Controlled charge and discharge of a 40-L monolithic adsorbed natural gas tank

The University of Missouri constructed a prototype adsorbed natural gas tank for low-pressure storage of methane on natural gas vehicles. The tank contains monolithic nanoporous carbon with storage capacities up to 0.11 kg methane/L carbon and 0.19 kg methane/kg carbon at 35 bar and 25 °C which is 4.5 times larger than a tank without any adsorption would store at 35 bar. In this paper, we report the performance characteristics of the tank under different charge and discharge protocols. The tank was found to be able to be reach 80% of its full capacity in 3 min with total filling times being better or comparable to electric vehicles. The ability to use different filling procedures to counteract the storage loss due to the 65+ °C temperature rise is also explored. Pressure control during discharges, using a proposed fuel extraction system, is also explored which resulted in doubling a car’s highway drivetime and discharge efficiencies of 90%. The temperature and storage evolution is also analyzed to give new insights on the dynamics of monolithic carbon systems which have not been extensively studied in the literature. The results support that adsorbed natural gas systems combined with an effective compressor, possibly also with switching from a cold tank module to a warm module, can become a viable alternative to compressed or liquefied natural gas.