With the HydroGen4, GM presents the fourth generation of its fuel cell technology. “Fuel cell propulsion with hydrogen as a fuel highlights General Motors’ commitment to take the car out of the environmental debate and reduce our dependency on oil,” said Carl-Peter Forster, President of GM Europe, at a press conference in Frankfurt. “HydroGen4 is powered by GM’s most ad¬vanced fuel cell system and marks an important milestone on the road toward com¬pletely emission-free, competitive fuel cell technology in the automobile. The HydroGen4 features considerable progress in everyday usability, dynamics and system durability compared to its predecessor.”

The GM HydroGen4 is the European version of the Chevrolet Equinox Fuel Cell. As early as fall 2007, the first of these fuel cell prototypes – a global fleet of more than 100 vehicles is planned – will be on the roads in the USA. They will take part in an extensive testing and demonstration program. The vehicles will be given to customers so that GM can contain all aspects of their use of the car and how they handle filling it with hydrogen. The findings will then be included in the further development. From mid-2008, a total of ten HydroGen4 vehicles will take part in day-to-day testing within the framework of the Clean Energy Partnership (CEP) in Berlin. In the second phase of CEP, various customers with different driving profiles will operate the fuel cell vehicles day after day to test the cars’ everyday usability.

The HydroGen4’s fuel cell stack consists of 440 series-connected cells. The entire system produces an electrical output of up to 93 kW. With help from a 73 kW/100 hp synchronous electric motor, acceleration from zero to 100 km/h takes around
12 seconds. The front-wheel driven vehicle’s top speed is around 160 km/h.

The HydroGen4 is designed for a lifecycle of two years/80,000 kilometers, and can start and run at sub-zero temperatures – a considerable advancement over the predecessor HydroGen3 and an important characteristic with regards to the everyday usability of fuel cell vehicles. This improvement is possible thanks to an intelligent combination of measures including thermal insulation, water management and operating strategy.

The four-seater offers the comfort, spaciousness and high safety level of today’s conventional cars, and includes driver and front passenger airbags and side airbags. ABS, Traction Control and ESP are also fitted. The HydroGen4 has a tank system with three, 700-bar high-pressure tanks made from carbon-fiber composite material, which can hold 4.2 kg of hydrogen. This provides an operating range of up to 320 kilometers.

The heart of the HydroGen4 is its fuel cell stack. Fuel cells convert chemical energy into electrical energy without combustion. Via an electro-chemical reaction, they combine hydrogen and oxygen to form water, and produce electricity at the same time.

The electro-chemical process in a fuel cell works as follows: Hydrogen on the anode catalyst splits into protons and electrons. The positively-charged protons pass through the membrane to the cathode, while the negatively-charged electrons travel in an external circuit, producing electricity on the way. On the cathode catalyst, oxygen reacts with the electrons and protons to form water. A stack connecting a large number of individual cells can thus produce enough power to drive an electric motor.