Liquid hydrogen dispenser

The fill line from the liquid hydrogen dispenser automatically connects to the vehicle tank. 

The internal operation of the liquid hydrogen dispenser will be significantly more complex than the operation of the current gasoline pump. Fortunately, the actions performed by the vehicle operator will be much simpler than that encountered in refueling today s automobiles. 

Storage of liquid hydrogen is achieved in large well-insulated tanks from which it is dispensed to liquid tankers for transport over the road. The use of hydrogen sensors (mostly flammable sensors) in and around such facilities is a common safety practice today. As hydrogen-specific sensors and solid-state sensors become more reliable, and if their cost is reduced they will replace the more common flammable gas sensors. 

Only a few experimental dispensers have been built for liquid hydrogen [4.10]. Like dispensers for liquefied natural gas, these dispensers will need to be able to... 

Hydrogen dispensers will likely make use of programmable logic controllers or PC-based control systems. Both liquid hydrogen and compressed hydrogen dispensers will need to be able to monitor pressures and temperatures, open and close valves, turn on pumps, and interface with fire and emergency shut-down systems. 

As BMW has shown, care in design can provide a solution to the problem of transferring liquid hydrogen. The liquid line are be insulated by placing it coaxial inside the gas return line from the tank. An outer covering of thermal insulation in turn protects the gas return line. It is also be necessary to include a small vacuum pipeline from the dispenser to the interface between the fill line and the fill receptacle on the vehicle. These various lines will be incorporated into a fill line about 6 cm in diameter. Figure 7.2 shows BMW s excellent answer to this design problem. 

When a proper leak tight joint has been verified the dispenser will evacuate the air from the joint interface and all portions of the delivery system experiencing the low temperature of the liquid hydrogen. 

After a moment, when a proper vacuum condition is obtained, the valves on the dispenser and the fuel tank will open and liquid hydrogen flow will be initiated. 

The gas displaced from the tank will flow up the outer coaxial line to the dispenser for liquefaction or disposal. Flow of liquid hydrogen will continue until the automobile tank is full. 

Dl, Cryogenic liquid station. Liquid hydrogen is stored in cryogenic tanks. On site plant includes vaporization units and compression up to the dispensing pressure for the final user. 

Methanol is a liquid fuel that is readily dispensed and stored but, compared with conventional liquid fuels, is by no means ideal it is both toxic and water-miscible and has an energy content per litre that is well below that of petrol see Table 1.4, Chapter 1. A further drawback of incorporating a reformer into the vehicle is the need to supply heat for its operation. At 80-90 °C, the waste heat from the fuel cell would be inadequate and it would be necessary to burn some of the methanol to provide the heat or to use electrical heating. Either of these two options would obviously reduce the effective efficiency of the fuel-cell system. Altogether, on-board methanol reformers pose as many engineering problems as on-board hydrogen storage. Furthermore, the combined cost of a reformer and a fuel cell is likely to prove prohibitive, at least for small vehicles such as cars. 

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