Various embodiments of the present invention are directed toward a linear combustion engine, comprising: a cylinder having a cylinder wall and a pair of ends, the cylinder including a combustion section disposed in a center portion of the cylinder; a pair of opposed piston assemblies adapted to move linearly within the cylinder, each piston assembly disposed on one side of the combustion section opposite the other piston assembly, each piston assembly including a spring rod and a piston comprising a solid front section adjacent the combustion section and a gas section; and a pair of linear electromagnetic machines adapted to directly convert kinetic energy of the piston assembly into electrical energy, and adapted to directly convert electrical energy into kinetic energy of the piston assembly for providing compression work during the compression stroke.

Systems and methods for converting energy are provided. In one aspect, the system includes a closed cycle engine defining a cold side. The system also includes a bottoming-cycle loop. A pump is operable to move a working fluid along the bottoming-cycle loop. A cold side heat exchanger is positioned along the bottoming-cycle loop in a heat exchange relationship with the cold side of the closed cycle engine. A constant density heat exchanger is positioned along the bottoming-cycle loop downstream of the cold side heat exchanger and upstream of an expansion device. The constant density heat exchanger is operable to hold a volume of the working fluid flowing therethrough at constant density while increasing, via a heat source, the temperature and pressure of the working fluid. The expansion device receives the working fluid at elevated temperature and pressure and extracts thermal energy from the working fluid to produce work.

A free piston apparatus includes a piston receptacle in which a piston device having a piston is reciprocable along an axis. The piston receptacle includes or forms a chamber delimited by a wall arrangement forming an inlet opening and an outlet opening. A cooling device is arranged on the piston receptacle for cooling the wall arrangement. The cooling device includes or forms a cooling channel arranged radially outside on the wall arrangement. The cooling channel has first and second cooling regions axially on opposing sides of the outlet opening. The piston receptacle includes or forms an outlet chamber, arranged outside on the wall arrangement, for exhaust gas exiting via the outlet opening. The cooling channel has a third cooling region which flow-connects the first cooling region and the second cooling region along the outlet chamber and is positioned at least in sections radially outside of the outlet chamber.

The present invention relates to a free-piston linear apparatus, comprising a piston arranged within a cylinder, said piston being configured for linear displacement within the cylinder; a combustion chamber arranged on one side of said piston and a gas expansion chamber arranged on an opposite side of said piston, wherein said piston is drivable under the action of a fuel medium expanding in the combustion chamber; an exhaust vent arranged to release exhaust gas from the combustion chamber to an exhaust system, wherein said exhaust system comprises a heat exchanger configured to transfer residual heat from said exhaust gas to said gas expansion chamber in order to heat the gas expansion chamber; and wherein said gas expansion chamber comprises at least one gas port for injecting and/or releasing gas into/from the gas expansion chamber.

Various embodiments of the present disclosure are directed towards free-piston combustion engines. As described herein, a driver section may be provided in a free-piston combustion engine for storing energy during an expansion stroke. The driver section may be configured to store sufficient energy to perform the subsequent stroke. In some embodiments, the driver section may be configured to store sufficient energy so as to enable the engine to operate continuously across engine cycles without electrical energy input. A linear electromagnetic machine may be provided in a free-piston combustion engine for converting the kinetic energy of a piston assembly into electrical energy.

A combined heat and power microgrid system is provided that stores energy in the form of compressed air that can then be utilized as needed in the form of electricity. The compressed air may be generated with energy from multiple electrical energy sources, such as renewable energy sources. The energy stored as compressed air/heat is used to charge a battery by utilizing a pulley system and a barrel housing that transfers kinetic energy generated by the release of the compressed air to an array of piezoelectric generators that can produce electricity, which is stored in the second battery. In addition, water may be extracted from the compressed air storage tank. In this way, energy produced by the renewable sources can be accessed during periods of high need or low production and water may be collected.

A homogeneous charge compression ignition free-piston linear generator is disclosed. The linear generator includes a housing having cylinders at opposite ends. A double-ended piston assembly is to move linearly in the housing to convert kinetic energy of the piston assembly into electrical energy, and to enable conversion of electrical energy into kinetic energy of the piston assembly. Sensors measure one or more states of the cylinders and/or piston assembly, and a controller controls the linear generator based on the sensor data.

Systems and methods for converting energy are provided. In one aspect, the system includes a closed cycle engine having a piston body and a piston assembly movable within the piston body. An electric machine is operatively coupled with the piston assembly and operable to generate electrical power. An electrical device is in communication with the electric machine. The system includes a control system having sensors, a controllable device, and a controller. The controller is configured to determine whether a load change on the electric machine is anticipated based at least in part on received data indicative of a load state of the electrical device; in response to whether the load change is anticipated, determine a control command for adjusting an output of at least one of the engine and the electric machine; and cause the controllable device to adjust the output based at least in part on the control command.

Various embodiments of the present disclosure are directed towards free-piston combustion engines. As described herein, a driver section may be provided in a free-piston combustion engine for storing energy during an expansion stroke. The driver section may be configured to store sufficient energy to perform the subsequent stroke. In some embodiments, the driver section may be configured to store sufficient energy so as to enable the engine to operate continuously across engine cycles without electrical energy input. A linear electromagnetic machine may be provided in a free-piston combustion engine for converting the kinetic energy of a piston assembly into electrical energy.

Multiphase electromagnetic machines, such as free-piston engines or compressors, may require, or supply, a pulsed power profile from or to a DC bus, respectively. The pulsed power profile may include relatively large fluctuations in instantaneous power. Sourcing, sinking, or otherwise exchanging power with an AC grid, via an inverter, may be accomplished by using an energy storage device and a DC-DC converter coupled to a DC bus. The energy storage device may aid in smoothing the pulsed power profile, while the DC-DC converter may aid in reducing fluctuations in voltage across a DC bus due to energy storage in the energy storage device.