LH2 = liquid hydrogen

LC Level controller LDV Let down valve LHV Lower heating value LH2 or LH2 Liquid hydrogen LN2 or LN2 Liquid nitrogen LNG Liquefied natural gas LSH High level switch LP Low pressure LT Level transmitter... 

The overall production of GHG emissions greatly depends on the electricity source, which feeds the electrolyser at an annual average. In the case of renewable electricity, the specific GHG emissions become almost negligible. Furthermore, if adding a liquefaction stage to provide liquid hydrogen (LH2) to the filling station, small amounts of specific GHG emissions have to be taken into account, which result from the transport of LH2 in diesel-operated trucks. 

In contrast, the yield of electricity from photovoltaics (PV) is about 337 500 kWh per ha and year, even if it is assumed that the area of the PV panels cover about one-third of the total plant area. If PV electricity were converted to liquid hydrogen (LH2), stored and then converted back to electricity by a combined cycle gas turbine (CCGT, efficiency 57.5%) about 104000 kWh electricity could be generated per ha and year. This yield is still more than three times the yield of the best biomass pathway (upper end of bandwidth electricity from biogas via large gas engine). 

For road transport, liquid hydrogen (LH2) is transported in cylindrical super insulated cryogenic vessels in a semitrailer (see Fig. 12.5). The gross weight of a truck capable of carrying the LH2 container is typically about 401. The investment for a LH2 semitrailer amounts to about 500 000. The investment for a tractor capable to haul a semitrailer is about 160000. Table 12.3 displays the technical characteristics of hydrogen trailers. 

Table 12.3. Technical data of a 53100 l liquid hydrogen tank used for LH2 semitrailers...

Although liquid hydrogen, LH2, can be used as a fuel source, much of the recent fuel cell research is focusing on the partial oxidation of methanol, natural gas, ethanol, or gasoline to produce the necessary hydrogen. Catalysts that aid in the partial oxidation of these fuels yields a readily available, rich source of hydrogen. Water is the primary exhaust emission produced by fuel cell powered vehicles. If a carbon-based fuel source is utilized, then a carbon-containing by-product will also be produced. 

Pehr K, Sauermann P, Traeger O, Bracha M, (2001). Liquid hydrogen for motor vehicles-the world s first public LH2 filling station. International Journal of Hydrogen Energy 26 777-782... 

Weight in Kilograms, Thrust in Newtons, Area in meters. Length in Meters, Cost in Millions, Noise in dB, Energy Utilization in Kilojoules per Seat Kilometer, LH2 is Cryogenic Liquid Hydrogen, Jet A is standard commercial Jet engine fuel... 

Measurement of the solubility of solid oxygen in liquid hydrogen (and low temperature gaseous H2) showed exactly what had to be done in 02 removal during the H2 purification process to avoid solid 02-LH2 explosions. Understanding of another oxidant of concern, N20, was also obtained. N20 may be present in hydrogen from electrolytic cells but it can be converted catalytically in H2 to water and N2 which in turn are removed by conventional means. 

Some of the problems listed by Williams—large tanks, engineering problems, boiloff—have been minimized by the two main developers of liquid-hydrogen transportation technology in the last two decades, BMW and the Musashi Institute of Technology. (N.B. Hereafter, liquid hydrogen will often be abbreviated LH2. )... 

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