We’ve been filling up conventional vehicles with liquid fuel for over a century, so it only makes sense that hydrogen fuel cell vehicles use liquid hydrogen fuel, right?
The upcoming Toyota FCV, for example, uses composite H2 storage tanks at pressures of up to 875 atm (12,859 psi), giving the car a theoretical range of 370 miles. Taking a look at the difference between gaseous hydrogen (H2) and liquid hydrogen fuels, one would correctly assume that LH2 is denser than even compressed gaseous H2. If Toyota FCV has a range of 370 miles on compressed H2, then couldn’t it possibly range upwards of 700 miles?
True, you could use LH2 in a fuel cell vehicle for extra range, but there’s not a single hydrogen fuel cell vehicle or hydrogen fueling station that stores, delivers, or runs on liquefied hydrogen (LH2) fuel. Why not? The problem is with the amount of energy that is required to produce liquid hydrogen fuel in the first place. The Department of Energy, in 2009, estimates that production of liquid hydrogen fuel uses 12-13.4 kWh/kg H2, but could go as low as 7-8 kWh/kg H2. Production of compressed hydrogen fuel to 875 atm was already as low as 2.9-3.2 kWh/kg H2 in 2009, and the DOE estiamtes that it could go as low as 1.5 kWh/kg H2. Clearly, hydrogen liquification isn’t nearly as efficient.
While liquid hydrogen can be kept at lower pressures, as little as 13 atm (191 psi), it needs to be kept at a blistering 33 °K (-240 °C). To maintain these frigid temperatures and prevent hydrogen fuel from boiling off or tank mechanical explosion, energy-intensive cooling systems are required, aside from specialized insulation tanks, adding bulk and expense to the system. Storage facilities may be able to afford the expense and space, but the energy expenditures would be daunting. Scale these down to the size of a fuel cell vehicle, and money and space cancel out any possible benefits. Even if the LH2 capacity was reduced to achieve the same range, the size of the system would end up being the same, while ballooning the cost of the vehicle itself.
From practically every point of view, expense, range, or emissions, liquid hydrogen fuel cell vehicles are simply not worth consideration.
Images © Olathe Toyota Parts Center
