Gravimetric energy density

Acceleration/handling Similar to or better than current ICE vehicles Minimal weight (high gravimetric energy density) Rapid hydrogen release kinetic properties... 

System gravimetric capacity usable energy density from H2 (net useful energy/max system mass) kWh/kg (kg H2/kg system) 1.5 (0.045) 2 (0.06) 3 (0.09)... 

The gravimetric energy density of a pressure vessel is very much dependent on the material of the container, which in the case of carbon fibres accounts for around 60% of total storage-system costs. 

Fig. 7.1 Comparison of gravimetric and volumetric energy density of lithium secondary cells with aqueous electrolyte-based systems...

Lighter negative electrode materials per unit charge (Li in particular, also Mg and Al), therefore higher gravimetric and volumetric energy densities. 

Besides the efficiency, the enormous difference in energy density (per mass or volume) deserves to be emphasized. Assuming a height difference of 100 m, the gravimetric energy density is 981 N m kg-1, or 0.27 W h kg-1 in units used in battery... 

As already mentioned, an important criterion to characterize the applicability of different battery technologies for certain applications is the energy density, which specifies how much electrical energy can be stored per mass or volume (gravimetric or volumetric storage capacity). 

Battery technology Electrolyte Mobile species in electrolyte Anode reaction during discharge Cathode reaction during discharge Standard cell potential / V Gravimetric energy density/ Wh kg-1 Notes... 

Energy density is expressed in terms of watt-hour per unit mass (usually kilogram) or watt-hour per unit volume (usually liter), and termed gravimetric energy density , and volumetric energy density , respectively. 

Figure 27 Comparison of the different battery technologies in terms of volumetric and gravimetric energy density. The share of worldwide sales forNi-Cd, Ni-MeH and Li-ion portable batteries is 23, 14, and 63%, respectively. The use of Pb-acid batteries is restricted mainly in automobiles or standby applications, whereas Ni-Cd batteries remain the most suitable technologies for high-power applications (for example, power tools). (Ref 47. Reproduced by permission of Nature Publishing Group (www.nature.com))...

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