in the search for aetal hydrides for hydrogen storage. A review of 

 abstracts of these 108 reports, published in Chemical Abstracts and 

 Nuclear Science Abstracts, was considered adequate as a first step in 

 screening out those not pertinent to the application under considera- 

 tion. For this reason, listing of all these references in this report 

 was considered unnecessary. 



This screening procedure showed that a majority of these publi- 

 cations dealt with hydrides useful in nuclear reactor applications as 

 shields, controls, noderators, and reflectors. Some of the properties 

 of aetal hydrides, such as their stability over wide ranges of tempera- 

 ture and pressure, that makes them useful in nuclear reactor applica- 

 tions, also prevent their usefulness in hydrogen storage applications. 

 These aspects of metal hydrides are dealt with more fully later. 



Most of the documents and reports selected from the DDC Data Bank 

 dealt with the application of hydrides in propellants and are not appli- 

 cable to this report. 



General inforaation on metal hydrides given in this report for 

 completeness was obtained from several sources [9, 10, 14]. A sumsary 

 of netal hydrides which cannot be used for hydrogen storage applications 

 and a discussion of the properties which prevent their usefulness are 

 also included in this survey to indicate the limited number of hydrides 

 which can be used for hydrogen storage. 



Desirable Properties of Metals for Hydrogen Storage Applications 



To determine which metals can be considered for hydrogen storage it 

 is first necessary to outline the required properties of metals and 

 their hydrides. These can be established fairly easily by considering a 

 typical application: hydrogen generated by the electrolysis of water, 

 using electrical energy either generated by nuclear reactors during off- 

 peak hours [5, 15, 16] or generated by conversion devices powered by 

 solar or wind energy or by the energy of ocean- currents [17, 18]. The 

 hydrogen thus generated is to be stored for use sometime in the future 

 and/or at locations or in equipment away from the source. If the hydro- 

 gen is to be used to generate electricity in central power-generating 

 plants or in plants located at or near the consumer's location, the 

 hydrogen can be transported either as a gas, using conventional pipe- 

 lines, or as a liquid, using specially designed pipelines for cryogenic 

 liquids, and then stored in appropriate storage tanks. 



However, if the hydrogen is to be used in transportation applica- 

 tions (e.g., land iioving vehicles or in applications requiring porta- 

 bility and relatively long storage times) neither of the above two 

 transportation and storage methods is completely satisfactory. A list 

 of desirable properties of metal-hydrogen systems is summarized below. 



1 . Most of the hydrogen present in the metal hydride should be 

 recoverable when the pressure is reduced to atmospheric. The tempera- 

 ture required to liberate most oi all the hydrogen present in the 

 hydride should be at or above ambient but well below the exhaust tempera- 

 ture of the hydrogen combustion device used in the application. 



