Free-Piston Power Generation Using Thermal Differences

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Unmanned underwater vehicles (UUVs) face challenges in obtaining adequate and independent power for prolonged operation due to limitations in existing power supply methods, such as tethering, small power generation from expanding wax, and the need for large fuel cell packages.

Innovation Solution

A system and method for free-piston power generation based on thermal differences, utilizing refrigerant tanks and pistons to generate electrical power through temperature-induced pressure differentials, allowing for efficient and prolonged power generation without the need for large power sources or tethering.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If tethering is used to supply power to UUV, then power supply is reliable, but range and deployment flexibility are limited

Engineering Contradiction:

Improvepower supply reliabilityVSAvoiddeployment flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The UUV generates its own electrical power autonomously through onboard thermal energy conversion, eliminating the need for external tethered power supply. The system uses temperature differentials between ambient water and onboard thermal storage to drive free-piston generators, enabling independent operation while maintaining reliable power generation.

Inventive Principle:

Principle #25Self-service

2Adaptability or versatility

If expanding wax based power generation is used, then power generation is independent, but power output is very small (less than 200 Watts)

Engineering Contradiction:

Improveindependent operationVSAvoidpower output

Core Design Contradiction:

Adaptability or versatilityVSPower

Solution Approach 1:

The system changes the physical parameters of the working fluid (refrigerant) by utilizing phase transitions between liquid and vapor states. Temperature-induced pressure differentials drive the free-piston generator, enabling significantly higher power output compared to wax expansion, while maintaining independent onboard operation.

Inventive Principle:

Principle #35Parameter changes

3Power

If fuel cells are used to generate power, then adequate power can be generated, but large packages and substantial space are required

Engineering Contradiction:

Improvepower generation capacityVSAvoidspace requirement

Core Design Contradiction:

PowerVSVolume of moving object

Solution Approach 1:

The system utilizes phase transitions of a refrigerant fluid between liquid and vapor states to generate pressure differentials that drive the free-piston generator. This approach achieves adequate power generation capacity without requiring large fuel cell packages, significantly reducing the volume and space requirements for the power generation system.

Inventive Principle:

Principle #36Phase transitions

4Duration of action of moving object

If thermal differences are used for power generation, then prolonged autonomous power generation is enabled, but system complexity increases

Engineering Contradiction:

Improveoperation durationVSAvoidsystem complexity

Core Design Contradiction:

Duration of action of moving objectVSDevice complexity

Solution Approach 1:

The system extracts thermal energy from ambient water and onboard thermal storage, separating the heat source function from the power generation function. The free-piston generator converts thermal energy to mechanical motion, which then drives the electrical generator. This extraction approach enables prolonged autonomous operation while managing system complexity through functional separation.

Inventive Principle:

Principle #2Taking out (Extraction)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution enables UUVs to generate electrical power autonomously and efficiently over a prolonged period, overcoming the limitations of existing power supply methods by leveraging thermal differences to move pistons and generate power, suitable for underwater operations.

Implementation Method 1

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

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 2

system and method for free-piston power generation based on thermal differences

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

The generator is configured to generate the electrical power based on movement of at least one of the first and second pistons

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS10502099B2System and method for free-piston power generation based on thermal differences

Publication Date: 2019.12.10 RAYTHEON CO

AI summary

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.