Adsorbent Storage for Natural Gas Vehicles

3 Royal Military College of Canada, Kingston, Ontario 

4 Sutcliffe Speakman Carbons Ltd, Ashton-in-Makersfield, England 

In the United States, in particular, recent legislation has mandated sweeping improvements to urban air quality by limiting mobile source emissions and by promoting cleaner fuels. The new laws require commercial and government fleets to purchase a substantial number of vehicles powered by an alternative fuel, such as natural gas, propane, electricity, methanol or ethanol. However, natural gas is usually preferred because of its lower cost and lower emissions compared with the other available alternative gas or liquid fuels. Even when compared with electricity, it has been shown that the full fuel cycle emissions, including those from production, conversion, and transportation of the fuel, are lower for an NGV [2], Natural gas vehicles offer other advantages as well. Where natural gas is abundantly available as a domestic resource, increased use 

The factory-produced, dedicated NGV is the ultimate goal of the NGV industry because it will reduce the incremental cost of the vehicle, the fuel system will be better integrated into the vehicle, and the vehicle performance can be optimized for natural gas. A dedicated NGV s emissions, power, and driveability can be superior to a comparable gasoline vehicle. There is however, a reluctance by some automobile manufacturers to produce dedicated NGVs until the refueling infrastructure is more fully developed. 

The generalized statement can be made that the energy density in a vessel filled with adsorbent will be greater than that of the same vessel without adsorbent when filled to the same pressure. The extent to which the above is true depends on many factors and considerations which are discussed more fully later. 

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Cook, T. L., Komodromos, C., Quinn, D. F. and Ragan, S., Adsorbent storage for natural gas vehicles. In Carbon Materials for Advanced Technologies, ed. 

Komodromos, C., Frickcr, N. Slater, G., "Development of Novel Tanks for Low-Pressure Adsorbed Natural Gas Storage in Vehicles", International Association for Natural Gas Vehicles, Toronto, 1994... 

Komodromos, C., Pearson, S. Grint, A., "The Potential of Adsorbed Natural Gas for Advanced On-board Storage in Natural Gas Fueled Vehicles", International Gas Research Conference, Florida, 1992. 

Applications of activated carbons are discussed in Chapters 8-10, including their use in the automotive arena as evaporative loss emission traps (Chapter 8), and in vehicle natural gas storage tanks (Chapter 9). The use of evaporative loss emission traps has been federally mandated in the U.S. and Europe. Consequently, a significant effort has been expended to develop a carbon adsorbent properly optimized for evaporative loss control, and to design the on board vapor collection and disposal system. The manufacture of activated carbons, and their preferred characteristics for fuel emissions control are discussed in Chapter 8, along with the essential features of a vehicle evaporative loss emission control system. 

The use of activated carbons as a natural gas storage medium for vehicles is attractive because the gas may be stored at significantly lower pressures in the adsorbed state (3.5 - 4.0 MPa) compared to pressurized natural gas (20 MPa), but with comparable storage densities. The development of an adsorbed natural gas storage system, and suitable adsorbent carbons, including novel adsorbent carbon... 

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