Hydrogen purity assessment using laser absorption Spectroscopy
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Date
2025
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University of Namibia
Abstract
Hydrogen purity assessment is a critical concern in energy applications, especially in
fields involving hydrogen injection into natural gas pipelines and fuel cell research.
This study addresses the limitations of current hydrogen measurement techniques by
developing a novel hydrogen spectrometer (𝐻2-Spectrometer) based on direct Tunable
Diode Laser Absorption Spectroscopy (d-TDLAS). The goal is to establish a traceable
and accurate methodology for hydrogen purity and concentration measurement
without relying on calibration gases. The main objective of this research is to develop
and evaluate the performance of the 𝐻2-Spectrometer, specifically investigating its
suitability for measuring hydrogen purity and hydrogen concentration in methane
hydrogen mixtures. The study also aims to support hydrogen injection into natural gas
pipelines by providing precise hydrogen concentration measurements.
An experimental design was employed, utilizing the 𝐻2-Spectrometer to measure
hydrogen line intensity and concentration. The measurements were taken for 99.999%
pure hydrogen and hydrogen-methane gas mixtures to test the spectrometer’s accuracy
and reliability. The obtained data were compared against reference values from the
HITRAN database and the certificate from the reference gas mix to evaluate
performance. The findings revealed that the 𝐻2-Spectrometer demonstrated a
significantly lower uncertainty of 1.6% in hydrogen line intensity measurements,
compared to the 10% uncertainty reported in the HITRAN database. The measured
line intensity obtained was 3.22 × 10−26 cm/molecule, which is slightly higher than the
HITRAN value of 3.189 × 10−26 cm/molecule. In terms of hydrogen concentration, the
spectrometer achieved an average mole fraction of 0.858 with a 1% uncertainty,
closely aligning with the expected value of 0.900 as per the certificate from the
reference gas mix with a 2% uncertainty. The 𝐻2 Spectrometer proved to be highly
accurate and reliable, with potential applications in hydrogen quality control from
electrolysis, fuel cell research, process control, and environmental monitoring. Its
ability to provide traceable and precise measurements makes it a valuable tool for
hydrogen-related research, optimizing system performance and ensuring compliance
with regulatory standards
Description
A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science in Renewable energy
Keywords
Direct Tunable Diode Laser Absorption Spectroscopy, Hydrogen spectrometer, Purity assessment, Traceable Infrared Laser Spectrometric Amount Fraction Measurement (TILSAM), Namibia, University of Namibia