) separating the first compartment from the second compartment, where the solid electrolyte layer is selectively permeable to sodium ions; (d) a first storage tank (100) connected to the first compartment, where the first storage tank contains the first solution; (e) a first pump connected to the first storage tank that is operable for pumping the first solution to the first compartment; (f) a second storage tank connected to the second compartment, where the second storage tank contains the second solution; (g) a second pump connected to the second storage tank that is operable for pumping the second solution to the second compartment; (h) a first electrical contact coupled to the first compartment; and (i) a second electrical contact coupled to the second compartment, where the first and second electrical contact are operable to transmit electrical current to or from the sodium-sulfur battery. An INDEPENDENT CLAIM is also included for a sodium-sulfur battery (II) comprising: (a)-(e) as above per se; a second and third storage tank connected to the second compartment, where the: second storage tank contains a suspension of metallic sodium in a solvent that is non-reactive with metallic sodium; and third storage tank contains liquid ammonia; a second pump connected to the second storage tank and the third storage tank that is operable for pumping the suspension of metallic sodium and the liquid ammonia to the second compartment; (h) and (i) as above per se.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic illustration of a flow sodium-sulfur battery.    Sodium-sulfur battery (1)    First storage tank (100)    First compartment (104)    Second compartment (204)    Solid electrolyte layer (301)