By Letter to the Editor on November 4, 2020.
A recent demonstration project was evaluated for a hydrogen-fuelled vehicle by the U.S. Department of Energy Division. This demonstration will be applicable to other means of transportation such as trucks and trains.
Several participating manufacturers, in an effort to study the problems involved in fuelling automobiles with liquid hydrogen, are carrying out the project to demonstrate a vehicle of conventional appearance and performance operating on liquid hydrogen, and to demonstrate a liquid refuelling station that can be operated by personnel with minimal training.
They used a 1979 Buick Century four-door sedan with 3.8-litre displacement, turbocharged V-6 engine. This vehicle provided a good compromise on trunk space for installation of the DFVLR tank, passenger accessibility for demonstration, engine compartment space for versatility in selection of substitute engines, available engine sizes, efficiency and suitability for modification of hydrogen operation.
Some goals of the vehicle performance are to provide a minimum fuel economy of 54 kilometres/4.5 litres of liquid hydrogen over a 259-km range before refuelling.
In regard to safety, the liquid hydrogen tank is equipped with pressure relief valves that are activated at 450 KPA, should a loss of insulating vacuum in the hydrogen tank begin to boil off liquid hydrogen.
As far as the economics are concerned, the cost of the liquid hydrogen as delivered to the automobile is $9.48/1.0551 x 109 Joules, which is equivalent to gasoline at $0.25/litre, however, the bulk rate is $0.21/litre.
The estimated cost for a hydrogen engine will add about $300 and the liquid hydrogen tank will add another $250-$900 to the cost of the vehicle.
The energy assessments for liquid hydrogen – energy liquefaction – losses in transfer and storage. For compressed gaseous hydrogen – energy of compression, and high tank weight, which decreases vehicle efficiency by about 1.2 per cent/kg. And for metal hydrides – energy of dissociation (use waste engine heat).
The operation of this vehicle on liquid hydrogen provides an accumulation of operating experiences and demonstrates to the public that liquid hydrogen is a practical alternative fuel for transportation.
The refuelling operation could be completed, automated and improved in several areas. Install a suitable mass flowmeter for determining quantity of hydrogen transferred to the fuel tank, a system that will minimize liquid hydrogen loss from cooling warm transfer lines and a system that will prevent contamination and ice build-up in the transfer lines because of the lines being open to the atmosphere while still cold.
Member, American Society of Mechanical Engineers