After yesterday’s announcement, the Audi A7 Sportback h-Tron Quattro technology demonstrator was unveiled at the 2014 LA Auto Show. According to Audi, the h-tron quattro uses a sporty electric drive with a fuel cell as its energy source, in combination with the hybrid battery and an addition electric motor in the rear.
The total output delivered by the electrical system is 229 hp (170 kW) and as expected it is transferred to both the front and rear wheels. Audi says that the A7 Sportback h-tron Quattro can hit 100 km/h (62 mph) in 7.9 seconds, while top speed is 180 km/h or almost 112 mph.
Meanwhile, with a full tank of fuel, the vehicle has a range of over 500 km (310.7 miles), while emitting only few drops of water. If the exterior shows just a standard A7 Sportback, beneath the stylish design there is a fuel cell installed at the front. Here is how the system works: Hydrogen is supplied to the anode, where it is broken down into protons and electrons.
The protons migrate through the membrane to the cathode, where they react with the oxygen present in air to form water vapor. Outside the stack the electrons supply the electrical power – depending on load point, the individual cell voltage is 0.6 to 0.8 volts. Other elements include a turbocharger that forces air into the cells, a recirculation fan and a coolant pump.
A7 Sportback h-tron Quattro is also a plug-in hybrid and arrives with a lithium-ion battery with a 8.8 kWh energy capacity, ‘borrowed’ from the A3 Sportback e-tron. Using just the energy stored in the battery, the vehicle has a range of up to 50 km or 31.1 miles.
The battery can be recharged using an industrial power socket (360 volts) in two hours, while using a domestic power socket (230 volts) takes up to four hours.
The electric motors used to drive the front and rear axles are cooled by a low-temperature circuit together with the voltage converters. Each electric motor delivers 85 kW or 114 kW if the voltage is temporary raised, while peak torque is 270 Nm (199 lb-ft).
The most important differences are found underneath the bonnet of the A7 Sportback powered by a fuel cell. These include the fuel cell system in the Audi technology demonstrator. This fuel cell system is complemented by a lightweight exhaust system made from plastic, as it only needs to take care of water vapor.
This fuel cell system in the version of the A7 Sportback is made up of more than 300 individual cells forming a stack. Each individual cell has a polymer membrane serving as a core, as flanked by a platinum-based catalyst on both sides.
The process consists of first having Hydrogen supplied to the anode, where it is split into protons and electrons. The protons are sent through the membrane to the cathode, where a reaction with oxygen in air results to the formation of water vapor. The electrons outside the stack, meanwhile, supply the electrical power. Depending on load point, the voltage is 0.6 to 0.8 volts per individual cell. This means that the entire fuel cell system delivers between 230 volts and 360 volts.
Meanwhile, the main auxiliary assemblies include a turbocharger that forces the air into the fuel cells, a coolant pump, as well as a recirculation fan that returns unused hydrogen to the anode for further efficiency. These components feature a high-voltage electric drive as powered by the fuel cell.