magnesium hydride ppt
TRANSCRIPT
1
Conception and test of a 10 kg
magnesium hydride tank
B. Delhomme, P. de Rango, P. Marty, S. Miraglia
Institut Néel – CRETA – LEGI, Grenoble, FRANCE
2Hydrogen storage
Hydrogen as energy vector :- Fitting of electricity production - Electricity production in off-grid sites- Uninterruptible Power Supply (UPS)
High pressure storage :Pressure = 200 - 350 BarEnergy needed = 25 % H
2 LHV
A safe and efficient mean of storage is still needed
Liquid storage :Temperature = 20 KEnergy needed = 30 % H
2 LHV
Solid storage : magnesium hydride :Moderate pressure : 1 - 15 barTemperature : 300 - 380 °CEnergy needed = 30 % H
2 LHV
Possibility to use wasted heat for the hydrogen desorption
3Magnesium hydride
Material :- MgH
2 ball-milled with TiVCr
- powders are then compacted with Expanded Natural Graphite (ENG)
Properties :- Storage capacity : 6.5 wt. %- Fast reaction kinetics- Improved thermal conductivity- Temperature range : 300 - 400 °C- Pressure range : 0.1 - 1 MPa
Exothermic
Endothermic
75 kJ.mol-1
Temperature (°C)
Pressu
re (MP
a)
Equilibrium pressure
410 kg MgH2 tank
73 MgH2 discs
High temperature heat transfer fluid : MARLOTHERM
Metallic mesh used to improve H2 circulation
5Test bench
Measurement :Temperature : 16 K type thermocouplesHydrogen mass flowPressure
6Tank loading
Loading time = 40 min
Typical loading conditions :- H
2 pressure = 11 bar
- Oil temperature = 240 °C
7Tank unloadingUnloading conditions :
- Oil temperature = 340 °C
- H2 flow = 35 Nl.min-1
Unloading time = 150 min
3 kWe (H2 LHV,
FC=50 %)
8Loading time improvement
Large improvement of the thermal conductivity from the first cycle
Loading time heat exchanges
9Loading time improvement
Deformation of the composites : Improvement of the thermal contact between the composites and the tank wall
10Loading time improvement
Evolution of MgH2 crystallite size :
- before ball-milling : broad peaks with low intensity crystallites with nanometer scale - this partially amorphous state disappears after the first cycle
11Loading time improvement
After ball-milling After 1 cycle
Hydride recrystallization observed by TEM :
100 nm 100 nm
12Evolution of the storage capacity
- Diminution of the storage capacity over the 14 first cycles, then a slight increase is observed.- the hydrogen capacity is linked with the imposed temperature
13Life time stability Small scale tank cycled 600 times :
mMgH2
164 g
Degradation of (un)loading times : no evolution after 390 cycles
Evolution of storage capacity : - diminution during the first cycles- slight increase until 80 cycles- slight decrease from 80 to 600 cycles
0.15 wt.% loss after 600 cycles
14Conclusions
A 10 kg MgH2 tank (600 g H
2) was realised and tested for different
experimental conditions : - High energetic density of 360 Wh.kg-1(composites + tank + measurement devices). - Loading performed in 35 min. - A mean discharging hydrogen flow of 35 Nl.min-1 can be maintained during 2h30.- During the first 10 cycles, an improvement of (un)loading time is observed due to improvement of heat exchanges.- Large microstructure modifications observed from the first hydrogenation cycles. However, reaction kinetic remain fast : (un)loading times limited by heat exchanges and hydrogen circulation.- A small scale tank was cycled up to 600 times. Only a slight diminution of hydrogen capacity is observed after 600 cycles.
15
Acknowledgement
NESSHYNovel Efficient Solid Storage for H2
FP6 Integrated Project SES6-518271 (2006-2011)
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Thank you four your attention