# US 10,502,099 B2 · System and method for free-piston power generation based on thermal differences > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,502,099 B2 - Document ID: US10502099B2 - Status: Granted - Kind: B2 - Application number: 15/873,422 - Filed: 2018-01-17 - Published: 2018-07-26 - Granted: 2019-12-10 - Earliest claimed: 2017-01-23 - Assignees: Raytheon Company - Applicants: Raytheon Company - Inventors: Gregory W. Heinen; Craig H. McCordic - Web page: https://patentgrep.com/patent/US10502099B2 ## CPC - F01K 25/103: {Carbon dioxide (F01K25/065 takes precedence)} - B63G 8/001: {Underwater vessels adapted for special purposes, e.g. unmanned underwater vessels; Equipment specially adapted therefor, e.g. docking stations (self-propelled or direction controlled diving chambers with mechanical link to a base B63C11/42)} - F01K 13/00: General layout or general methods of operation of complete plants - F01K 13/02: Controlling, e.g. stopping or starting - F01K 15/04: the vehicles being waterborne vessels - F01K 27/005: {by means of hydraulic motors} - B63G 8/08: Propulsion ({schnorkels B63G8/36;} nuclear propulsion B63H21/18; submerged exhausting apparatus F01N13/12) - B63G 2008/002: {unmanned} - F01K: STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES (gas-turbine or jet-propulsion plants F02; nuclear power plants, engine arrangements therein G21D) - B63G: OFFENSIVE OR DEFENSIVE ARRANGEMENTS ON VESSELS; MINE-LAYING; MINE-SWEEPING; SUBMARINES; AIRCRAFT CARRIERS (means of attack or defence in general, e.g. turrets F41H) ## Abstract An apparatus includes a generator configured to generate electrical power. The apparatus also includes first and second tanks each configured to receive and store a refrigerant under pressure. The apparatus further includes a first piston assembly having a first piston that divides a volume within the first piston assembly into first and second spaces each configured to receive refrigerant from at least one of the tanks. In addition, the apparatus includes a second piston assembly having a second piston coupled to the first piston. The generator is configured to generate the electrical power based on movement of at least one of the first and second pistons. During use, flows of the refrigerant between the tanks and the spaces can be created based on a pressure differential, such as a pressure differential created by a temperature difference between the tanks. ## Claims ### Claim 1 An apparatus comprising: a generator configured to generate electrical power; first and second tanks each configured to receive and store a refrigerant under pressure; a first piston assembly having a first piston that divides a volume within the first piston assembly into first and second spaces each configured to receive the refrigerant from at least one of the tanks; a second piston assembly having a second piston coupled to the first piston; and a linear gear extending between the first piston assembly and the second piston assembly, a circular gear attached to and movable with at least one f the pistons and configured to move along the linear gear, and a gearbox configured to translate a rotational speed of the circular gear into a higher rotational speed for the generator; wherein the generator is configured to generate the electrical power based on the higher rotational speed produced by the gearbox. ### Claim 2 (depends on 1) The apparatus of claim 1, further comprising: at least one first valve fluidly coupling the first tank and at least one of the first and second spaces; and at least one second valve fluidly coupling the second tank and at least one of the first and second spaces. ### Claim 3 (depends on 1) The apparatus of claim 1, further comprising: first and second insulated water jackets each configured to receive and retain water, the first tank located within the first insulated water jacket, the second tank located within the second insulated water jacket. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein: the second piston is configured to pull a fluid into a volume within the second piston assembly and push the fluid out of the volume within the second piston assembly; and the apparatus further comprises an orifice configured to slow movement of the fluid and reduce a loading placed on the gearbox. ### Claim 5 An apparatus comprising: a generator configured to generate electrical power; first and second tanks each configured to receive and store a refrigerant under pressure; a first piston assembly having a first piston that divides a volume within the first piston assembly into first and second spaces each configured to receive the refrigerant from at least one of the tanks; and a second piston assembly having a second piston coupled to the first piston: wherein the second piston is configured to pull a fluid into a volume within the second piston assembly and push the fluid out of the volume within the second piston assembly; and wherein the generator is configured to generate the electrical power based on movement of the fluid. ### Claim 6 (depends on 5) The apparatus of claim 5, further comprising: at least one valve configured to control the flow of the fluid through the generator. ### Claim 7 (depends on 5) The apparatus of claim 5, further comprising: a reservoir configured to hold the fluid; wherein the second piston is configured to pull the fluid from the reservoir and push the fluid into the reservoir. ### Claim 8 (depends on 7) The apparatus of claim 7, wherein the generator is positioned within the reservoir. ### Claim 9 (depends on 5) The apparatus of claim 5, wherein: the second piston divides the volume within the second piston assembly into multiple spaces each configured to receive the fluid; and the second piston is configured to pull the fluid into one of the multiple spaces and push the fluid out of another of the multiple spaces during movement of the second piston. ### Claim 10 A system comprising: a vehicle comprising a body; the vehicle also comprising a power generator, the power generator comprising: