Dual-cycle system for combined-cycle power plant

An Organic Rankine Cycle (ORC) system for operation with a gas turbine combined-cycle power plant comprising a fuel system, the ORC system comprising:

• a fluid pump for pumping a fluid;
• an ORC turbine in fluid communication with and disposed downstream from the fluid pump, the ORC turbine for expanding the fluid;
• a regasification and expansion system for a fuel of the fuel system, the regasification and expansion system configured to cool the fluid between an outlet of the ORC turbine and an inlet of the pump;
• a first heat exchanger positioned between an outlet of the pump and an inlet of the ORC turbine to heat the fluid with heat from a heat recovery steam generator of the gas turbine combined-cycle power plant;
• and
• a fuel expansion turbine of the fuel system to produce power from the fuel before it enters a gas turbine engine of the gas turbine combined-cycle power plant.

A method of operating a gas turbine combined-cycle power plant, the method comprising:

• circulating a working fluid through a closed loop using a working pump;
• heating the working fluid with a first heat exchanger using heat from the gas turbine combined-cycle power plant;
• expanding the heated working fluid through a working fluid turbine;
• condensing the working fluid leaving the turbine with a fuel regasification and expansion system;
• expanding gas fuel of the fuel regasification and expansion system through a fuel turbine;
• and
• generating electrical power with the working fluid turbine and the fuel turbine.