2008 Volume 87 Issue 9 Pages 753-762
This paper describes the results of life cycle environmental analysis of hydrogen energy systems. It is proposed that hydrogen can be produced from coke oven gas (COG), and then stored and distributed to consumption sites in the form of organic hydride (methylcyclohexane/toluene). In this study, such a hydrogen energy system is analyzed in terms of primary energy requirement and CO2 emission, with a special attention to the hydrogen distribution using organic hydride. The results show that energy requirement and CO2 emission at consumption sites (i.e. dehydrogenation reaction of methylcyclohexane, refining of hydrogen) account for a large percentage of the whole system. From the results, it is understood that this is a special characteristics of the organic hydrides option. It also implies that primary energy requirement for the organic hydride option is almost equivalent to the liquid hydrogen option, but it is lager than the compressed hydrogen option. Furthermore, improvement analysis is carried out focusing on the characteristics of organic hydride. The results reveal that CO2 emission from the whole system are considerably reduced if waste heat from fuel cells at consumption sites can be used as energy source for dehydrogenation reaction of methylcyclohexane.