Many friends have asked if Audi can make diesel from thin air.
Yes Audi can make diesel from air but only with a lot of added energy. There are no free lunches in America and there is no free energy in the universe. The process can use solar electricity or wind electricity to electrolyze water to produce hydrogen. Even with their claimed steam electrolysis this will only be approximately 55% efficient. Then the reaction of CO2 with hydrogen to yield Carbon Monoxide and water is approximately 80% efficient. Then they must react carbon monoxide with hydrogen to make diesel and water. This is again about 70% efficient. All in all the process is about 35% efficient and kid of pointless. The fuel is then used in a diesel engine that is 30% efficient and hence only about 10% of the Kwh in the electric power will get to the wheels of the diesel Audi.
One could easily take the electrons from the solar or wind farm and charge lithium ion batteries in a plug in car. This will be 90% efficient in getting power to the wheels. Audi is proposing a Rube Greenberg Scheme. The cost of this diesel will be enormous and it simply wastes 90% of the energy in the renewable electricity rather than using 90% of the energy in the electrons.