Nonlinear Piezoelectric Generator for Compact Stirling Engine Power

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Solution Overview

Problem

Traditional Stirling engines face challenges in converting mechanical energy to electrical energy due to the weight and size constraints of large AC electromagnetic generators, making them less suitable for spacecraft and other applications where compactness is crucial.

Innovation Solution

A nonlinear piezoelectric generator system utilizing a flexible beam and an electrically responsive member, such as a piezoceramic stack, that compresses and decompresses to generate electrical output signals from mechanical inputs, leveraging the flexible beam's bowed configuration to amplify mechanical motion into electrical energy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a large AC electromagnetic generator is used to convert mechanical energy to electrical energy in a Stirling engine, then the conversion efficiency is improved, but the weight and size of the system increase significantly

Engineering Contradiction:

Improveenergy conversion efficiencyVSAvoidgenerator weight

Core Design Contradiction:

ProductivityVSWeight of moving object

Solution Approach 1:

The patent replaces the electromagnetic generator (electromagnetic field-based system) with a piezoelectric generator system that uses mechanical stress directly on piezoelectric wafers to generate electricity. This substitution eliminates the need for large rotating electromagnetic components, dramatically reducing weight while maintaining energy conversion functionality.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the operating parameters by using high-frequency mechanical vibrations (rather than low-frequency rotational motion) to drive the piezoelectric wafers. This parameter change enables efficient energy conversion at much smaller scales, allowing compact generator design without sacrificing productivity.

Inventive Principle:

Principle #35Parameter changes

2Power

If a large AC electromagnetic generator is used to convert mechanical energy to electrical energy, then the power output is improved, but the device size increases

Engineering Contradiction:

Improvepower outputVSAvoidgenerator volume

Core Design Contradiction:

PowerVSVolume of moving object

Solution Approach 1:

The patent transitions from a rotational mechanical system (electromagnetic generator) to a linear vibrational system (piezoelectric wafers). This dimensional change allows power generation in a compact linear configuration rather than requiring large rotational space, reducing volume while maintaining power output capability.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The invention uses composite structures combining flexible beams with piezoelectric wafers. The flexible beam material allows for efficient mechanical energy transfer to the piezoelectric elements, enabling high power density in a compact volume through optimized material composition and structure.

Inventive Principle:

Principle #40Composite materials

3Reliability

If traditional electromagnetic generators are used in spacecraft applications, then reliable power generation is achieved, but the weight constraints are violated

Engineering Contradiction:

Improvepower generation reliabilityVSAvoidgenerator weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent replaces the complex electromagnetic system with a simpler piezoelectric system that has fewer moving parts and no electromagnetic fields, reducing weight while maintaining or improving reliability through mechanical simplicity and solid-state operation suitable for spacecraft environments.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The system effectively converts mechanical energy into electrical energy with high efficiency and in a compact, lightweight form, enabling the use of Stirling engines in applications previously hindered by the size and weight of traditional generators.

Implementation Method 1

an electrically responsive member supported adjacent one end of the flexible beam so as to be under a compressive force exerted by the flexible beam; and the flexible beam being adapted to move towards a flattened shape from the bowed shape in response to the mechanical input, to transmit the mechanical input to the electrically responsive member, to cause a compression of the electrically responsive member that results in an electrical output signal being generated by the electrically responsive member

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Data Source

PatentUS7732994B2Non-linear piezoelectric mechanical-to-electrical generator system and method

Publication Date: 2010.06.08 THE BOEING CO

AI summary

A non-linear power generator system that may include a flexible beam for receiving a mechanical input, the flexible beam being supported in a bowed configuration; an electrically responsive member supported adjacent one end of the flexible beam so as to be under a compressive force exerted by the flexible beam; and the flexible beam being adapted to move towards a flattened shape from the bowed shape in response to the mechanical input, to transmit the mechanical input to the electrically responsive member, to cause a compression of the electrically responsive member that results in an electrical output signal being generated by the electrically responsive member.