Session 4.1: Solid Storage Technology Dr. N. Eigen (GKSS) 25 th 29 th September 2006 Ingolstadt Session 1.2: Introductory Lectures K. Hall
4.1 Solid Storage Technology CV Dr. N. Eigen Address: GKSS Research Center Geesthacht Institute for Materials Research Max-Planck Str. 1 21502 Geesthacht Phone: ++49 4152 872647 1991-1997 Studies of Mechanical Engineering at University of Hannover, D since 1998 Researcher at Research Center Geestacht with scientific focus on Nanostructured Materials 2004 PhD at Technical University of Hamburg-Harburg, D since 2004 Scientific focus of Production methods of nanostructured hydrides and design of metal hydride tanks 4.1 Solid Storage Technology Dr. N. Eigen 2
4.1 Solid Storage Technology Lectures on Solid H 2 Storage Technology, Dr. N. Eigen Tank design and Up-scaling of Material Production for Solid Hydrogen Storage Abstract: The integration of hydrides into a mobile tank system necessitates a consideration of heat management, hydrogen distribution and a suitable production method for larger amounts storage material. The basic influences determining a tank design are explained and examples of prototypes are presented for room temperature hydrides and sodium alanate. 4.1 Solid Storage Technology Dr. N. Eigen 3
Tank design and Up-scaling of Material Production for Solid Hydrogen Storage Nico Eigen Dept. of NanoTechnology GKSS Research Center Geesthacht Institute for Materials Research 21502 Geesthacht, Germany www.gkss.de/hydrogen 4.1 Solid Storage Technology Dr. N. Eigen 4
Content Introduction Technical Features of Storage Materials Up-Scaling of Material Production Tank Design and Layout Integration into Car 4.1 Solid Storage Technology Dr. N. Eigen 5
Principle of Solid Storage Tank for Automotive Applications Fueling Starting/ Driving H 2 H 2 H 2 at elevated pressure Solid storage tank heat for desorption H 2 at low pressure heat released by reaction Cooling for constant temperature required Heating for constant temperature required Efficient heat management system is required 4.1 Solid Storage Technology Dr. N. Eigen 6
Typical Reversible Hydrogen Storage Material Tank has to store about 4 kg hydrogen (for about 400 km range) Mass of storage alloy [kg] 250 200 150 100 50 0 1.8 wt.% 4 wt.% 7 wt.% RT alloy NaAlH4 MgH2 High temperature Hydrides High temperature hydrides have better gravimetric capacity 4.1 Solid Storage Technology Dr. N. Eigen 7
Thermodynamic Conditions 1000 Temperature [ C] 500 400 300 200 170 120 80 45 0 1000 Temperature [ C] 500 400 300 200 170 120 80 45 0 Pressure [bar] 100 10 desorption RT alloy hydride metal absorption absorption desorption Pressure [bar] 100 10 Mg NaH RT alloy Na 3 AlH 6 NaAlH 4 1 Mg MgH 2 1 1,0 1,5 2,0 2,5 3,0 3,5 1,0 1,5 2,0 2,5 3,0 3,5 1000/T [1/K] 1000/T [1/K] Required working temperature: -40 85 C NaAlH 4 is a good compromise concerning thermodynamics 2/3 of H 2 at ~80 C and 1/3 of H2 at ~150 C 4.1 Solid Storage Technology Dr. N. Eigen 8
Heat Release during H 2 Absorption Heat absorbed in tank itself: Q = m c p ϑ Sodium alanate (NaAlH 4 ): c p = 1,5 kj / kg K Filling a 4 kg hydrogen tank in 3 min.: Heat [MJ] 150 125 100 75 50 25 Figures for 4 kg hydrogen tank Heat of reaction Heat absorbed by alloy Heat absorbed in tank shell Q = 450 kw 0 RT alloy NaAlH 4 MgH 2 Heat cannot be stored in tank itself cooling required Efficient heat exchanger is required 4.1 Solid Storage Technology Dr. N. Eigen 9
Summary: Storage Alloys RT hydrides (~2 wt.%) fast, optimum temperatures/pressures MgH 2 (7,6 wt.%) fast (catalyst), desorption temperature > 300 C NaAlH 4 (5,6 wt.%) compromise between above mentioned Absorption Mechanism of NaAlH 4 : NaH + Al + 1,5 H 2 1/3 Na 3 AlH 6 + 2/3 Al + H 2 NaAlH 4 Metal atom diffusion, complex reaction mechanism synthesis problematic tendency for slow hydrogen sorption 4.1 Solid Storage Technology Dr. N. Eigen 10
