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* 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

~ Hydrogen Safety Sensors ~ Performance under anaerobic conditions

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1.JRC IET/NREL Collaboration

2.Research rational

3.Sensor performance testing facilities

4.O2 dependence test method

5.Results/observations

6.Conclusions

Outline

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Collaborators

EC JRC-IET DOE NREL

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Collaborators

EC JRC-IET DOE NREL

Hydrogen Safety Sensor Hydrogen Safety Sensor Performance EvaluationPerformance Evaluation

End users

Manufacturersdevelopers

SDOsThe ultimate purpose of the sensor test laboratories is to ensure

that sensor technology is available to meet end user needs

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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 atmospheresInert 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)

Rational

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O2 Dependence?

Most H2 sensors detection principle require O2:

Catalytic/pellistor Chemical oxidation Electrochemical Electrochemical oxidationMetal oxide Oxygen surface interactionsWork function type Oxygen surface interactionsOptical Oxygen assisted recovery

Some don’t:

Thermal conductivityAcousticThin/ultra-thin film metal resistors

Evaluate influence of oxygen

concentration on sensor output

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Testing facilities….

EC JRC-IET

DOE NREL

Test chambers conditions:• Temperature • Pressure• Relative Humidity• Gas composition• Gas flow

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Test protocol

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Results – CGS (1)

H2 + O2 → H2O + Δ

T = To + ΔTΔT = F ([H2])

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

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Results – CGS (2)

Anaerobic operation cause irreversible shift in baseline

Oxygen is required for stable repeatable operation

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Results – TC (1)

Heated thermoresistor Signal is ΔR via ΔT (heat loss) H2 high thermal conductivity No O2 involvement

Response affected by matrix change Net response to H2 unaffected by O2

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Results – TC (2)

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Results – TC (3)

Net response to H2 unaffected by [O2] Sensor slightly over estimates [H2] Results comparable Matrix dependence – correctable!

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Results – PTF (1)

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

Commercial resistive sensor showed no oxygen dependence Reversible, quantitative consistent response for oxygen levels Slight impact for anaerobic operation

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Results – PTF (2)

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Results – PTF (3)

H2 response only negligibly affected by [O2]

Sensor under estimates [H2] Results comparable

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Conclusions

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

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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