Test Audi A7 Sportback h-tron quattro, bet by the hydrogen


The Audi A7 Sportback h-tron is still a prototype, is not for sale

We have had occasion to drive the Audi A7 Sportback h-tron quattro, a prototype plug-in hybrid that has an electric propulsion system with a fuel cell as a source of energy. The technology h-tron refers to the hydrogen that is used as a fuel and is part of the alternative propulsion systems developed by Audi, among which also include the e-tron (electricity) and g-tron (gas).

Outwardly the sedan h-tron for the German flag has an aspect similar to that of the production model conventional of the Audi A7 Sportback. There is little evidence to suggest that under your skin there is a fuel battery (Fuel Cell) converts the hydrogen into electrical energy, promising a range of more than 500 kilometers, during which your exhaust does not emit nothing more than water vapor.

The Audi A7 Sportback h-tron quattro is the fourth generation of fuel cells developed by the German brand. The first model, the Audi A2 H2, presented in 2004. After this came the Audi Q5 HFC in 2009 showed the second generation and in 2011 the third.

For the moment it’s a prototype, although Audi says that they will launch on the market in the future when the manufacturing cost is reduced, the infrastructure for this type of fuel is greater and the demand will increase. The bet of the German brand is obvious and in 2013 he began to use a pilot plant that produces hydrogen through electrolysis taking advantage of wind energy renewable.

How does the fuel cell Audi?

The Audi A7 Sportback h-tron quattro stores the hydrogen in four tanks located below the trunk, in the centre tunnel and the front of the rear axle. They have a spherical shape and feature an aluminium frame with a protective outer shell made of polymer reinforced with carbon fiber (CFRP). In the tanks can store around five kilograms of hydrogen at a pressure of 700 bar.


The four hydrogen tanks are in a position as low as possible to reduce the center of gravity

In the berlin of germany, the fuel cell is located in the front, under the hood, where an A7 Sportback conventional would conventional combustion engine. The stack comprises more than 300 individual cells, each one of them with a catalyst made of platinum on each side of a polymer membrane.

The fuel cell stack operates in a voltage range of 230 to 360 volts. The operation of the technology Fuel Cell is the following: through the anode is supplied the hydrogen is split into protons and electrons. The protons pass through the membrane to the cathode, where they react with the oxygen present in the air forming water vapor. For its part, the electrons go to the cathode by an external circuit, generating an electric current.

main auxiliary components of the system found a cooling pump of the stack -you need to operate in a temperature range of about 80 degrees-, a twin-scroll turbocharger that forces the air into the cells and the so-called “exhaust fan recirculating”. This fan returns to the anode the hydrogen is not used in the process, thereby increasing the efficiency and making the most of the fuel.

As a plug-in hybrid, the A7 Sportback h-tron uses the battery ion lithium which is also used in the Audi A3 Sportback e-tron. It is located under the boot floor and has a capacity of 8.8 kWh. The battery supplied power to drive the motor in situations of maximum demand of power and also stored energy retrieved on withholding and braking: when the brakes are applied the motors start operating as generators, converting the kinetic energy into electrical energy.

The battery drives two electric motors, located one on each axis formed the wheel drive e-quattro. Are synchronous motors excitation permanent and each one of them develops a power of 85 kW-although temporarily can reach the 114-kW – with a maximum torque of 540 Nm. In total we have an output of 170 kW (231 HP) and an electronic control adjusts the torque that reaches each axis, there is a mechanical connection.


Each electric-only mode operates on an axis

Using this battery the Audi A7 Sportback h-tron can travel up to 50 km in mode 100% electric, without resorting to hydrogen. Recharge in a wall outlet and a full charge is done in two hours if you use a decision of an industrial power, at 360 volts, or in four hours using a domestic power socket at 230 volts.

Goodbye to the pollution

If the outside of the h-tron hardly differs from an A7 Sportback with combustion engine, in the cabin, the changes are not very great but yes more and more evident. Despite the presence of the four hydrogen tanks of habitability is not affected, except by the reduction of cargo space in the trunk.

In the box of instruments a power gauge replaces the classic tachometer, so that we can have controlled the power flow at each time point, the level of hydrogen and the charging of the battery. The information of the hybrid system also we can visualize on the screen of the multimedia system MMI.


The instrumentation is the visual difference more obvious versions with a combustion engine

The steering wheel you will note something heavy, and not in vain at the scale throws 1.950 kg, a figure superior to the versions of the combustion engine. However, it is not lacking in power: the 540 Nm of maximum torque available virtually from the first moment and provides a nice immediacy of response to the accelerator.

In some accelerations you will hear a faint hiss from the rear of the car, showing when you open the flow of hydrogen from the tanks. This sound is the only one that disturbs the silence with which it circulates and is disculpable and natural since it is a prototype: they are small details that are not yet in tune.

the performance of The A7 Sportback h-tron are those that can be expected of a premium saloon like this and reaches 100 km/h from standstill in only 7,9 seconds. In this sense, the only thing striking is his dry maximum speed of 180 km/h, limited by an obvious question of efficiency.


The recharging of hydrogen is fast and easy

The change is automatic, of course, and we can choose the level of energy recovery in retention or braking and in this way optimize the recharging of the battery. In addition, on the dashboard of the sedan German there is a button to EV which causes the car to move in electric mode, using only the energy of the battery.

The fuel battery promises an autonomy of more than 500 kilometers and the best thing of all is that the h-tron says goodbye to the pollution, only emits water vapor. This has allowed the exhaust system is made of plastic material, which is a reduction of weight. The tank cover is located on the right side of the coupe, five-door, concealing a connector for the refuelling of hydrogen.

Refueling the hydrogen tank is as simple as opening the lid and plugging in the connector, it is filled in just three minutes. Basically it is like going to the gas station as normal, but in a station of hydrogen (hidrogenera). As you can assume, the current limitation is to find a point of supply of hydrogen. Although in Europe is growing slowly, the network of hydrogen stations has still a lot to grow in order to encourage the use of this type of vehicles.