The Future of the Hydrogen Economy: Bright or Bleak?

ABSTRACT

In the past, many have considered the production and use of hydrogen, assuming that it is just another gaseous fuel and 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 an elemental hydrogen economy, with particular reference to road transport. High-grade electricity from renewable or nuclear sources is needed not only to generate hydrogen, but also for all the other essential stages. However, because of the molecular structure of hydrogen, the infrastructure is much more energy-intensive than in an oil and natural gas economy.

In a “Hydrogen Economy” the hydrogen, like any other commercial product, is subject to several stages between production and use. Hydrogen has to be packaged by compression or liquefaction, transported by surface vehicles or pipelines, stored, and transferred to the end user. Whether generated by electrolysis or by chemistry, and even if produced locally at filling stations, the gaseous or liquid hydrogen has to undergo these market processes before it can be used by the customer. Hydrogen can also be derived chemically at relatively low cost from natural gas or other hydrocarbons. However, because there are no energetic or environmental advantages, we do not consider this option.

In this study, the energy consumed by each stage is related to the true energy content—the higher heating value (HHV)—of the delivered hydrogen. The analysis reveals that much more energy is needed to operate a hydrogen economy than is required for fossil energy supply and distribution today. In fact, the input of electrical energy to make, package, transport, store and transfer hydrogen may easily exceed the hydrogen energy delivered to the end user—implying a well-to-tank efficiency of less than 50%. However, precious energy can be saved by packaging hydrogen chemically in a synthetic liquid hydrocarbon like methanol or ethanol. To decouple energy use from global warming, the use of “geocarbons” from fossil sources should be avoided. However, carbon atoms from biomass, organic waste materials or recycled carbon dioxide could become the carriers for hydrogen atoms. Furthermore, energy intensive electrolysis may be partially replaced by the less energy intensive chemical transformation of water and carbon to natural and synthetic hydrocarbons, including bio-methanol and bio-ethanol. Hence, the closed natural hydrogen (water) cycle and the closed natural carbon (CO₂) cycle may be used to produce synthetic hydrocarbons for a post-fossil fuel energy economy. As long as the carbon comes from the biosphere (“bio-carbon”), the synthetic hydrocarbon economy would be far better than the elemental hydrogen economy—both energetically and thus environmentally.