Dual Comb Spectrometer for Methane Leak Location and Sizing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methane leak detection technologies face challenges in precision, stability, and cost, particularly in accurately measuring and locating kilometer-scale methane leaks due to low wavelength resolution, turbulence-induced fluctuations, and interference from other molecules, requiring frequent calibration and operator involvement.
Innovation Solution
A low-cost dual comb spectrometer system that uses broadband laser absorption and combines path-integrated spectroscopic data with meteorological data through transport and inversion models to locate and size gas leaks, accounting for background emissions without calibration or operator intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If mobile FTIR systems are used for long-path methane measurement, then measurement coverage area is improved, but measurement precision deteriorates due to low wavelength resolution and large instrument distortion
Solution Approach 1:
The patent replaces the mechanical FTIR spectrometer system with a dual-comb spectroscopy system that uses two mode-locked lasers generating frequency combs. This substitution eliminates the need for moving parts and mechanical scanning, providing stable, high-resolution spectral measurements over long paths without the distortion problems of mobile FTIR systems.
Solution Approach 2:
The patent changes the fundamental measurement parameter from broadband FTIR spectroscopy to dual-comb frequency domain spectroscopy. By using two frequency combs with slightly different repetition rates, the system achieves high wavelength resolution and precision while maintaining long-path measurement capability, directly resolving the contradiction between coverage area and measurement precision.
2Measurement precision
If diode laser-based systems or LIDAR systems are used for methane detection, then measurement precision is improved, but reliability deteriorates due to turbulence-induced laser intensity fluctuations and interference from overlapping absorption
Solution Approach 1:
The dual-comb spectroscopy system simultaneously measures multiple gas species (methane, water vapor, other hydrocarbons) across broad spectral ranges, unlike single-wavelength diode laser systems. This multi-functionality allows the system to capture complete absorption spectra for accurate methane detection while accounting for interfering species, improving both precision and reliability.
Solution Approach 2:
The system uses the second frequency comb to probe the absorption features while the first comb serves as a stable reference. By comparing the heterodyne interference signals, the system automatically compensates for turbulence-induced intensity fluctuations and drift, maintaining reliable measurements without external intervention.
3Device complexity
If sparse wavelength laser systems are used for methane measurement, then device complexity is reduced, but measurement precision deteriorates and additional measurements of water vapor, temperature, and pressure are required
Solution Approach 1:
The dual-comb spectroscopy system inherently measures water vapor, temperature, pressure, and multiple hydrocarbon species simultaneously through broadband spectral coverage. This eliminates the need for separate sensors and complex calibration procedures required by sparse wavelength systems, achieving high precision without increasing operational complexity.
4Measurement precision
If commercial cavity-ringdown laser spectrometers are used for methane detection, then measurement precision is improved, but productivity deteriorates due to periodic calibration requirements and high cost
Solution Approach 1:
The dual-comb spectroscopy system is inherently stable and drift-free due to the rigid frequency spacing of the combs, eliminating the need for periodic calibration. The system self-maintains its measurement accuracy over long periods, significantly improving productivity by removing calibration downtime and reducing operational costs compared to commercial CRDS spectrometers.
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
Enables accurate, drift-free, and interference-free detection of methane leaks with high sensitivity, capable of identifying small leaks over long distances and multiple locations simultaneously, reducing measurement uncertainty and operational costs.
Implementation Method 1
A low cost dual comb spectrometer design uses the method of deploying a line of sight, broadband, laser absorption sensor to locate and size trace gas leaks
Implementation Method 2
The two frequency combs (e.g. near infrared light) have slightly different tooth spacing that are combined as source light that passes through a gas... the resulting heterodyne interference signals of the combs
Data Source
AI summary
A system for detecting gas leaks and determining their location and size. A data gathering portion of the system utilizes a chosen geometrical configuration to collect path-integrated spectroscopic data over multiple paths around an area. A processing portion of the system applies a transport model together with meteorological data of the area to generate an influence function of possible leak locations on gas detector measurement paths, and applies an inversion model to the influence function, prior data, and the spectroscopic data to generate gas source size and location.