CONCLUSIONS 



The overall conclusions of this study are that there are no single 

 element hydrides with satisfactory characteristics for the applications 

 considered in this report. Of the ssany intensetallic hydrides that have 

 so far been studied, the magnesium-nickel hydride appears to be the 

 cheapest to produce and the lightest in weight. Magnesium-copper hydride 

 is the next best, followed by iron- titanium hydride. A sore expensive, 

 but low-teaperature alternative, is provided by the various rare -earth 

 pentanickel hydrides with the Bischmetal-pentanickel hydride providing 

 acceptable storage characteristics at the lowest teasperature. It must 

 be emphasized that the figures for unit costs of the hydrides listed in 

 Table 3 are estimates and are subject to increases and decreases depen- 

 dent on the availability of the materials. 



The survey of literature concerning these hydrides indicates that 

 che rates of desorption of hydrogen from them is consistent with the 

 needs of automotive engines and can be controlled sufficiently for the 

 many uses for which hydrides can be envisioned. 



A brief study was made of possible alternative fuels. This study 

 showed that hydrogen is a very versatile fuel, nontoxic, and of use in 

 making all of the other synthetic fuels. Energy can be conserved in 

 practically every instance by using hydrogen rather than other alterna- 

 tive fuels. Next in line of the possible alternati-se fuels are methanol 

 and ethanol. 



Of the four methods for storing hydrogen, the aetal hydride method 

 weighs more than liquified hydrogen and its container but less than 

 pressurized hydrogen and its container. In terms of voltane the liquid 

 and metal hydride systems are about the same and both are much less 

 bulky than the pressurized system or the low pressure taak storage 

 system. In short, for transportation purposes, pressurized and tank 

 nvdrogen can be ruled out. Thus the question is whether it is better to 

 liquify the hydrogen and contend with all the problems that liquid 

 hydrogen brings out or to carry more weight made uj of the hydride 

 material and have the ease of using a gaseous hydrogen. 



The benefits of liquid hydrogen are that it is light and fairly 

 compact. Its disadvantages are that (1) the energy needed to perform 

 the liquif action is equal to about one-third of the stored energy, (2) 

 under normal conditions the lock up time for liquid hydrogen is only a 

 few days, and (3) transporting and distributing liquid hydrogen is 

 difficult. 



In looking at gaseous hydrogen and metal hydrides t!v disadvantages 

 are its weight and, in the case of magnesium-nickel hydride, its temper- 

 ature. In the metal hydride system, the advantages distinctly outweigh 

 che disadvantages. Refueling is fairly simple, requiring only a cooling 

 system which can use the heat for other purposes and a source of low- 

 pressure hydrogen. The lockup time is indefinitely long, depending only 

 on the contamination rate of the hydride. The energy needed to release 

 the hydroge . is also about one-third of the amount of stored energy but 

 it is returned during recharge. 



38 



