4th International Conference on Hydrogen Safety (ICHS) September 12-14, Low Energy Hydrogen Sensor Linke, S., Dallmer, M., Werner R. and Moritz, W. Humboldt University of Berlin, Brook-Taylor-Str.2, Berlin, Germany; Sensor structure Hydrogen response Thermal reactivation Fire detection LFL Explosion alarm
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Sensor structure Si 3 N 4 SiO 2 Si Palladium Disadvantages of available hydrogen sensors: energy consumption too high for battery powered systems due to elevated working temperature price to high for mass products poor selectivity
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Electrochemical mechanism ((different to Lundström type)) Palladium SiLaF 3 CV-measurement
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Response of the Pd/LaF 3 /Si 3 N 4 /SiO 2 /Si field effect structure (solid line and left scale) to different concentrations of hydrogen (doted line and right scale) in synthetic air; room temperature; measurement 1 hour after preparation of the Pd layer
4th International Conference on Hydrogen Safety (ICHS) September 12-14, days after preparation
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Heating and temperature measurement 1 - Pt; 2 - LaF 3 ; 3 - SiO 2 /Si 3 N 4 ; 4 - n-Si; 5 - ohmic contact No method for fast surface temperature measurement 4-point measurement resistance of Pt
4th International Conference on Hydrogen Safety (ICHS) September 12-14,
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Calculations of temperature distribution 100ns 1000W 100 WS LaF nm SiO 2 /Si 3 N 4 80nm 1 s 10 W 10Ws 10 s 100W 1mWs
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Constant surface temperature Parameters of the electrical heating pulse used in Fig. above Max. current 8,4A Cur. dens. 2,8*10 7 Acm -2 Max. voltage 293 V Max. power2365 W Total energy1,82*10 -3 J ((average 2x10 -8 W)) T Si =0,025 K 500 activations simulating 2 years
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Micro hotplate structure
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Temperature distribution for different impulse duration Average power consumption 2x10 -6 W Fast decay to room temperature
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Hydrogen signal in air after thermal reactivation room temperature Low concentration range 136 mV/decade Limit of detection 500 ppb
4th International Conference on Hydrogen Safety (ICHS) September 12-14, A Fire Experiment in a Wooden House T- Amamoto et al., Sensors and Actuators, B1 (1990)
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Early state of Fire (smoldering) TF 2 wood on electrical heater
4th International Conference on Hydrogen Safety (ICHS) September 12-14, High concentration range LFL 4% ( ppm) alarm level 1,6% Response time t 90 ppm)= 4 s 150 mV/dec
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Stress test simulating 330 days of activations and mesurements Day 2, 50, 150 and 300 all 330 measurements
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Mechanism Oxygen sensor O 2 + A* O 2 (A*)(1) O 2 (A*)+ H 2 O+ e - HO 2 (A*) + OH - (2) OH - +(F*) OH - (F*)(3) Additional hydrogen action O 2 (A*) +H 2 H 2 O (A*) (4)
4th International Conference on Hydrogen Safety (ICHS) September 12-14, Conclusions - room temperature hydrogen sensor in ppm range and for high concentration - thermal reactivation is possible - Low energy consumption for heating impuls - early fire detection - alarm at lower explosion level - Battery power application for long time - Combination with energy harvesting technology possible