A heat transfer system, comprising: an electrochemical cell comprising a first electrode and a second electrode separated by a separator comprising an ion transfer medium, a first electrode fluid flow path in operative fluid communication with the first electrode between a first electrode fluid flow path inlet and a first electrode fluid flow path outlet, and a second electrode fluid flow path in operative fluid communication with the second electrode between a second fluid flow path inlet and a second fluid flow path outlet; a heat exchanger condenser including a heat rejection side in operative thermal communication with a heat sink; a heat exchanger evaporator including a heat absorption side in operative thermal communication with a heat source; a first heat transfer fluid flow loop (22, 24, 26) from the first electrode fluid flow path outlet to a heat rejection side inlet of the heat exchanger condenser and from a heat rejection side outlet of the heat exchanger condenser to the second electrode fluid flow path inlet; a second heat transfer fluid flow loop (28, 30, 20) from the second electrode fluid flow path outlet to a heat absorption side inlet of the heat exchanger evaporator, and from a heat absorption side outlet of the heat exchanger evaporator to the first electrode fluid flow path inlet; and a heat transfer fluid in the first and second heat transfer fluid flow loops, comprising an electrochemically active agent that reversibly transforms from a first compound to a second compound at the second electrode, and from the second compound to the first compound at the first electrode, wherein: the electrochemically active agent comprises a fluorinated organic compound including an electrochemically active substituent group, which reversibly transforms between said first and second compounds having different boiling points to provide a phase change of the first and second compounds in the heat exchanger condenser and in the heat exchanger evaporator, or the heat transfer fluid comprises the electrochemically active agent and an electrochemically non-active refrigerant in a mixture, wherein the electrochemically active agent reversibly transforms between the first and second compounds to provide different boiling points of the mixture and a phase change of the electrochemically non-active refrigerant in the heat exchanger condenser and in the heat exchanger evaporator. an electrochemical cell comprising a first electrode and a second electrode separated by a separator comprising an ion transfer medium, a first electrode fluid flow path in operative fluid communication with the first electrode between a first electrode fluid flow path inlet and a first electrode fluid flow path outlet, and a second electrode fluid flow path in operative fluid communication with the second electrode between a second fluid flow path inlet and a second fluid flow path outlet; a heat exchanger condenser including a heat rejection side in operative thermal communication with a heat sink; a heat exchanger evaporator including a heat absorption side in operative thermal communication with a heat source; a first heat transfer fluid flow loop (22, 24, 26) from the first electrode fluid flow path outlet to a heat rejection side inlet of the heat exchanger condenser and from a heat rejection side outlet of the heat exchanger condenser to the second electrode fluid flow path inlet; a second heat transfer fluid flow loop (28, 30, 20) from the second electrode fluid flow path outlet to a heat absorption side inlet of the heat exchanger evaporator, and from a heat absorption side outlet of the heat exchanger evaporator to the first electrode fluid flow path inlet; and a heat transfer fluid in the first and second heat transfer fluid flow loops, comprising an electrochemically active agent that reversibly transforms from a first compound to a second compound at the second electrode, and from the second compound to the first compound at the first electrode, wherein: the electrochemically active agent comprises a fluorinated organic compound including an electrochemically active substituent group, which reversibly transforms between said first and second compounds having different boiling points to provide a phase change of the first and second compounds in the heat exchanger condenser and in the heat exchanger evaporator, or the heat transfer fluid comprises the electrochemically active agent and an electrochemically non-active refrigerant in a mixture, wherein the electrochemically active agent reversibly transforms between the first and second compounds to provide different boiling points of the mixture and a phase change of the electrochemically non-active refrigerant in the heat exchanger condenser and in the heat exchanger evaporator. the electrochemically active agent comprises a fluorinated organic compound including an electrochemically active substituent group, which reversibly transforms between said first and second compounds having different boiling points to provide a phase change of the first and second compounds in the heat exchanger condenser and in the heat exchanger evaporator, or the heat transfer fluid comprises the electrochemically active agent and an electrochemically non-active refrigerant in a mixture, wherein the electrochemically active agent reversibly transforms between the first and second compounds to provide different boiling points of the mixture and a phase change of the electrochemically non-active refrigerant in the heat exchanger condenser and in the heat exchanger evaporator.