Advances in Sensor Technology May Expand Hydrogen Applications
by David
Haberman, President, DCH Technology, Inc.
Hydrogen sensor technology has advanced rapidly
within the last few years with major contributions from the U.S. Department
of Energy (DOE) national laboratories. The availability of higher fidelity,
robust, highly selective sensors will enable many new and expanded applications
of hydrogen-based processes and systems. The operational principle of using
a first order sensing reaction and providing long operational lives is common
to three types of new generation hydrogen sensors.
The Robust Hydrogen Sensor, developed by Sandia
National Laboratories, is an application-specific integrated circuit (ASIC)
which offers wide-range, controllable sensing in a tactical package. A palladium-nickel
(PdNi) catalyst is deposited directly on a standard process multilayer Complementary
Metal Oxide Semiconductor (CMOS) device.
The CMOS ASIC hosts logic cells which perform
the computations of low-range hydrogen measurement, high-range hydrogen
measurement, and measurement of the catalytic substrate junction temperature.
The catalyst may be purged on demand via dual power resistors also located
on the CMOS, allowing quick resets. This sensor has flown successfully on
NASA’s DC-X/A vehicles and offers a new flexibility due to robustness
and miniaturization. The use of nanoporous sol-gel coatings (silicon nitrate,
SiN) on the ASIC significantly enhances the chemical selectivity and durability
of the catalyst in complex or poisonous chemical environments. Equipment
is available for purchase.
The Fiber Optic Hydrogen Sensor System is being
developed under a Cooperative Research and Development Agreement (CRADA)
with the National Renewable Energy Laboratory. This sensor technology offers
accurate, fast, intrinsically safe measurement of hydrogen using coated
fiber optic elements introduced directly into the environment of interest.
A palladium coating applied to an optically designed cap on a polymer optical
fiber is interrogated using visible light. The reflected beam is detected
and characterized.
This system’s nonintrusive approach is
easily retrofitted into existing installations and supports large-scale
networking of arrays. The commercial hydrogen vehicle safety requirements
of the future have been used as basic design-to-cost criteria in this development
to ensure life cycle economic competitiveness, reliability, and ease of
integration. Evaluation equipment will be available for applications verifications
in 1997.
A Thick Film Hydrogen Sensor is being developed
under a CRADA with Oak Ridge National Laboratory. This sensor is optimized
around hydrogen’s lower explosive limit range to provide an extremely
low cost, highly reliable safety device. The sensor is a thick film of palladium
adhered to an inert ceramic base which may be easily embedded or affixed
to tank or pipe materials. The sensor control electronics compute a voltage
imbalance proportional to the hydrogen exposure. These electronics are optimized
in a collocated or umbilicaled module with standard signal outputs. The
sensor may be contour-fitted to transport, storage, or distribution equipment.
Evaluation units for beta testing will be available in 1997.
[The CRADAs are supported by the DOE Hydrogen Program and DCH
Technology, Inc., under a cost share arrangement. The licenses to commercialize
the sensors are granted by DOE to DCH. For additional information, contact:
DCH Technology, Inc., 14241 Ventura Boulevard, Suite 208, Sherman Oaks,
CA 91423, U.S.A.; phone: +1.818.385.0400; eMail: dchinc@aol.com.]
©1997. All Rights Reserved. A Publication of
the National Hydrogen Association.
This material may not be reproduced in any form without permission.
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