Box 3: The hydrogen economy
Hydrogen is the most common element in the universe although it does not exist in large quantities in a useful form. It can be produced from water or from hydrocarbons in fossil fuels or biomass. Hydrogen can be converted into energy using existing energy technologies, such as fuel cells, engines, and combustion turbines, with water the only waste product. It can be used as a fuel for vehicles (where development is progressing rapidly), as a means of storing energy, to provide heat or in stationary applications to generate electricity. It is therefore both a fuel and an energy carrier.
An energy infrastructure that relies on hydrogen could enable much greater use of
distributed energy systems in which small, modular electricity generators
can be placed right where they are needed for heating, cooling, and powering
offices, factories, and residences. In the short term, hydrogen will come from fossil fuels with CO2 produced as a by-product but its use would have advantages particularly in fuel cells whose higher efficiencies could lead to reductions in carbon emissions. Although on a weight for weight basis, hydrogen has more energy than any other fuel, it has a very low density. The production of hydrogen from non-carbon sources provides a significant challenge, as do storage and transport.