Volumetric Energy Density of Various Fuels

The fuel cell is a strong contender as a power source for portable applications. Currently, the power source for portable applications is various batteries, such as Li-ion batteries, Ni-metal hydride batteries, Ni-Cd batteries, Zn-air batteries, and even Pb-acid batteries. Batteries are convenient to use, especially for low power loads (e.g., a few watts or less), but the time they can power the load is often quite short, and recharging of secondary batteries takes a few hours. A fuel cell has the potential to provide longer running time and with minimal refueling time. 

If we assume MH itself stores 1.5% wt of releasable H2 (many metal hydrides can store 2.0% wt of H2, but about 0.5% cannot be released at about 1 barg) and its density is 5.0 g cm (varying with types of metal hydride materials), then its H2 storage capability is 0.075 g cm (1.5% x 5.0 g cm ). 

Fuel LHV (kj/mol) Density (kgd.) Molar Density (mole/L) Volumetric LHV (kJ/L) Ratio of LHV to DOE Target 

Assuming that MeOH steam reforming is carried out with equal moles of MeOH and H2O. 

Reaction 7.2 shows the steam reforming process of methanol. 

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