Hydrogen Storage Materials Basic Properties and First Safety Studies - - PowerPoint PPT Presentation

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Hydrogen Storage Materials Basic Properties and First Safety Studies - - PowerPoint PPT Presentation

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Hydrogen Storage Materials Basic Properties and First Safety Studies Maximilian Fichtner Institute for Nanotechnology Department of Nanostructured Materials Karlsruhe Research Center 1 | M. Fichtner | ESHSS | 30. July 2007 Content

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1 | M. Fichtner | ESHSS | 30. July 2007

Hydrogen Storage Materials

Basic Properties and First Safety Studies Maximilian Fichtner Institute for Nanotechnology Department of Nanostructured Materials Karlsruhe Research Center

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2 | M. Fichtner | ESHSS | 30. July 2007

Content

  • Introduction / Problem
  • Principles of hydrogen storage

Physisorption and chemisorption materials

  • Safety studies with nanoscale hydride
  • Summary
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Permanent Issue: Energy storage in vehicles

Speed record: Jenatzy´s world record vehicle „La Jamais Contente“ (1899) reached 106 km/h

The first cars were electric vehicles (1885) !

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Fossil fuels on a historical timescale

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Why Hydrogen?

Liquid fuels can store more energy per volume and mass compared to H2 storage-systems (incl. Tank, Valves etc.). Energy Storage in H2 is by a factor 8 better than the best batteries.

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$0 $5 $10 $15 $20 $/kWh Chemical Hydride Complex Hydride Liquid H2 350 bar 700 bar

Current Cost Estimates

(based on 500,000 units) 2010 target 2015 target

* State of the art in hydrogen storage technologies 2007

source: G. Thomas, US-DoE, 2007 (priv. comm.)

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Physical limits for H storage

Mean distance between H2 molecules and H atoms volumetric storage density

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Binding principles for hydrogen

Physisorption Weak binding of H2 –molecules at the surface (long range Van der Waals interactions) Chemisorption Splitting of H2 molecule Chemical bonding of H atoms in host lattice

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Energy Diagram for Physisorption/Chemisorption EPot Physisorption

  • f H2

H2

z Ephys solid EDiss Eact Chemisorption

  • f 2 H

2 H Echem Ea

Desorb

Ea

chemisorb

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Physisorption Materials: Carbon-nanotubes?

First reports about high H-contents were most probably experimental errors !

  • M. Hirscher, 2005
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Examples Physisorption Materials: Metal-organic frameworks (MOFs)!

Yaghi et al., Angew. Chem. Int . Ed. (2005)

ZnO clusters

  • rganic linkers

(carboxylates) Self assembled structures

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MOFs : H storage capacity

7.5 wt% H @ 77 K, 40 bar

Yaghi et al., JACS, 2006

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  • M. Fichtner, Adv. Eng. Mater. 6 (2005) 432

Development of low / medium temperature solid storage materials for hydrogen

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Today´s systems: Nanocomposites on hydride basis

H-Carrier Complex light metal hydrides: Alanates M(AlH4) Boranates M(BH4) Amides M(NH2) Dopants TM Basis Nanoscale Nanoscale mixture

  • f:

The nanocomposite is the actual storage material. Compared to pure H-carrier: considerably improved H exchange properties.

&

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~ 4.5 wt.% H ~ 4.5 wt.% H reversible reversible @ 80 @ 80 – – 120 °C 120 °C

Sodium alanate, NaAlH4 , as hydrogen carrier

Bogdanovicć 1997 (MPI-KF): “Ti-doped alkali metal aluminium hydrides as potential

novel reversible hydrogen storage materials“ (JALCOM 97)

3 NaAlH 3 NaAlH4

4

Na Na3

3AlH

AlH6

6 + 2 Al + 3 H

+ 2 Al + 3 H2

2

3 NaH + Al + 3/2 H 3 NaH + Al + 3/2 H2

2

C.M. Jensen et al. , J. Appl. Phys. A 72 (2001) 213 – 219

Temp p

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Safety Issues …

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Physisorption Materials / Safety issues

Low temperature (77 K) ! No immediate release of stored amount H2 Sorbent combustible ? Combustion energy of: Hydrogen + Sorbent (carbon, MOF)

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Chemisorption Materials (Hydrides) / Safety issues

No immediate release of stored amount H2 Flame rate Combustion energy of: hydrogen + metal Self ignition in contact with air / water ? General recommendation: Avoid dust explosions with finely dispersed solid storage materials!

