Hydrogen and fuel cells in city transport

City transport needs to be improved to reduce emissions and increase fuel flexibility and economy. Because electric drive trains display advantages of low emissions, renewable refuelling and improved performance compared to combustion vehicles, the benefits of hydrogen and fuel cells as range extenders of battery electric vehicles have become apparent, especially to obtain rapid refuelling times and 500-km range. This paper describes the situation in China where electric bikes have competed successfully with combustion bikes. Unfortunately, this has not proved effective for cars which are too heavy and consequently require increased energy storage capacity over present battery levels. Weight is therefore a primary factor in choosing the drive train. It is demonstrated that hydrogen can provide that energy storage for cars in the 500-kg mass range, augmenting the battery to extend the range from 100 km to 500 km, as demanded in standard gasoline vehicles. A theory of the weight influence in cars is presented and verified by experiments on the Microcab city car. A hydrogen fuel cell battery hybrid composite car of 7-kN weight has now been tested to give results better than all existing hydrogen cars in terms of low energy use. The new theory fitting these results shows how the sum of many car component losses as a function of weight resolves into a Coulomb curve. The conclusion is that Coulomb's Law can be used to predict city car energy demand quantitatively. Vehicle weight is therefore the major variable in city transport but hydrogen fuel cell drive can halve the energy requirement at a given mass compared to combustion cars. Copyright © 2015 John Wiley & Sons, Ltd.