Mechanical Synthesis of Na-alanate hydride Composite formation 4 Activation metal Al NaH NaH / Al composite with catalyst after 1h of high-energy milling 4 µm H 2 -concentration [wt.%] 3 2 1 0 125 C 100 bar / vacuum First absorption, 12 h 1st Desorption 2nd Absorption 2nd Desorption 3rd Absorption 0,5 1,0 1,5 2,0 2,5 3,0 Time [h] After activation in a relatively slow first absorption, fast cycling possible with catalysed NaH/Al 4.1 Solid Storage Technology Dr. N. Eigen 11
Costs of Na-alanate Storage Material Raw materials: Na (~ 0,30 Euro / kg) and Al (~2,50 Euro / kg) are cheap Catalyst: Ti nano clusters no economic kg scale production possible Ti powder expensive TiCl 3 very expensive TICl 4 precursor of Ti and TiCl 3 cost-effective Synthesis method: conventional synthesis methods for NaAlH 4 are expensive todays marked price: ~1000 Euro / kg high-energy milling of components to produce nano composite ready for hydrogen absorption cost-effective 4.1 Solid Storage Technology Dr. N. Eigen 12
Optimized Hydrogenation by Improved Synthesis Dry milling Wet milling (pentane) H 2 -concentration [wt.%] 5 4 3 2 1 125 C / 100 bar 2nd Absorption 1 h 20 h 5 h 10 min. 0 0 3 6 9 12 15 Sorption time [min.] H 2 -concentration [wt.%] 5 5 h 4 3 2 1 1 h 10 min. 0 0 3 6 9 12 15 Sorption time [min.] Short milling times for optimum kinetics High capacity cannot be reached Optimum capacity achieved Fast kinetics 4.1 Solid Storage Technology Dr. N. Eigen 13
Sorption Kinetics of Na Alanate Goal: absorption in 3 min. H 2 -concentration [wt.%] 5 4 3 2 1 preparation from NaAlH 4 with Ti-nano preparation clusters, 100 C from NaH/Al with TiCl 4, 125 C preparation from NaAlH 4 with TiCl 3, 125 C 0 0 10 20 30 40 50 60 Time [min.] High sorption kinetics by simple synthesis with cost-effective initial materials 4.1 Solid Storage Technology Dr. N. Eigen 14
Up-scaling of Storage Material at GKSS Vibratory tube mill used for large scale powder production Large-scale milling and handling under inert gas atmosphere 20 cm Sodium alanate powder charge 4.1 Solid Storage Technology Dr. N. Eigen 15
Up-scaling of Production Process H 2 -concentration [wt.%] 5 4 3 2 1 0.5 kg, 2 h+0.5 h with graphite vibratory tube mill 10 g, 5h plantary ball mill 0.5 kg, 2 h vibratiory tube mill 0 0 10 20 30 40 50 60 Time [min.] Production of fast Na-storage material in kg scale possible 4.1 Solid Storage Technology Dr. N. Eigen 16
Tank Design: Material Selection for Tank Container Pressure vessel for 100 bars and 150 C required Steel Aluminum alloys Composite materials + + does not react with hydrides sufficient corrosion resistance? + behaviour during hydriding unknown in connection with alanates good corrosion resistance + low heat transfer? high corrosion resistance + low loss of strength up to high temperatures high loss of strength above 100 C + Low loss of strength up to 100 C however strong loss at higher temperatures low gravimetric strength + high gravimetric strength ++ excellent gravimetric strength 4.1 Solid Storage Technology Dr. N. Eigen 17
Heat Exchanger Concept heating/cooling heating/cooling heating/cooling heating/cooling pressure vessel pressure vessel Hydride ~100 bar Hydride ~100 bar Hydride ~100 bar Hydride ~100 bar + + Low volume Low weight Heat trasfer area + + + Low volume Low weight with composite vessel High heat transfer area Low volume Low weight High heat transfer area Double H 2 containment 4.1 Solid Storage Technology Dr. N. Eigen 18 + + + +
Example: 26 kg Alanate Tank Relatively high gravimetric storage density: ~2 wt.% Slow kinetics due to material, low heat removal area, low conductivity of material 4.1 Solid Storage Technology Dr. N. Eigen 19
Optimum Geometry of Hydride Container A W /2 p A i σa W >pa i A W /2 Problem: elevated pressure + low mass/volume required System of long tubes Kesselformel : Minimum of material for given pressure: Spherical shape However: Lowest surface to volume area Low packing density of balls (max. 67%) packing density up to 90% Variation of diameter variation of the heat transfer area Tube diameter has no influence on the weight of ideal tube system Hemispheres and manifold system: Longer tube at given diameter better 4.1 Solid Storage Technology Dr. N. Eigen 20
