An electrochemical direct heat to electricity converter includes a primary thermal energy source; a working fluid; an electrochemical cell comprising at least one membrane electrode assembly including a first porous electrode, a second porous electrode and at least one membrane, wherein the at least one membrane is sandwiched between the first and second porous electrodes and is a conductor of ions of the working fluid; an energy storage reservoir; and an external load. The electrochemical cell operates on heat to produce electricity. When thermal energy available from the primary thermal energy source is greater than necessary to meet demands of the external load, excess energy is stored in the energy storage reservoir, and when the thermal energy available from the primary thermal energy source is insufficient to meet the demands of the external load, at least a portion of the excess energy stored in the energy storage reservoir is used to supply power to the external load.