Hydrogen fuel cells create electricity by combining hydrogen fuel and oxygen, using that energy to power the electric motor or motors that drive the vehicle. Refilling the hydrogen fuel tanks takes just four minutes, about the time it takes to refuel a conventionally powered vehicle. One of the obstacles that fuel cell vehicles have to overcome is the size and weight of the hydrogen fuel tanks. To reduce the weight of the tanks, Audi engineers made the fuel tanks with an advanced polyamide material wrapped in carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP).
On the Audi h-tron quattro concept, three of these tanks are placed throughout the vehicle, with one close to where a traditional transmission would sit, one beneath the rear bench seat and one in the cargo area. These tanks are connected via an infrared interface that helps equalize pressure and temperature levels.
Improving the fuel cell itself is an area to which the engineers have devoted a great deal of resources. Working with Volkswagen and other technology companies in what is known as the HyMotion 5 project, the teams have been testing new materials to create the bipolar plates that separate the individual cells. The goal is to make the fuel cell significantly lighter, smaller and more powerful, which can help with cold starting, service life and hydrogen consumption. The cost of production also can decrease by replacing the platinum currently used in fuel cells with the new materials.
The h-tron quattro concept unveiled in Detroit, Mich., in early 2016 is the first Audi fuel cell vehicle to incorporate quattro® all-wheel drive and create the electrified quattro®, thanks to a second electric motor that powers the rear wheels. Power comes from a fuel cell rated at 110kW and a 100kW lithium-ion battery that supplement drivetrain demands.
Synthetic & natural
In addition to the advances in fuel cell technology found in the h-tron quattro concept, Audi engineers and their energy technology collaborators have developed innovative fuel production methods. Grouped under the name Audi e-gas, these new fuels—also known as synthetic natural gas—are made with renewable materials instead of petroleum.
In the city of Werlte near Bremen in Northern Germany, natural gas is made by a process known as power-to-gas. Started in 2013, the first-of-its-kind production method starts by using electricity generated by wind turbines, which is fed into the power grid. That electricity is used to power an electrolysis plant that splits water into oxygen and hydrogen.
The hydrogen reacts with carbon dioxide to produce the end product, e-gas. It is then fed into the region’s natural gas system and can be used to power the Audi A3 g-tron, Audi A4 Avant g-tron and Audi A5 Sportback g-tron—vehicles currently available to German buyers.
Better than sugar beets
In the city of Hobbs, N.M., Audi and the biotech company Joule have been researching methods to produce e-ethanol with microorganisms that use sunlight, carbon dioxide and salt or brackish water. Their tests have shown that this innovative process can produce more ethanol than traditional ethanol production using corn or sugar beets.
By taking on the challenge to broaden the mobility landscape, Audi has found viable solutions that are available today or will be in the near future. As a result of this research, the drivers of tomorrow should be able to choose from a wider range of drivetrain systems and fuel source options. While it may seem as though the future will be battery-powered, Audi has shown that viable options can compete on our roadways.