^* Bn - -"-n 



the heat transfer properties of the materials. A magnesium- 

 nickel hydride systeia for hydrogen storage costing between 

 $500 and $700, v, sighing about 500 pounds, and taking up a 

 volume equivalent to the voluee occupied by a liquid hydro- 

 gen Dewar holding the same amount of hydrogen appears fea- 

 sible, however. 



Figure 1 provides a visual comparison of two hydriue 

 alternatives with gasoline and liquid and gaseous hydrogen. 

 Figure 1a compares these systeas in terms of costs. For the 

 hydrides the costs include the costs of the containments and 

 the metal hydrides. For the other systeas the costs include 

 only containers. Figure 1b compares the systems in terms of 

 weight, and Figure 1c compares them in terms of volume. A 

 60Z void fraction is assumed for the hydrides, but as men- 

 tioned earlier the void fraction is presently unknown. 

 Figures 5 through 7 are pressure-composition graphs taken 

 from the literature. 



USES OF METAL- HYDRIDE STORAGE SYSTEMS 



It has been determined that hydrogen is an excellent fuel, that it 

 can be stored in relatively small volumes at low pressures by using 

 metal hydrides or intermetallic hydrides, and that many hydrides exist 

 with several ranges of applicability. Now some applications can be 

 considered. 



Remote-Base Energy Storage 



In situations where volume is at a premium and where hydrogen is 

 generated by wind, sea, or solar energy, metal hydrides can provide an 

 excellent storage unit. In cases such as these, one would not want to 

 waste hard-won energy in compressing hydrogen to high pressures, in 

 liquifying and maintaining it at low temperatures, or in chemically 

 synthesizing methane or methanol. A system where the hydrogen could be 

 utilized at a relatively low pressure and temperature is highly desir- 

 able. Metal hydrides and large volume tank storage are presently the 

 only systems that can provide this type of storage. 



Combat Zone Energy Storage 



In combat zones where construction time is limited or where invisi- 

 bility is important, a low volume, easily transportable system would be 

 invaluable. Metal hydrides can store hydrogen in volumes similar to 

 the volume of liquified hydrogen; and the weight, though large, would 

 not be too great to handle. 



27 