Cross Flow Tube Bundle Heat Exchanger d s Standardized calculation for tube bundle heat exchanger can be applied using emperical data bases Standardized calculation only possible for high tube distance s: s > 0,2 d high volume Efficient heat transfer but high volume and cooling fluid flow required 4.1 Solid Storage Technology Dr. N. Eigen 21
Tube Bundle Heat Exchanger Parallel Flow filling elements outer shell filling elements Hydride containers Parallel flow allows the highest packing density of tubes High cooling fluid velocitys possible by narrow spacings and filling elements 4.1 Solid Storage Technology Dr. N. Eigen 22
Heat Conduction in Strorage Material Problem: stationary heat conduction in cylinder with heat source/heat sink adsorption ϑ r ϑ = q''' & r 2 4 λ ϑ x λ in the range of 0,5 W/mK for hydride particle beds inner structure hydride container wall How can overheating of hydride be avoided? Reduction of tube radius Increasing heat conductivity in particle bed Inner structure, e. g. plates into particle bed 4.1 Solid Storage Technology Dr. N. Eigen 23
Volume Change in Hydride Bed - Solutions Bernauer et al.: United States Patent No. 4,583,638, (1986) Any deformation of pressure vessel avoided Expansion in axial direction Disks move in axial direction Central tube for faster hydrogen release and uptake Complicated construction 4.1 Solid Storage Technology Dr. N. Eigen 24
Example: Room Temperature Hydride Tank Mercedes-Benz 230 E 75 kw Range (in city traffic): 120 km Developed in 1980s Low temperature hydride Material grav. storage density Heat balance Tank mass Tank volume Stored hydrogen mass Tank grav. storage density Tank vol. storage density Refueling pressure Refueling time Ti-Zr-V-Fe-Cr-Mn-alloy 1.8 weight% - 28 kj/mol exothermic 320 kg 170 L 4 kg H2 1.3 weight% 2.4 kg H2 / 100 L 50 bar ca. 10-15 min 4.1 Solid Storage Technology Dr. N. Eigen 25
Advanced Heat Exchanger Investigated in StorHy Sintered filter Hydride Cooling fluid Hydrogen StorHy labscale tank with heat transfer system Principle Testing heat transfer in defined geometry 4.1 Solid Storage Technology Dr. N. Eigen 26
Advanced Heat Exchanger Investigated in StorHy cylinder hydrogen heat transfer medium Hydrogen distribution by concentric sintered filter Heat transfer medium in parallel flow in concentric slits around tube Spacing between tubes allows higher heat transfer area 4.1 Solid Storage Technology Dr. N. Eigen 27
Concept for High Temperature Hydrides Fueling Starting Driving H 2 H 2 H 2 Filling in 3 minutes Cold start: like Diesel engine Short response time H 2 at elevated pressure heat for warm-up heat released by hydrogenation heat for warm-up H 2 H 2 heat for desorption 4.1 Solid Storage Technology Dr. N. Eigen 28
Example of supplement heating Catalytic combustor for heating Surce: Texaco Ovonic 4.1 Solid Storage Technology Dr. N. Eigen 29
Combination Fuel Cell Hydride Tank 80 C PEM fuel cell Internal heat exchanger T(ambient) 75 kw Q(des) External heat exchanger T(ambient) Q(hyd) 80 C- ϑ Hydride Tank 90-150 C electrical heat or combustion heat Q(hyd) = >250 kw for RT hydride Q(des)<<Q(hyd) External heat exchanger necessary Higher fuel cell temperatures necessary to desorb hydrogen 4.1 Solid Storage Technology Dr. N. Eigen 30
Example: Room Temperature Hydride Tank in Toyota Prius Surce: Texaco Ovonic Quick adoption of cooling / heating supplies Texaco Ovonic tank in Toyota Prius demonstration car 3.0 kg H 2 1500 psi filling pressure 4.1 Solid Storage Technology Dr. N. Eigen 31
Future Prototype and Demonstration cars with reversible HT hydride tank? BMW 7 series prototype with liquid hydrogen tank Toyota Prius self recharging hybride electrical/gasoline car Daimler Crysler FCell Demonstration Car 700 bar hydrogen tank 4.1 Solid Storage Technology Dr. N. Eigen 32
Session 4.1: Solid Storage Technology Dr. N. Eigen (GKSS) 25 th 29 th September 2006 Ingolstadt Session 1.2: Introductory Lectures K. Hall