Variable Capacitance Circuit for Vibratory Energy Harvesting
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Solution Overview
Problem
Existing vibrational energy harvesting devices face challenges with low energy harvesting efficiency, narrow frequency bandwidth, and difficulty in adjusting mechanical resonance frequency to match varying vibration sources, particularly in environments with changing vibration frequencies.
Innovation Solution
A device with a converter system featuring parallel branches of variable capacitance capacitors, a control circuit to modify capacitances, and optional components like piezoelectric systems, accelerometers, and comparator circuits to optimize mechanical resonance frequency and electrical damping, ensuring efficient energy conversion across varying vibration frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a piezoelectric beam with a single variable capacitor is used to tune mechanical resonance frequency, then the resonance frequency can be adjusted, but the energy recovery optimization is insufficient and electrical damping cannot be matched to mechanical damping
Solution Approach 1:
The electrical circuit is segmented into two separate branches: first branch with variable capacitor C1 for resonance frequency tuning, and second branch with variable capacitor C2 and electrical load for energy recovery optimization. This segmentation allows independent optimization of resonance frequency adjustment and energy recovery without mutual interference.
Solution Approach 2:
Both capacitor values C1 and C2 are made dynamically adjustable through control circuitry that can modify their respective capacitances in real-time. This dynamic capability enables the system to simultaneously optimize mechanical resonance frequency matching and electrical damping to mechanical damping ratio across varying operating conditions.
2Adaptability or versatility
If the vibration frequency moves away from the system's mechanical resonance frequency, then the system can operate at different frequencies, but the energy harvesting efficiency decreases significantly
Solution Approach 1:
The control circuit implements feedback mechanisms that monitor the vibration frequency and adjust the capacitance values of C1 and C2 accordingly. This feedback enables the system to maintain optimal energy harvesting efficiency by dynamically tracking and adapting to varying vibration frequencies, ensuring the mechanical resonance frequency remains matched to the excitation frequency.
Solution Approach 2:
The system changes electrical parameters (capacitance values of C1 and C2) in response to varying vibration frequencies. By adjusting these parameters, the mechanical resonance frequency and electrical damping are dynamically modified to maintain optimal energy harvesting efficiency across a wide range of vibration frequencies.
3Device complexity
If a fixed capacitance system is used, then the circuit is simpler, but the bandwidth of vibrational energy harvesting is narrow
Solution Approach 1:
The system employs dynamic capacitance adjustment in both branches through controlled variable capacitors C1 and C2. This dynamic capability broadens the vibrational energy harvesting bandwidth by enabling the system to adapt to different vibration frequencies, while the control circuit manages the complexity of coordinating both variable capacitors.
Solution Approach 2:
The two-branch circuit configuration provides multi-functionality: the first branch with C1 handles resonance frequency tuning, while the second branch with C2 and electrical load handles energy recovery optimization. This universal design enables the system to simultaneously achieve frequency adaptation and energy optimization across wide bandwidth conditions.
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 solution enhances energy recovery by dynamically adjusting capacitances to match vibration frequencies, optimizing mechanical resonance and electrical damping, thereby increasing the efficiency and stability of energy harvesting from vibrational sources.
Implementation Method 1
a converter generating a potential difference when subjected to vibrations; According to a known principle for transforming vibratory mechanical energy into electrical energy is based on the vibratory excitation of a beam provided with piezoelectric elements
Implementation Method 2
an electrical circuit connected to the terminals of the converter and comprising first and second branches in parallel, the first branch comprising a first system of variable capacitance capacitor, the second branch comprising a second system of variable capacitance capacitor in series with an electrical load; a control circuit configured to modify the respective capacitances of the first and second capacitor systems so as to modify the mechanical resonance frequency of the converter
Data Source
Figure 1~3
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Figure 6~7
AI summary
The disclosure relates to a device for converting vibratory mechanical energy into electrical energy (1) comprising : a converter (11) generating a potential difference when it is subjected to vibrations; an electrical circuit (9) connected to the terminals of the converter and comprising first and second branches in parallel, the first branch comprising a first capacitor system with variable capacitance (C1), the second branch comprising a second capacitor system with variable capacitance (C2) in series with an electrical load (4) to be powered; a control circuit configured to modify the respective capacitances of the capacitor systems so as to modify the frequency of mechanical resonance of the converter.