Energy storage density

The major drawback to using hydrogen as a fuel is the storage medium. Compared to all other fuels, hydrogen has the lowest energy storage density. Hydrogen... 

In spite of the great acceleration in battery development since the 1970s, there is still a large gap between the energy storage density readily available (about 100 W hr kg-1) and the theoretical maxima. The latter (see Fig. 13.51) reaches about 500 W hr kg-1 for cells using aqueous solutions at room temperature, and 2000 W hr kg-1 for the high-temperature (molten salt) batteries (Fig. 13.52). 

For a mobile application, the water required for thermal control and hydrogen reaction is provided by condensed water from the hydrogen fuel cell. Only a small reservoir of water is required for startup, makeup, and surge demand. Thus, the required water does not significantly affect the volumetric and gravimetric energy storage densities. 

At the current state of technology, the BEV has range and vehicle mass limitations due to the low energy storage density of batteries, but it shows potential for commercial success in such applications as city buses and small urban vehicles. Nowadays, EREV technology allows the end customers to drive an average distance of 40-80 km/day on electricity without the need for a second vehicle or restrictions to vehicle use. The Voltec technology is therefore a substantial enabler for the widespread use of EVs. 

Volumetric versus gravimetric energy storage density on a double logarithmic scale (for visualization reasons only) for the most common storage systems used today. Close to oil and coal, but less than half of the energy density as compared to oil, we find ammonia, hydrides, and biomass... 

Electrochemical devices have come in recent years to the forefront in many applications. An example is the provision of electrical energy for electrical vehicles, where high energy storage density is provided by (rechargeable) batteries. Another example is pulsed lasers, where high power, as delivered by supercapacitors, is needed. 

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