Methane energy density

Several alternative methods have been considered in order to increase the energy density of natural gas and facilitate its use as a road vehicle fuel. It can be dissolved in organic solvents, contained in a molecular cage (clathrate), and it may be adsorbed in a porous medium. The use of solvents has been tested experimentally but there has been little improvement so far over the methane density obtained by simple compression. Clathrates of methane and water, (methane hydrates) have been widely investigated but seem to offer little advantage over ANG [4]. Theoretical comparison of these storage techniques has been made by Dignam [5]. In practical terms, ANG has shown the most promise so far of these three alternatives to CNG and LNG. 

Figure 9.3. Energy densities of various alternative fuels (LHY) (LPG 50% propane, 50% butane natural gas 83% methane).

Liquefaction means a volume reduction of approximately 600 times. This corresponds to an energy density that is 600 times higher than natural gas at atmospheric conditions. Since LNG has no odour, leak detection requires special instrumentation. Furthermore, LNG is colourless and non-toxic, and non-carcinogenic. The specific weight of LNG is 45% of water. In vaporised phase - mixed with air - LNG can only ignite if the concentration of gaseous methane is in the range 5-15%. Neither LNG, nor its vapour can explode in an unconfined environment [8],... 

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