Hydrogen storage options

Burke, A.F. and Gardiner, M. Hydrogen Storage Options Technologies and Comparisons for Light-duty Vehicle Applications, Research Report UCD-ITS-RR-05-01, Institute of Transportation Studies, University of California, Davis, 2005. 

Sarkar, A. and Banerjee, R. Net energy analysis of hydrogen storage options, International Journal of Hydrogen Energy, 30,867-877, 2004. 

Lasher, S., Comparison of hydrogen storage options, NHA Annual Hydrogen Conference 2005, Washington, March 29-April 1, 2005. 

Figure 16.6. Carbon emission reduction for 1 kWh stored and re-electrified wind electricity for CAES and hydrogen storage options (Wietschel et al., 2006).

TABI.F. 2. SOME HYDROGEN STORAGE OPTIONS FOR VEHICLES... 

Borohydrides such as NaBH4 in an aqueous solution of caustic soda have the highest gravimetric and volumetric storage densities compared with all other hydrogen storage options, including liquid hydrocarbons (see Section 2.1). The reaction with water is exothermic ... 

As a hydrogen storage option, the MOFs are attractive because in addition to the high surface area, and physisorptions of the type observed in the carlxMi stmctures, the framework can incorporate coordinatively unsaturated metal centers, and these metal centers can form sigma bonds with H2 molecules. The molecule does not dissociate into a hydride at the metal, but remains a molecular ligand. Indeed, MOF-5 takes in 7.1 wt.% H2 at 77 K and 40 bar. 

Other options such as carbon nanotubes and conformable materials are being researched for hydrogen storage [43,44]. These are funded through the DOE hydrogen storage program however, the commercial applicability of these options are at least 10 years away. 

The fossil hydrogen production option dominates during the first two decades while the infrastructure is being developed, and also in later periods if only economic criteria are applied initially on the basis of natural gas, later with increasing gas prices more and more on the basis of coal (where available). Carbon capture and storage will be critical for these pathways, if hydrogen is to contribute to an overall C02 reduction in the transport sector. The production mix between gas and coal is highly sensitive to the ratio of feedstock prices a switch occurs at a gas coal price ratio of about 2.5. 

The carbon emission reduction of the two considered storage options is calculated with reference to a conventional gas turbine or gas and steam turbine. The result is shown in Fig. 16.6. The emission reduction refers to 1 kWh surplus wind electricity. The black bars reflect the reference emissions of the conventional gas turbine (GT) and gas-steam turbines (GST). The other bars show the figures for the CAES and the hydrogen paths. The emissions that occur during the storage paths are marked in grey the emission reduction is visualised in grey and white stripes. 

For the economic comparison of the two storage options, the specific re-electrifi-cation costs of the stored wind energy are calculated. These costs are made up of the investment, operation and maintenance costs, input electricity costs (wind electricity) and the fuel costs (natural gas). As hydrogen technologies are not in a commercial state, the calculation is also performed with target costs for electrolysers. Carbon emissions are also monetarily included, assuming a certificate price of 20/t. Table 16.2 summarises the major economic assumptions. 

Automotive paths It has been shown that hydrogen as a storage option for surplus wind electricity has no advantages neither with respect to carbon emission reduction... 

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