In the news of the past few months there have been numerous items on big car manufacturers making a hybrid vehicle with a fuel cell. The first one is expected to roll out of the factory around 2015. In the discussions around fuel cell powered vehicles, often the discussion goes over to efficiency, which for the total cycle of well-to-wheels for a hydrogen powered fuel cell is less good as for example a pure electric vehicle powered by a not so efficient power plant. Despite this lower efficiency, fuel cells are the hybrid way to go, for one big reason only: convenience.
How the Fuel Cell works
First a recap on the efficiency of a hydrogen powered fuel cell hybrid vehicle. It starts with creating the hydrogen, either by electrolysis of (pure) water or reforming of natural gas. Preferably the water is pure, though it is possible to use water with some impurities, it will be a less efficient conversion process to start with. After the the hydrogen is made, it is a common practice to compress it, a pressure of 350 bar is not uncommon. This is another energy sink in the process chain from well-to-wheels, but it allows one to haul along a significant amount of extra hydrogen compared to non-compressed hydrogen.
The conversion from hydrogen in the fuel cell to electricity is theoretically around a maximum of 50-60%, in practice this is usually a bit lower, though at the designed operating points and conditions this does not deviate significantly. The rest of the drive train in a fuel cell hybrid vehicle does not differ much from a pure electric vehicle; an electric converter, an electric motor and a battery (sometimes adding its own converter). The result is that the well-to-wheel efficiency for a hydrogen fuel cell vehicle is somewhere between 25-30%, depending on the source used for the creation of hydrogen. For more details on the well-to-wheels efficiency of hydrogen fuel cell vehicles, please check out the report from EFCF and an article at Electropaedia.
The well-to-wheel efficiency of a fuel cell vehicle is better than the efficiency of the internal combustion engine, but it it less than the well-to-wheel efficiency of the pure electric vehicle. In the current state of technology however, the pure electric vehicles have the best efficiency, but the shortest range. The fuel cell vehicle provides the possibility for clean transport, has a longer range, but misses a lot of efficiency when compared to the pure electric vehicle. The biggest motivation to use the fuel cell application now is for the increased range, take for example the Mercedes B-Class F-Cell in Floriday, which has a range of 400 miles, while an electric vehicle has around 100 miles of range (not counting the Tesla Roadster, but that is a different price range as well).
The Mercedes B-Class F-Cell, currently being used in a pilot project in Florida
With the current prices for fuel cell vehicles they are not really competitive with the electric vehicle, but if the prices would be comparable and even hydrogen would be readily available at the gas stations, fuel cell vehicles would allow people to travel longer distances without having to stop for a refill and still be green. The only real threat for a fuel cell hybrid is the speed of the technological advancements; the advancements with fuel cells, but also for the pure electric vehicle.
The success of the fuel cell hybrid will really depend on how the technological developments will go for battery technology, quick charging and inductive charging. All the mentioned technologies have the potential to increase the range of the electric vehicle, help speed up the refill and increase the convenience of the technology and limit the area in which a fuel cell vehicle will be beneficial for people.