Technology Status of Hydrogen Road Vehicles

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The most abundant and accessible hydrogen-dense feedstocks are water, coal, oil and natural gas. ....... Of course, fossil fuel hydrogen is not a clean, renewable resource. Most of the hydrogen research community agrees that eventually hydrogen should be produced from water. Nevertheless it may be easiest to sustain a transition to hydrogen by expanding commercially-available, relatively inexpensive production processes, such as the manufacture of H 2 from coal for many decades, environmental considerations aside...... ....... Hydrogen also can be produced from the gasification of biomass.... However the biomass resource base, although renewable, is many times smaller than the coal resource base. ....... For simplicity, this paper considers only the most abundant hydrogen feedstocks: coal to represent a low-cost base in the near-to-medium term, and solar water electrolysis as a low-environmental impact case in the longer term. ....... Water can be decomposed thermally at temperatures above 2500 K.....(but) many researchers do not think thermochemical production is very promising, and favor electrolytic and photolytic water-splitting techniques instead..... In my analysis, I consider water electrolysis only... Non-fossil feedstocks should be used....of these, solar energy and nuclear energy are available in the long term.....; this cost analysis examines solar hydrogen. 3. Hydrogen Distribution Typically, hydrogen would be transported from the site of production to end users as a gas, via pipeline. Ideally, the current natural gas system would be used for at least the initial stages of a transition to hydrogen. However, pure hydrogen reacts at the surface of certain pipeline steels, embrittling them and accelerating the growth of fatigue cracks.....(but) compounds can be added to hydrogen to inhibit embrittlement, (but) none is safe, inexpensive and effective. Otherwise, dedicated pipelines would have to be built. ....... Hydrogen also could be shipped in liquid form, in 49 000 l tank trucks, 132 000 l rail cars, or, for short distances, in vacuum-jacketed pipelines. 4. Vehicular Fuel Storage and Refueling Hydrogen may be stored on board a vehicle as a gas bound with certain metals, as a liquid in cryogenic containers, or as highly compressed gas (690 bar) in ultra-high-pressure vessels. Other forms of hydrogen storage, such as glass microspheres, cryoadsorbents, and liquid hydrides, are discussed in the literature... ....... The metals most used in hydrides are iron, magnesium, nickel, manganese and titanium. Vehicular hydride storage systems are usually long thin hollow cylinders, tightly bundled, and pressurized with hydrogen to about 34 bar. When the vessel is charged, a good deal of heat is released... and during discharge the reaction is reversed and heat is required. ....... The most serious shortcoming of hydrides is their low mass and volumetric energy density...The low mass density of most hydrides means that hydride vehicles are much heavier and less efficient than comparable gasoline or LH 2 vehicles, and are limited by storage weight to about a 150-300 km range. ....... Hydrides are susceptible to contamination by impurities in the hydrogen gas.....(and) a 99.999% purity is necessary to insure that hydrides have relatively long lives. ....... 42
Refueling hydride vehicles is relatively simple. It appears that hydride vehicles can be refueled in 10 min or less, although a wide range is given in the literature, and usually a good deal more time is needed to fill the last units of capacity. ....... A significant advantage of using liquid hydrogen is that LH 2 systems are much lighter and often more compact than hydride systems providing an equal range. Liquid hydrogen storage is not significantly heavier than gasoline storage, on an equal-range basis; it is however much bulkier. ....... Thus an advanced LH 2 tank probably would weigh only 10 kg more than a full gasoline tank.......