This is how an electric car conquers the toughest rally in the world


This is how an electric car conquers the toughest rally in the world

The Audi RS Q e-tron behaves like a battery electric car, which is not powered by plugging it in, but is generated by an energy converter installed on board

Audi has developed one
innovative racing car concept in the Dakar Rally in a sustainable way. The option of a battery powered electric propulsion system was impossible due to the energy density and performance required for the Dakar. However, the Audi RS Q e-tron uses an electric drive system, but the battery power comes from a built-in power converter.

For example, the powertrain of the Audi RS Q e-tron has two Audi MGU05 motor-generator units, one on each axle. Very similar to the ones used in the Formula E e-tron FE07 single seater, they are the ones that move the wheels of the car and create a
maximum combined power of 680 hp. These electric motors are powered by energy stored in a high-voltage battery. The battery, which is placed in the middle of the car, weighs 370 kilograms and has a capacity of 52 kWh.

In a conventional electric car, the energy from that battery would be obtained by connecting the car to a charger or home network. In the Dakar, this option is not feasible, as it would require a battery that is too large and too heavy to handle and complete the daily stages, with hundreds of kilometers, sandy terrain generating a lot of resistance and high outside temperatures. The innovative solution developed by the brand’s engineers is the installation of an on-board energy converter that produces the electricity stored in the high-voltage battery, in combination with the energy recovery systems of braking. This converter is composed of a TFSI internal combustion engine, from the DTM, together with a third MGU unit.

The TFSI engine is incredibly efficient and at the forefront of weight and fuel consumption. It operates in a particularly efficient range between 4,500 and 6,000 rpm, enabling specific consumption well below 200 grams per kWh. In addition, this year it uses renewable fuels (reFuel) with 80% sustainable components, made from waste and without the use of food. As a result, the emissions of the Audi RS Q e-tron E2 have been reduced by 60% compared to last year’s vehicle.

“The TFSI engine is only used to charge the battery while we compete in the special stages, as there is no other way to do that in the desert,” he explains.
Oliver Hoffman, director of technical development of the brand. “At Audi, we follow a consistent decarbonization strategy,” he says. “Our vehicles with renewable electricity and batteries use leading technologies. In addition, renewable fuels offer the possibility of working with combustion engines in a more environmentally friendly way. As a result, we will now be even more sustainable in the toughest automotive competition for electrical technology.”

To generate the reFuel, a process must be carried out that converts the biomass of biogenic plants into ethanol in a first phase. Then, in other subsequent stages, the final fuel is produced. The process is abbreviated as ethanol-to-gasoline (ETG).

The maximum power of the motor-generators installed on the front and rear axles is limited to a maximum of 288 kW to comply with regulations. However, the power converter can only deliver a maximum charging power of 220 kW. So in extreme cases consumption is slightly higher than power generation.

Audi engineers and electronics specialists have developed an electronic management system that keeps the SoC (State of Charge), ie the charge level, of the battery within defined ranges based on energy demand. But “over long distances, the balance must always be in balance: for this we must ensure that energy consumption is low, so that the battery charge level remains within set parameters. The total available power must be sufficient to cover the entire journey,” says Lukas Folie, a high-voltage battery engineer.

In addition, the energy recovery system also provides extra energy during braking to recharge the batteries. MGU units installed on the front and rear axles can convert the rotational movement of the wheels into electrical energy. This, which seems so simple, requires a complex Intelligent Braking System (IBS), which combines the hydraulic braking function with regenerative electric braking.

Once on the road, the Audi RS Q e-tron drives like an electric car. Only one forward gear is required and there is no mechanical connection between the front and rear axles. Software developed by Audi handles the distribution of torque between the axles and serves as a freely configurable virtual center differential, which has the positive side effect of saving the weight and space that driveshafts and a differential would have required.

Source: La Verdad


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