Page - 55 - in Our Car as Power Plant

55 Light-weight, low-volume hydrogen storage systems are needed for the development and viability of hydrogen- powered vehicles. Approximately 5 kg of hydrogen is required to drive 500 km. All emerging commercial fuel cell cars contain compressed-hydrogen gas tanks, with pressures between 350 and 700 bar. Alternatives for storing hydrogen are liquid hydrogen tanks, cryogenic compressed hydrogen, metal hydrides, high-surface-area adsorbents, and chemical hydrogen storage materials (30). The long-term targets of the US DRIVE research program (31) are 0.075 kg hydrogen per kg storage system and 0.07 kg hydrogen per liter storage volume. With 5 kg hydrogen, this equates to a tank volume of 70 l and 65 kg, comparable to present-day gasoline tanks. The cycle efficiency of storage is important, as energy is lost during the cycle. HYDROGEN STORAGE