D. Alternative Chemical Storage
Description: Reversible chemical storage, regenerated off-board.
Goals (2010 EERE): System Gravimetric Density (>2.0 kWh/kg = 6 wt%), System Volumetric Density (>1.5 kWh/lit =
0.045 kg-H2/lit), Storage Cost (< $4/kwH = $133/kg-H2), Fuel-Station Cost ($1.50/kg)
1. Liquid Carrier Materials
Description: Identify and evaluate liquid carrier materials with respect to life-cycle cost, energy efficiency, hydrogen storage density, emissions, and environmental impact.
a) Hydrolysis hydrides
Description: Hydrolysis hydrides release hydrogen when added to water. This is not a directly reversible process. Regeneration of the hydride from the hydroxide byproduct can be accomplished through a multi-step process using methane. The regeneration process is highly endothermic, relatively inefficient, and expensive. Handling and disposal of the potentially toxic byproduct in large quantities presents a further challenge.
i. Borohydrides (e.g., NaBH4)
Description: Sodium borohydride releases hydrogen in a conversion to borax (NaBO2).
ii. Light-metal hydrides (e.g., LiH, NaH, CaH2, MgH2)
Description: These hydrides form hydroxides upon release of hydrogen.
b) Reversible liquid carriers
Description: These are hydrocarbons that can be regenerated. Characterize the energy efficiency of these processes.
i. Decalin
Description: Decalin releases hydrogen in a conversion to naphthalene at 210 deg.C.
ii. Hydrocarbons
Goal: Reduce catalyst requirements, Reduce temperature/pressure requirements
a. Benzene-Cyclohexane
b. Ethylbenzene
c) Natural gas-based carriers
Description: These liquids release hydrogen in an irreversible process.
i. Methanol
ii. Fischer-Tropsch liquids
d) Ammonia
Description: Ammonia (NH3) can be cracked into hydrogen and nitrogen (which is released to the atmosphere) in an irreversible process at high temperatures (up to 900 deg.C at atmospheric pressure), with no co-reactants. The synthesis process requires a catalyst.
e) Novel materials
2. Liquid Carrier Processes
Description: Assess the cost, efficiency, environmental impact, safety, and feasibility of process alternatives
for various liquid carriers.
a) Regeneration methods
Goals: Cost, Feasibility
i. Electrolysis
ii. Radiolysis
iii. Plasma/high energy
iv. Carbothermic processes
v. Other
b) Infrastructure requirements
i. Chemical synthesis and pretreatment
ii. Chemical dispensing / fueling
iii. Recovery of spent product (and separations)
iv. Regeneration of spent material
v. System components
c) Other process components
Goals: Cost, Efficiency, Environmental impact.
i. Oil dispersants for slurry
ii. Catalysts and catalyzed systems
iii. System materials
a. Investigate pretreatment for caustic materials.
b. Evaluate durability of materials.
iv. Synthesis of carriers
Goal: Effective, solvent-free synthesis approaches
3. Novel Chemical Storage Materials
a) Organic crystals
Description: These crystalline materials, composed of metal-organic frameworks with a cubic, 3-D, extended porous structure, can adsorb up to 2 wt-% H2 at room temperature and about 10 atm of pressure [Science, 300, 1127 (2003)]. At lower temperatures, H2 uptake as high as 4.5 wt-% has been reported.
b) Amino acids
Description: Hydrogen might be stored efficiently using the effects of protein conformation.
c) Clathrates and Porous materials
Description: In methane clathrates, a methane molecule is trapped in a cage-like ice structure at high pressure and low temperature. A similar approach might be feasible for hydrogen storage.
4. Characterization of Physical Mechanisms
a) Hydrogen bonding
Description: Understand the fundamental atomic processes in absorption and desorption of hydrogen.
b) Lifetime degradation issues
c) Kinetics
Description: Determine the effect of the following factors on kinetics and cycling characteristics.
i. Processing
ii. Dopants
iii. Catalysts
iv. Decomposition products and chemical pathways
d) Surfaces
Description: Investigate the effect of surface barriers and surface catalysts on hydrogen storage.
e) Mass transport issues
Description: Investigate the role of hydrogen-promoted mass transport on phase transformations.
f) Thermophysical properties
Description: Combine experimental data with state-of-the-art characterization tools and establishment of
standards for comparison.
i. Thermodynamic
ii. Physical
iii. Chemical
|
