Liquid-Hydrogen Technology for Vehicles
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Liquid-Hydrogen Technology for Vehicles Joachim Wolf Abstract This survey focuses on the use of liquid hydrogen as an automotive fuel in comparison with the use of compressed gaseous hydrogen. The energy penalties associated with liquefaction versus gas compression are compared, followed by an examination of the weight of hydrogen relative to carrier weight for the two alternative approaches. The optimum form and design of LH2 tanks are discussed, followed by the important topic of how to achieve quick and easy transfer of LH2 from a storage tank to a vehicle.
uefier is of the order of 30% of the specific energy content. The entire work for a gaseous compression unit, in comparison, is up to 18% of the specific energy content. Nevertheless, the use of LH2 for vehicle applications offers many advantages that clearly stand out and compensate the greater work required to prepare the liquid state of aggregation. As can be seen in Figure 2, the comparison of storage volume and storage weight highlights the advantages of LH2, especially concerning its use as a vehicle fuel. To round out the comparison of the states of aggregation of hydrogen, it is useful to look at the current methods of commercial transport for LH2 and CGH2. Figure 3 shows a trailer for LH2 (total weight, 40 tons; hydrogen load, 3370 kg). Compare this with the trailer for CGH2 shown in Figure 1 of the article by Irani in this issue (total weight 40 tons; hydrogen load, 530 kg at 20 MPa). The LH2 trailer is able to transport more than six times the hydrogen load of the CGH2 trailer.
Liquid-Hydrogen Storage Keywords: compressed gaseous hydrogen, hydrogen storage, liquid hydrogen, liquid-hydrogen transfer, hydrogen transport.
Introduction More than 100 years ago, James Dewar succeeded in the first liquefaction of hydrogen. Liquid hydrogen (LH2), with a cryogenic temperature of 20 K (253C), has been produced and distributed in a safe and reliable manner by the gas industry for all kinds of industrial needs for more than 70 years. Twenty years ago, car manufacturers began the implementation of LH2 applications in prototype cars. The expected public use of cryogenic fuels like LH2 will require suitable, safe, and reliable storage and filling facilities, in particular, safe and easy-to-use filling equipment comparable to conventional gas stations. This article outlines the advantages of LH2 in comparison with compressed gaseous hydrogen (CGH2). The necessity of purpose-designed tank systems to fit the restricted available space within vehicles will be highlighted. A hermetic, clean, and leak-free break coupling for the filling and refilling of cryogenic fuel systems will also be discussed; this coupling enables the safe and easy handling of LH2, short filling and
This is an edited and abridged version of an article that will appear in the Handbook of Fuel Cells, to be published by John Wiley & Sons Ltd. in 2003.
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coupling times, and a high filling rate (number of vehicles filled per unit of time).
Liquid Hydrogen and Compressed Gaseous Hydrogen: A
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