(but) complete LH 2 systems are about 6-8 times larger than gasoline tanks holding the same amount of energy. However the LH 2 will go up to 50% farther on the same amount of energy, so that, on an equal-distance basis, LH 2 systems will be 5-6 times larger. ....... A safely-run, easy-to-use, public LH 2 refueling station is probably within the scope of current technology and practices. ....... Beginning in 1979 LANL operated a LH 2 vehicle and refueling station for 17 months; the results indicated that fast and safe LH 2 self-service was possible. The LH 2 vehicle was refilled in less than 10 min when the tank was cold. In 1982 Peschka remarked that an LH 2-powered BMW was refueled “without any major difficulties” also in under 10 min when the tank was cold. ....... A simple way to store hydrogen on board is as a compressed gas in high-pressure vessels.... (For) a more manageable volume the pressure must approach 690 bar. Lightweight carbon-wrapped aluminum cylinders capable of storing hydrogen safely at this pressure are available, but heretofore have been used in aerospace applications, and would be very expensive for vehicular use.......At 690 bar, a carbon/aluminum storage vessel providing a 420 km range would be about three times heavier and nine times larger than the gasoline tank....... ....... Hydrogen can be stored in glass microcapsules at high pressure. This system is comparatively simple and has the potential to be relatively lightweight and inexpensive.....(but) is not nearly as advanced as hydride research........ ....... A liquid-hydride based system for trucks and buses has been developed... (but) thus far the cost, bulk and weight of the total system appear to limit it to heavy-duty vehicles...... 5. Performance of Hydrogen Vehicles The overall fuel efficiency of a hydrogen vehicle, relative to a comparable gasoline vehicle, is a function of the difference in weight , and the difference in thermal efficiency. The weight differences are due to pollution control equipment, fuel storage systems, and engine components. A 1% increase in vehicle weight causes about 0.8% decrease in overall efficiency. Hydrogen can be considerably more thermally efficient than gasoline, primarily because it runs better in excess air, and permits the use of a higher compression ratio.... Data from engine tests indicate that hydrogen combustion is 15 to 50 % more thermally efficient.. Some claim as much as 100 % with ultra-lean operation. The actual value depends on the air-fuel ratio, how well the engine is optimized for hydrogen combustion, whether GH 2 or LH 2 is used, the fuel injection scheme, and other factors. For example, late injection of LH 2 offers the potential of higher efficiency by reducing the pressure rise in the cylinder, and reducing thermal losses through the cylinder walls. In general, engine power..... is proportional to the volumetric heating value of the air-fuel mixture. The greater the charge density, the greater the power. At near-ambient temperatures, gaseous hydrogen displaces much 43
Page 1 and 2: IEA Agreement on the Production and
Page 3 and 4: 1.0 Introduction This report was co
Page 5 and 6: Memories of the Hindenburg disaster
Page 7 and 8: During the past 5 years, a carbon s
Page 9 and 10: Wetzel (1996) gives a comprehensive
Page 11 and 12: The 11th WHEC shows increasing inte
Page 13 and 14: ! There is higher efficiency at low
Page 15: Some overall observations may be ap
Page 20 and 21: Europe--Fuel Cells Table 2. Hydroge
Page 22 and 23: 11, Florence, 1992. Dufour, A.; B.G
Page 24 and 25: Lamy, C; J.-M. Leger, “Les piles
Page 26 and 27: Hydrogen Energy Progress XI, 1569-1
Page 28 and 29: Fischer and Eichert (1995) provide
Page 30 and 31: ! Take cryogenic precautions. ! Det
Page 32 and 33: A1.4 The Challenger Accident Certai
Page 34 and 35: The air on the inlet stroke is ofte
Page 36 and 37: of approach: ! A mechanical/hydraul
Page 38 and 39: y Furahama et al. (1991) for high-p
Page 40 and 41: difficulties must be overcome: ! Hi
Page 42 and 43: Turning finally to the electrical t
Page 46 and 47: more air in the combustion chamber
Page 48 and 49: noticed.... 7. Environmental Impact
Page 50 and 51: 8. Liquid Hydrogen and Hydride Vehi
Page 52 and 53: 8.4 The cost of liquefying hydrogen
Page 54 and 55: tensions and conflict related to im
Page 56 and 57: Proceedings of the 11th World Hydro
Page 58 and 59: Moore, R.B.; V. Raman, “Hydrogen
Page 60 and 61: ! Cryogenic GH 2 is still in the R&
Page 62 and 63: Pizak, V. et al., “Investigations
Page 64 and 65: Initial tests on a representative e
Page 66 and 67: Cleghorn, S., et al., “PEM Fuel C
Page 68 and 69: vehicles (as well as stationary) ap
Page 70 and 71: To ease the introduction of a new t

Technology Status of Hydrogen Road Vehicles

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