Retroreflected Laser Paths for Accurate Methane Emission Quantification
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Solution Overview
Problem
Existing methods for detecting methane emissions, such as optical gas imaging and Method 21, are weather-dependent and require frequent surveys, while emerging technologies need validation to meet EPA emission reduction standards, and methane emissions from various sources are significant and challenging to quantify accurately.
Innovation Solution
The use of optical gas detectors with retroreflected laser beams that propagate along multiple paths, combined with data analysis to determine emission information, allows for accurate characterization of methane emissions by measuring path-integrated absorptions and background concentrations, using dual-frequency-comb spectrometers or tunable-diode laser absorption spectroscopy to detect gases like methane, acetylene, and others.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical gas imaging (OGI) is used to detect methane emissions, then emission detection capability is improved, but the method becomes weather-dependent and requires frequent surveys
Solution Approach 1:
The patent replaces the mechanical/optical imaging system (OGI camera) with an acoustic detection system using microphones and signal processing. This substitution eliminates the weather dependence of optical systems while maintaining emission detection capability through acoustic signature analysis of leaking methane.
Solution Approach 2:
The patent changes the detection parameter from optical absorption (weather-dependent) to acoustic properties (weather-independent). By detecting the sound waves generated by expanding methane gas during leakage, the system achieves reliable emission detection regardless of weather conditions.
2Measurement precision
If multiple optical beams and spectrometers are used to measure multiple paths simultaneously, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent divides the detection area into multiple sectors, each monitored by a specific optical beam path. This segmentation allows precise localization of emissions while using simpler individual measurement paths rather than one complex all-encompassing system.
Solution Approach 2:
The patent introduces retroreflectors as intermediary elements that bounce optical beams back to detectors. This allows multiple path measurements without requiring multiple complex transmitter-detector pairs, simplifying the overall system configuration while maintaining multi-path measurement precision.
3Area of stationary object
If retroreflectors are deployed at multiple locations to create multiple beam paths, then area coverage is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes each retroreflector a multi-functional element that serves multiple measurement paths simultaneously. A single retroreflector can reflect beams from multiple different transmitters back to their respective detectors, allowing extensive area coverage with minimal equipment.
Solution Approach 2:
The patent combines multiple measurement paths through shared retroreflector locations. Different optical paths converge at common retroreflector points, allowing the system to monitor large areas using fewer discrete equipment components rather than requiring separate equipment for each path.
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 method provides cost-effective, weather-independent detection of methane emissions by reducing equipment size and cost, enhancing accuracy through simultaneous multi-path measurements, and improving emission quantification by accounting for background concentrations and wind conditions.
Implementation Method 1
measuring path-integrated absorptions and background concentrations, using dual-frequency-comb spectrometers or tunable-diode laser absorption spectroscopy to detect gases like methane
Implementation Method 2
optical beams (e.g., laser beams or incoherent light beams) propagate along various paths, after which they are detected to obtain path-integrated absorption measurements
Implementation Method 3
optical beams (e.g., laser beams or incoherent light beams) propagate along various paths, after which they are detected to obtain path-integrated absorption measurements
Data Source
AI summary
A method for characterizing gas emissions includes sampling each of a plurality of sectors having a common geographic center. For each sector, a first laser beam is transmitted from the geographic center to a first retroreflection location, where it is retroreflected into a first retroreflected beam. Near the geographic center, the first retroreflected beam is measured to obtain a first absorption. A second laser beam is then transmitted from the geographic center to a second retroreflection location, where it is retroreflected into a second retroreflected beam. Near the geographic center, the second retroreflected beam is measured to obtain a second absorption. The first and second retroreflection locations are both located within the same sector. First and second concentrations are determined from the first and second absorptions and processed to determine emission information about a known or potential gas source whose source lies within the sector.