Multi-engine aircraft power and propulsion systems and methods of starting the engines of multi-engine aircraft disclosed, including supplying electrical power from an electrical power source to electric machines of the a first gas turbine engine and operating electric machines as motors to drive rotation of spools of the first gas turbine engine; starting the first gas turbine engine by lighting combustion equipment of the first gas turbine engine; operating the electric machines of the first gas turbine engine as generators to extract mechanical power and generate electrical power from spools of the first gas turbine engine; transferring the electrical power to electric machines of a second gas turbine engine and operating the electric machines as motors to drive rotation of spools of the second gas turbine engine; and starting the second gas turbine engine by lighting combustion equipment of the second gas turbine engine.

Aircraft power and propulsion systems, aircraft comprising such power and propulsion systems, and methods of restarting a gas turbine engine of such power and propulsion systems during flight are provided. One such aircraft power and propulsion system comprises: a propulsive gas turbine engine comprising a plurality of spools, combustion equipment, one or more electric machines mechanically coupled with one or more of the spools and an electrically-powered fuel pump for delivering fuel to the combustion equipment; an electrical system connected with the one or more electric machines and the electrically-powered fuel pump, the electrical system comprising an energy storage system; and a control system configured to: responsive to a determination to the effect that a flame in the combustion equipment has been extinguished, control the electrical system to supply electrical power from the energy storage system to the fuel pump during an engine restart attempt.

A gas turbine engine for an aircraft comprises, in axial flow sequence, a compressor module, a combustor module, and a turbine module. The gas turbine engine further comprises a first electric machine that is rotationally connected to the turbine module, and an electrical energy storage unit. The gas turbine engine is configured to generate a maximum dry thrust T (N). The first electric machine is configured to generate a maximum electrical power P.sub.EM1 (W). The electrical energy storage unit has an energy storage capacity E (Wh), a maximum charge rate C (h.sup.−1), and a maximum discharge rate D (h.sup.−1). The electrical energy storage unit is configured to store electrical energy that may be generated by the first electric machine.

A plant for storing energy comprises a casing for the storage of a working fluid other than atmospheric air, in gaseous phase and in equilibrium of pressure with the atmosphere; a tank for the storage of said working fluid in liquid or supercritical phase with a temperature close to the critical temperature. The plant is configured to perform a closed cyclic thermodynamic transformation, first in one direction in a charge configuration and then in an opposite direction in a discharge configuration, between said casing and said tank. In the charge configuration the plant stores heat and pressure and in the discharge configuration the plant generates energy. The plant is also configured to define a closed circuit and to perform a closed thermodynamic cycle in the closed circuit with at least a part of the working fluid.

A plant for storing energy comprises a casing for the storage of a working fluid other than atmospheric air, in gaseous phase and in equilibrium of pressure with the atmosphere; a tank for the storage of said working fluid in liquid or supercritical phase with a temperature close to the critical temperature. The plant is configured to perform a closed cyclic thermodynamic transformation, first in one direction in a charge configuration and then in an opposite direction in a discharge configuration, between said casing and said tank. In the charge configuration the plant stores heat and pressure and in the discharge configuration the plant generates energy. The plant is also configured to define a closed circuit and to perform a closed thermodynamic cycle in the closed circuit with at least a part of the working fluid.

An energy storage system and method employ electrolysis to convert excess electrical energy into hydrogen gas and oxygen gas stored in cryogenic flux capacitor units. When needed, the hydrogen and oxygen are liberated from the CFCs and mixed with supercritical CO.sub.2 and combusted in a combustion chamber without any nitrogen or air present to form a heated mixture of water and sCO2 that drives a turbine that creates energy that is returned to the power grid. The water in the sCO2 mixture is then extracted and returned to a reservoir for electrolysis when needed again, resulting in a closed system for storing electrical energy.

A system includes a generator using a fluid mixture obtained via a generator inlet, a compressor having a compressor inlet that is connected to a generator outlet by a first set of conduits, a second set of conduits connected to the compressor outlet and the generator inlet, and a sensor in communication with the second set of conduits, where a portion of the fluid mixture includes gas from a gas emission source, and where exhaust fluid of the generator is provided to the compressor. A process includes obtaining a target fluid property and a fluid measurement using the sensor and modifying a parameter of a fluid control device to modify a first flow rate of the flow of the exhaust fluid through the second set of conduits relative to a second flow rate of the flow of the gas provided by gas emission source through the first set of conduits.

A system includes a generator using a fluid mixture obtained via a generator inlet, a compressor having a compressor inlet that is connected to a generator outlet by a first set of conduits, a second set of conduits connected to the compressor outlet and the generator inlet, and a sensor in communication with the second set of conduits, where a portion of the fluid mixture includes gas from a gas emission source, and where exhaust fluid of the generator is provided to the compressor. A process includes obtaining a target fluid property and a fluid measurement using the sensor and modifying a parameter of a fluid control device to modify a first flow rate of the flow of the exhaust fluid through the second set of conduits relative to a second flow rate of the flow of the gas provided by gas emission source through the first set of conduits.

An energy storage system includes: a combustion turbine configured to output heated sweep gas; a reformer configured to receive natural gas and steam and to output reformed natural gas; a molten carbonate electrolyzer cell (“MCEC”) comprising an MCEC anode and an MCEC cathode, wherein the MCEC is configured to operate in a hydrogen-generation mode in which: the MCEC anode receives the reformed natural gas from the reformer, and outputs MCEC anode exhaust that contains hydrogen, and the MCEC cathode is configured to receive heated sweep gas from the combustion turbine, and to output MCEC cathode exhaust; and a storage tank configured to receive the MCEC anode exhaust that contains hydrogen.

An energy storage system includes: a combustion turbine configured to output heated sweep gas; a reformer configured to receive natural gas and steam and to output reformed natural gas; a molten carbonate electrolyzer cell (“MCEC”) comprising an MCEC anode and an MCEC cathode, wherein the MCEC is configured to operate in a hydrogen-generation mode in which: the MCEC anode receives the reformed natural gas from the reformer, and outputs MCEC anode exhaust that contains hydrogen, and the MCEC cathode is configured to receive heated sweep gas from the combustion turbine, and to output MCEC cathode exhaust; and a storage tank configured to receive the MCEC anode exhaust that contains hydrogen.