Question

For storage options a, b, and c, what volume of storage tank for hydrogen would be needed for a hydrogen fuel cell car to have the same delivered transport energy (that is, total vehicle-km of travel) as a conventional car with a full 50 litre petrol tank (note that the actual volume of the tank is more than 50 litre). a- If the hydrogen is stored as compressed gas at a pressure of 350 bar (1 bar = 101 kPa) b- If the hydrogen is stored cryogenically as a liquid c- If the hydrogen is stored in a metal hydride in solid form Important assumption and information required to answer this question: • The energy content of hydrogen (HHV) is 142 MJ/kg (~40 kWh/kg)The average energy efficiency of the fuel cells used is 44% (based on HHV), and that of the electric motors 86%. • Note that the following gravimetric and volumetric energy storage figures are based on 50% fuel cell energy efficiency, but the energy efficiency that you need to use (based on question 2) in order to answer this question is 44%, HHV. Assumptions for the volumetric and gravimetric electrical energy densities of different hydrogen energy storage options based on 50% electrical energy efficiency (HHV) for the fuel cell: - High-pressure hydrogen at 350 bar: 0.75 kWhe/kg and 0.35 kWhe/litre - Cryogenic hydrogen storage 1.46 kWhe/kg and 0.89 kWhe/litre - Metal hydride 0.5 kWhe/kg and 0.5 kWhe/litre.

Answer 1