Fugitive emission source characterization using a gradient-based optimization scheme and scalar transport adjoint

Brereton, Carol A.; Joynes, Ian; Campbell, Lucy; Johnson, Matthew R.

doi:10.1016/j.atmosenv.2018.02.014

Cited by 10 publications

(30 citation statements)

References 38 publications

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“…Two main test cases were chosen, which matched those used in Brereton et al (2018a) allowing results with and without the pre-computation approach to be directly compared.…”

Section: Resultsmentioning

confidence: 99%

“…Details of the scalar transport-adjoint method for characterizing unknown fugitive sources are provided in Brereton et al (2018a) and are summarized in approach is used to compute the sensitivity of the mismatch from the sensors, which feeds a gradient-based quasi-Newton optimization scheme (L-BFGS-B, Liu & Nocedal, 1989).…”

Section: Emission Characterization Methodologymentioning

confidence: 99%

“…Transport solvers were implemented with the OpenFOAM toolkit and the L-BFGS-B algorithm used the code by Zhu et al (2011) as described in Brereton et al (2018a). The optimization implementation was the same for both the CTC and pre-computed approaches, but requests for the cost function and its gradient were satisfied differently.…”

Section: Methodsmentioning

confidence: 99%

“…where the misfit was selected to provide a least-square minimization of the difference between model and measured concentrations where observations exist (Brereton et al, 2018a). Once the cost function and its gradient are known, these are used by the optimization loop to improve the source parameters or end the optimization process.…”

Section: Cost Function and Its Gradientmentioning

confidence: 99%

“…The more challenging test case was based on an Alberta gas plant geometry and consisted of a collection of buildings ranging in height from 3 m to 10 m within a 400 m × 350 m × 100 m domain. As described in Brereton et al (2018a), when simulating wind fields to generate the initial case, this inner domain was placed within a larger triangular 3200 m × 3200 m × 400 m domain with buildings copies placed upstream as a fetch.…”

Section: Bluff Body Test Case Based On An Alberta Gas Plant Geometrymentioning

confidence: 99%

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Adjoint-Based Optimization Scheme for Characterizing Sources of Fugitive Emissions

Brereton¹

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Fugitive emissions, such as leaking components, are important sources of methane and other pollutants within the oil and gas sector. These gas emission sources are difficult to mitigate because their existence, location, and magnitude are unknown, especially within facilities which may have thousands of potential source components. Improving the speed at which these sources are characterized (located and quantified) can improve these mitigation efforts. Using sparse concentration information (from finite sensor locations) and estimated wind fields, a scalar transport adjoint-based optimization approach was developed to characterize both single and multiple simultaneous gas releases representative of the fugitive emissions problem. This approach was tested using data from an open-field gas release to determine a single source location within 5 m and source magnitude within 13%. Simulated simultaneous releases over a complex 3D geometry based on an Alberta gas plant were also characterized using both detailed transient wind and wind fields approximated with a series of steady-state wind simulations more readily implemented in a field application. Magnitudes were predicted within 10% and major regions located. By extending the method with a database of pre-computed retro-tracers generated on simplified steady-state wind fields, the required computational time for the solution optimization was reduced by a factor of 200-600, making computations feasible on a desktop machine and raising the possibility of near-continuous fugitive emissions quantification in the future. Major sources were successfully located, and magnitudes estimated within-75 to-32%, even with limited wind coverage (60° direction variation). Turbulent Schmidt number selection (which scales diffusivity) had little effect on estimated source locations, but strongly influenced estimated magnitudes. For a tested turbulent Schmidt number range of 0.33 (diffuse) to 2.0 (highly advective), the predicted emission rates for the open field release varied between-35 to +128% of actual. Buildings dampened this effect, suggesting that open-field estimates can act as an error bound. iii Preface This thesis contains chapters which have already been published or have been prepared for publication jointly as journal articles. Chapter 4 has been peer-reviewed and was published in Atmospheric Environment and reproduced according to the journal's copyright policy. Only minor clarifications and formatting edits have been made following feedback from the thesis examination committee and for formatting consistency. This paper was co-authored by the thesis author, Carol Brereton, her thesis supervisors Prof. Matthew Johnson and Prof. Lucy Campbell, as well as former student Ian Joynes who was involved in initial discussions and background development work. Ms. Brereton setup , developed, and tested the relevant procedures and code; generated synthetic test data; performed the test simulations and

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“…Two main test cases were chosen, which matched those used in Brereton et al (2018a) allowing results with and without the pre-computation approach to be directly compared.…”

Section: Resultsmentioning

confidence: 99%

Section: Emission Characterization Methodologymentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Cost Function and Its Gradientmentioning

confidence: 99%

Section: Bluff Body Test Case Based On An Alberta Gas Plant Geometrymentioning

confidence: 99%

See 3 more Smart Citations