a generator configured to generate electrical power; first and second tanks each configured to receive and store a refrigerant under pressure; a first piston assembly having a first piston that divides a volume within the first piston assembly into first and second spaces each configured to receive the refrigerant from at least one of the tanks; a second piston assembly having a second piston coupled to the first piston; and a linear gear extending between the first piston assembly and the second piston assembly, a circular gear attached to and movable with at least one of the pistons and configured to move along the linear gear, and a gearbox configured to translate a rotational speed of the circular gear into a higher rotational speed for the generator; wherein the generator is configured to generate the electrical power based on the higher rotational speed produced by the gearbox. ### Claim 11 (depends on 10) The system of claim 10, wherein the power generator further comprises: at least one first valve fluidly coupling the first tank and at least one of the first and second spaces; and at least one second valve fluidly coupling the second tank and at least one of the first and second spaces. ### Claim 12 (depends on 10) The system of claim 10, wherein the power generator further comprises: first and second insulated water jackets each configured to receive and retain water, the first tank located within the first insulated water jacket, the second tank located within the second insulated water jacket. ### Claim 13 (depends on 10) The system of claim 10, wherein: the second piston is configured to pull a fluid into a volume within the second piston assembly and push the fluid out of the volume within the second piston assembly; and the power generator further comprises an orifice configured to slow movement of the fluid and reduce a loading placed on the gearbox. ### Claim 14 A system comprising: a vehicle comprising a body; the vehicle also comprising a power generator, the power generator comprising; a generator configured to generate electrical power; first and second tanks each configured to receive and store a refrigerant under pressure; a first piston assembly having a first piston that divides a volume within the first piston assembly into first and second spaces each configured to receive the refrigerant from at least one of the tanks; and a second piston assembly having a second piston coupled to the first piston: wherein the second piston is configured to pull a fluid into a volume within the second piston assembly and push the fluid out of the volume within the second piston assembly; and wherein the generator is configured to generate the electrical power based on movement of the fluid. ### Claim 15 (depends on 14) The system of claim 14, further comprising: a reservoir configured to hold the fluid; wherein the second piston is configured to pull the fluid from the reservoir and push the fluid into the reservoir. ### Claim 16 (depends on 14) The system of claim 14, wherein: the second piston divides the volume within the second piston assembly into multiple spaces each configured to receive the fluid; and the second piston is configured to pull the fluid into one of the multiple spaces and push the fluid out of another of the multiple spaces during movement of the second piston. ### Claim 17 A method comprising: storing a refrigerant under pressure in first and second tanks; moving a first piston in a first piston assembly based on flows of the refrigerant to and from the tanks, the first piston dividing a volume within the first piston assembly into first and second spaces each configured to receive the refrigerant from at least one of the tanks; moving a second piston of a second piston assembly, the second piston coupled to the first piston; moving a circular gear along a linear gear extending between the first piston assembly and the second piston assembly, the circular attached to and gear attached to and movable with at least one of the pistons; translating a rotational speed of the circular gear into a higher rotational speed; and generating electrical power based on the higher rotational speed. ### Claim 18 (depends on 17) The method of claim 17, further comprising: warming one of the tanks and cooling another of the tanks to create a pressure differential between the tanks; and creating the flows of the refrigerant from the first tank to the first space and from the second space to the second tank based on the pressure differential. ### Claim 19 A method comprising: storing a refrigerant under pressure in first and second tanks; moving a first piston in a first piston assembly based on flows of the refrigerant to and from the tanks, the first piston dividing a volume within the first piston assembly into first and second spaces each configured to receive the refrigerant from at least one of the tanks; moving a second piston of a second piston assembly, the second piston coupled to the first piston; creating a flow of fluid onto or through a generator using the second piston assembly; and generating electrical power using the generator. ### Claim 20 A method comprising: storing a refrigerant under pressure in first and second tanks; warming the first tank and cooling the second tank to create a pressure differential between the tanks; moving a first piston in a first piston assembly based on flows of the refrigerant from the first tank to a first space and from a second space to the second tank, the first piston dividing a volume within the first piston assembly into the first and second spaces each configured to receive the refrigerant from at least one of the tanks, the flows of the refrigerant created based on the pressure differential; moving a second piston of a second piston assembly, the second piston coupled to the first piston; generating electrical power based on movement of at least one of the first and second pistons; and reversing the warming and cooling of the tanks in order to reverse the movement of the first and second pistons.