Publisher's Synopsis
Between production and use, any commercial product is subject to the following processes: packaging, transportation, storage, and transfer. The same is true for hydrogen in a "Hydrogen Economy". Hydrogen has to be packaged by compression or liquefaction, it has to be transported by surface vehicles or pipelines, it has to be stored and transferred. Generated by electrolysis or chemistry, the fuel gas has to go through these market procedures before it can be used by the customer, even if it is produced locally at filling stations. As there are no environmental or energetic advantages in producing hydrogen from natural gas or other hydrocarbons, we do not consider this option, although hydrogen can be chemically synthesized at a relatively low cost. In the past, hydrogen production and hydrogen use have been addressed by many, assuming that hydrogen gas is just another gaseous energy carrier and that it can be handled much like natural gas in today's energy economy. With this study, we present an analysis of the energy required to operate a pure hydrogen economy. High-grade electricity from renewable or nuclear sources is needed to generate hydrogen and all other essential steps of a hydrogen economy. But because of the molecular structure of hydrogen, hydrogen infrastructure is much more energy-intensive than a natural gas economy. In this study, the energy consumed by each stage is related to the energy content (higher heating value HHV) of the delivered hydrogen itself. The analysis reveals that much more energy is needed to operate a hydrogen economy than is consumed in today's energy economy. Depending on the chosen route the input of electrical energy to make, package, transport, store and transfer hydrogen may easily double the hydrogen energy delivered to the end-user. But precious energy can be saved by packaging hydrogen chemically in a synthetic liquid hydrocarbon like methanol or dimethyl ether DME. We, therefore, suggest modifying the vision of a hydrogen economy by considering not only the closed hydrogen (water) cycle but also the closed carbon (CO2) cycle. This could create the intellectual platform for the conception of a post-fossil fuel energy economy based on synthetic hydrocarbons. Carbon atoms from biomass, organic waste materials, or recycled carbon dioxide could become the carriers for hydrogen atoms. Furthermore, the energy-consuming electrolysis may be partially replaced by the less energy-intensive chemical transformation of water and carbon to synthetic hydrocarbons. As long as the carbon comes from the biosphere ("biocarbon") the synthetic hydrocarbon economy would be as benign concerning the environment as a pure hydrogen economy. But the use of "geocarbons" from fossil sources should be avoided to uncouple energy use from global warming.
