3.5- OTHER HYDROGEN VEHICLES

3.5.1- ON-BOARD REFORMING FCV

This variation of the previously described fuel cell vehicle doesn't store the fuel in form of hydrogen; instead, this car uses a device called on-board reformer, which is capable to convert common fossil or biologic liquid hydrocarbon fuels into hydrogen gas through a complex chemical process, emitting CO2 during its activity. Due to the possibility of using a wide range of fuels, this vehicle requires a specially developed fuel tank able to allow them without suffering corrosion.

The use of an on-board reformer tends to increase the weight and decrease the energetic efficiency of a FCV. Furthermore, the hydrogen produced in this device may contain small amounts of CO that can corrupt the PEMFC. By the other side, it avoids the necessity of a dedicated energetic infrastructure, along with the drawback of the hydrogen storage. Anyhow, the use of this system would hardly represent a switching from fossil sources.

Scheme of Renault's on-board reforming system. Image: <http://www.autospectator.com/cars/renault/ 0024092-renault-presents-progress-its-research-fuel-cells>

3.5.2- HYDROGEN INTERNAL COMBUSTION VEHICLE (HICV)

A short-term alternative to the technologically complex fuel cell vehicle is the adaptation of the four-stroke ICE to work directly on hydrogen combustion. This variant is not as extended and relevant as the FCV, since only a few carmakers, such as BMW, are investing in this sort of vehicle.

The actual dissimilarity between the hydrogen internal combustion vehicle and the fuel cell model is, besides the technologic difference, the minor efficiency of the combustion engine in comparison to the electrochemical process carried in a PEMFC, as well the unavoidable N2O releases because of the high temperatures achieved inside the cylinder (a trait of any ICE).