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Methods to extinguish a metal hydride fire Dilute burning powder with inert material (*dry* sand, NaCl) Use a metal fire extinguisher (NaCl + melting polymer

  • crust)

Interrupt air contact Cool it down with liquid N2

  • Laboratory !

Never use ! Water CO2

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Hydrogen Safety Scoping Tests With Hydride Based Nanocomposite

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Largest (public) research activity on hydrogen in Germany 50 Researchers in 6 institutes Working on:

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Hydrogen Safety Center

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Question: What can we expect if a device filled with a nanoscale complex hydride

  • is at operating conditions (p,T), and then
  • the shell breaks and the material is ejected into the environment ?
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Principle setup

SS-Tube filled with Ti-doped NaAlH4 Burst Disk Operation: T

  • 130 °C

P rises Disk bursts at p = 10 bar Material shot into various environments

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4 tests were performed with ca. 100 ml Ti-doped SAH at typical operation temperatures (130°C) and pressures (10 bar) of the material: 1. Reproduction of earlier experiment (ejection in dry air) 2. Spark ignition of hydrogen-dust cloud 3. Ejection into water shower 4. Comparative test with equimolar amount of pure hydrogen

Small scale device failure test

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Basic Equipment for Experiments: ► High speed camera, Speed Cam Visario 1500 ► Infrared camera, Thermovision A40 ► Digital Video camera, DCR-TRV30E ► Digital camera, Camedia C-1 ► Control unit, LABJACK U12 ► Transient recorder, Krenz PSO 9080 ► Fast sound level meter, RO 1350 ► Fast pressure sensors ► Fast T-sensors

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Reactor Setup

Electrodes for spark ignition

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Experiment 1: Shot in dry air

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Result experiment 1: Reproduction of „Dry Experiment“ from 2005

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Experiment 2: Spark Ignition / IR camera

0.2 sec 0.6 sec Burning hydrogen ignites dust cloud. Relatively slow combustion

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Setup experiment 3: Water shower

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HighSpeed images of rain shower experiment

Ignition by water droplets

30 ms 60 ms 240 ms 560 ms

Flame

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Experiment 4: Equimolar amount of pure H2 + spark ignition Small flame but very fast combustion (approx. 70 ms)

  • turbulent deflagration
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Soundlevels, first millisecond

reproduction 2005 Spark ignition Rain Shower Pure hydrogen

  • pening of burst disc
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Summary

First safety tests with nanocomposite:

  • Dry air experiment was reproduced.
  • Hydrogen/dust cloud with sparks
  • Ignition. High T in the cloud
  • Water shower
  • Self-ignition @ several places. Lower T in the cloud.
  • Experiment 2 with equimolar amount of pure hydrogen (and no hydride) was

much more aggressive

  • explosion !
  • 2., and 3.: flame-thrower like events, no explosion
  • ∆

∆ ∆ ∆p < 5 mbar @ 1 m distance

  • Heat of reaction is damped by the presence of water
  • Combustion of powder/H2 cloud > propagation of flame 10x slower than with

pure H2

  • More energy involved, but much slower propagation of the flame
  • reduced

violence. Solid storage materials have the physical potential to reach the goals set for hydrogen storage

  • t.b.d.
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Financial support by: Helmholtz Initative „FuncHy“ EU-IP „NESSHy“ EU-IP „StorHy“ EU-RTN „COSY“ Forschungsallianz Brennstoffzelle BW Acknowledgements

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Krzysztof Chłopek Christoph Frommen Nobuko Hanada Johannes Kostka Aline Léon Wiebke Lohstroh Ravimohan Prasad Stephan Wetterauer Oleg Zabara Maximilian Fichtner Nanostructured Materials Olaf Fuhr Cluster Chemistry Olaf Hübner Theoretical Chemistry

People at the INT…

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Thank Thank Thank Thank you you you you for for for for your your your your

PATIENCE