Question 16.4: In France the total distance driven by cars in 2006 was 555 ......
In France the total distance driven by cars in 2006 was 555\times10^{-9} km. Assume that all French cars are to be powered by fuel cells. Further assume that conventional electrolysis will be used to produce the hydrogen needed (energy density 4 kWh/Nm³ ) for this purpose. If 1 kg of \mathrm{H}_{2} is needed per 100 km driven, calculate the quantity of electricity needed each year to meet the demand.
One normal cubic meter contains 90 g of \mathrm{H}_{2} . The amount of electricity to produce 1 ton is 4.4\times10^{5}\,\mathrm{kWh}/\mathrm{t.} To produce 1 Mt of \mathrm{H}_{2} , one needs 4.4\times10^{10}\mathrm{kWh~or~44{T}W h.} Driving a total distance of 5.55\times10^{11}{\mathrm{km}} requires 5.55\times10^{9}\,\mathrm{kg} of \mathrm{H}_{2} or 5.55 Mt of \mathrm{H}_{2} .The quantity of electricity needed for transportation is then 244 TWh, that is, about half the current annual French consumption of electricity. This is the amount of electricity that can be produced by about 25 nuclear reactors or about fifty thousand 2-MW wind turbines.