In 2006, Renault and Nissan decided to pool their efforts to produce a demonstration vehicle powered by a fuel cell. It would draw on technologies the two companies had developed together and separately, as well as on new work.
The Scenic ZEV H2 was designed in just 15 months, including testing. Once the detailed engineering had been finished, assembly work on the first vehicle kicked off in France in the summer of 2007. At the end of September 2007, the French and Japanese partners met to carry out a joint check. Its aim was to be sure that both Renault and Nissan components worked within the car’s design in all the right ways. The first prototype was then transferred to Japan for final assembly.
At the end of 2007, the first vehicle was on the road, and the project was declared finished at the end of April 2008.
The ZEV H2 is derived from Renault’s Grand Scénic. Nissan supplied the fuel cells stack, the high-pressure hydrogen tank and the lithium-ion batteries. Renault repackaged the car so that its underbody could incorporate the fuel cell stack, H2 tank and battery pack. Renault also redesigned the floor and raised the vehicle’s ground clearance by 60mm. The Scénic’s passenger accommodation is unaffected by the unusual drivetrain.
The Renault-Nissan Alliance’s long-term powertrain strategy focuses on continuing work on prototypes powered by fuel cells. Although they offer significant gains in range, they are more complex than plug-in electrics or hybrids to mass-produce and market. Not the least of the problems manufacturers face is that fuel cell technology requires production, transport and distribution infrastructure for the hydrogen fuel. There are very few H2 filling stations at present. A further requirement is reducing the cost price of the fuel cells, particularly by using smaller quantities of precious metals.
Renault’s Vehicle Engineering team incorporated electrical and electronic systems from both Renault and Nissan into the Scénic. The fuel cell itself is a relatively self-contained electronic system, which was designed to communicate with vehicle components and features like the dashboard, ABS/ESP, climate control and airbags. All of the vehicle’s elecrical systems perform normally.
Some of the Scénic’s instrumentation has been adapted to the vehicle’s new drivetrain and control systems. The fuel gauge, for example, is now a hydrogen pressure indicator, while the temperature display shows the fuel’s temperature. The rev-counter displays the electric motor’s running speed.
Renault is boastful of the driveability they have achieved with the Scénic ZEV H2. Certainly, electric power is always impressive at low speeds, because an electric motor produces its best torque output at low revs. We — like all other outsiders — haven’t had the chance to drive it, but road performance should be more than adequate: Renault quotes a maximum speed of 100mph and 0-100km/h acceleration in 14.6s.
Predictably, there is a substantial weight premium for the fuel cell vehicle over a conventional car. The hydrogen-powered Scénic weighs in at 1850kg empty, 300kg more than the 1.9 dCi version.
Although it’s only a prototype at present, the Scénic ZEV H2 makes its point well. Like others of its kind, it shows clearly that H2 fuel cells are a very convincing technology — but also that we still have a little way to go before it’s practical or economic to start building them.
How it works
The fuel cell system that powers the Scénic comprises five main sub-assemblies: the hydrogen tank, which supplies fuel to the fuel cell stack; the power electronics, in conjunction with a regulator, which interfaces between the stack and the electric motor; and the lithium-ion batteries.
The vehicle can operate in five main modes.
The battery alone supplies power directly to the electric motor. This power supply mode operates when the vehicles starts, when parking, or when driving in the city. It also kicks in when the car accelerates sharply, as the battery can deliver bursts of high power to complement the fuel stack.
The fuel stack alone supplies power to the electric motor. The vehicle generally uses this mode when travelling at a steady speed. Power from the fuel cell stack that’s not used by the electric motor is directed to the battery pack.
The stack and the battery deliver power to the electric motor when the vehicle requires an extra power boost — for example, when climbing a long gradient or overtaking at speed.
When the vehicle is at a standstill with its systems powered up, the electricity produced by the
fuel cell stack is used to recharge the battery.
Kinetic energy capture feeds the battery pack when the car is decelerating. Obviously, the fuel cell stack also recharges the battery when its power is not in demand to drive the car.