ARMY AL&T


volume as small as possible. In general, smaller (↓) mass and volume (M&V) alternatives increase the operational effectiveness of vehicles and, therefore, become part of our equation as follows:


(Energy Carrier → Conversion Device) + (↑) COM + (↓) M&V = Mechanical Energy (Best Performance Characteristics)


With respect to batteries in both single and dual energy systems, the three alternative energy technologies considered here resulted in dramatically different total powertrain mass and energy carrier volumes—much larger than for diesel fuel systems. Use of NiMH batteries results in a total mass 15 to 22 times larger and energy carrier volume 25 times larger than the diesel fuel system. Li-ion batteries are a dramatic improvement over NiMH, resulting in a total mass only 4.5 to 7 times larger and energy carrier volume 4 times larger than the diesel fuel system.


FIGURE 2


Even with this improvement, the large mass and volume increase over a diesel fuel system presents a significant challenge to its implementation, as driving performance and usable volume would likely fall dramatically. Te effect of large mass and volume increases for Li-ion battery systems in similar large vehicles is evident in the short 300–500 mile range of the Tesla semitruck, which uses Li-ion batteries, compared with a more typical 1,000- mile range for a diesel semitruck.


Relative to diesel fuel, both hydrogen and methane yield similar total powertrain masses but significantly larger (3-5 times) energy carrier volumes. Tis highlights the primary issue with the low energy density of gaseous fuels and indicates that at existing and near- term technology levels, if these fuels are used as the single energy carrier for military ground vehicles, a large portion of their usable payload carrying capacity (volume) would be lost.


HOW THEY PERFORM


An analysis comparing the performance of various possible energy carriers for Army vehicles, including commercial energy carriers and promising future technologies, shows a marked superiority for diesel and gasoline fuels. Specific energy is energy per unit of mass; energy density is the amount of energy stored in a battery or tank per unit of volume. (Graphic by the authors)


https://asc.ar my.mil


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