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2. The hydride should have good kinetics of operation, it should 

 be able to absorb and desorb hydrogen at a rate consistent with its use. 



3. The seta! should be able to store hydrogen for long periods at 

 ambient temperatures that may range between -20 F and +120 F. 



4. The density of hydrogen in th metal-hydrogen system should be 

 quite high to keep the weight and volume of the storage tank down to a 

 practical level. 



5. The hydrogen storage system should be capable of thousands of 

 cycles of absorption and desorption of hydrogen. 



6. The operating temperatures and pressures during the absorption 

 and desorption cycles should be well within the capabilities of today's 

 most abundant storage container materials. 



7. i.he hydrogen absorption process should be exothermic. The 

 heat of dissociation should be low so that the heat exchanger is of a 

 manageable size. The temperature of dissociation should be below the 

 waste heat generated during the combustion of hydrogen in the energy 

 conversion device so that the latter can provide the necessary thermal 

 energy for the heat of dissociation. 



8. The metal and its hydride should be nontoxic and should resist 

 spontaneous combustion when brought in contact with air or oxygen. 



9. The metal should be inexpensive to produce and widely avail- 

 able in large quantities. 



10. The overall environmental effect of using a eetal hydride to 

 store hydrogen should be neutral or positive compared to the environ- 

 mental effects of using other fuels. The effects of mining and proces- 

 sing the metal hydride and manufacturing the container must not outweigh 

 the neutral effect of using hydrogen as a fuel. 



All the above properties of a suitable metal-hydrogen system are 

 fairly obvious with the possible exception of number 7. Metals which 

 react with hydrogen endothermally are not suitable for hydrogen stor- 

 age applications because heating the metal is necessary for the absorp- 

 tion of hydrogen, which is subsequently released upon cooling. In such 

 systems, the solubility of hydrogen in the metal increases with increas- 

 ing temperature. Therefore, only those metal-hydrogen systems which 

 absorb hydrogen exothermally may ba useful for hydrogen storage 

 applications. Furthermore, unless the metal-hydrogen system is to be 

 considered only for a limited number of specialized applications, it 

 will be necessary that the metal-hydride system be relatively inexpen- 

 sive and available in large quantities without causing unacceptable 

 strains in the nation's economy and its resources. 



The above listed properties s'.iould be considered for any situation. 

 However, the specific application may require that some properties be 

 given more emphasis than others. For instance, a remote base which is 



