A cascade process for the production of power from variable temperature heat sources, includes: circulating a main working fluid selected from perfluorinated compounds (like Perfluoro-2-methylpentane/Perfluoro-i-hexane) in a main circuit according to a main supercritical organic Rankine cycle, operatively coupling in a boiler a variable temperature heat source with the main working fluid of the main circuit to heat and vaporize the main working fluid; circulating an auxiliary working fluid in an auxiliary circuit according to an auxiliary Rankine cycle; thermally coupling in cascade the expanded main working fluid of the main Rankine cycle with the auxiliary working fluid of the auxiliary Rankine cycle, in order to cool the main working fluid and heating the vaporizing the auxiliary working fluid by heat transfer from the main Rankine cycle to the auxiliary Rankine cycle before the expansion of the auxiliary working fluid in an auxiliary expander.

A cascade process for the production of power from variable temperature heat sources, includes: circulating a main working fluid selected from perfluorinated compounds (like Perfluoro-2-methylpentane/Perfluoro-i-hexane) in a main circuit according to a main supercritical organic Rankine cycle, operatively coupling in a boiler a variable temperature heat source with the main working fluid of the main circuit to heat and vaporize the main working fluid; circulating an auxiliary working fluid in an auxiliary circuit according to an auxiliary Rankine cycle; thermally coupling in cascade the expanded main working fluid of the main Rankine cycle with the auxiliary working fluid of the auxiliary Rankine cycle, in order to cool the main working fluid and heating the vaporizing the auxiliary working fluid by heat transfer from the main Rankine cycle to the auxiliary Rankine cycle before the expansion of the auxiliary working fluid in an auxiliary expander.

A cogeneration system to generate thermal energy in form of hot water, using the system's solar collector directly as an evaporator and a heat exchanger integrated in a thermal tank used as a condenser. A variable capacity expander (turbine) is used and the organic working fluid selection is specific for this application. Thus is provided a technological alternative for the production of electricity and thermal energy using a renewable energy source.

A cogeneration system to generate thermal energy in form of hot water, using the system's solar collector directly as an evaporator and a heat exchanger integrated in a thermal tank used as a condenser. A variable capacity expander (turbine) is used and the organic working fluid selection is specific for this application. Thus is provided a technological alternative for the production of electricity and thermal energy using a renewable energy source.

A power generation system and method including a first heat exchanger, a first thermal engine, and a first power generator on a first working medium line L1 that circulates a first working medium W1, a second heat exchanger, a third working medium supply device that supplies a third working medium W3, and a mixing device for mixing a second working medium W2 and the third working medium. A second thermal engine, and a second power generator are included on a second working medium line L2 that circulates the second working medium. On both of a downstream side of the first thermal engine on the first working medium line and a downstream side of the second thermal engine on the second working medium line, a third heat exchanger is included. Also included is a third working medium discharge device for discharging the third working medium to the third heat exchanger.

A power generation system and method including a first heat exchanger, a first thermal engine, and a first power generator on a first working medium line L1 that circulates a first working medium W1, a second heat exchanger, a third working medium supply device that supplies a third working medium W3, and a mixing device for mixing a second working medium W2 and the third working medium. A second thermal engine, and a second power generator are included on a second working medium line L2 that circulates the second working medium. On both of a downstream side of the first thermal engine on the first working medium line and a downstream side of the second thermal engine on the second working medium line, a third heat exchanger is included. Also included is a third working medium discharge device for discharging the third working medium to the third heat exchanger.

An energy storage apparatus includes a first circuit containing a first phase change material, a second circuit containing a second phase change material, and a heat pump having a cold side heat exchanger thermally coupled to the first circuit and a hot side heat exchanger thermally coupled to the second circuit. The apparatus is operable in a charging mode, a storage mode, and a discharge mode. In the charging mode the heat pump is energized to cool the first phase change material and heat the second phase change material. In the storage mode the first phase change material is stored in a first storage vessel and the second phase change material is stored as a pressurized vapor in a second storage vessel. In the discharge mode vaporized first phase change material is expanded by a first expander, or the vaporized second phase change material is expanded by a second expander.

An energy storage apparatus includes a first circuit containing a first phase change material, a second circuit containing a second phase change material, and a heat pump having a cold side heat exchanger thermally coupled to the first circuit and a hot side heat exchanger thermally coupled to the second circuit. The apparatus is operable in a charging mode, a storage mode, and a discharge mode. In the charging mode the heat pump is energized to cool the first phase change material and heat the second phase change material. In the storage mode the first phase change material is stored in a first storage vessel and the second phase change material is stored as a pressurized vapor in a second storage vessel. In the discharge mode vaporized first phase change material is expanded by a first expander, or the vaporized second phase change material is expanded by a second expander.

A combined cycle power plant and method for operating a combined power plant with stack energy control are presented. The combined cycle power plant includes a gas turbine, a heat recovery steam generator including a plurality of heating surfaces, and a steam turbine. The heating surfaces may be partially bypassed to reduce steam production in the heat recovery steam generator during power plant startup. Less energy may be extracted from exhaust gas of the gas turbine. More energy may be dumped through an exhaust stack. The steam turbine may start without restriction of a gas turbine load during power plant startup. The steam turbine may start without increasing a size of an air cooled condenser while maintaining a higher load of a gas turbine during power plant startup.

A combined cycle power plant and method for operating a combined power plant with stack energy control are presented. The combined cycle power plant includes a gas turbine, a heat recovery steam generator including a plurality of heating surfaces, and a steam turbine. The heating surfaces may be partially bypassed to reduce steam production in the heat recovery steam generator during power plant startup. Less energy may be extracted from exhaust gas of the gas turbine. More energy may be dumped through an exhaust stack. The steam turbine may start without restriction of a gas turbine load during power plant startup. The steam turbine may start without increasing a size of an air cooled condenser while maintaining a higher load of a gas turbine during power plant startup.