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~ Hydrogen Safety Sensors ~ Performance under anaerobic conditions. * W.J. Buttner, R. Burgess, C. Rivkin, M.B. Post † L. Boon-Brett , G. Black, F. Harskamp, P. Moretto * National Renewable Energy Laboratory - NREL † Joint Research Centre - Institute for Energy and Transport – JRC IET.
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~ Hydrogen Safety Sensors ~ Performance under anaerobic conditions *W.J. Buttner, R. Burgess, C. Rivkin, M.B. Post † L. Boon-Brett, G. Black, F. Harskamp, P. Moretto *National Renewable Energy Laboratory - NREL †Joint Research Centre - Institute for Energy and Transport – JRC IET
Outline • JRC IET/NREL Collaboration • Research rational • Sensor performance testing facilities • O2 dependence test method • Results/observations • Conclusions
Collaborators EC JRC-IET DOE NREL
Collaborators EC JRC-IET DOE NREL End users Manufacturers developers SDOs The ultimate purpose of the sensor test laboratories is to ensure that sensor technology is available to meet end user needs Hydrogen Safety Sensor Performance Evaluation
Rational Hydrogen sensors are a key enabling technology for a safe H2 infrastructure - essential for detecting unwanted H2 releases Integrated safety designs include design (valves, PRDs, material) & operational (inert purges) elements Issue: Use of hydrogen sensor in inert atmospheres Inert gas purges may alleviate risks, but may deactivate sensors O2 requirement depends on technology Results for three technologies presented (complete study on-going and will be presented elsewhere)
O2 Dependence? Most H2 sensors detection principle require O2: Catalytic/pellistor Chemical oxidation Electrochemical Electrochemical oxidation Metal oxide Oxygen surface interactions Work function type Oxygen surface interactions Optical Oxygen assisted recovery Some don’t: Thermal conductivity Acoustic Thin/ultra-thin film metal resistors Evaluate influence of oxygen concentration on sensor output
Testing facilities…. EC JRC-IET DOE NREL • Test chambers conditions: • Temperature • Pressure • Relative Humidity • Gas composition • Gas flow
H2 + O2 → H2O + Δ T = To + ΔT ΔT = F ([H2]) Results – CGS (1) • Industry standard (e.g., petroleum industry) for combustible safety • Signal is ΔR induced by ΔT arising from surface-catalyzed combustion • Oxygen is fundamentally required • Remains responsive in depressed oxygen (down to 5% oxygen) • Unresponsive and unstable when operated an aerobically
Results – CGS (2) • Anaerobic operation cause irreversible shift in baseline • Oxygen is required for stable repeatable operation
Heated thermoresistor Signal is ΔR via ΔT (heat loss) H2 high thermal conductivity No O2 involvement Results – TC (1) • Response affected by matrix change • Net response to H2 unaffected by O2
Results – TC (3) • Net response to H2 unaffected by [O2] • Sensor slightly over estimates [H2] • Results comparable • Matrix dependence – correctable!
Various platforms exploit Pd (optical, resistance, mass sens.) Fundamentally no O2 requirement; should be verified for each type Protective coating (on some) alleviates Pd susceptibility to poisons Results – PTF (1) • Commercial resistive sensor showed no oxygen dependence • Reversible, quantitative consistent response for oxygen levels • Slight impact for anaerobic operation
Results – PTF (3) • H2response only negligiblyaffectedby [O2] • Sensor under estimates [H2] • Results comparable
NREL and JRC laboratories are available for manufacturers, developers, end-users, and SDOs The NREL and JRC laboratories exist to assure that hydrogen sensors are available and are used properly Topical studies initiated to document sensor use and limitations Operation of sensors under depressed oxygen Some platforms (e.g., Pd resistance) show negligible impact Some platforms (e.g., TCD) have (compensable?) matrix drift, but invariance with hydrogen Some platforms (e.g., CGS) incompatible with anaerobic operation Future direction/additional work Complete survey for EC, MOX, and other platforms Expand for impact of interferences Other “topical” studies in support of SAFE hydrogen infrastructure Conclusions
THANK YOU ! For more information on the sensor test laboratories: NREL: William J. Buttner, Ph.D. +1 303-275-3903 http://www.nrel.gov/hydrogen/facilities_hsl.html JRC/IET: Lois Brett, Ph.D. +31 224-56-5065 http://iet.jrc.ec.europa.eu/ SINTERCOM Sensor Evaluation Report: http://iet.jrc.ec.europa.eu/content/scientific-publications